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1G Bad Intermittent misfire when warm, and warm starts

1slw3sgte

Probationary Member
17
1
Jul 3, 2020
Los Angeles, California
My 91 tsi randomly when warm gets a bad misfire as if it’s running on 2 cylinders, basically not drivable. When it happens also my wideband reads super rich (at 10.0).

After waiting for like 10-15 minutes for the car to cool off it will turn on and run fine until it wants to misfire again. I’ve replaced coil pack, spark plug wires, and power transistor but still have the issue. I’ve also took my injectors to get cleaned and tested and their good. No check engine light.

This issue has to be electrical because the car runs solid until that happens then have to wait for it to cool off, no overheating issues.
 

XC92

Proven Member
1,382
284
Jul 22, 2020
Queens, New_York
Despite everyone telling you that the proper way to fix this is to NOT keep replacing parts you guess might be at fault, you're still doing this? How do you expect people to try to help you if you're not following their advice?
 

steve

DSM Wiseman
14,458
1,392
Feb 3, 2002
St. Charles, Illinois
I've only looked quickly at the first log but I have to ask what's up with your wideband? You tell DSMLink it's connected to the front O2 but DSMLink doesn't think so in the ECU Inputs tab but NBO2 isn't enabled on the NBO2 sim tab.

You have made a few changes to the fueling DA tables, do you have strong cases for each of them?
 

1slw3sgte

Probationary Member
17
1
Jul 3, 2020
Los Angeles, California
Despite everyone telling you that the proper way to fix this is to NOT keep replacing parts you guess might be at fault, you're still doing this? How do you expect people to try to help you if you're not following their advice?
I’m very sorry I was replacing parts its my fault. This problem started before I changed said parts I changed the narrowband o2 sensor before. Alternator battery are new like a year old and the coolant temp sensor is new aswell.
I've only looked quickly at the first log but I have to ask what's up with your wideband? You tell DSMLink it's connected to the front O2 but DSMLink doesn't think so in the ECU Inputs tab but NBO2 isn't enabled on the NBO2 sim tab.

You have made a few changes to the fueling DA tables, do you have strong cases for each of them?
I have the narrowband sensor still in the from o2, the wideband I have is not connected to the ecu. Do you mean the fuel table? They are 1200cc but you need to add your global fuel due to e85. The airflowsperrev go up a a whole lot always when it starts to misfire maybe that indicates something, also the timing goes down a whole lot aswell, as if it’s not advancing timing.
 

waltah

Proven Member
308
128
Mar 2, 2011
fairfield, Virginia
Spark plugs? The spark plug gap sets the maximum voltage seen by the coils and transistors. If the gap is excessive (worn or incorrectly gapped when installed as for 'pre-gapped' plugs that aren't for a turbo car) there's higher stress on the other parts and they may fail.

Pull the plugs, check the gaps, set them per the service manual -- that would be 0.028 on a 2G but 1G may be different. If this makes your problem better you also have a coil or transistor problem but if you now replace whatever is the failing part, it'll have a normal lifespan.
 

steve

DSM Wiseman
14,458
1,392
Feb 3, 2002
St. Charles, Illinois
SD guys, I thought the MAP sensor got logged as Baro but in these logs it's flatlined @ 30.1 inHg. With all the reported problems with the Omni sensors lately and the spikes in AFRest and InjOn in these logs I wanted to make sure the MAP wasn't also spiking but I can't seem to see the real values.

IAT also seems to be flatlined and I would expect a little change as time goes on.

The log also shows why I don't like simulating the IPS. It misses the throttle opening on several blips.
 

We're on Boost

Proven Member
1,446
330
Aug 25, 2007
Seattle area, Washington
SD guys, I thought the MAP sensor got logged as Baro but in these logs it's flatlined @ 30.1 inHg. With all the reported problems with the Omni sensors lately and the spikes in AFRest and InjOn in these logs I wanted to make sure the MAP wasn't also spiking but I can't seem to see the real values.

IAT also seems to be flatlined and I would expect a little change as time goes on.

I log my MAP sensor with the Baro input, and "Baro" in my logs is always flatlined at 30.1 like his is. I don't know why. But he needs to pick "Omni Power 4-bar" in "Captured Values" to log his MAP. Then we would see it. I see mine as "LinBoost".

Something like that with his IAT. He needs to pick "GM IAT" in his Captured Values list to set it up. My IAT always logs as 77 deg also, but I actually don't have an IAT sensor. I'm looking at one of Marty's logs right now and he does have a GM IAT sensor. His logged IntTemp value is always 77 also. But you can find IAT in his Displayed Values list and that does give a varying number that looks real. I think his shows up as "IAT" rather than "GM IAT" because he actually named it "IAT" with the middle column on that page where you can give it your own name.
 
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