2G Intermittent Injector Firing Problem

[Artago]

Getting a P302 code. Injector 2 stops firing sometimes. At a red light it just stops. Sometimes, if I turn off the car and crank it back up, it will work until I hit a red light then stop firing again.

Troubleshooting:
1. Swapped 1/2 plugs, wires, injectors. No change.
2. Bench tested injector 2. Works.
3. Spark test on cylinder 2. Have spark.
4. Unplugged / replugged injector 2 plug. Sometimes, it kick on, other times it doesn't.
5. Tested all 4 injector pigtails. 44.7, 44.7, 42.7, 44.7 Ohms

What can I test to diagnose the problem?
What's the injector resistor pack?
Could that be the problem?
How do you test that?

 

[jakk220]

The injector resistor pack could be an issue I suppose, but I would think that more than likely all of the injectors would be effected.

If you want to test it, here is the procedure:

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4. Unplugged / replugged injector 2 plug. Sometimes, it kick on, other times it doesn't.

This screams wiring problem IMO. I would be looking for an intermittent connection from a broken wire if this statement is true.

1. Swapped 1/2 plugs, wires, injectors. No change.

If by this statement you mean that the problem does NOT follow the injector, then again I would be looking at an issue with the wiring. I would wiggle the loom around while the injector is plugged in and mess with the injector harness connector to see if it kicks on /off.

If this checks out then I might suspect that there is an injector driver in the ECU that is beginning to go bad.

If the problem is following the injector, then I would obviously say the injector is intermittently sticking shut.

Lastly are you sure that this is not an intermittent spark issue?

 

[Artago]

I tried wiggling the harness and pigtail and it didn't seem to kick on. However, I did unplug / plug it back in with the engine running. It kicked on once or twice and then it stopped completely.

At this point, nothing I do get's it to kick back on again.

The problem did not follow the injector so that's not the issue. I tested it multiple times on and off the car. It seems to work.

How do I test / find a broken wire in the harness? Do I have to take it apart completely? Is there a simple way to test? IE: Conductivity test from ECU to Pigtail?

How do I test the ECU injector driver? I have ECMLink 2.5. Any way to use that to diagnose it?

One important clue is that, when the clyinder stopped firing, if I turned off the car and turned it back on it started working again. I did this about 10-15 times before it stopped working altogether.

I'm starting to lean towards ECU or injector resistor pack. Thoughts?

 

[gofer]

Is the "Cylinder Misfire" box checked under the DTC tab in ECMLink?

 

[jakk220]

How do I test / find a broken wire in the harness? Do I have to take it apart completely? Is there a simple way to test? IE: Conductivity test from ECU to Pigtail?

Grab some a noid light and plug it into the injector harness. This will tell you if you have power and pulse.

How do I test the ECU injector driver? I have ECMLink 2.5. Any way to use that to diagnose it?

You can take the cover off of the ECU and check for any obvious visual damage like this:

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The only real way to tell is to send the ECU to ECMlink and have them bench test it.

I'm starting to lean towards ECU or injector resistor pack. Thoughts?

Did you test the Resistor pack according to the diagram that I posted above? That will rule it out.

 

[Artago]

Tested the resistor pack. 15 Ohms on all pin outs.

Yellow/Black injector 2 wire to Pin 14 on the harness. 0.6 Ohms. Has connectivity.

Green/Black injector 2 wire to Pin 12 on the harness. 6.6 Ohms. Tested Green/Red on injector 3 just to be sure. Also, 6.6 Ohms.

I'm going to go ahead and say the wiring harness is ok.

 

[Artago]

Is the "Cylinder Misfire" box checked under the DTC tab in ECMLink?

I'm throwing a CEL for P302 if that's what you're asking.

 

[motomattx]

Cas sensor or ecu is bad.

 

[Artago]

Here are the photos of the ECU.

https://photos.app.goo.gl/pbS8dNW1DyZqBmx92

 

[Artago]

Cas sensor or ecu is bad.

Would a bad CAS cause only cylinder 2 to misfire? All others are firing normally. Also, it cuts in and out. At this point it's 99% not firing and occasionally it will fire for a few seconds.

