I thought the ECM ran on base tables until it warmed up and ran on the sensors... !!!

I can start the car on cold mornings, and every once in a while BAM! CEL and code 34... car will run like ***... all on a cold motor...

WTF is up with that? My car hasn't been warm enough to lock up the convertor for months... this can't be right, but it will still produce a code 34 after long WOT runs and at start up... it's really wierd...

Everything else seems to be fine ECM wise, unless you count the part about the car running like crap and getting <15 MPG.. but I think thats my exhaust leak...

Also related to code 34... why is it so intermittent and wacky? One second it's fine, the next.. bam... ***... Huh?! Where is the relay, maybe I'll replace it...

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If it is shot, about how much are new ones? Should I get a new prom too?

 

On my 1985, my ecm was shot when the fan stayed on constantly.
Later shown to me as a melted something on the circuit board.
I got a V-8 one, I think from a Corvette for $17.
I swapped the V-6 prom into it & primo operating conditons ever since.
This is my situation.
Serioulsy just could be a lousy MAF & bad/worn fuel pump combined. TC is ?
Parts do wear out, Inconvient when they all fail at same time.

 

Okay I never heard of this before. Are GM's computers the same? As long as you have the orignal V-6 prom you can use any older styled computer to run your engine. Or was this for another vehicle.

 

ON CERTAIN (you feel lucky) CARS/MODEL/ETC. the computers swap, proms remain with car.

YOU HAVE TO FIND OUT FROM THE HOLLANDER BOOK, which ones can be safely swapped.

I got lucky.
This guy at Corvette Forum (I used to hang out there) had no need for it.
It was from his Corvette, I THINK!
Could been a Camaro also. Really not sure.
All I know is find the Hollander Book and ask for common ECM usage for your car model.

 

The ECM recieves info from the MAF sensor at all times. Dunno what your problem is, but GENERALLY speaking, an intermittent problem is USUALLY an electrical problem and not the sensor itself.

Check the tabs inside the connector and see if any have a large gap that could cause a bad connection. Check for damaged wires. Also, with the key ON, you should have a 5 volt reading at the MAF connector.

EDIT: Oh yeah, make sure your intake duct clamps are tight. On MAF equipped cars, a loose clamp can cause a metered air leak and it will screw with the ECM.

 

a car at school had just the opposite problem

the ECM wouldn't give ground to the fan relay, thus it would NEVER come on...........

as for ECM interchangebility........certain ECMS are exchangabe between cars.......you'll need the correct PROM for your car though


xeno- what did you mean by the base tables??
is this an open/closed loop kinda thing?

 

K, for the guy who said he knew a guy at school to whom the ECM wouldent give the ground for the fan to come on , i think i have the same problem, how did he solve it ???

 

new ECM

 

By "base tables" I ment the info the car runs off of when it's in open loop. CaliCamaro answer that though when he said the ECM recieves data from the MAF at all times.

I doubt this is a wire problem, and I also doubt this is a sensor thing... Take tonight for example... I'm leaving my g/f's house... get in the car, crank, it starts, right as the RPM's start coming down ... CEL comes on... I've done this rutine before so I shut the car off, and then crank again and it starts, RPM's come down fine no problems... If the sensor was bad how come it's so completely random like that?

both sensors I've had on this car I could tap and beat the crap out of without the engine stumbling at all... I've jiggled wires, slammed wires, f'ed with the relay, traced the wires around and shook that stuff... doesn't stumble... it's just random.

I'm not ruling anything out. It's possible both sensors are shot (one junkyard one original).

Any other thoughts?