MASS AIR FLOW SENSOR?

[paxton350]

ok, i recently moved to florida, and drove my z28. its been about 3 months but now the problems are starting... Lately theres been missing here and there, seemed like no biggy. however today i was headed to the beach and stopped for gas at the shell and put 93 in. i started her up and drove to the end of the parking lot and she died. the problem seems ignition related, thinking the msd box was fouled up, i reverted back to the stock igition in the parking lot and tried starting it, it started for about 2 seconds, idled at 1k then died. next thing i checked was my fuel pressure, i turned the key on i got an analog gauge it read 40#. then i checked for burnt spark plug wires or a bad connection from the coil to the optispark, everything was cool. checked all fuses everything was good. pulled off the mass airflow sensor and it is descreened and noticed one of the 3 diodes seemed dirty... would that cause this type of situation? The motor wouldnt seem to start until it sat for about 20 minutes in between cranks then started, idled for 3 seconds then died. the motor has 103k on it i replaced the optispark at 93 so i would really hate to accuse the optispark. Since i just moved i dont have my tools which is maing this that much more frustrating. Its also not throwing any codes...

thanks!

[Trans Am]

I think its either ignition coil or optispark, possibly icm too...it should still run even if the maf is bad, pcm just switches to speed density when maf is bad or unplugged

[Johnyd2]

yeah. the speed density takes over if the MAF is faulty..... once again ICM or coil.... IMO the opti would steadly go, and wouldnt just fail competely.... but i could be very wrong. The ignition system is very touchy especially with that stupid ass opti...

[Injuneer]

Dirt on the MAF sensor elements can cause a problem, although making it refuse to start and run would seem extreme. The little resistors aren't the problem, its the entire surface of the metal structure suspended in the middle of the housing. On the other hand, if the "dirt" on the resistor was in fact evidence that it had overheated and burned, it would cause failure.

If the MAF was dirty and reading incorrectly, the PCM would not default to speed-density. It only does that when there is no signal in OBD-I. And, with a blower, defaulting to speed-density might not be good enough to run the engine, since the VE tables would be rendered invalid by the blower.

You checked the fuel pressure with the key on/engine off. Did you also check it when the engine started and ran for the few seconds. Is it possible the gas station just had their tank filled, stirring up any settled dirt in the tank, and it coated your fuel filter? A plugged filter will not reduce the pressure much if the engine isn't running and using fuel, but it may be plugged enough to not pass enough fuel to keep the engine running. The station should have a filter on their pump to prevent the situation, but who knows?

[MDMike]

got codes?

Get the codes.
clean MAF with CRC MAF Cleaner.
SeaFoam.
Grd wires.

[paxton350]

It was the optispark... again lol autozone had a rebuilt one for 158 which was a pretty good deal, i think that the msd box burnt it out since i only replaced it 10k miles ago what do you guys think? Is an msd box crucial to a mildly blown car like mine? im thinking of just running off the stock ignition and selling it, its a 6a box...

[4THGEN Z]

I believe the same thing happened to my bone stock LT1....I had a 6A box and it smoked my opti to the point the contacts inside the opti were turning into carbon dust in approx 20K...pulled the MSD, changed the opti and coil and its been fine since. This was while my car was a daily driver.

Not sure on the need for an upgraded ignition in your blown application though.

[Injuneer]

I ran the MSD-6A box for 50K miles, and did not have a problem with the Opti from the MSD/burned contacts. While I did have a failure, it was from rust particles packed into the optical sensor.