Hey All, We're looking at an '87 S-10 with a 2.5L TBI "4tech". It passed the e-test on the drive, but on the idle, the HC's went through the roof, 1040 ppm on a 300 limit to be exact. The drive reading was 132 ppm on a 148 limit. The engine seems like it has a misfire at idle -- the RPM's will drop down to almost 100, and then jump up to 1000 or so for a few seconds, then back down, almost stalling and stumbling a lot, then back up. I pulled the PCV with no difference, checked air filter, pulled plugs (they were on the lean side of tan). The top of the throttle body is all black, and the air filter smells like gas sometimes. Question is, what could make it run so rich at idle, and also misfire? I thought it was the PCV, but it didn't make a difference with or without it at idle. Any ideas would be appreciated! Thanks! :TU:
A plugged charcoal cannister will give off a strong gassy smell. A common problem area I've seen on the 2.5's from that era, are the middle guides/stems galling and/or wearing faster. I've fixed many of those heads.....usually had to do at least one guide and one exh. valve when re-conditioning those heads. At that age, there a host of sensors that could be faulty by now. Not to mention, clogged EGR valve/passageways, etc. If the TBI unit is that dirty, good chance the IAC valve could be crudded up too. Sounds like a thorough cleaning, diagnosis is in order.
