1974 1.8 with L- jet. Been playing with a wide band air fuel meter and noticed that when I lift the throttle the AFR goes to max value on the gauge. I thought it was supposed to go lean. I checked the throttle position switch and it checks out fine. Going to check the wiring harness next.

What else should I check? Decel valve?

My mustang goes super lean on throttle lift, as it should. My djet does not and often does as you describe and never goes super lean on lift. I wonder how many others have observed this.

I haven’t measured my AFR to compare so, I can’t say how mine does.

Do you ever get idle hang on deceleration i.e. it gets stuck above idle when you’re slowing down?

I did have that problem in the past. One thing that helped was to adjust the decel regulator to bring the rpms down quickly to 1000 without going below. Of course this changes with engine temp so it was a balance. I switched to the 123 distributor and my transition to idle became nearly perfect. Idle is really steady now.

Ok so, two thoughts:

1.) set your decel valve to begin opening at 20 in-hg of vacuum.

2.) Does your 123 retain it’s advance on decel? I might be wrong here but I think the OEM dual vac pulls timing on decel

Good question. I have the vac capable 123 and I will have to check for sure if pulls the vac advance out on decel. I think it can be mapped to do both adv and retard but not sure. We are expecting some rain tomorrow so I will report my findings mid week. Maybe someone reading this can confirm if adv is active during decel.

Ok, I’m too tired to think straight but yes, your timing should retard when the throttle is closed regardless of RPM.

Timing retard vacuum is pulled from the bypass port on the throttle body, which is only used when the throttle plate is closed.

Look at line B

you are not getting tired, you are getting really good.

correct on all counts.

why it would be rich....?
could be connected to that?
but i would have to think about that too.

those two ports behave slightly differently.

when throttle is fully closed the one on the manifold side of throttle plate activates retard can on distributor.

the other one, on the inlet side works at part throttle and cruise to advance the distributor.

and in typical VW fashion the advance one serves to cushion the distributors response to load.

but, its meant to lean for emissions when you close off throttle.

i'm just trying to remember how it goes.
might have to go back and re read manual to remind myself.
or alternatively clay perrine can just come in and say it in 5 words or less.

but i know the fuel pressure regulator does a bit at that point too.
backs off the fuel pressure - because its linked by vacuum to the plenum as well.
there is that t connection to the same vac line as the decel valve.
and there is something else that goes on with L jet probably in the afm.

get back to you if someone smarter doesn't do it first.

------

those double can distributors are amazing.
there are f$ck all cars in aus with them.
they belong to a period in time and USA cars in particular.
i have only really got my head into them since getting mine going again.
basically its the main emissions device? sort of.
we still had just advance can distributors on VWs here from same period in time.

-------
but in a carb car we wouldn't be worried if it was going full rich on throttle off deacceleration.
we only expect it to be lean because of emissions regs and fuel injection artificial intelligence combined with cuckoo clock mechanical devices aiding it.

???

or am i wrong.
but if its behaving properly as per EPA and being L jet, yeah it should go lean.

But here he is running a 123 right? so you have to choose retard or advance. My rich on lift didn't change when I switched from retard to advance (and moved the vacuum line appropriately).

I suspect with the butterfly closed, the pcv closed (on my 73, others may not have that), that the decel valve really can't let enough air in at meaningful rpms to thin the mix much. On a 1.8 I bet the vacuum operated fuel regulator (it is vacuum on the 1.8 right?) is a critical part of the lean on lift. Wonder if you have some issue there?

Definitely possible.
As you've seen through my quests, the air from the decel valve is still measured air since it pulls from the intake boot after the AFM barn door. If the decel valve is flowing air when it shouldn't be, then the AFM will fuel the engine. I'm thinking maybe it could be too much fuel given the throttle body is fully closed in those moments.
In my view, you only want the decel valve to open at moments of high vac... throttle chops etc.

My point about timing is that if it remains advanced when the throttle is closed, then the burn won't be right and will almost certainly show a low AFR (rich)

Now that I think about what I just posted, I bet there is more than one cause/tuning issue at play here.

Is the AFM before or after the boot? I need to put up a diagram of these two systems. Advance should pull out as long as you have it attached to ported vacuum. Perhaps that might be an issue here? If the vacuum advance is hooked to the plenum you would end up with advance when you lift rather than during slight throttle opening.

