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

[stlrj]

"..I did not build this car, and when it arrived at my shop (with the 3.2 installed) it never ran correctly..."

I suspect the firing order was probably screwed up from the start. Can I assume that was checked?

Sorry, but I just hate assuming anything.


Cheers,
Joe

[Wayne 962]

Originally Posted by stlrj

"..I did not build this car, and when it arrived at my shop (with the 3.2 installed) it never ran correctly..."

I suspect the firing order was probably screwed up from the start. Can I assume that was checked?

Sorry, but I just hate assuming anything.


Cheers,
Joe

Thanks, that has been checked multiple times, and I just installed new plug wires so that is definitely correct now.

-Wayne

[ischmitz]

subscribed.... (still reeling from all the information, it's quite a read)

Maybe time for a summary post that puts all observations into one place. Sometimes organizing thoughts like that will give you and others a clue.

[john walker's workshop]

No way it could have a sucked/blown intake gasket is there? the spacers can crack too.

[mysocal911]

Originally Posted by Wayne 962

So, I missed uploading a video that gives another data point.

Please, more videos! You're very close to finding the problem, right?

[Wayne 962]

John - that should create a huge leak that would have shown up with the smoke test presumably? Also, these were supposedly replaced (although in 2008 - maybe less than 200-300 miles on the car since then).

Ingo - I am planning on summarizing, perhaps into a single post / word doc - if this disaster continues on!

Today's thoughts (haven't worked on it yet):

- I have a new pressure regulator coming, heading out to pick that up shortly.

- I have my fuel pressure gauge hooked up to the test rail and have been running it with it there. I had a long length of hose that I used just because I had it on hand. I'm wondering if the fuel hose itself could be acting as a rubber spring on the fuel pressure and the test equipment could actually be causing problems? I will disconnect today to see.

- Robert at DC Auto is hunting for a pressure damper to loan to me. There's also a few on eBay, but who knows if they are any good (they presumably have to hold vacuum. Speaking of that, I tested the pressure using vacuum from the manifold, but I never "sucked" on the units to make sure that they were holding vacuum on their own. I will do that today.

- As mentioned previously, I will swap injector #6 with #1 and see if the problem stays with cylinder number six, or moves to number 1. Wouldn't it be nice if this were just a problem with a single injector?

- I will check the resistance of the injectors with my new harness - I didn't do that yesterday and some here called me out on it . Agreed, the new harness should be an improvement over the old one and should match the other injectors.

The oddest thing about all of this is the fact that the engine seemed to run okay on three cylinders on the left, and then three cylinders on the right, but when put together, it starts missing. This just plain doesn't make any sense, unless there is something odd or wrong with the fuel rail and/or hoses, and/or fuel pressure regulator / damper. I had a thought that one of the fuel circulation hoses might be getting clogged in the engine compartment, but my gut is that not the case (due to the fuel flow I saw into the gas can on Sunday).

-Wayne

[jpnovak]

I don't think that your full poor running engine is specifically related to #6. Something is acting on the engine to make it globally run poor.

I don't think its ignition or ECU related given your suite of tests. (very thorough BTW makes me want to build a breakout box)

Does fuel pump get hot after running for a few minutes?

[Wayne 962]

Here are the plugs from yesterday (maybe an hour of "idling time" on them), for cylinders 5 and 6. Cylinder 6 seemed to have the problem as far as I could tell, but these plugs look remarkably similar.

Cylinder #6 is the plug on the top.





-Wayne

[proporsche]

does it look like unburned fuel on those spark plugs?

Ivan

[ischmitz]

Wayne,

Have you ever closed on the reported discrepancy between the WB O2 sensor and the regular O2 sensor used by the DME. I thought I saw something a couple of pages back in that regard. From my simple observations (my DME test stand simulating an ALL-LEAN or ALL-RICH O2 signal) I can see how the mixture (inj pulse duration) gradually changes at a given RPM/load/sensor snapshot in response to the simulated condition.