Before it got worse, I could turn off the ignition and fire it back up and it would work for a few minutes. After which it would stop firing again.

 

[Artago]

Found something. I hooked up a volt meter to the injector pigtail. Injector pigtail shows about 3.5V (while the car is running). Injector 2 pigtail shows 0V. So injector 2 is not getting a "fire" signal. ECU looks ok though.

 

[motomattx]

The cas sets the sequencing so it could in theory cause the problem I suppose.

 

[gofer]

Be a bit more specific about your setup before jumping to the conclusion the ECU is bad.

• What CAS is on your car, stock 2ga under the intake cam gear or has it been converted to a 1g or 2gb?
• What version ECU do you have, is it a '95-'96 or a '97-'98?
• Why don't you post a log?

 

[Artago]

Be a bit more specific about your setup before jumping to the conclusion the ECU is bad.

• What CAS is on your car, stock 2ga under the intake cam gear or has it been converted to a 1g or 2gb?
• What version ECU do you have, is it a '95-'96 or a '97-'98?
• Why don't you post a log?

• Stock 2g CAS under intake cam gear
• Not sure about the ECU. Can you ID it with these photos -> https://photos.app.goo.gl/pbS8dNW1DyZqBmx92
• Not sure what to log that would point at the problem. I can post one if you let me know what would be useful to log

PS: I appreciate all the help. This is very frustrating and I'm stumped.

 

[Artago]

Update:

Checked and double checked everything. Got spark and fuel. Did a compression test. Was Low. Pulled the valve cover. 1 rocker had popped out. That would do it. Pulled the head. Bent a valve.

Going to buy a new valve set, valve seals, and MLS HG. Once it's all back together I will post back.

 

[Artago]

Head was rebuilt and reinstalled. Same issue. If fact it's worse. Won't even idle and sounds rough. Should I get a noid light? If so, which one fits our pigtail?

 

[gofer]

Head was rebuilt and reinstalled. Same issue. If fact it's worse. Won't even idle and sounds rough. Should I get a noid light? If so, which one fits our pigtail?

Since you pulled the head you could have fixed the original problem and induced 5 more that would cause what you're describing, not idling and sounds rough.

Having the car down for that long, doing that amount of work, you'll have to start at square one.

Check timing, check for BLTs, hook up the laptop and make sure your injector settings make sense. Might be shit gas in the tank too.

 

[Artago]

Since you pulled the head you could have fixed the original problem and induced 5 more that would cause what you're describing, not idling and sounds rough.

Having the car down for that long, doing that amount of work, you'll have to start at square one.

Check timing, check for BLTs, hook up the laptop and make sure your injector settings make sense. Might be sh** gas in the tank too.

I think I got the timing right. Cam gears line up. Just not a 100% on the crank. Does this look ok at TDC?

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Would a boost / vac leak cause it to die on start up? I thought that would just cause a high idle. Mine fires up, jumps to 2000-2500 and drop back down to 0 and dies. Sounds like it's firing on 3 cylinders.

Hooked up a laptop and loaded my old settings. Will double check though.

Gas might be shit, but I have Chevron 94 in it which is good stuff. Never had an issue with old gas before but I'll add it to the list of suspects.

Ordered a noid light and inline spark tester. Should be here today. Will check and post back.

Appreciate all the advice. Thanks.

EDIT: I can keep it running by giving it some throttle but it sounds like it's running on 3 or misfiring really badly.

 

[rEclipserGST]

Did you ever fix the #2 injector 0v problem? Why was it reading 0?

 

[Artago]

Did you ever fix the #2 injector 0v problem? Why was it reading 0?

I just got a noid light. Going to use that and post back. (Probably this weekend)

 

[gofer]

I think I got the timing right. Cam gears line up. Just not a 100% on the crank. Does this look ok at TDC?

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Would a boost / vac leak cause it to die on start up? I thought that would just cause a high idle. Mine fires up, jumps to 2000-2500 and drop back down to 0 and dies. Sounds like it's firing on 3 cylinders.
EDIT: I can keep it running by giving it some throttle but it sounds like it's running on 3 or misfiring really badly.

