Need some input -> Problem with 3.2 transplant going lean and misfiring after two min

[Wayne 962]

Hmm. Took it out again tonight, and when I brought it back, it was missing again at idle. So I took it out again, and this time it wasn't missing but was running lean at idle. At least now the issue has become somewhat intermittent, which I guess is an upgrade from before...

-Wayne

[randbe]

Hi Wayne,

My name is Rod, I’m a new subscriber to this forum and have been following your mechanical woes. Great thread by the way.

I’m a retired mechanic. I’m not going to suggest a fix, you know what you are doing. I would like to point out a possible observation.

I noted in your previous videos that at cold start the engine ran fine. However as the motor warmed up, a tapping noise from what appears to be the valve train grew louder and the engine began to run rougher.

As you know, metal expands as it warms up. I’m wonderIng if your valve guides may be worn. At cold idle everything is tight, however as the engine warms up the valves are moving
within the lose expanded valve guides and not sealing. At high rpm it’s likely no noticeable, but at idle the engine would run rough due to the valves dancing around in their seats.

I’m with you in spirit, be safe in these trying times.

[Wayne 962]

Videos / logging of the issue. It's now turned into an intermittent issue, where sometimes it does it and sometimes it does not. In general, the car seems to run and drive perfectly fine. It's a bit frightening how quick and responsive it is when pushed. I was able to "chirp" the tires going up a hill when I was performing the WOT throttle tests in 2nd gear (this has the stock 914 transmission gearing, so it's geared for a lowish-power engine (80 HP versus 200+). the 3.2 also has tons of torque as everyone knows.

These videos are quite telling - they don't seem to indicate anything wrong at non-idle speeds...

1429: COLD START
- Revs at about 1,100-1,200 or so, no missing on the engine, no problems.
- Mixture is rich, 12.5-12.6 or so
- Rpm drops to about 800-900
- Mixture is high 13-14 -> no missing (1:44)
- Idle is a little uneven, car then starts missing – you can hear it in the video, sounds like a rubbing / thumping / vibrating noise, mixture shows 17-18 (lean due to lean running condition or misfire? unknown)
- The thumping noise that is now present at 800-900 rpm -> you couldn’t hear it at 1,100-1,200 when the car first started
- 3:34 – I show that the O2 sensor is unplugged
- The missing / thumping noise is very difficult to discern standing next to the engine, but it shows up on the iPhone recording very, very clearly.
- 5:43 – listening to the engine, you can hear the noise
- 5:50 – tailpipe – running better than it has in the past, but still not terribly good. Frankly, it sounded much better
- 6:32 – hand on intake – I can’t feel any vibrations or anything amiss
- 7:11 – under the car. No loud valve noise no flapping chains. The only oddball noise I repeatedly hear is oil sloshing around in the oil tank somewhat haphazardly.
- 8:00 – sitting in the car you can hear the missing more clearly due to the sound deadening panel filtering out the louder noises




1430: RUN UP CRENSHAW (Large hill about a mile or two long):
- Take off, AFR 12-13 with some in the 10s.
- Let off, goes lean (as expected)
- WOT #1 11.9-12, third gear
- WOT #2 11.3-12
- WOT #3 10.5-12
- Second gear, 4,000 rpm partial throttle – 13.5
- WOT 11.5-12


1432: DRIVING MOSTLY LEVEL
- 3,000-3,500 1/8th throttle, 13.8-14.2
- Shift to 3rd, accelerating, 12.8


1433: RUN UP CRENSHAW #2:
- Driving the snot out of it
- Rounding the corner, 14
- Accelerating in 2nd, 11.5-13 – more than enough power to almost chirp the wheels
- WOT 11.1
- WOT 11.8
- WOT 11.3
- WOT 10.9 (extended WOT)
- Part throttle 14.3
- Driving along, part throttle, 14.7
- Partial accel 13.8


1434: DRIVING MOSTLY LEVEL
- Accel, 11.8-13.8
- Coast back, 22 (no throttle)


1435: BACK HOME IN FRONT OF HOUSE
- Idling – too much glare on the LM-1, but the numbers are in the 15s


1436: BACK HOME IN FRONT OF HOUSE
- Idle – the problem is not showing itself!, 800-900 rpm, AFR of 14.7 – 15
- 2,500 rpm seems to be slightly flubbing, AFR 13.8
- 3,000 rpm 13.5 AFR


1437: BACK HOME AGAIN
- Idle, 800-900 rpm, AFR is in the 14.5-15 range, not lean like previously, and the engine is idling fine (but still making that odd “vibration noise”, which I honestly did not hear live, I only heard on the recording. This video doesn’t seem to show any problem at all?

