Okay, so I bought a 90 Iroc with a 305 TPI in it. Car ran like a dream for roughly a month, and now, more like a nightmare. It doesn't stay running from a cold start(have to feather the gas once it catches spark) and once it's at OT if I open it to WOT it hesitates, backfires in the manifold, and seems to completely cut out. If I slowly go to WOT it will hesitate for a moment in certain spots but continue to climb steadily. If it is under load it backfires in the manifold all the time. Now I'm stumped and starting to think it's a timing issue.

Things I've replaced-
FPR
Ignition coil
Cap & rotor
Spark plugs
Spark plug wires
MAP sensor
TPS sensor
EGR valve
Coolant temp sensor


Things I've tested-
Fuel injectors
ICM

Things I've cleaned-
IAC valve
Throtle Body/runners/ect

I'm thinking maybe a timing belt may do the trick? The car has 185,238 miles on it, And I have no clue how well it was taken care of.

 

You should put this thread under the TPI forum.....not TBI.

 

Did you figure out the problem? I have the same symptoms with my 305 tpi 90 iroc convertible! Please let me know if you've found a resolution. Thanks