My car is an 87 trans am with a 305 tpi auto, long story short, car died while backing up. It would crank but not start, I checked fuel pressure(at 40) and tried starting with starting fluid. So I went through the service manuals diagnostic check of the hei system. That turned up a bad ign module. Replaced ign module and the car started but runs rough, hesitation, misfire, backfire and gave a code 42. Went through service manuals check of code 42 and it pointed at bad ign module. Again replace ign module from another working car with same result. Once in awhile it will start and run fine till I move the gear selector (rpm drop) then the rough running resumes. Seems to run decent after 800-1000 rpm.

The tps is operating correctly, checked cir 424(by-pass) for opens, connections look good. My concerns are that the dis cap is only tightened on one side, old dis cap bolt broke. Also the old rotor has the little numbs on the inside top wore down(see pic), I replaced this with a new one with the same result from just a couple of startups.

Any thoughts are much appreciated.

 

The loose dizzy cap could be a problem. I had the same problem with my 86, the hold down screw broke off in the plate, had to yank the dizzy and drill the screw out.

Don't see any pics.

 

pic was too big, working on that. The thing that puzzles me is that if i get it above a certain rpm(800-100) it seems to run good, can hear a miss tho. Could that be a iac problem?

 

just checked iac and it is good, going to swap dis this weekend and see what happens.

 

Good call. The loose cap rubbing on the rotor tells me that its also affecting timing. Fix the dist and you should be fine. While you have the dist out, test the pick up coil. They are a common failure item.

 

pickup checked out fine(800ohms) but I will replace anyways while it is out.

 

loose cap was the problem, thanks for the input!

 

Cool. Thanks for posting your fix. Very helpful to others.

 

My cars throwing a code 42 after i went ahead and did and AC delete. I didnt notice that a couple weeks ago that it had a hard time starting and that it had been idling rough for awhile. Now my car idles like ****, and falls flat on its face. FP good as well as voltage to the injectors. You think it could be something like my iac, tps, or pick up coil. Im not very good with electronics so ill need alot of help on this.