car ('94 trans am lt-1)was running bad, took it to a garage, he replaced an injector, and all the plugs and it still has a miss, runs fine on the upper rpm range, but misses down low, took it to another garage as the first garage was too busy to do anymore on it and its my daily driver so i need it back! So anyways, they go and replace the opti spark, and wires and it still runs terrible! Mechanic calls me says they dont know what to do with it, it has new opti, new wires, new plugs, showing no codes!! wtf next????? any suggestions, besides smashing it into a concrete wall????? thanks, just real frustrated!!

 

fuel pump or fuel pressure regulator

 

I would start with a fuel pressure test

 

the coil?

 

mechanic checked the fuel pressure, he said it was between 35-40 psi ......now what?

 

hmm...the stock lt1 coils suck...mabye check that...mabye get the cat checked out, a clogged cat will make the car run like ***

 

Does it miss when cold (open loop)? If not check the IAT (inlet air temp sensor). They sometimes start putting out erratic signals when they get old. Cost about $10.00 at Autozone.


93Z M6 RED
B&M Shifter
egr, tbb, offroad pipe

 

car doesnt have cats.......mechanic said it sounded like the timing had been retarded (or maybe he was referring to himself)

 

well change the coil then

 

have you had a real scan done when the car is cold? Some sensors will not show after they have heated up from what I hear. I had the same problems and it was the opti but i also have a new coil now too. Have the MAF checked too. Do you know if anyone has ever messed with the computer? Also the shop that did the opti, we're they a very reputible place?

 

I had the same problem as you. You know what my problem was? I had burned an o2 sensor wire in the engine bay near my headers and it was touching the primary. ONly an occasional code came up so it threw me off. Spliced the wires and put clean wire where the burnt spot was and it runs perfect now. Now more bottom end stumble.

 

it was at the dealership last week, the manager runs his own repair business there after hours and he scanned it on there machine, no codes, ran this way before and after the fuel injector replacement, plugs, and wires........second place (where it is now) scanned it, replaced the opti, they do quite a few cars with opti, so i would think they would be as reputable as anyone would/could be!?!?!?

 

gonna call the mechanic in the morning, talk to him. by the way, the car isnt very far from you, its in Douglasville.




Thanks for all the replies from everyone!!!!!

 

Ehh, stock LT1 coil do not "suck." Check fuel filter and O2 sensors.

 

cool, i go to school in carrollton, like 25min. from douglasville...and at least in 95 the coils were crap, i dunno bout the other years