Today I took my car out for a drive and when I got about 10 mile away the SES light came on so I checked it and got a code 34. Also When the car is warmed up it will idle at and 600-650 while in gear, but i just would stay at one idle speed, it is constatly going up and down by about 200 RPM's. I just read in another thread that it might be my MAF burn off relay or MAF power relay would one of these mabye help. I just bought a new MAF about 9 months ago. I have already made sure all connections where clean. But do not have a voltmeter to check my TPS.

Please give me some idea's.

 

Is this a 1985 TPI system? The 85's had a problem in the PROM chip that caused a "false code 34" and numerous other problems. They needed to have the PROM replaced, about $50 from GM.

 

Yes, this is an original 85 TPI, all of the relays are stock though except for fuel pump relay. So should I try and replace the relays first?

Also, where is the MAF relays on an 85 T/A? (pic)

 

There are no MAF power or Burn Off relays on the 85 TPI's, both of those functions were handled by the MAS module. It is a small silver box piggybacked on the ECM case and costs $700 new from GM.
If you have time, drop your ECM and open the PROM cover. There will be a silver sticker on the PROM, what letters are on it? (HKM, HKL, etc).

 

Ok, thanks I will open it up tommorow and post results. Also how common is this problem and why did it happen now? Could it actually be a bad MAF?

 

This problem happened on ALL 85 TPI's. The factory that was burning the chips let the UV window on them get exposed to light before the stickers were put on to cover the window. What is happening is a very slow erasure of the chip, slowly corrupting the data on it. Also there were several programming "errors" in the bin for those chips (TCC lock up problems, cold drive off..etc)

 

Ok, I see, so even if my MAF really is bad then I still need to replace the prom.

Thanks

 

OK guys I fixed the code 34 with a new chip from GM but now when I start it up it wants to rev to about 1800 for about 5 sec then it will idle down to about 900-1000 And the PRM's just won't stay in one one spot when it is cold, is that normal?

I also got a new TPS and set it .55 volts. But I never could set the IAC like the tech article says to. (I could never get it down to 400 RPM's with the IAC unpluged)

 

When my engine is cold in the mornings it will idle between 1,000 and 1,200rpm. After about 5 minutes or so it'll drop down to 600rpm out of gear, and about 500rpm in gear.