Originally Posted by theterminator93
Still could be a MAF issue. See what happens with it unplugged entirely. A:F or spark is off when it's missing/stuttering/bucking. The MAF sensor is the single most important player that influences all of these. If the electrics are going bad, it could be giving bogus output only in a certain airflow range. Running with the MAF unplugged will help rule that out as the car relies on separate tables to compute fuel/spark with a failed MAF.
Also unhook the electrical leads to the EVR solenoid to disable EGR (do this NOT at the same time you try running with the MAF unplugged) to see if that has an effect. Too much EGR that isn't compensated for by extra spark will slow the combustion process down significantly enough to cause a slight misfire.
California car, right? EDIS (no distributor)? Crank sensor controls spark; if it's gone screwy it can do weird things too (although usually when it goes you get a no-spark condition). There's a separate EDIS module (I believe near the air box) that could also be doing strange things.
Funny thing about having a car so long is that the repairs you make start to get old after a time and it's like starting over. My MAF is not original. According to my records the original went bad 11 years and almost 60k miles ago. It was causing bad
stuttering, even stalled once, and was generating CELs. Replaced it with a new one (remanufactured). So, could be issue, but it's not original at least.
EGR's all original so if there's an issue with it then that could make sense. Do the EGR components have any sensors that would generate a CEL? And with disconnecting the MAF or EGR, what sort of behavior am I looking for? The car will run poorly with either disconnected anyway, right?
And the car is Californian: distributorless. I had a different stutter some time ago (would randomly manifest with consistent throttle while on the road and sometimes generate CELs) and fixed it by replacing both the cam and crank position sensors. That was about 30k miles ago. The EDIS module is precisely where you described it and is original. They're not all that expensive. I'll take a look at all these parts on my next days off.
Like any old car and especially those that have lived in areas of higher than normal heat it's really a good idea to have a close look at ALL the vacuum lines. High underwood temps eventually cook and hasten dry rot of the rubber hoses. This could be a reletively minor vacuum leak that's masked at larger throttle openings. This wouldn't be the first car that idled rough from a vacuum not leak and ran fine at higher RPMs.
Very true. I've been lucky and as much as I'd like to see the car run forever it's so old and has so many miles that it has the right
to break down. But if I can keep it going without spending too much, I will. To be specific about my current issue, if it makes a difference, the engine idle is smooth. It's when you feather the throttle, particularly when the car's in park, that the stutter occurs, starting at a little over 1000 RPM.
Unless you guys have any advice against it, I think my next move is going to be to try the Seafoam spray into the throttle body. When I cleaned the throttle body and IAC before, I had the engine off so I wasn't really getting deep into the intake. After that, we'll see.