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My 1991 Firebird 3,1L has been having issues ever since i did some work on the engine. It ran perfectly before i replaced anything.

I have changed;

Thermostat
Coil
Distributor Cap
Distributor Rotor
Spark Wires
Spark Plugs
Injector O-rings
Fuel rail line O-rings
Vaccum lines Upper intake plenum

I've read a few posts but havent seen anyone with the exact same problem.
Now what I'm thinking is either ECM or ICM has to be replaced.

I'd be happy to hear if anyone has any sugguestions or answers!
Feel free to ask for more information aswell.

 

What are you missing, spark, injector pulse , low fuel pressure?

 

What happens when you turn the key in the ignition? Do you get just a “click” or a bunch of “cranks” with the engine not turning over?

 

I hear the fuel pump priming, then when i turn the key the engine will crank and occasionally misfire, but no consistent combustion.
Also the exhaust smells of fuel after i crank the engine so i'm getting fuel, not sure if its enough fuel though

 

Hmm... a couple more questions:

1. Are you sure you didn't miss any vacuum lines? If there's a big vacuum leak somewhere the engine will turn over but won't sustain.
2. When you replaced the distributor cap and rotor, did you pull the dist out and do the work or replace in-place? If you pulled it out, the timing might be off when you reinstalled (might explain the misfires and bad smell)

 

Check for constant spark and fuel pressure bleed off.
sounds like your just shooting a parts cannon

 

Pretty sure all the vacuum lines are in and without a leak, did a vacuum test a few days back.

There was weak spark before i changed the ignition coil, haven't had a chance to test it due to being home sick.

 

Just checked now, and there's no constant spark, and or weak spark.
Fuel pressure seems alright.

Is this an ICM/ECM issue?
I have replaced alot of the ignition system so far.

 

Case closed; Car is running again!

I checked over the grounds on both cylinder heads, passanger side was not constant, after fixing/re-tightening the grounds i still didnt get a current through my spark plugs. It seems BOSCH PLATINUM sparkplugs with the pointy electrode have too high a gap for the voltage I'm outputting, I'd recommend steering clear of these.
Replaced them with a set of NGK BPR4FS-11 and got voltage through with ease


After replacing ICM and Pickup Coil in the distributor i had managed to put the distributor in 180* wrong, and this of course wouldn't show up as i adjusted the timing while cranking the engine.

So after trying to start it with ether i noticed that after a fireball to the face that the intake valves must have been open at the spark timing,
therefore i concluded that the timing was 180* off, switched the dist over and boom, it was running.

Now it ran great for about 30 miles or so (about 50kms) and i noticed i had a loss of power, there was an intermittent issue where i could keep my speed
but it was not possible to accelerate, so i stopped at a nearby gas station and popped the hood.

i could disconnect both the plugwires for cylinder 5&6 without it affecting the idle and vibration the engine was making.
I decided to park the car and search the forum. and bought a set of 17#lb injectors from southbay injectors (about 140$)

just popped them in and the car runs perfectly!


Summary;


ICM was bad
OEM Multec injectors were bad
Also steer away from the Rock Auto Recommended BOSCH PLATINUM with pointy electrode

Car runs good!