The timing mark on the crank trigger plate looks like it maybe off by an 1/8" (like I mentioned in your posted thread about it) but it could be just the angle of your photo, how does the crank pulley look on the timing belt cover?

100% yes, the WB AFR reading will give you a good indication of what's going on too. I just started my car after it being down for over 2yrs and I tried starting it up before doing a BLT because I got lazy and it was acting exactly as you're describing, had to give it gas just to keep it running or it would just die. Noticed AFR's were lean and I did a BLT and found a vac leak right on the head at the #3 lower injector seal. Once I verified all my vac/boost leaks were fixed I started it up again and it was still having a hard time idling on its own and it was because my injector settings needed tweaked. I had globals set for 2150's but they were wanting a global closer to a 2000cc injector. I had to drain my tank too because it wouldn't even try to fire up on the E85 I had in there but again, it was 28mos old and not 6 months like yours. Something to consider though...

A trick to tuning a car at first start-up is locking it in open loop (Misc. tab) so you're not trying to fight the o2 sensor/ECU, then just use the WB to tune your injectors. If it's too rich make globals more negative, too lean more positive until you can get the WB close to 14.7'ish. Then you can unlock OL and let the o2/ECU control idle while you put a good idle tune on it.


I'm not saying you don't have the same issue with your injector but after all that work you've got to eliminate everything else first before jumping right back to what was causing the problem 6 months ago and a head rebuild in between.

 

[steve]

I haven't followed this thread but I didn't see this mentioned. As a reminder a 2G ECU will cut fuel on a cylinder suspected of having misfire. So once the CEL is on for misfires on any cylinder it's not trying to drive that injector anymore.

The ECU is a early 95 EPROM, the 1672E on the edge connector refers to the E2T61672 part number for a MD312464 ECU.

Found something. I hooked up a volt meter to the injector pigtail. Injector pigtail shows about 3.5V (while the car is running). Injector 2 pigtail shows 0V. So injector 2 is not getting a "fire" signal. ECU looks ok though.

Which of the two wires @ the injector were you measuring?

 

[Artago]

I haven't followed this thread but I didn't see this mentioned. As a reminder a 2G ECU will cut fuel on a cylinder suspected of having misfire. So once the CEL is on for misfires on any cylinder it's not trying to drive that injector anymore.

The ECU is a early 95 EPROM, the 1672E on the edge connector refers to the E2T61672 part number for a MD312464 ECU.



Which of the two wires @ the injector were you measuring?

I've reset the ECU and cleared all codes so the P302 is gone.

I was measuring across the pigtail itself. I didn't have a noid light at the time so this is the only method I could think of to see if it was getting a fire signal. All of the other ones were showing 3.5V (while the car was running) Inj 2 was 0V.

This was a while ago so I will test again with a noid light.

I did also check each pigtail, 1 lead at a time, to the wiring harness at the ECU as per an ECU diagram. I had a good connection on all of them.

I will check all of these again and post back. If they check out, then I suspect it's has to be a bad ECU. If any fail or have different resistance than the others, then it could be a bad wire or resistor pack (although I test that previously and it passed).

Since the car was down for a while (head rebuild) I will need to retest everything (like gofer said)

Stay tuned for more info.

 

[steve]

I was measuring across the pigtail itself. I didn't have a noid light at the time so this is the only method I could think of to see if it was getting a fire signal. All of the other ones were showing 3.5V (while the car was running) Inj 2 was 0V.

The ECU provides a ground for the current to flow through the injector when it wants to fire the injector. The voltage source is the battery through the injector resistor. Your 3.5v was due to how you meter measure a switching voltage at some frequency. Your 0v was likely because the ECU was never switching it's side of the injector to ground, it was just floating at the same voltage as the battery side of the injector.

 

[Artago]

I'm starting to suspect the CAS or ECU. Can ECMlink log those values or do I have to test it some other way?

I started a thread on it here: http://www.dsmtuners.com/threads/2g-cas-test.519611/