D-jet idle and lean issues. Options

[Literati914]

@JamesM and @emory350gt

I'd already kind of moved on from the AFR thing for the time being.. it never changes so that's probably not the engine so much as the AFR analyzing system. I'll be delving into trying to rectify it once I accomplish an idle in the 850+- range. I see that as my first issue. This is why I'm looking into the AAR atm.

The 1100rpm is actually pretty steady and doesn't seem particularly rich or whatever.. so without the AFR working properly or a gas analyzer, I'm just guessing. However, it is backfiring while out driving it, so something's off.

The facts are: my idle is a little too high (after adjustment) and I get backfiring on hard decel.

If I can not get it to idle properly, looking at the AFR is probably a waste of time. I'll report back after tracing the white wire to the 12pin connector and see what we have there.

[Ishley]

Shoot some wd40 or just plain oil into the AAR valve. Cycle it a couple times and it should loosen up. I give mine a little oil each spring.

[Literati914]

Shoot some wd40 or just plain oil into the AAR valve. Cycle it a couple times and it should loosen up. I give mine a little oil each spring.

I'm thinking it did the 6+ minutes because I'd inserted some lite oil. Still watching it move was a slow "notchy" affair. I think I'm gonna take it apart, clean and lightly polish the vertical section with the air opening hole, to see if I can get it to work smoother and faster.

[Literati914]

OK - I can confirm that I'm getting 12v at the White Wire only when the engine is actually running (fuel pump running as pointed out earlier). To test this I capped off the hoses that would normally go to the AAR (it's still removed), started the car and that white wire showed 12V - also the 1100 rpm's I had before was down to apprx 850 now. Well it actually bounced from 850 to 950 for several minutes then finally settled at like 950rpm - again my air bleed screw on the TB is closed.

[emerygt350]

Just plug the aar until you figure this out

[Ishley]

I didn’t go into the bottom end of the AAR. Once you work the top of… I sprayed some penetrating oil the top edge. This is the rotating part. I soaked it and cycled it with 12v a few times and got it moving pretty good. You might not get so lucky depending on the environment it lived in etc.

Good luck. It sounds like you’re making progress.

[JamesM]

@JamesM and @emory350gt

I'd already kind of moved on from the AFR thing for the time being.. it never changes so that's probably not the engine so much as the AFR analyzing system. I'll be delving into trying to rectify it once I accomplish an idle in the 850+- range. I see that as my first issue. This is why I'm looking into the AAR atm.

The 1100rpm is actually pretty steady and doesn't seem particularly rich or whatever.. so without the AFR working properly or a gas analyzer, I'm just guessing. However, it is backfiring while out driving it, so something's off.

The facts are: my idle is a little too high (after adjustment) and I get backfiring on hard decel.

If I can not get it to idle properly, looking at the AFR is probably a waste of time. I'll report back after tracing the white wire to the 12pin connector and see what we have there.

tuning to AFRs is not a waste of time, just AFR at idle.

Bad AAR is a 30 second test as you just pull the hose at your air filter and cover it with your thumb. Everything else being correct though a stuck open AAR will usually put your hot idle 1200+ rpm.

People to often overlook the impact that timing has on idle speed and the fact that pretty much every stock distributor is shot at this point.

and I get backfiring on hard decel.

Thats not going to be an AAR problem. Trying to figure out idle while you have bad components in the system is putting a band aid on a broken leg and once you solve the running issues its going to mess your idle up all over again. Start testing components and verifying part numbers. My guess would be you have issues with the distributor, the MPS, or both, though its entirely likely you have small issues with a lot of things.


Edit: depending on the how its backfiring that could also be just an exhaust leak.

[emerygt350]

Have you posted what your timing is when it is at 'idle'? At 1100 you will be getting some advance from the dizzy, but not much. You should be less than 11 degrees. Do you have Bluetooth or the old style 123 with the pot?
It's been a while but did you verify your mps holds a vacuum?

Checking these two things would take 5 minutes.

Have you let your engine get good and hot? Mine doesn't drop down from 1100 to 900 untill it's completely at running temp. That takes my car about 20 minutes of driving. That is entirely due to the ECU richenining the mix with the 2 temp sensors.

I have an extra degree of timing in mine and it idles at 900-950.

And did you fix your TPS?

[emerygt350]

I am going to post some pictures of my warm up this morning. I started the car at 8:32am. It was 58F this morning, so pretty cool.

Here is what is going on after the AAR has closed completely and verified by pulling the hose and checking for any vacuum. 8:45am (drove to the office)




8:47 ECU still richening the mix quite a bit.



8:53 ECU is still keeping it rich.




8:55 even the flaps are still not fully open.



