In my quest for factory spec perfection on my 86 Iroc, since solving my Temp problem (topic titled 'What is too hot?), I'm ready to tackle my other 'problems'.
What would cause my car to drop rpm's briefly when I tap the gas from idle, before it revs up? I had a slight miss (a quiet piffing bumping sound in the exhaust at idle) so I changed spark plugs (ac rapid fire) spark plug wires (ac delco) and cap and rotor. Still have the problem. Tach also bounces a little to the sound. Now I have come up with two possible causes on my own, 1) TPS, can these things get dirty like a bad volume control on a radio, and my other thought and I hope no one agrees 2) Sloppy timing chain
If it sounds feasable that it is the Tps, I'll change it (it is adjusted to factory spec right now .54) if it is the timing chain, some one direct me to a page that describes how to put a LT1 into my car because if I'm going to go to that trouble with the timing chain, I might as well put the '95 LT1 that's in my garage in the car.

 

you could just be going lean at your 'slight tap'

 

Hmm, and how do I fix that? When I changed my spark plugs they smelled like gas but the car doesn't run like it is flooding. But lean? Hmmm...

 

Start with a scan tool to verify it, and you fix it via prom tuning, you can take care of your tip in conditions.

If its rich maybe you're tipping in to much fuel, either way the correction is in the prom (which wont effect your stockness like an AFPR would)


:lala: :lala: Yayyyy 1,000 posts :lala: :lala:

 

Well to answer your question, yes it could be the TPS, more likely if the problems at idle, the IAC. Unlikely the timing chain, the car would most likely run like complete crapola if that was it. Is it just missing on one cylinder? If so which one? Or is it randomly missing on all of them? Also how's your catylitic converter? that can cause a noise like that in you exhaust if it's clogged, and some driveability issues like you mentioned, as can a muffler that's internally collapsed (though the muffler would have to be really screwed). You'd likely have some power issues with a clogged cat, sometimes it's wierd though. Once had a customers car that had a little trouble at idle, crappy acceleration at part throttle, but no problem at WOT, turns out the exhaust pressure at WOT was enough to force the gas out through various exhaust connections, but not at idle and part throttle. Anyway I'd check all these little gremlins first, as well as fuel pressure and checking for vacuum leaks, and maybe a minor egr issue before panicking and trashing the engine, thoguh it would be a good excuse to get that LT1 in there

 

Ok, last weekend I got a new IAC and adjusted it, old one was bad from a hydrolocking I had a couple of months ago, (who'd a thunk a gallon of water through your intake could be that bad?!), works great. Last year my convertor was glowing cherry red in the day light, gutted it (welded air tube shut, and pinched of tube from engine). Actually the car has alot of new parts ("honey, car's running funny, I'll be back, getting some parts") I like new parts But the TPS is one I haven't changed yet. On a side note, my car just started throwing a code 13 once up to temp. No drivability problems when this occurs, but the damn O2 sensor is new too.