AFM is literally the barn door. it attaches to the air filter box and precedes everything. However, the car he's running here has two vac ports for the distributor. one for retarding and one for advancing. That's what I was showing on the page I posted. what that means is that there is progressive vac advance or no advance + vac retard and no retard.

Honestly, though, I have no clue what AFR should be expected from an L-jet at elevated RPM with a closed throttle. Without this ref we're just theorizing and having conversation for the sake of conversation lol...

The AFM in an L-Jet system will push fuel into the ports as long as there is airflow through it. So on decel, you will have a lot of air moving through the AFM even if the flap is closed due to the engine spinning fast.

That may be causing the rich mixture you are seeing.

Clay

So a decel hooked to the boot would be unmeasured air? AFM -> Boot -> throttle body? or is it Throttle body -> AFM -> Boot? If it is the first situation, the closed throttle body should reduce flow across the AFM and result in high plenum vacuum and the decel leading to the boot would cheat the AFM. I would think you would want the decel after the throttle body to be most effective and cheat the AFM.

I believe he said he was using a 123, so just one port on the dizzy.

Everything is measured. Remember my first thread?

http://www.914world.com/bbs2/index.php?s=&...t&p=2958074

Right. Which is why I went with pertronix instead.

Is this correct?
I know they changed stuff every month on these things.

Click to view attachment

the little subset square on the airbox is meant to represent the AFM... poorly lol

If it is, man that doesn't make much sense to me. Why would you pull air through the AFM bypassing the throttle blades? There must be an 'on off' with the TPS. If throttle is closed, don't listen to the AFM. At that point, why not just suck it before the AFM for the decel?

TPS really only knows when the throttle is open (not at idle) and when it's full throttle. Everything is driven by the AFM. It's a v1 MAF really.

If @Brian Fuerbach can confirm the opening vac for his decel valve than that will give a clue into whether the AFM is sending extra fuel even when the throttle is closed. I'm a little skeptical about that because if the decel valve was sending air, I would expect to see rev hang i.e. very slow wind down of the engine from high RPM.

My money is on the timing. too much advance at high RPM + not enough air = incomplete burn that is picked up by the AFR.

Too much advance could certainly do it, but there should be a healthy fuel cut too. If the TPS is saying the throttle is closed, the AFM should be ignored (well, idle level), and the decel pulling air from the boot and dumping it into the plenum should (should) cause a lean mix. And add to that the vacuum on the fuel regulator. If that is all working correctly then the only thing left is advance. Or just normal behavior. Not like many of us have AFRs. Wish they were more common and less expensive..

Speaking of that, Brian, out of curiosity, where is your O2 sensor located?

Regardless of the vac adv or retard, the centrifugal advance in a stock distributor will keep the advance at 27 degrees. Not sure pulling out 5 degrees timing would change the afr that much.

I will check my decel valve opening values tonight.

I am running a 2.0 Bursch exhaust. The 02 sensor is located about 10" downstream from the collector.

Yeah,we were only speculating on 'way too much' advance. Or at least I was. My O2 is in about the same spot on an Ansa setup.

the throttle switch on the 1.8 operates at two positions.
idle. throttle closed.
wide open. (a position wonki occasionally enjoys torturing it with).

in between the flap in the afm does the fuel measurement (reacting to air amount).

i guess therefor fuel is metered by throttle body switch for the two extreme points.
when you snap the throttle closed the afm may be getting pulled open via the decel valve, but the fuel mix will be dictated by the throttle switch? ????

think i have that right. but happy to be corrected and unlearn something.

i'd have to think more about it precisely.
and go back and read some of the tech manuals.

i don't have a decel valve operational in mine.
and i haven't measured a/f mix on throttle closed, to know what it does.
but i suspect i don't have a rich air fuel mix on throttle closing as i don't get backfires.
ie not dumping fuel rich mix into a hot exhaust where it can detonate.
but i suppose it could still be rich, just not rich enough to backfire.

the decel is supposed to stop the engine going below idle, dying and coming back to life.
that can happen with my car, but only when still cold.
a weird thing where you snap closed the throttle and then there is a second of silence before normal service resumes.


so....the rich thing is interesting.

i don't know how fast the dist would return to full retard idle position.
its in its centrifigal phase as revs come down.
the vac can would have very little advance action going on from the port in front of the throttle blade. it would be in full retard action if hooked up properly to the retard port on the tb or to a vacuum source in the plenum. which means all the way down as revs decline the dist will be that 3-4 degrees further retarded than if it were a pure centrifigal dist. and that would be making the burn more complete. which is what the emissions oriented design is meant to do.

