another opti story/problem.. i just put the msd unit on a friend's 95 LT1 Firebird Formula m6. the wires were replaced, as well as the coil. the plugs on the driver's side were replaced as we ran out of time to get to his pass side. (he took some days off and had to go back to work). my problem is this: the car starts up and runs great UNTIL... it warms up. then it kicks and sputters. one of his problems with the gm opti was that it wouldnt go to redline. it does now, so im sure it was his opti going bad. ive gone back over and checked that his wires arent touching metal or each other and that theyre snapped on the plugs and terminals. there is still a miss when it warms up. can anyone help me out with this one? thanks

 

Did you replace the plugs & plug wires when you replaced the opti? Also you should have replaced the coil and ignition module, being that you spent all that money already.

 

replaced half the plugs when we ran out of time. replaced coil, wires. and im gonna give him an extra module that i dont need, but will it help? it only misses when it gets up to temp (runs about 175)

 

It could be that the ECT, engine coolant temp sensor or the IAT, intake air temp sensor, have drifted and giving the PCM the wrong temp, but you should replace the other 4 plugs before going too far. Is the check engine lite lit or flashing?

 

check engine light is not on.. im leaning toward the plugs as well, can they act normal when cool and misfire when heated up?

 

It could happen, the fuel mixture is richer when the engine is cool and a little easier to ignite.

 

It sounds like your module. Mine done the same thing. You can take it off and take it AAP or Autozone they can test it.

 

ok. i have another ignition module i bought a while ago i never needed so i guess ill save him $90 there. i thought it could be that but i was leaning towards the plugs. i guess we'll try the module before tearing it apart to change the plugs.. thanks for the help everyone

 

ok.. replaced ignition module AND the pass side plugs. STILL missing when the engine warms up... ive gone back over everything and nothing seems to be wrong. wires are in the right places, distributor only goes on one way, plugs are in, boots are all connected, and so on.. is there anything else? the ses is not on.. Pete, you said something about the ECT or IAT? can you explain that a little for me? any other suggestions would help.. thanks

 

You really need a scan tool to look at this problem. Is the check engine lite lit or blinking?

These are 4 main sensors that the PCM uses to adjust spark timing and fuel mixture:
MAF (Mass air flow sensor) in the air intake duct. Try cleaning the inside gently as the wires are very delicate.
IAT (Intake air temp sensor) plugged into the air intake duct.
Use a scan tool to verify it reports the proper temp
ECT (engine coolant temp sensor) plugged into the water pump.
Use a scan tool to verify it is reporting the proper temp
O2 sensors (screwed into each exhaust manifold before the cat)
Use a scan tool to see that each side is sending a changing voltage to the PCM

Try unplugging the wires on the MAF & see if the car still misses, disregard the check engine lite at this time. This will force the PCM to work off the MAP sensor instead of the MAP

Check that the EGR valve is closed when the car is warmed up, it is only supposed to open when the car is cruising steadily at highway speed.

There is also an unlikely possibility that the fuel injection is having problems.
Try a couple of cans of injector cleaner into a full tank of gas. Check the fuel pressure and pressure regulator. Check resistance on injector coil.