Given that the 914 probably doesn't have the stock 3.2 exhaust layout maybe the NB O2 sensor isn't seeing a representative gas mix (position, exhaust leak, etc). Your core problem statement seems to be "poor idle after warm-up". Let's assume it is a wrong mixture at idle. Mixture is impacted by the following:

- setting of air bypass screw in AFM (defines how much air has to pass through the barn door and sets it's position at idle, independent of ICV position)
- any modifications someone might have made to the AFM spring tension
- O2 sensor age, location, dynamics, noise on signal line, etc.
- functioning CHT, IAT and idle contact
- Any non-zero amount of 'other' unmetered air (aka leaks in intake). Sounds like you tested that

A quick test with the break-out box could be to jam the O2 sensor response to full-rich or full-lean and see how the idle behaves after all is warmed up. A simple 1.5 V battery connected to the signal or the signal grounded accomplishes that. Just a thought.

Ingo

[Wayne 962]

Originally Posted by jpnovak

I don't think that your full poor running engine is specifically related to #6. Something is acting on the engine to make it globally run poor.

I don't think its ignition or ECU related given your suite of tests. (very thorough BTW makes me want to build a breakout box)

Does fuel pump get hot after running for a few minutes?

I can check (I think). The fuel pump is located underneath the car in the front. I was thinking that the location of the fuel pump might have something to do with all of this, but the fuel pressures checked out, so that possibility was and still remains remote in my opinion? Still, it could be an issue.

As for something globally? That's what I thought originally. Then I saw that #6 was:
1) running cooler according to the FLIR thermal camera,
2) had higher resistance on the injection harness,
3) had the dirtiest spark plug,
4) seemingly causing the miss to go away when the #6 injector was unplugged

However, saying all that, my gut is that there is something indeed globally wrong, which may be manifesting itself in issues on #6. The miss is seemingly random. I can stop the miss (I believe) by unplugging the injectors on the opposite side. If I look at the injector pulses in the oscilloscope, each time they look very consistent in frequency (if not voltage amplitude).

I'm going to make those changes I put in the previous post and then see what happens...

-Wayne

[gtc]

Originally Posted by Wayne 962

The oddest thing about all of this is the fact that the engine seemed to run okay on three cylinders on the left, and then three cylinders on the right, but when put together, it starts missing.

The injectors are fired in batches, as 1-3 and 4-6 are wired in parallel, so that does make some sense.

[manbridge 74]

Hmm... some suggestions that you might've already tried:

Has the air flow meter show signs of having been opened?
Have you checked to see if in a dark garage you have the same spark intensity (bright blue, not orange) as on other cylinders?
Sprayed diluted saltwater (helps conductivity) while engine is running to force any ignition voltage loss?
Smoke tested the intake system?
Does your 3.2 have the correct oil trap screen in the vent line back to intake from oil tank? Plugs look oily to me...

[ischmitz]

Originally Posted by gtc

The injectors are fired in batches, as 1-3 and 4-6 are wired in parallel, so that does make some sense.

All six injectors are wired in parallel to each other and fire at the same time. The fact that the DME has two outputs (one for the left bank and one for the right bank) throws people. Internally both pins are connected to each other and driven by the single injector stage.

The injector driver circuitry "sees" 6 injectors wired parallel to each other. Each injector's DC resistance is ~2.6 Ohm. The effective resistance of all six in parallel is 1/Rtot = 1/R1+1R2+....+1/R6 - it comes out to about 0.43Ohm. This is not a trivial matter and hence the peak&hold PWM driver scheme.

One bad injector (internal short) will inhibit everything. A bad injector (internal open) will just not participate but leave the other five happly fire away....

[ischmitz]

Originally Posted by Wayne 962

I can stop the miss (I believe) by unplugging the injectors on the opposite side. If I look at the injector pulses in the oscilloscope, each time they look very consistent in frequency (if not voltage amplitude).