My experience with this is two things.
1) a dirty distributor advance plate area. The OEM grease is now like hard gooey plastic, and it is no longer a lubricant, its more like glue now.
Remove dizzy, take it all apart and clean it, make sure the advance plates move freely and fast. Make sure they snap into the non advance position.
Add wheel bearing grease...about 0.05 cents worth. Car will be happy.
2) you have a vacuum line plugged into the wrong place, or the wrong way.
try nothing on vacuum advance (at the dizzy) then try nothing on the retard.
If I recall, you may end up with a hose on vacuum advance, and nothing at all on the retard, just leave it open to the air.
2a) a vacuum leak with make the car have a higher idle..so that too,

Overall, the car will run with all vacuum ports closed off at the plenum, then you can add one hose at a time until you find the culprit.
Dont trust that after almost 50 years that something is not leaking, has a hairline crack (plenum) or some fitting or hose is no longer perfectly tight.

EFI is all about measured air/fuel to get it right.
You have an air issue.

Rich

no. not quite emery.

the decel valve is cheating the throttle body is all that is happening.
and its pulling the flapper open as a kind of second throttle body.

the decel gets pulled open by vacuum in the plenum when the throttle is closed.
this operates an alternative route for air which is (and can only be) drawn past the flapper - and therefor operating it.

vacuum declines as revs drop and the decel gradually closes.
closing the air route.

its basically just slowing down the action of closing the throttle so its not so violent, on and off. which is why a lot of the 911 guys used to rip the decel valves off.
i think in the case of the 911 guys it was on the K jetronic system? they hated them.
they wanted violent on off throttle. (something to do with having an engine in the wrong place in the car and going around corners?).

the decel valve is operated by the same vacuum line that branches off to the fuel pressure regulator. so on decel the same vacuum opens up the fuel pressure regulator a bit more and drops fuel pressure.

which is why i am still thinking. because fuel pressure and dropping fuel pressure does come into it with L jet. exactly how it affects things i can't really say. but L jet is wanting to drop the fuel pressure on throttle closing situations.

But wonkipop, that completely ignores the ecus response to the throttle being in the closed, idle position. If that is in fact one of the signals the tps sends then at idle you would expect some kind of over ride on the afm. I may be completely wrong on that, it just seems logical since a like circuit exists in the djet. Things run differently if the throttle is closed.

yes

thats the bit i am still thinking about. where i say so in above posts.

which one gets over-ridden. because one must? i agree with you.

i have to go back and read manuals to answer that.

but the throttle is in the closed position. and that definitely does say something to the ECU. where it is quite unlike D jet is that is the only time it says something to the ECU, except for the other time when you have your foot mashed into the firewall. and when you do that, it just says to the ECU, give me all the fuel you got. all of it.

and the flapper is being pulled open (sustantially so) by the decel route while the decel route is open. so does that dictate anything in air fuel mix? don't know.

I would bet it does, otherwise they would have just run it into the air cleaner pre-afm. But what does it say!!!? Perhaps the same thing it says when the aar is open? What does the fox say?

here is a bit of the story emery.

i knew L jet did something where it cut off fuel.
hence the reason the fuel pressure regulator is plumbed into plenum vacuum along iwth decel.

we like to joke about these things being from the jurassic age.
but really its the ice ages and wooly mammoth era.

carbies were around with t-rex.

there is a bit of talking going on to the old lunar module era ECU and it can sort of think in a preconditioned pregrogrammed routine way.
its getting sensor information also from the dizzy to tell it what is going on during coasting after throttle closes.

Click to view attachment


so if you come off revs with the engine spinning fast enough it knows what is going on.
cuts off fuel until a certain point where revs are low enough and resumes supply despite throttle switch being at idle position. so there is a primitive neuron dedicated to that input.

must be similar with decel valve. knows that if flap is being pulled open a certain amount but throttle switch is in idle position then its got to do the decel thing and another neuron flashes on and does that routine.

so not exactly an overide, more a response to very particular environmental inputs.

its dumb, but kind of like a three year old or a chimpanzee. pick up the red box and you can have a peanut sort of thing.

still can't answer the fuel rich thing on deacceleration exactly.
but in a standard L jet set up with the original dizzy, there are a few things going on.
and all of them are really leaning it out. first no fuel. then some fuel and some air to stop it dying in its tracks (the decel valve) and then finally we are idle revs and it settling down.

but i had remembered right about the fuel cutting off. and i think it does it quite differently with D Jet but again i just know its different, but not how its different because i don't do D jet.

