I've been having some issues with my TPI 305 stuttering/missing/running rough. It is a 87' TPI MAF setup. Car ran ok before I stopped driving it last fall(first week of November). Over winter I have done quite a bit of work to the car, but nothing really with the engine. Re-coated the headers and a new cat-back system and alot of suspension/brake upgrades. I did put on the proper 90-92 TPI hard fuel lines(brand new GM) under the hood(car has serpentine belt setup), that is the only engine related work.

Fast forward to about 2 weeks ago when I first fire it up. Car idles somewhat rough but the idle does smooth out when it warms up. The main problem is under part and full throttle it misses and chugs, the car actually shakes somewhat. No SES light comes on. I have put on new plugs, wires, coil, cap and inspected the rotor which is only about 2 years old. Injectors are 19 lb Ford Bosch items that are also about 2 years old. The fuel filter is about 2 years old, EGR valve is a 2 year old Delco part too. Checked the timing and it is set at 6 degrees advanced. Put in new gas yesterday in case that was the issue but nothing changed. Tapped the MAF at idle and no change, also unplugged each injector as it was idling and the car would run slightly worse with each one unplugged at a time. The injectors measure between 15.3-15.6 ohms each. I'm quite befuddled of what to do next or where to go. I will invest in a vac gauge and fuel pressure gauge to check those next. Does it sound like a fuel or ignition problem? The only item ignition wise not replaced was the rotor even though it looks good and the ignition module. Would the car still run half decent with a bad module?

Running the ScanTool shows the temp was at 235-240 which alarmed me, considering the engine gauge and my Autometer show at steady operating temps, between 180-200...and I have had Ramcharger dual electric fans on low and high yet it still shows that temp. It does show it gets in closed loop relatively quick and is neither rich nor lean. Is it possible with the high temp rating its dumping more fuel into the engine for some reason causing these issues? Also in park the engine revs just fine, it seem to be more of an issue in gear.

One additional tidbit is that this motor will be pulled in about 2 months for a 350 with Vortec heads but I'd rather not hope that will magically solve the issue.

Hoping some others have had a similar issue and resolved it . TIA!

 

I had a problem like that on my 87 GTA and it turned out being the pickup coil in the distributor.

 

maybe the CTS sensor is shot . It causes it to run rough when hot . But ggod when cold . How are the plugs . Any indications you are runnnig rich/lean ?

 

The plugs are new Delco's. According to the scantool it flips between lean/rich like normal. Would a bad ignition module cause to run rough? It was my impression it just wouldn't start if bad.

 

take it out and get it checked at autozone or the likes.

also take out the whole distributor remove the dist gear(replace if worn) pull the shaft out of the housing and replace the pick-up coil.

Did wonders for my car

 

I think I will do that next. It just seems ignition related and almost everything else has been replaced or checked.

For the CTS, the car runs rough before even getting warm so I'm not sure that is the cause after thinking about it, in relation to the high temp causing more fuel to be dumped in. Hmm.

 

I replaced the ingnition module with no luck. I guess the pick up coil is next...

I also purchased a fuel pressure gauge and hooked it up, 36-38 psi at idle and jumps to 42 ish under throttle....seems normal. With the key on and engine off it only reads 10-12 psi, I read it should read 43...is that true?

Beginning to run out of ideas...

 

does the car have to be warm for the cts to start showing problems?


and can the pickup coil cause the problems that you listed? because i have the EXACT same problems and i purchased a new pickup coil... just dont know how to install it lol