D-jet idle and lean issues. Options

[emerygt350]

Pretty long thread so apologies if someone else has mentioned this:

I had similar problems trying to get a good idle without causing running issues. In my case it turned out the be the PCV. Running without a PCV resulted in too much air at idle.

http://w.914world.com/bbs2/index.php?showtopic=347986

On a 75 it should be passive... Does your pcv go straight to the air box?

[Literati914]

I'm actually so frustrated with this right now... I get a different resistance range every time I check the CHT. Batteries have been replaced in the DMM.

The other day (the last time I checked) resistance was around 2300 ohm .. hey that's close to what it's supposed to be - I'll go ahead and re-install. Go to do that today and we're around 1600 ohms (IMG:style_emoticons/default/headbang.gif)

So - I guess the best thing to do is order a new part.

[emerygt350]

Not sure if you should run off to that. Just put a pot in line replacing the cht. Set it to whatever it should be as cold. If you think it is nefarious signals from the cht that will tell you right away

[Literati914]

I'm trying to get to the items that are being suggested, thank for keeping after it with me!

I checked my CSV and resistance is 4.3ohms - Bosch has it listed at 4.2 .. too high?

[Literati914]

Pretty long thread so apologies if someone else has mentioned this:

I had similar problems trying to get a good idle without causing running issues. In my case it turned out the be the PCV. Running without a PCV resulted in too much air at idle.

http://w.914world.com/bbs2/index.php?showtopic=347986

On a 75 it should be passive... Does your pcv go straight to the air box?

This '72 1.7 has the PVC connected to the plenum (into a rubber "F" shaped connector at the plenum), not to the air filter housing - is that not correct?

[Superhawk996]

I'm actually so frustrated with this right now... I get a different resistance range every time I check the CHT. Batteries have been replaced in the DMM.

The other day (the last time I checked) resistance was around 2300 ohm .. hey that's close to what it's supposed to be - I'll go ahead and re-install. Go to do that today and we're around 1600 ohms (IMG:style_emoticons/default/headbang.gif)

So - I guess the best thing to do is order a new part.

Easy man - chill. You’re getting too stressed.

That region of the CHT has a very steep slope to the curve. If you’re holding the sensor in your hand to measure, it’s going to warm up in response to body temperature and resistance will decrease rapidly. Even just exposing it to hot air temp could be affecting it. What the temperature there in Texas today - probably 120F in the shade? (IMG:style_emoticons/default/barf.gif) See circled region below.



This region only affects mixture at startup and has no relevance to running temperature and mixture at operating temp.

Not saying you can’t have something going on with corrosion in the sensor, the wire, or even with your DMM but I wouldn’t be freaked out by what you’re measuring.

[Superhawk996]

I'm trying to get to the items that are being suggested, thank for keeping after it with me!

I checked my CSV and resistance is 4.3ohms - Bosch has it listed at 4.2 .. too high?

That’s Perfect . . Chill (IMG:style_emoticons/default/smoke.gif) it’s a 50 year old part! That it has only drifted 0.1 ohms is a testament to original German quality.

(IMG:style_emoticons/default/bye1.gif)

Hopefully you recognize I’m just being playful. . . No offense meant. You’re doing a good job working through the component verifications. (IMG:style_emoticons/default/aktion035.gif) (IMG:style_emoticons/default/smilie_pokal.gif)

[emerygt350]

Yes, for a 72. Sorry, so many threads. Is your pcv working? For trouble shooting the active pcv we have is terrible. My suggestion is take it out of the system (unplug and block) and understand that it is supposed to leak a little so your idle should undershoot with it missing. They are nla and although there are suggestions on replacements they are not the same. That pcv is gold so if you take it out and clean it treat it accordingly. All it is is plastic and a spring.

After you are done troubleshooting put it back together, pcv is good.

[Literati914]

Resistance at the Air Temp Sensor is 203.3 ohms @ 81 deg. F. = looks like that's probably ok.. one more thing out of the way.

[Literati914]

Hopefully you recognize I’m just being playful. . . No offense meant. ..

Of course! I appreciate the help. This old D-jet crap is (IMG:style_emoticons/default/bs.gif) tho (IMG:style_emoticons/default/hissyfit.gif)

[Literati914]

Have you checked you decel valve?
You need a vacuum source to check it and adjust.

Next on my list, stay tuned.

.. Is your pcv working?

followed by this!

[Literati914]

.. Also, don't discount that TPS. If your ECU doesn't know you are at idle all kinds of badness could result.

BTW, here’s a shot showing where I locked my TPS down. I did it as close to the instructions as possible but the ohm meter jumps around like crazy and it’s very hard to be consistent - maybe that’s just the characteristics of a TPS that could stand to be replaced though. Also Zero ohms could technically mean 0.9 to 0.1 I suppose, so I'm hoping 'close enough' - like I said, the car pulls well. Idle correction/perfection is the issue though.

[rjames]

I've lost track of things in this thread. IIRC, Your first post said the car idled at ~900RPM, later you said 1100RPM and the idle adjustment screw on the TB is all the way in. AFR showed 16+ at idle and at cruise. You are experiencing some backfiring and TPS may be in question because you can't zero it out at idle.