It would be interesting to know what the dizzy connection is since in this case we have a 123 rather than the original.

You might want to check this chart, we’re not talking about just 5 degrees

74 model would be using 205 AA

yes.


anyway

Van is right. it is retarding with the original dist so thats doing a later burn and getting rid of hydrocarbons that might be sensed by the probe that OP has.

and

its doing a little fuel thing as well via the ECU where its getting some info also from the original style distributor.

but i mean a carbie car just does the rich thing on throttle lift off.
so ........its no worse than that?
or am i missing something.

i know here all the old school mechanics hated that lean thing that emissions cars did on throttle lift. thought it was worse for cars than the rich dump from carbies.
swings and roundabouts?

worst it can do is pop and bang through the exhaust when you come off the gas?
not exactly a backfire, more a detonation in the exhaust system.
bad for catylisers sure. but all this stuff was designed for preserving cats and cleaning up exhaust at the dirty times. idle and the big one, coming off the gas.

ps

i was trying to look for info on the fpr in the factory manual.

i know its a sealed unit with the 1.8s.
no adjustment nut like a d-jet.

delivers normal standard fuel pressure.
and when the off throttle business happens manifold vacuum operates it and it opens and drops the fuel pressure in conjunction with the fuel cut off business the distributor sends signal to ECU for.

and really if the fpr is screwed on the L jet you throw them away.

but if they fail, ie the membrane its going to be dumping fuel via the vac line into the plenum. and thats going to be a lot of fuel i would think.
but there could be something in that. not sure.

@Emerygt350 .

always have to go back and re-read this Ljet stuff carefully.

not sure if 1,8s incorporated the fuel shut off thing.
may not have been in all L jet systems, just for some cars.
someone like clay perrine would know.

1.8s definitely had spark cut off via the rotor for over rev.
whether that cut off fuel too i don't know, but i don't think so.
reason i say that is 75 calif 1.8s had a whole separate switch to cut off fuel to stop catyliser being ruined.
but as to coasting over-run, not certain. maybe note posted above inaccurate.

def adjust fuel pressure.
at low vac situations its 35 lbs.
and at high vac it reduces to 28 ilbs.
you test that as part of standard testing.

very definitely the throttle switch takes over at WOT.
just full on gives you fuel.
less clear about what tps does at idle (or throttle closed).
thinking about it, i believe its the AFM does it all.
when the throttle is closed the switch is simply sending a signal to the ECU that its closed. and ECU then knows this and does its routines based on other inputs.
i think only time ECU overrides the AFM is WOT and gives full enrichment.

so......
just not sure what could cause richness on over-run other than Van's suggestion that the distributor does the clean up via the timing. the fuel pressure lowers to assist due to high manifold pressure. and the ECU knows that the throttle is closed, but the engine revs (spinning) are high so it does an adjustment to the enrichment the AFM would usually signal at the flap position it is at because the decal valve being open (which is happening simultaneously with the fuel pressure regulator lowering fuel pressure).

Click to view attachment Click to view attachment Click to view attachment

Tonight I measured the opening vacuum of the decel valve and it starts at 18 in-hg and is fully open at 20.

I also checked the wiring harness from the controller connection to the TPS (Pins #18 and #3 WOT). Idle checks out with "no connectivity", as soon as I crack the throttle I have a connection all the way to WOT. Not sure if it supposed to have continuous connectivity throughout the throttle range? The book I have says that idle uses #18 and #2 but "is no longer used". If this is not correct, let me know.

I tested the switch when it was off the throttle body not long ago and the contacts function properly but I thought there was some dead space in between idle and WOT?

Your vac readings are what my decel valve yielded when my car was giving me high idle problems after deceleration. I turned the screw in until I got 20” and 23”.

Regardless, your numbers seem ok. Maybe it’s somewhat of a contributing cause, since we’re talking about a tuning issue and not a fault?


Throttle switch checks out. It doesn’t do anything between idle and WOT on an L-Jet. So, most importantly it does know that your throttle is closed. If it didn’t, I think you would have other issues.

Maybe that table I posted can help you improve your tune on the 123 distributor? Knowing vac levels for when the timing should retard or advance, and by how many additional degrees, as well as centrifugal data for the OE distributor would allow you to better mimic OE.