[Wayne 962]

Originally Posted by Wayne 962

Hmm. Took it out again tonight, and when I brought it back, it was missing again at idle. So I took it out again, and this time it wasn't missing but was running lean at idle. At least now the issue has become somewhat intermittent, which I guess is an upgrade from before...

-Wayne

So, I took it out again today to see what it would do, and saw the same issues that we saw before. Starts up cold, with no missing. After two minutes, it starts "flubbing" and missing. I did the same test that I did previously, pulling the injectors:

- Pulling any one single injector does not seem to make a discernible difference overall.

- Pulling injectors 4-5-6, engine runs on 1-2-3 only, and there is no missing.

- Pulling injectors 1-2-3, engine runs on 4-5-6 only, and there is no missing.

- Plug all injectors 1-2-3-4-5-6 back in and the engine starts missing.

This behavior has been consistent for the past month. None of the fixes / changes that I have done have made a bit of difference in this behavior. There is no easily imaginable situation that would fit this current set of evidence.

-Wayne

[cabmandone]

Is your Innovate setup capable of running two wideband o2 sensors? At this point I think I'd want to see data from each bank. I don't recall what you said your exhaust setup is (1 in 2 out or 2 in 2 out). If it can't do 2 banks I think I'd put a bung in each bank and go do some runs to see what each side looks like.

Sucks since it seemed like things were going in the right direction. Your AFR numbers looked right from the previous post. I want to think it's ECU related but you did so much investigating and I think said you swapped ECU's that it almost can't be. To me, intermittent almost can't be mechanical, it seems to be electrical which goes to the Motronic.

[ischmitz]

Can you compare the o-scope trace over one injector of the active bank while you disconnect and connect the other bank. I don't know the model of your o-scope but it may have a trace-storage function. Ideally you pierce the insulation of the wires into the injector very close to it with needles and hook up GND and signal of the o-scope.

I want to see how the initial opening pulse looks like (duration and magnitude). That will tell tell us what the injector sees as net signal. See below for an example:

[Wayne 962]

Well, I just took it out again and beat the snot out of it. Got it plenty warm (although with the front oil cooler, it will not get above 180 on the gauge). I'm trying to clean / clear out any crap that may be inside. Part way through this test, I stopped to watch it idle, and it was running / idling fine?!? Then when I got home -> same thing. So, this problem seems to be related perhaps to, well, hmm, I have no idea, because I haven't been able to determine the pattern yet. What we're seeing is:

- two min warmup = fine
- two+ idle, flubbing and missing
- Driving = fine
- Hot = fine (sometimes, not enough data at this point).

Indeed, I have swapped Steve W.'s ECU when it was idling bad, and that made no difference. BUT - it drives hard and runs well -> very well. I'm nearing the stage where I just call it a day and give up on this, as it only seems to be happening at coldish idle, and now it also seems to be somewhat intermittent.

Here are two videos of it running / idling when hot (wereas before it was missing and showing numbers in the16-18 AFR):



and



-Wayne

[Wayne 962]

Originally Posted by ischmitz

Can you compare the o-scope trace over one injector of the active bank while you disconnect and connect the other bank. I don't know the model of your o-scope but it may have a trace-storage function. Ideally you pierce the insulation of the wires into the injector very close to it with needles and hook up GND and signal of the o-scope.

I want to see how the initial opening pulse looks like (duration and magnitude). That will tell tell us what the injector sees as net signal. See below for an example:

So, you want to see the signal sent to the injectors as I disconnect more of them, in order to see if there is a change in when more are removed from the load? Makes sense. I'm not sure if I did this already previously. The scope is a Chinese model, but it had more features than I can even fully understand. Plus it has a USB data interface to dump all the raw data to a computer, but I haven't quite figured out how to get exactly what I'm looking for out of it. I haven't used scopes in decades, and the ones I used in the old days were all analog anyways...

-Wayne

[Wayne 962]

Sal's questionaire:



-Wayne

[LJ851]

In my experience, running an O2 sensor at the end of the exhaust like you are doing will not give accurate O2 readings particularly at idle. The exhaust pulses pull fresh air back at the sensor and affect what it sees.

The typical way to get an accurate reading at the tailpipe is get a tube that will insert inside the exhaust several inches and stick out 6 inches or a foot. Weld a bung for the O2 sensor right where it exits the tailpipe so there is the 6 inches to 1 foot of tubing after the sensor.




EDIT:
Something like this. The longer past the sensor the better.

