donromani

Lots of things can cause the system to run lean. With the codes you're getting a bad EGT or O2 seems likely. It could also be leak in the vacuum system, either a torn hose, bad valve, etc.

I would say that an actual fuel leak, while possible, is less likely than the others. These are all pretty common problems with this engine. You can do a pressure test to check the vacuum system, or get a rough reading from a boost gauge if you have one.

dspang

I had intermittent codes for a bad passenger EGT a while back, they haven't been back yet, but that might explain why bank 1 is leaned out? EGT could be sending a value that makes it seem "cold", requiring the mixture to be leaned out. I'll look into that.

My gauge reads ~19-20 inHg of vacuum at idle, which would indicate no vacuum loss correct?

dspang

UPDATE:

Reinstalled the ICM's after trying to test them last night and do some more logging. I noticed that Bank 1 was now a negative value for the lambda control percentage and Bank 2 was positive, the reverse of the way it was last night when I charted it. I turned the car off, swapped the ICM's, and restarted. Bank 1 was now back to being positive, as well as Bank 2 being back to negative.


Not sure if this is what's the direct cause of the misfires, but it's definitely not good. Looks like I'll be putting new ICM's in.

Schwaggen

Had a similar issue- turned out to be one bad EGT, the other delivering intermittent faults.

Also had a small boost leak, which didn't help. Replaced the one bad EGT and fixed boost leak. Ran great for a while- getting a rare (once a week) misfire/check engine light - looks like time to replace other EGT.

donromani

EGT issues can be hard to diagnose and unfortunately the EGTs are expensive to replace. It's not something where you say, well I might as well buy one and try it to see if it solves the problem, they're like 600 bucks a piece.