If that is all set up, I’d say the AFR you get is what it is and nothing to worry about.

yes, that is how i read it. the ECU knows when the throttle is closed.
the rest of the time its hand off to AFM. but even at idle the flapper is moved.
? still it seems to want to know the throttle is closed.

although its not clear to me if it does another thing at full wide open.
or it just assumes if its not idle, then after that its open or on the way to wide open and lets the AFM do its job.

the test done by Brian says his throttle switch is fine.

part throttle decelerating might be another thing?
where you don't close the throttle off but only come down partly off revs rather than a hard release of the gas pedal. but just the same the flapper moves and electrons travel faster than air to the valve so the ECU is way in front of the O2 by the time it gets there, and its giving the right amount of fuel.

got to be all hard wired to the original expectations around the distributor and timing?

one thing i do know is those california EC-As in 74 just operated the distributor in retard mode only. so even when you were cruising they were forcing the engine to be retarded (slightly retarding the centrifigal position) and run "cleaner" on certain emissions. whereas the EC-Bs in 74 at least let you do advance at cruise and get fuel economy. and that was all just done off the distributor and pretty much nothing else. as far as i can figure out the california retard only distributor was a bit of blunt instrument that took a nice sophisticated instrument like a double can distributor and turned it against itself?

which might point to the 123 and just how the advance and retard work.

i'll translate the above rambling thought.

because i have an 74 EC-B and so does Van B and Starbear, i'd be really curious to know what the AFR is after coming off the gas.

because those engines really only had to be non polluting at idle stationary.
that was the main test.
the federal emissions tests were different to the standards in california (CARB).
CARB was way stricter and became USA standard a year later.

so the idea of being rich as you come off the gas might not be out of line with the earliest version of the L jets.

i don't know for sure.

but the 74 EC-B engines were the only ones to make full use of the double can distributor.

the other three, the 74 california EC-A and the two versions in 75 don't. they leave the advance section of distributor un-used.

so maybe being a bit rich ain't all bad is what i am saying.

if it was a carb set up it wouldn't be bad necessarily.

but because you have a probe in your exhaust you almost know too much?

i only say this because i am almost sure (not 100%) that the way those original cars cleaned up hydrocarbons (unburnt fuel) was to do a late burn and also to burn it in the first sections of the hot exhaust. which would mean they would not show up at the end of the exhaust pipe where a probe might be detecting them. but they might have been still dumping fuel, just kind of crudely or bluntly dealing with it?

i did a bit more reading.

because i was interested in the way that d jet has a fixed fuel pressure regulator but L jet has the vacuum adjusted regulator. i know the D jet injector is adjustable with the nut, but its a set and forget job. ie a static adjustment.

what L jet is doing is trying always to keep fuel pressure equal to manifold pressure in relative terms. when manifold pressure drops, (vacuum at idle or throttle close) it lowers the fuel pressure so that in relative terms it stays the same. injector delivers the same amount of fuel against the same relative pressure for certain time opening of injector.

there are more involved things it does too, which are to do with damping but thats beyond the simple principle. (and i got lost reading that).

i wonder if the fuel pressure regulator is not functioning properly when activated by vacuum. maybe an old stiff membrane? and fuel pressure is staying at 35 psi rather than dropping to 28 psi. i read they can fail in this way, not just by rupturing the membrane. back when the cars were newer it was rare for this kind of failure it seems.
but the cars are getting older.

i wonder if that could be doing anything as you come off throttle causing more fuel to dump in through injectors.

its just a thought.

you can do the test on the pressure regulator very easily to check the two values.
the procedure is in the factory manual.

That makes good sense.

Appreciate all the replys. Took me a bit to read through and digest.

The car had a dual can distributor with both adv and retard connected. I hated the way it idled with the retard so I plugged it off, idled better. Finally changed to 123, best upgrade yet.

I will check the fuel pressure regulator to see if is functioning properly. The regulator looks like it has been replaced in the past as the cad plating looks nearly new.

