Help! I have an '85 l98 with 84,000 miles on it and has a progessivly increasing problem. I recently swapped the head gasket/ everything else in between and the car runs beautiful. The problem is that it used to have a very small problem even before the half rebuild. In 4th gear and kind of in third around 2200-2400 rpm it would hesitate slightly and miss a little, more hesitation and more towards 2200 rpm actually. It was never a big deal, but lately i have been drivin it a little more. It seems to be progressivly getting worse. Under normal driving its perfect. But now even under slightly aggressive gas it will hesitate and miss even in second gear! It seems as if the heavier the load (aka higher the gear) the worse it is. Last time i drove it was ridiculous, it flys up to 2200 rpm or so, misses, hesitates, than goes back to full power acceleration until it misses and hesitates a little more (while in the same gear) and continues in the gear at full power til i shift. Every once in a while there is a random miss in there but basicaly its at those two or three points in the gear. at idle and in neutral reving it runs fine. it doesnt backfire, pop, or sputter, just kind of cuts out.
I recently replaced the fuel pump and filter (maybe 1000 or 2000 miles ago), replaced the plugs, ignition coil (brand new), cap and rotor are fine, had the ignition module tested and it's fine, timed it. In my mind it could be a few things; Distributor, Fuel Injectors, MAF sensor, some other random sensor, or something i have already replaced (which prblby isn't the prob). One of the key things i believe is that it is both somewhat consistent and still operates perfectly at idle, in neutral, and at full throttle when not in those bands. Please give your expertise and narrow down the possibility of problems before i have to resort to throwing money at the problem (which usually never works).

 

Sounds a little like an IAC valve, others will correct if otherwise. Just my thoughts.

Bob

 

Sounds like it could be a clogged fuel filter. When was the last time you changed yours. I always try the simple and cheap possibility first and work out from there. Worth a try?

 

Have a friend who found an anoying miss-turned out to be his coolant temp sensor, seems like it would miss without throwing any codes-he guessed the computer would correct it before it had a chance to throw a code.Said it took him two years to find it.

 

i replaced the fuel filter a few months back but i might as well again.