I have 88 gta with a miss that started a week ago, miss is on cyl 4 &6 . I have changed plugs , wires , cap, rotor, pickup coil, injectors ,control mod, spark control mod & still have miss. did compression test 180lb.-192lbs. on all cylinders. checked valves , checked grounds on head & checked wires between ecm & control mod. timing is at 10 deg . car ran great monday morning & went to **** that afternoon. Help please

 

Suspect a leaking intake gasket.

 

I replaced intake gaskets when i did the injector swap , they came in the kit so i figured what the heck. I also got a check engine light when this started . code 42 thanks

 

I was going to guess pickupo coil and reluctor, but you've apparently already checked that. Did you happen to notice and cracks in the reluctor ring above the pickup coil?

 

I did not notice any cracks, but i did not look that close. I did however see a very small chip in the magnet. Iwill pull dist and look for cracks . thanks

 

OOO! OOO! OOO!

I think you may have found at least part of the problem. If you can connect an oscilloscope and watch the actual pickup coil output (input to the HEI module trigger circuit) you may see why this is a problem.

 

Vader that was it. I pulled dist to try another one . put it in and NO MISS. i looked at old dist pulled rotor off and plate under rotor has two cracks . thanks for all your help now i can stop pulling my hair out.

 

So, it's the old "hairline crack in the reluctor" ploy, eh? Thought you could sneak that one past us, did you? You silly, silly person.

Those sunnamiches can be a real pain to diagnose. The only reason I mentioned it is becasue I stiull have teeth marks in my posterior from that kind of thing. Glad you found it.

The up-side is that now your ignition system should be 100% and ready to fly. You also know the compression is good, you have no vacuum leaks, and all the sensors are operating. That's gotta be worth something.

 

The spark problem has returned, I have now tried dist, and ecm from friends car. no change, plus his car runs fine with my parts. help please before i pull all my hair out .

 

After pulling my hair out trying to figure out why my car starting missing again, my girlfriend admits to spraying it when racing a mustang on the expressway . Never mind that the timing was not set for nos. . I have now pulled both heads , and found blown head gasket and three plugs that are fryed. I got it all back togeather sat morning at about 2:30 am so i could drive it to work a 6:00AM . I have now added another switch to arm the nos. so she can't use it . but i will sa y i runs better than it has in awile . thanks for everyones help