Sorry this is a little bit OT...but hopefully the discussion will be helpful to everyone.

Tonight I filled up my other Chevy (the IROC-Z, not the Corvette) at a local BP station with 93 octane Amoco Ultimate. Proceeded to run some errands around town, went to my gf's house, etc. All in all, about 30 miles worth of driving. I get ready to leave her house, the Camaro fires up fine, drives A-OK for a few miles, then all hell breaks loose. Car falters on acceleration on the interstate, stalls, and I coast off to the shoulder. Bummer. No engine light yet. I turn the ignition off, try to start it again. It starts, but is running very rough and idling at 5-600 RPM. It stalls again within a few seconds. I start it again, get out to look under the hood. Runs very rough still, engine tries to stall, I try to work the throttle to keep it running, then it backfires, dies, and throws code 34 (MAF voltage low). I get it towed home. Oil pressure and coolant temp were OK all along.

I have not tinkered with it yet, but ostensibly it SEEMS like a bad fuel pump to me. However, I am wondering if it could be water in the fuel from our local BP station. I have never had the misfortune of getting water in my fuel before, so I don't know if it is conceivable that I could drive 30+ miles on that tank of fuel before experiencing a problem if there is indeed water in the fuel. Any experiences here to suggest that I should be looking at bad gas as a potential cause?

Thanks for the help

 

If the ignition system is intact, the easy way to resolve the fuel pump/filter/pressure question is to test fuel pressure.

Water can be found in fuel for many reasons, and is present in the tanks at most stations. I'd more suspect a filter problem from picking up some contaminated fuel instead of water, but it's possible.

 

Sounds MAF related, and the code just confirms it. I'm not too familiar on the '85 MAF set up, but you may want to search a bit on the piggyback module the '85 uses. I really don't remember if it uses the same relay set up as the 86-up.

 

Water in the gas will cause problems imediatly. Doesnt sound like that is your problem. I start with the maf and go from there. The ecm didnt throw you that code for no reason.

 

That's why I hesitated. The '85 Delco FM MAF setup is a little odd, very slow to react, not quite as refined as the later FM MAFs, and seems to be a lot more tolerant of errors. If the ECM detected a running engine and there was any sort of hesitation and/or backfire, the MAF may have briefly reported a low flow. I'd clear the ECM and try starting again, If you can get the engine to run at all without immediately generating an MAF error, I wouldn't be so quick to condemn the MAF.

No, the FM MAFs use a different power, signal, and burnoff scheme entirely. And I thought the '86 in my garage was a bastard-child of the breed, The '85 is just a little more peculiar.

 

THanks for the fast replies gentlemen.

The car has no fuel pressure today. I can hear the pump run with the key on, but it builds virtually no pressure at the rail. Thus, I am led to believe that either the filter is totally plugged (for all I know, it could be original with 123K miles on the car) or the pump is DOA. I will investigate the filter first and work from there until I can get fuel pressure.

Is it possible that backfiring could damage the MAF permanently? I understand why it would cause code 34, but will the sensor now require replacement (cosmetically it looks new inside--all three filaments intact).

Thanks,

 

Now you know why they put two screens in that thing.
Swap out your filter (carefully) and test pressure again.