D_jet trouble shooting question - car is home, journey continues, June, update- no more problem-- the fix was simple.... Options

[DRPHIL914]

Was that mps a brand new one?
Sounds jet exactly like the scenario I've seen previously
Put Kent's mps in and verify your numbers get better

Chris is right that your afr is still wrong. I'm betting you have adjusted the one in the car? Way off.

If Kent's mps truly proves to the you good numbers.
Then take the diaphragm from your good mps and rebuild your old one.
I think there a something wrong with your new mps. I've seen this only once before. Carefully compare the two diaphragms and use nothing else.
Maybe have Geoff calibrate it if you want it perfect

The one that got me home was one i picked up a few years ago that was opened up and revealed by someone else at some point. It holds vac good. Epoxy plug was taken out so at some pint I had it sent to Scott to set to factory settings. Had not use it until now and it appears that the factory settings are lean on my car. Scott used a LCR set it up.

[JeffBowlsby]

The only published MPS calibrations are on Brad Anders page, which are a collection of measured calibrations of existing known good and NOS MPS. I have found that they are also lean for unknown reasons. The Wavetek meter (I have one) can be useful to get the calibration close and that is all. The only way to get the A:F ratio exact is to use an exhaust gas analyzer or WB O2 to calibrate the MPS. Each engine will be different based on its condition, wear, differential flow rates of injectors, fuel pump settings and performance, sensor variations, etc and the EGA/WBO2 is the only way to get it optimized.

Convincing evidence that the factory fine tuned each car individually is indicated by the mark on the ECU idle knob ring.

[brant]

I agree
the factory setting are far from ideal
remember how different gasoline formula's were back then!

todays gas is a lot different
perhaps the factory settings were better? for gasoline of the day
or perhaps the factory settings were too lean even back then for fuel mileage and simplistic testing equiptment.


as you rebuild one of your cores, make sure that its a 2.0 housing...
the 1.7 housing have a WOT stop in the casting that you would need to grind out if you are using one of them on a bigger motor.

I still can't wait to hear what happens when you plug a different, known good MPS into the car. I think that your entire problem was caused by this MPS. Hell if I know why, but i've seen it once before.

you never replied.... was this MPS a NOS one?

[DRPHIL914]

I agree
the factory setting are far from ideal
remember how different gasoline formula's were back then!

todays gas is a lot different
perhaps the factory settings were better? for gasoline of the day
or perhaps the factory settings were too lean even back then for fuel mileage and simplistic testing equiptment.


as you rebuild one of your cores, make sure that its a 2.0 housing...
the 1.7 housing have a WOT stop in the casting that you would need to grind out if you are using one of them on a bigger motor.

I still can't wait to hear what happens when you plug a different, known good MPS into the car. I think that your entire problem was caused by this MPS. Hell if I know why, but i've seen it once before.

you never replied.... was this MPS a NOS one?

No, as stated in my previous post, it was rebuilt at some point but too lean. I spent a hour on it tonight adjusting slowly the mps trying to bring the mix closer to 12.7 that anders says is the target for part load mix. It's still hitting about 14 on acceleration up a slight grade. That was after adjusting the center screw about 3/4 turn. At.least it starts and runs. Tomorrow I'll work a bit more on it but will take it a quarter turn at a time , test drive, and I will keep working it down closer to the 12-13 under part to full load. I've been going back over all of anders data etc. For some.reason the idle is a bit high but that could be the lean setting as well. I have to recheck the tps setting. It seems like it is not set exactly where I set it after it was in the shop. I think there a are is fine. It was fully closed tonight after the engine warned up.

[76-914]

FWIW Phil, that one is for a 75-76 so may run a bit lean. But it will sure as Hell work for your needs.

[76-914]

Any news?

[DRPHIL914]

Any news?

Spent part of one day messing with it , reading up on the mps tuning, it did start right up Friday night, and took it for a drive but have not done anything with it the past 2 days. Yesterday I spent the day inspecting and test driving the Audi tt, - bought it and brought it home. Big reason was really all day rain yesterday and today.

[DRPHIL914]

Any news?

So I have not been able to try out the mps that you sent to test until today.

The car started but was a bit rough at first. I let it warm up and see where the idle would settle to and see what the A.F. meter was reading then took it for a drive around the neighborhood.
Upon starting the a.f. reading was 10, after warming up went to 12-12.5 during drive on acceleration it was reading about 15-16 ,y cruise was about 13.5-14. . This is a never opened or adjusted one from Kevin (rhoadguy)
Buy I think I can say that this thing is still not running right. There is something else causing problems. It just does not run smooth, feels like it misses here and there. Yes my other MPS was a major cause of it not starting but there is something else going on here too that I have not figured out yet. It will be running fairly well and idling and suddenly the idle drops l I me it's going to die. Also feels like it's misses or skips here a ND there. Almost like a short.

