blue86z28

I have a 1986 Camaro Z28 5.0 TPI Auto Tranny


I have had a code 34 ever since i bought the car 3 months ago. I have tried EVERYTHING and still cannot figure this out.

PROBLEM--
When im accelerating, usually when its around half throttle, the car will cut out for a sec or two, then the power comes back where its supposed to be, relative to throttle position. Its feels exactly as if i had let off the gas pedal. The TPS is set at .54V. I unplugged the MAF and noticed NO change at all. I have all new relays and even tried swapping them. The mechanic said he hooked it up to his computer and said the MAF is working fine, it cant be since i can unplug it and notice no change. It didn't do this cutting out thing until now. But there was still the code 34, he says "It's probably just a glitch". I have a hypertech stage 3 chip, i can rule out the 86 recall for bugged prom. If anyone can figure out why its cutting out like this it would be very appreciated. I also notice that when i reset the codes the SES lights stays off and seems like everything is fine, but it will set the code 34 when it cuts out. Oh and also my engine does the idle search thing, it will go up and down up and down all day long. between like 800-1500.

Thanks.
Blue

rezinn

Ever tried a different sensor? Or the stock chip?

1991tealRSt-topGuy

sounds like an intermittent problem with one of the circuits dealing with the MAF

blue86z28

Yea the stock chip doesnt change anything with the 34

If we can't solve this by Friday im taking that one up to Autozone and getting a new one.

Well, i looked at the Frequency Film, the orange flat part... and i can barley see two VERY TINY holes in it...i know this can cause problems but can it cause the MAF to act they way it is?

Vader

Frequncy film? On a stock TPI MAF? The stock MAF is a hot wire, not a thick-film type. What MAF are you using? Did someone perhaps inadvertently install an FM MAF on the car?

Have you taken a MAF output voltage reading at idle?

blue86z28

I have a wells su-145 maf. the readings are good, according to book. but the cutting out is intermittent, although very common, i just dont know when it wants to do it. I have a theory the maf is not bad. i think this becuase the car runs the EXACT same with it plugged in and with it unplugged. I noticed when it was unplugged it got a code 33, and with it plugged in it got a 34. hope this info helps anyone figure it out. perhaps the tps it going bad? if we cant figure this out by about 3 weeks, bye bye tpi.

Thanks,
Blue

rezinn

See why that doesn't make any sense?

blue86z28

I have find something that should greatly aid in finding the problem. I hooked a fuel pressure gauge up to it and put it up to the windsheild, help it up so i could see with duct tape, anyways when the engine cuts out the pressure goes to about 15psi. Any other time the fuel pressure is where its supposed to be. So does this mean the regulator is bad, or the fuel pump is going south?

Vader

Blue,

It seems like you've found your problem. Rail pressure should never drop below 34 PSIG. Start by checking the filter (replacement). You can also perform a flow test of the pump. The fuel pump should be able to deliver at least one pint of fuel in 15 seconds to an open container. If not, you have a resitriction (filter) or the pump is failing. If the flow is at least 1 pint, you may have a regulator problem.

blue86z28

I will investigate the regulator and pump more, but after talking to b4ctom1 for a while we decided to replace the maf for the code 34, and the cutting out may be because my gas gauge is broke and i dont know how much gas i had in there, and there is very little, so a pretty much empty gas tank can stall like that cause the gas is sloshing right?

Vader

Replacing without diagnosing? Could be an expensive habit. It may be a good idea to get a mV reading from the MAF at idle to see what the output is like. Not much would be more frustrating than installing a new MAF to find out that you had a wiring problem.

chymos

A friend of mine had a problem with his 87 IROC 5.7 TPI......IIRC, it was a code 34....idle bouncing from 600-650......he replaced the MAF *and* the ECU with brand new ones. then he took it to a shop and found out the timing chain had slipped a tooth. don't just go out and buy parts w/o knowing exactly what's going on.

From the sound of it, I'd say it was related to your fuel flow

blue86z28

I am having a fuel flow problem, but would that cause 34?

rezinn

34 is caused by an improper MAF reading. That can be due to the sensor being dirty, dead, bad wiring or relay, or a vacuum leak.