-Wayne

The waveform of the injector voltage is simply a result of the hold-stage in current feedback. Depending on the connected load (# of injectors) the duty cycle will vary a bit.

There is an initial opening pulse of about 400us (peak phase) that is to shock the injectors open and then the driver switches to hold mode where PWM waveform is used to maintain a set reduced current in current feedback mode. At the end when the injectors close you get an inductive dump spike. This is when the magnetic field breaks down and it is addressed in a dump stage to prevent damage to the main driver output.

The frequency of the hold phase is set via an external RC network and fix. Amplitude is near 12V VBat and duty cycle and end pulse dependent on # of injectors.

[Wayne 962]

Okay, so the results of today (NO CHANGE).

Here's what I did:

- Swapped injector 1 with injector 6

- Removed the fuel test gauge and reinstalled the plug

- Checked the resistance of the injectors (through harness using 87 and pin 14 or 15). This has improved on injectors 5 and 6. Not completely surprising as I cleaned all the contacts with either isopropyl alcohol, and/or some q-tips or sand paper, etc.:
1- 3.1 ohm
2- 3.0 ohm
3- 2.9 ohm
4- 3.3 ohm
5- 3.3 ohm
6- 3.2 ohm

- I took a closer look at the fuel pump after cleaning the injectors. It's occasionally making some noise, but nearly all fuel pumps seem to make some random noises. Sometimes it will go 30+ seconds without any noise. The fuel level is now slightly low (I added some more clean fuel prior to starting it up today), so this may be a clue, or may be nothing. It may also be circulating some of the bubbles out of the system from when it was cracked open swapping the injectors. Not sure yet, I will check it again tomorrow for any noise. Here's a video of the noise:







- I tested the pressure regulator and pressure damper to see if they held vacuum. I don't have my vacuum tester here at home, so I used the "grassroots" approach:







Started the car after this -> no changes. But, again, it seems to run much better when stone cold:






Running on 1-3 runs consistently, poor running on all six, and then fine on 4-6. Interesting, here's a video with timeline:

1- Started car with it running on 1-2-3 only (4-6 injectors are unplugged, O2 sensor unplugged)

2- Replugged in 4-5-6, runs and stumbles

3- Unplugged 1-2-3, runs fairly consistently and evenly on the three cylinders 4-5-6






Okay, so here's a weird video:

1- Running on all six cylinders (poorly). AFR shows it's running lean on 1-2-3 (the O2 sensor port is on this side)

2- Unplug 4-5-6, runs consistently on 1-2-3, AFR shows it's running much less lean (near 14.8-15.0, which is close to 14.7 - normal/ideal).

3- Then replug in 4-5-6, and the AFR goes from about 1.47 to 16+ (goes very lean on 1-2-3)






Finally, here is the "Ingo Test", where I used a 1.5-volt C-battery to simulate rich and/or lean conditions:

1- Running on all six cylinders, running very lean (17 AFR), voltmeter shows reference voltage of 4.9 from ECU.

2- Added in the 1.5 battery to simulate a rich mixture, which means the car will try to lean itself out (which happens as the car goes to 23+ - how is that even still running?).

3- Removed battery (back to reference voltage of 4.9 volts), AFR around 17

4- Grounded out O2 sensor (which simulates a lean mixture) - car went richer, 14-15 and ran better, but then went lean again randomly (at around 1:21)






Finally, I swapped out the sport muffler, just in case it was causing some weird reversions, etc. Didn't help. Here's the video from that.

Starts, sputters, etc, but now it appears to be running rich, and then goes lean and starts to sputter. Higher rpm revs are fine, but the engine still sputters and misses during those too. There's also an air whine / whistle that can be heard - the car had a big whistle last few times I drove it. I thought it was related to the revamped boots and the air filter too, but who knows now - maybe it has something to do with something.



I haven't had a chance to really think about all of this tonight, got some other family stuff going on right now that is distracting me from the really important 914 stuff!