Going back to the first issue of the high/inconsistent idle, I'm betting that you're TB needs a rebuild. I had both a high idle and an inconsistent idle (I'm not talking about surging) until I had my TB rebuilt.

Your AFR readings seem a bit suspect. If the mixture is wrong then that could account for your backfires.

You should be able to get the TPS to O Ohms. If not, it may impact your ability to get a steady idle, especially if the signal it's providing the ECU is constantly fluctuating.

[emerygt350]

Grab an eraser and clean the contacts. That position looks more like mine now.

[Literati914]

I've lost track of things in this thread. IIRC, Your first post said the car idled at ~900RPM, later you said 1100RPM and the idle adjustment screw on the TB is all the way in. AFR showed 16+ at idle and at cruise. You are experiencing some backfiring and TPS may be in question because you can't zero it out at idle.

Going back to the first issue of the high/inconsistent idle, I'm betting that you're TB needs a rebuild. I had both a high idle and an inconsistent idle (I'm not talking about surging) until I had my TB rebuilt.

Your AFR readings seem a bit suspect. If the mixture is wrong then that could account for your backfires.

You should be able to get the TPS to O Ohms. If not, it may impact your ability to get a steady idle, especially if the signal it's providing the ECU is constantly fluctuating.

Yes - the title of this thread is now a little misleading.. I was originally concerned that my A/F ratio was pointing way lean. However, I've gone back and realized my wiring was not exactly perfect. See, the 14point7 processing unit needs two separate inline fused wires at the unit, where switched power comes in. They only sent me one (a small 5V blade style) .. I need to pick up a glass tube style 250Ma inline fuse and holder for the lamda sensor's heater wire. The install instructions call for it, why they didn't include it is a mystery. I now remember questioning this back when I was installing the unit - but just carried on because I had so much on my plate to install during restoration. Point is - it's probably not too lean, Actually I think it's running too rich (gonna pull spark plugs later to verify).

So currently - I'm trying to rectify an idle that is slightly too high w/ the idle adjustment screw cranked down .. and a slight backfiring issues that could be (more) exhaust leaks (I addressed this already, but maybe not as thoroughly as needed).

[rjames]

I've lost track of things in this thread. IIRC, Your first post said the car idled at ~900RPM, later you said 1100RPM and the idle adjustment screw on the TB is all the way in. AFR showed 16+ at idle and at cruise. You are experiencing some backfiring and TPS may be in question because you can't zero it out at idle.

Going back to the first issue of the high/inconsistent idle, I'm betting that you're TB needs a rebuild. I had both a high idle and an inconsistent idle (I'm not talking about surging) until I had my TB rebuilt.

Your AFR readings seem a bit suspect. If the mixture is wrong then that could account for your backfires.

You should be able to get the TPS to O Ohms. If not, it may impact your ability to get a steady idle, especially if the signal it's providing the ECU is constantly fluctuating.

Yes - the title of this thread is now a little misleading.. I was originally concerned that my A/F ratio was pointing way lean. However, I've gone back and realized my wiring was not exactly perfect. See, the 14point7 processing unit needs two separate inline fused wires at the unit, where switched power comes in. They only sent me one (a small 5V blade style) .. I need to pick up a glass tube style 250Ma inline fuse and holder for the lamda sensor's heater wire. The install instructions call for it, why they didn't include it is a mystery. I now remember questioning this back when I was installing the unit - but just carried on because I had so much on my plate to install during restoration. Point is - it's probably not too lean, Actually I think it's running too rich (gonna pull spark plugs later to verify).

So currently - I'm trying to rectify an idle that is slightly too high w/ the idle adjustment screw cranked down .. and a slight backfiring issues that could be (more) exhaust leaks (I addressed this already, but maybe not as thoroughly as needed).

Roger that. Make a simple smoke machine for less than $10 and figure our where your vacuum leak is. If it's never been rebuilt before, you'll likely find that the TB is the culprit, or one of the culprits of your high idle.
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[Literati914]

My Decel Valve is apparently stuck - I pulled a vacuum on it which never releases after screwing the bolt waay out.

Gonna soak it a bit and re-check, will report back.

[Ishley]

Stuck open or closed? Do you know what your vacuum is at Idle? I set mine so it’s activated 2 over that. Problem is that when you idle high your vacuum is higher typically. I had to fiddle with it a few times.

[Literati914]

I’m not sure I understand how it works completely. I just saw that it held well over the 17nHg vac (that is mentioned by pbander’s site), while no air could be blown thru it.

I interpreted that as stuck closed.

[Literati914]

Ok I flooded the ports of the decel valve with a penetrant oil mix followed by carb cleaner and then penetrant again.. worked the bolt to extremes many times and finally was able to get air thru the two larger ports. The carb cleaner blew out a bunch of crud.

I found a spot along the bolt’s length that I could get close to 17inHg AND get air thru the ports also. It slowly leaks - I timed 16 to 14inHg in about 3 minutes. The bolt is still waay extended.