Now that I have an mps that is known good, I may have to go back thru and try a couple things like plug wires, points etc.
I should get a chance to test a few things tomorrow, might even hook up the spare ecu. I might even try some other plug wires

[JeffBowlsby]

I wonder if this is related to the advance weights binding in the dizzy? Have you lubed it in the last year? 1 drop of 30 weight in the center of the dizzy shaft, annually per the manual, to lube the advance weights. It may cause the hiccups you describe.

[DRPHIL914]

No I've not done that.

[DRPHIL914]

Is it possible for this one part, the temp sensor to cause the issues if ev described?

[DRPHIL914]

so yesterday i decided to try and figure out where my other issues were coming from and then tune the MPS a bit more;
- ended up recheck ing the TPS setting because it was off after being at the mechanic and reset that, and i had to pull that temp sensor to make it easier to get the cover on and off the TPS, not sure why but in my box of parts i ran across a brand new one i had inmy stash so i put that new one in there because i noticed that if that temp sensor is disconnected the car will not run, same as a CHT or MPS AND it is the one part i had not tested or tried a replacement of. IT is possible there is another short somewhere in the system and i had a few ideas from reading other similar theads. so i went back thru the grounds- all good. one post mentioned the 3 red wires that attach to the positive terminal of the battery. No corosion there but that whole connector could be re-done so i might do that.
-anyway yesterday i could not get the car to idle , or stay running , but after replacing that sensor, car ran perfect with no sputtering or cutting out at all, perfect idle with out surge or variation. Yes we had a bad MPS but car ran when the vac hose was off due to it being super lean other wise and i now think it was this sensor causing that lean running condition.

How common is it for that plenum temp sensor to go bad? i am going to spend some time over the next week driving the car and seeing if i can get it dialed in. Because i have spent weeks chasing my tail on this car and have had it running only to find another part that was part of this problem coming and going, i am optimistic but cautious. i feel like i could get in the car 2 days from now and find it not running again. I hope this is it, time will tell.

[JeffBowlsby]

Interesting. Never heard of a D-Jet 914 that did not run because of that sensor (TS1). Its a temp sensor that sends a signal to the ECU to correct the A:F mixture for air temperature variation. Many simply unplug the harness from it, which has the effect of richening the mixture about about 10%. The car should easily run without it, some would say better without out it than with it, but I run my 2.0L with it connected and no issues.

[r_towle]

its the ambient air temp, and I have never had one fail, but this stuff is 40 years old now.

In the end, you had a bad MPS sensor.

maybe with all the moving of the wiring harness you may have loosened the connection to the ambient air temp sensor, which may have done something.

I cannot recall what the conditions are for that to work/not work.

rich

[DRPHIL914]

its the ambient air temp, and I have never had one fail, but this stuff is 40 years old now.

In the end, you had a bad MPS sensor.

maybe with all the moving of the wiring harness you may have loosened the connection to the ambient air temp sensor, which may have done something.

I cannot recall what the conditions are for that to work/not work.

rich

well that is certainly a possibility. we do know for sure that MPS was bad, and putting a different one, ones in made it run, but i was still having an issue. i know the harness is good but that doesnt mean there wasnt a bad connection either there or somewhere else. I thought it might even be the CHT connection. the CHT tested good but if that connection is not right that would cause issues. . it seems odd that sensor would go bad, but i do know that right now its running pretty good. I will have to wait and see if that lasts.

Phil

[r_towle]

if you still have an issue, I would go back to the basics.

Valve adjustment cold
Dwell
Timing
Vacuum leaks

Rich

[Dave_Darling]

The intake air temp sensor doesn't contribute a whole lot to the mixture--it should not be enough to make a massively lean condition on its own. It is more of a fine-tuning adjustment.

Not sure what could be going on with your mixture. Could it have anything to do with the TPS that you adjusted?

--DD

[Larmo63]

After reading this thread and screwing around with my own '73 1.7 FI, I think carbs are a better solution. I know just stating this may start a whole sh*tstorm, but my new engine will have carbs.

With all these acronym parts, hoses, wires, vacuum, testing, the whole mess has me worn out.

[BeatNavy]

After reading this thread and screwing around with my own '73 1.7 FI, I think carbs are a better solution. I know just stating this may start a whole sh*tstorm, but my new engine will have carbs.

With all these acronym parts, hoses, wires, vacuum, testing, the whole mess has me worn out.

(IMG:style_emoticons/default/WTF.gif) Don't do it, Clint! I've probably replaced every sensor and component on my DJet, and I enjoy the challenge. I spend a lot of time on Anders' page, and to me the FI is well worth it. Keep researching and trying!

[r_towle]

After reading this thread and screwing around with my own '73 1.7 FI, I think carbs are a better solution. I know just stating this may start a whole sh*tstorm, but my new engine will have carbs.

With all these acronym parts, hoses, wires, vacuum, testing, the whole mess has me worn out.

Not going to argue you out of it, but I would suggest you research what you want to do so you can achieve the goals you want.

With carbs you can use a more aggressive camshaft which could deliver more power.
With carbs you will have constant maintenance of the jets to keep it clean.
You will need new fuel lines for today's fuel.

Overall, if you approach it the right way, both carbs and FI can be fun and simple.

Rich