9:00am still not fully warmed up according to the ECU

[emerygt350]

And here it is almost completely warmed up.
9:08am



If I took it for a little drive on the highway it would drop another 50-100 rpms.

Not saying my system is perfect but I think it's pretty close to running as designed but with an extra degree of timing, no vacuum retard (123dizzy), and 2056 displacement.

https://youtu.be/GUr3A9G-lAA

[Literati914]

@emerygt350
Thanks for documenting that, it does highlight that mines not really off much from the norm, if at all, as far has how my d-jet is behaving. I will check timing again after a good warm up run and see where it's at then, and out of curiosity I'll also try to time how long it takes me to get up to 300 at the CHT gauge next time I take it for a test run. Replacing the TPS is on my list but haven't done it yet.

@JamesM I've checked before that the distributor is the correct one for this 1.7, don't remember the number off hand but it's the correct one - it has a new looking electronic insert replacing the original points (don't know the brand). Car woke up nicely once I got timing set to 27deg/3500rpm several weeks back. You certainly could be right, the backfiring may just be more exhaust leaks.

The thing is - it actually seems rich to me when driving .. just a feeling or engine sound while excellerating though.

I'll keep looking into this, and report back any findings. I appreciate all the help guys !! (IMG:style_emoticons/default/beerchug.gif)

[JamesM]

@JamesM I've checked before that the distributor is the correct one for this 1.7, don't remember the number off hand but it's the correct one - it has a new looking electronic insert replacing the original points (don't know the brand). Car woke up nicely once I got timing set to 27deg/3500rpm several weeks back. You certainly could be right, the backfiring may just be more exhaust leaks.

The thing is - it actually seems rich to me when driving .. just a feeling or engine sound while excellerating though.

I'll keep looking into this, and report back any findings. I appreciate all the help guys !! (IMG:style_emoticons/default/beerchug.gif)

Correct part number is only half the battle with distributors. If the internal springs are weak or broken (which after 50 years most are) and/or the vacuum canister is bad you will have to much advance which will kick up idle speed. These cars use vacuum retard to pull the idle speed down so if the engine isnt producing proper vacuum due to mixture or potential engine damage or the vacuum canister is bad/improperly connected you will have a high idle.

I wouldn't be surprised at all if you are running rich as that is a common failure mode of a few components. #1 being the MPS unfortunately. Thankfully good 1.7 MPSs are somewhat easier/cheaper to come by than the 2.0 stuff. Replacement diaphragms are again no longer available leaving us with limited options, and also why I caution people about putting to much time/money into d-jet these days. Anything adding extra resistance to the CHT circuit could also cause a rich condition, but I find MPS failures more common. Few other things can cause a rich condition as well but those are the big two.

[Literati914]

Without the car being started at all and about 84 deg. F outside - I just pulled the wire connection to the stock CHT sender and checked resistance to ground. It's showing 1.792 ohms. - I think that may be low but need to go check.

The '72 1.7L has no resistor as stock and mine has none installed, just the wire from the sender plugging into the wire from the harness via simple spades.

This would cause mix issues if off, right?

[Superhawk996]

1.7L should have the 012 CHT according to Anders but your measured value looks more like an 017 but is sorta’ split between the two. 017’s are rare and NLA so definitely don’t pitch it.

Note: I’m not convinced Anders is 100% correct on the part numbering for the early cars CHT part numbers. I don’t have enough data nor have I dug into the Bosch cross reference to dispute what he has published and similarly - cars have have so many part swaps it would not be unlikely to find the wrong CHT on any given vehicle. Wouldn’t be surprised if you had an 017 in your car.

Note: per Emery’s comments - by the time the engine is fully warm the CHT would not be affecting your mixture or idle speeds.

[Literati914]

Latest Findings [CHT Sensor] :

I removed my CHT sensor, checked that it is still showing 179 k ohms - it was, I then cleaned a good amount of rust off the hex bolt shaped head and checked ohms again - now it dropped down to around 136 k ohms and very slowly kept climbing. Not sure it would have stopped.

Then I boiled some water, 212 F and checked ohms resistance again - now it starts around around 230 ohm (total) and quickly starts to increase - leveling off as it cools around 2125 ohm at 76 deg room temp. I give up on the number stopping, it moves one decimal point at a time. So maybe the cleaning and the boiling woke up the sensor (IMG:style_emoticons/default/confused24.gif) (went from a pretty steady 1792 to a pretty steady 2125). Would you say this is a good sensor or a bad sensor ?

The CHT has no p/n anywhere on it - so I'm not sure what it is.

Pbanders pages seem to point to an EA 1.7 from '72 as needing the "003" CHT unit (not mentioned in the graph @Superhawk996 posted but still available apparently) - someone please doublecheck me on that. With these current numbers, I'm thinking it does not need to be replaced, thoughts?