-Wayne

[Wayne 962]

Originally Posted by manbridge 74

Hmm... some suggestions that you might've already tried:

Has the air flow meter show signs of having been opened?
Have you checked to see if in a dark garage you have the same spark intensity (bright blue, not orange) as on other cylinders?
Sprayed diluted saltwater (helps conductivity) while engine is running to force any ignition voltage loss?
Smoke tested the intake system?
Does your 3.2 have the correct oil trap screen in the vent line back to intake from oil tank? Plugs look oily to me...

Air flow meter - haven't taken it off, but the output from it looks good (tested with oscilloscope).

Everything on the ignition system has been replaced now (plugs, cap, rotor, coil, wires, and the ECU), and checked with the timing light (extensively). This doesn't feel like an ignition issue. The distributor could be a problem I suppose, and I haven't checked #6 since I identified it as a problem. I will check it with the timing lamp tomorrow.

"Sprayed diluted saltwater (helps conductivity) while engine is running to force any ignition voltage loss?" - I'm not familiar with this one, can you elaborate? Perhaps you mean from a spray bottle on the outside of the wires? Again, everything is new, so I'm not sure that would be an issue.

Smoke tested multiple times, hot and cold.

The oil trap system has been removed, but I will recheck everything...

thx,

Wayne

[Wayne 962]

Originally Posted by ischmitz

All six injectors are wired in parallel to each other and fire at the same time. The fact that the DME has two outputs (one for the left bank and one for the right bank) throws people. Internally both pins are connected to each other and driven by the single injector stage.

The injector driver circuitry "sees" 6 injectors wired parallel to each other. Each injector's DC resistance is ~2.6 Ohm. The effective resistance of all six in parallel is 1/Rtot = 1/R1+1R2+....+1/R6 - it comes out to about 0.43Ohm. This is not a trivial matter and hence the peak&hold PWM driver scheme.

One bad injector (internal short) will inhibit everything. A bad injector (internal open) will just not participate but leave the other five happly fire away....

Okay, I didn't know this. So, if 14 and 15 are wired together, then 14/15 --> six wired injectors in parallel --> pin 87 of the DME relay should be .43 ohms.

So, my measured amounts are:

1- 3.1 ohm
2- 3.0 ohm
3- 2.9 ohm
4- 3.3 ohm
5- 3.3 ohm
6- 3.2 ohm

So, these measurements include a portion of the harness that is unique to each cylinder plus a portion of the harness that is shared by the set of three.

Total resistance calculated should be .52 ohms. But if I measure from pins 14 and 15 to pin 87 (with the ECU connected), I get .9 ohms.

If if unplug the ECU (separating the two sides of the circuits), I get 1.5 ohms from pin 15 to pin 87 (through injectors 4-5-6). I also get 1.2 ohms from pin 14 to pin 87 (through injectors 1-2-3).

I guess I'm not really sure what allowable or acceptable resistance is supposed to be through the harness?

-Wayne

[Wayne 962]

Originally Posted by ischmitz

There is an initial opening pulse of about 400us (peak phase) that is to shock the injectors open and then the driver switches to hold mode where PWM waveform is used to maintain a set reduced current in current feedback mode. At the end when the injectors close you get an inductive dump spike. This is when the magnetic field breaks down and it is addressed in a dump stage to prevent damage to the main driver output.

From my oscilloscope readings, it would seem like the initial pulse can be sometimes high and sometimes low. The rest of the phase looks okay, although when the motor stumbles, it appears to throw the scope off a bit. I'm not sure if this is the chicken or the egg (causing the stumble, or are we just seeing the results of the stumble).

-Wayne

[proporsche]

another question would be ..............is the exhaust system really good for this engine on 914?
When you put on stock muffler it seams the engine runs differently.
Is there another 914 with Carrera engine in the States with the same exhaust system?
I guess you cannot remove it and try different one Pita work,right?

Ivan