[creaturecat]

you gonna write another book?
is this still the prequel? : )

[scarceller]

Wayne, replace the spark plugs with W7DC non resistance plugs, it may help the idle issue. You already have resistance ignition wires you do not need resistance plugs.

[scarceller]

These results are really good, test case 2 & 3 you don't need to worry about much. The rest of the test cases are in range and good, if anything you can richen it just a tad more to hit idle AFR of 14.0 to 14.2, that may help the idle stability a bit. Just turn the CO screw in one full turn see what that does, then maybe turn it another turn for 2 full turns.

And as per prior post, replace those plugs with W7DC plugs!

Originally Posted by Wayne 962

Sal's questionaire:



-Wayne

[scarceller]

The best place for the WBO2 sensor is in the stock bung or just after the collector on the header. You get best accurate data in those locations.

I agree, that the tail pipe is not the best place as it will show slightly leaner results that what's actually at the header.

Originally Posted by LJ851

In my experience, running an O2 sensor at the end of the exhaust like you are doing will not give accurate O2 readings particularly at idle. The exhaust pulses pull fresh air back at the sensor and affect what it sees.

The typical way to get an accurate reading at the tailpipe is get a tube that will insert inside the exhaust several inches and stick out 6 inches or a foot. Weld a bung for the O2 sensor right where it exits the tailpipe so there is the 6 inches to 1 foot of tubing after the sensor.




EDIT:
Something like this. The longer past the sensor the better.

[scarceller]

Wayne,

After reading what you wrote here I'm wondering what the system voltage is at at the injector compared to at the battery. Each injector has constant 12vdc on one side and then the other pin goes to the DME to fire the injector by pulling this other pin to ground.

I suggest you test the voltage at the power pin of injector #1 and #4. pull back the rubber boot on this injectors so you can get the meter lead into the backside of that harness at the injector. Then ground the meter to the main ground screw on intake runner #1.

Just want to be certain you have battery voltage on the injectors. Also test battery voltage at idle and compare it to the voltage at the injector(s).

Originally Posted by Wayne 962

So, I took it out again today to see what it would do, and saw the same issues that we saw before. Starts up cold, with no missing. After two minutes, it starts "flubbing" and missing. I did the same test that I did previously, pulling the injectors:

- Pulling any one single injector does not seem to make a discernible difference overall.

- Pulling injectors 4-5-6, engine runs on 1-2-3 only, and there is no missing.

- Pulling injectors 1-2-3, engine runs on 4-5-6 only, and there is no missing.

- Plug all injectors 1-2-3-4-5-6 back in and the engine starts missing.

This behavior has been consistent for the past month. None of the fixes / changes that I have done have made a bit of difference in this behavior. There is no easily imaginable situation that would fit this current set of evidence.

-Wayne

[HaroldMHedge]

Wayne,

I've been following this since I have an 87 3.2. Today while preparing my throttle body for modification by Steve Wong I removed the idle screw. This was dirty even after using carb cleaner in the idle jet port.



After reviewing the thread, I don't see where you have verified the idle screw is clean.

Not sure this will help, it's just a thought.

[nickd]

Since everybody is throwing out suggestions- I saw that you found the wot microswitch was not working correctly, but I haven’t seen the idle microswitch mentioned? If it’s not getting triggered, then you’re running on the partial load fuel/ignition maps, which are likely set lean. The recent intermittent good idle seems like a red flag.

[sithot]

Wayne: Reading the thread tells me you are not a quitter! Hard to find stick-to-itiveness these days. I have no answers and would likely have shucked the fuel injection about 22 pages ago.

Good luck!


The Luddite Solution.

[cabmandone]

^^^
I like that solution. "Hmmm... car isn't quite running right... might want to clean my jets" vs "hmm car isn't quite running right... might want to go beat my head against a wall and then guess which electrical component is failing then more beating my head against a wall"

BTW, those are perty!

On topic:
Wayne,
Have you checked voltages while the car was acting funny. I think you said you checked for pulse but I don't recall voltage. Could this be something as simple as a voltage regulator failing?

[sithot]

Originally Posted by cabmando

^^^
I like that solution. "Hmmm... car isn't quite running right... might want to clean my jets" vs "hmm car isn't quite running right... might want to go beat my head against a wall and then guess which electrical component is failing then more beating my head against a wall"

BTW, those are perty!

Thanks.

Paul Abbott - Performance Oriented "42 mm" Webers.
SCRS (open both sides) style air cleaner thanks to Scott McPherson - Automobile Associates of Canton.
Good guys to know!