No misfire is happening at idle. I checked for vacuum leaks and couldn't find anything apparent. Trying to figure out if I do have a bunch of air coming in behind the mass airflow sensor or if the thing is bad. Or possibly it's an idle control valve or EGR. With the car sitting at idle you can definitely really relate the trim numbers to how the car is idling.

 

Changing the 02, with nearly identical trim numbers, tells me the 02 can likely be trusted.


Use the propane (or intake cleaner, much easier and more precise) with the car running and watch fuel trim. If it drops, that point is your leak. You can pull off the EGR and make an aluminum or steel blanking plate very easily. If idle trim changes, EGR problem. If it's the same with the block off plate, EGR is fine.

 

Changing the 02, with nearly identical trim numbers, tells me the 02 can likely be trusted.


Use the propane (or intake cleaner, more precise and much easier to use) with the car running and watch fuel trim. If ST trim drops when you spray an area, that point is your leak. You can pull off the EGR and make an aluminum or steel blanking plate very easily. If idle trim changes, EGR problem. If it's the same with the block off plate, EGR is fine.


The whole "does rpm increase" test only really works for huge gaping vacuum leaks. I don't even bother with that test unless I'm watching fuel trim.

 

I'll make a plate tomorrow morning after running the starter fluid/propane/map gas test and looking at the short term trim numbers.
Screwing with the thing yesterday I noticed I can turn the injectors in the seat/ rail quite easily on the #4 and #3 cylinders. Perhaps engine vacuum is pulling air past. I was thinking about clearing the ecu trim again and applying a little Redline cv grease around them to see if it sealed it, but realized the trim numbers would tell me the same thing without the hassle/ being an ***-hat.

 

Late to this thread, but did you figure it out? And unless I missed it did you check fuel pressure? Especially under a load?