Bought a 85 Iroc Z28, 305, V8, TPI about a month ago. The guy we bought it from thought it had some bad cylinders. Come to find out, the moron mechanic that had changed out the spark plugs didn't custom cut the wires and 2 were laying on the exhaust manifold and melted . Well, we custom cut a new set and saw that it was running too rich on spark plugs 1, 3, 5 & 7 because of the deposits on them. Did some minor work and was able to fix all the codes its was throwing out. Now, the car will run fine for about 30 minutes before the engine light coming on (code 34 - MAF sensor?). Then it starts to run too rich again (blowing smoke). Does anyone know which MAF sensors are compatible with my car or how to skirt around the problem? I'd like to get one from the scrap yard verses $190 from the auto parts store. Any suggestions will be greatly appreciated!!

 

i thought a v8 didnt have a MAF???

good luck with it cuz ive replaced one every year,brand names,off names & everything in between...royal PITA gets old after a while...anyhow im looking into my problem but good luck with yours

 

I don't know much about the 85 MAF system, but I know enough to avoid it. People tend to forego replacing the sensor(it costs more than upgrading to a better system->speed density). If that's possible for you, I'd advise doing it. You'll save yourself a lot of headaches ditching the MAF system. If you had an 86+ MAF car, you could probably just replace the relays and clean the sensor to get it to work better.

As far as v8s not having a MAF, where did you hear that bad piece of info?

 

If you keep getting a code 34 the pervious owner may not have had the service bulliten for the prom chip done. There was a service bulliten on the 85 prom chips for a false code 34 (among other problems), the prom cost $44 from GM when I did mine...13 years ago, a lot cheaper than a MAF sensor which runs about $150 for a remanufactured one.

 

Before doing much else, I would try changing the MAF power relay. It's cheap ($12), and if it doesn't fix it, I guarantee that you'll be needing that relay soon anyway.

if it doesn't fix it, then by all means try the new PROM. If that doesn't do it, then it might be time to get a new MAF. The 85 TPI cars have the distinction of having a specific MAF that is different from the 86-89 units, which will not work on an 85 car. Fortunately, it seems that the 85 MAF has a thicker wire element, and seems much more durable than the 86-89 units. Wells sells the SU 144 for the 85 cars. I don't know if it uses the same thick-film resistor setup as the SU 145, or if it uses the conventional heated wire, but in either case, it's the cheapest one out there and comes with a lifetime warranty.

 

Oh... morley, do you know specifically what GM changed in the PROM to eliminate the code 34? It's pretty obvious in the programming to see how to desensitize the car for a code 33, but I can't see how to modify the chip for the code 34 sensitivity.

 

ive been telling people when they ask me about my car how much i hate that MAF sensor & how much trouble ive had with it & they told me that whenever i do get my 350 i wont have any more problems with the MAF sensor cuz they dont have one

is it only the 305 v8 that has a MAF sensor & the 350 v8 doenst have one?

 

All TPI engines 305/350 have the Maf Sensor except the very later models went to a Speed Density system. Depends on now your car was set up Maf or SD.

 

more detailed answer:

85-89 TPI cars had the MAF. The 85 MAF is unique to that year, but the 86-89 MAFs are all the same. 90-92 used speed density, which didn't have a MAF.

 

well i had the car looked into about the MAF > SD & the guy told me it would probably be close $1000 or more just to have that update done....one day i will have the 350 so i figure ill just keep that money for the new engine instead of having that update done

 

It had to do with commanded idle speed and MAF voltage thresholds, not real sure what else they mat have tweaked for the MAF. Also this updated prom fixed the TCC lock/unlock stuttering and cold drive away problems.

 

Thanks. I'll look at some of that stuff next time I'm digging through some BINs.

 

Well, thanks for all the advice everyone! :hail: I've passed all this info over to dad, so hopefully we can get her running correctly!! I'll keep everyone posted as to how it goes. Thanks again!!!