I have an 85 L-98 with 66000 miles on it. I just got the car back from having a new Centerforce clutch put in, and now the car runs like crap.

The first problem I noticed was pinging(detonation) on the way home from the shop. When I got home, I let the car idle for a short time, and noticed that it was hunting a little and was extremely rich at the muffs.

None of these probs existed prior to the new clutch. The car has no cat, Flowmasters, a Mid America chip, airfoil, and a K&N. Other than that, it is stock.

I put my buddies Snap On Diagnostic Scanner on it, and got the following codes. 13 open oxygen sensor circuit, 34 mass air flow sensor(signal voltage too low), and finally 43 electronic spark control.

I just installed a new oxygen sensor about a week before the new clutch, and had no codes at that time. Car was running great.

Could the detonation cause the code 43 as a knock signal? I am running 91 octane(the same as always with no detonation). If so, could the detonation be due to a bad MAF creating a lean condition which is also triggering the oxygen sensor code?

My feeling is that all of the probs are related due to the fact that I went from no codes, to all of a sudden having all of this garbage wrong. Under a partial load, there is no detonation and the car runs smooth. Just rich and kind of rough at idle, and detonation under a heavy load.

Thanks in advance for any and all suggestions.

I almost forgot. When i bought the car about a month ago, I put the scanner on it, and had a code 33 (MAF). I unplugged the ECM to clear the codes, replaced the o2 sensor just for routine maint. and then put the scanner back on numerous times and had no codes and the car ran great.

Once again thanks for any info.

Sturtzy

 

Make sure the O2 sensor and knock sensors are connected.

For the MAF check the MAF relay and look into the MAF just after you turn off the ignition to see if the burn off is working.

 

If you suspect any MAF problems you should try swapping out the 2 MAF relays 1st. These will cost you a total of $20 vs the $160 for a used MAF. These can be bought at NAPA.


[Modified by hngacurv, 7:12 AM 3/18/2003]

 

Check the ground wire that attaches to one of the bell housing bolts.Mine was loose and gave me some trouble after transmission work.