At part throttle coasting the afr is not too rich, maybe high 10's -11. When I completely lift and coast it pegs full at 9. I live in the hills and if I use my gears to slow down the idle will be a little rough at the bottom but soon clears up. Was thinking it might be loading up a little bit. I started this topic because I had read that the AFR should go to 22 with the throttle closed during decel and mine did not, and partly because I am always looking for something to fix/improve on my 914.

full test for the regulator is on previous page.
with car idling.
you pull off the vac hose to reg. should read 35 on a gauge.
put hose back on, should read 28. (all values approx or thereabouts).

both my fuel pressure regulators look beautiful and shiny cad plated.
both are at least 33 years old, suspect one is 48.
they did a nice job on plating them back in time.
(i have 2 because one is a visual emission cheat install for decel valve from back in the day).

topic is good, glad you started it.
i got into reading the patent documents for L jet.
and a technical explanation about how fuel despite being atomised by injectors coats surfaces of intakes rather than all hangs in air, but at another point in acceleration breaks free of surfaces. this causes two spikes and if it wasn't compensated for by the way L jet works the result would be a jolting rise in engine revs during acceleration. boy. i didn't fully understand it but i sure appreciated L jet a whole lot more. nothing to do with your issue, but i did at least stumble across the description of the why and how of the pressure regulator in L jet. which i had not understood properly at all.

i'll do some more searches when i get a spare moment and need a break from CAD.
see what i can turn up re rich on coasting. i'm interested to find out.

Thanks for the input and appreciate you sharing your research. I come from years of tuning Weber and Dellorto carbs and now messing with L-jet. Will check the fuel pressure next.

try measuring the Air Fuel Mix at idle too to compare to what you have on throttle lift and coasting.

the decel valve scenario is not unlike the AAV scenario at cold start?
sort of.

the throttle is at closed/idle switch position.
but during that AAV cold start scenario the AAV causes the flapper to open, causes the injector duration to increase and its part of how you get that quicker idle.
its got a scenario to over-write the warm idle scenario that involves more fuel.
there is other stuff going on too, like temp sensors.

at lift off coast its kind of similar but obviously different.
you have the decel valve in combo with the flapper over writing the throttle switch in closed position. its in combo with the fuel pressure drop.
the decel valve is letting the AFM draw air and move the flapper - it follows then it must also be getting a little fuel to burn on its way down to idle?
i mean thats what a decel valve does - at least in L jet?
but if i am correct its got no way of knowing how much fuel its giving other than by spec parameters around what fuel flows through the injector at the lower pressure. if the fuel pressure was higher its going to put more fuel in?
the injector opening is in a routine that conforms to amount of flapper movement, engine revs (from white wire on coil) and closed throttle position. its a timed opening?
so if fuel pressure is off then the timed opening of injectors will deliver too much or too little fuel.

i came across something that said min amount of pressure in system has to be 26 psi to open the injectors. don't know how accurate that is. but it does show that the injectors may have a narrow band of operation below 28 psi and that pressure drop takes them down to something close to the point where they won't open.

its just a thought. there will be L jet experts here that really know.
i am a bit like you. really trying to get my head around my L jet without giving myself too much of a migraine.

@Emerygt350 asked how does it know how fast the engine is spinning.
see here.
i like the way emery is curious about how the L jets are working.
the more stuff i read the more i came across explaining in historical terms just how hell bent bosch was on really simplifying the fuel injection system. anything they could do they did to not have an extra component in it.

Click to view attachment

@Brian Fuerbach
that description above about L jet really having no way to adjust for how much fuel its actually putting in provoked the next inprovement. closed loop systems with 02 sensors at the end of the track. at least then it could adjust itself on the fly and compensate for another part of the system that might be screwing up slightly.

thanks to your question i know that the harmless looking fuel pressure regulator is doing an important job with its vacuum section in the L jet cars. all the electronic injection german hokum pokem, then its got a cuckoo clock vacuum unit controlling half the hand cuffs on the amount of fuel coming out of the injector.

in a funny way you have given yourself a closed loop system?
you know too much about what its doing but there is no capacity to adjust itself on the fly.

i am sort of glad i don't know whats going on when i lift off the gas.
probably worse than yours.


what you said about getting to the bottom of the hills and having a rough idle -
sounds like its dumping a bit of gas in its not able to burn and fouling the plugs a bit?

I am always looking for something to fix even if doesnt need it. I started using the wideband meter because I bought a rebuilt AFM from Fuel Injection Corp. and it was setup pig rich when initially delivered. The clock wheel was a half turn off. I have my AFR's pretty dialed now and all the other l-jet systems are functioning properly. I just wanted to get the decel afr's in line but sounds like that is just the way it operates.

This is what led me to think the TPS was malfunctioning. Just so I am clear, the only two pins used on the TPS are #18 and 3 which are input and WOT. The TPS switch is open between 18 and 3 at idle and closed just after tip in all the way to WOT. This is how mine is behaving.

that is correct brian

Click to view attachment