1991 Oldsmobile 88 High block learn values and maf sensor

Tiny
QUARTERMILECAMEL
  • MEMBER
  • 1991 OLDSMOBILE 88
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 14,000 MILES
Hi, I have a 1991 olds eighty eighty royale. Using the tech 1 scan tool, the block learn values are almost at or at 150 while freeway driving. Idleing, the block learn will go to 150 when it is in open loop mode, and 144 in closed loop mode. The factory service manual tells me to unplugg the maf sensor and if lean condition goes away, replace maf sensor. Well I unplugged the sensor while in closed loop mode, and the block learn went from 144 to 129. I have replaced all 6 injectors with summit racing accel brand injectors 19/lbs and hour. The engine runs better in open loop mode, closed loop mode at idle is not as smooth. Things I have tried. Tested fuel pressire. 35psi running, 43 when revved. Couldnt find any vacuum leaks, New o2 sensor, sprayed throttle body inside with b12 chemtool injector cleaner with mass air removed. Sprayed mass air flow cleaner at sensor with engine running. New spark plugs. New fuel filter, new fuel pressure regulator, spark plug color is white. Lean condition I guess.
Do you
have the same problem?
Yes
No
Tuesday, March 9th, 2010 AT 3:51 PM

5 Replies

Tiny
DOCFIXIT
  • EXPERT
Hi
Please post code numbers and was MAF replaced?
Let me know
Was this
answer
helpful?
Yes
No
Wednesday, March 10th, 2010 AT 9:41 AM
Tiny
QUARTERMILECAMEL
  • MEMBER
I dont have any engine codes. No the maf was not replaced. Thats what Im trying to do is decide if the maf needs replacing. The block learn tops out at 150 while driving. 150 is the limit of change. Spark plug color is white, not tan, another indicator so Im told the engine is lean.
Was this
answer
helpful?
Yes
No
Wednesday, March 10th, 2010 AT 2:27 PM
Tiny
DOCFIXIT
  • EXPERT
MAF is directly related to air fuel ratio so with good O2 and tempp sensor then MAF is suspect as culprit.
Was this
answer
helpful?
Yes
No
Wednesday, March 10th, 2010 AT 2:35 PM
Tiny
QUARTERMILECAMEL
  • MEMBER
So even with the scantool showing 5.0 gps, the maf still could be faulty? The factory service manual shows 4 to 7 gps is normal but if I unplug the maf, the block learn goes to 128. I wish someone could tell me how unplugging the maf is affecting blocklearn. Id really hate to drop almost 160 bucks on a maf, if that doesnt cure the lean condition
Was this
answer
helpful?
Yes
No
Wednesday, March 10th, 2010 AT 3:07 PM
Tiny
DOCFIXIT
  • EXPERT
OBDI not very reliable it was an educated guess to fix. The rule is if problem goes away when MAF unpluged then MAF faulty. When unpluged ECM relies on PROM to adjust A/F so block goes down and stable. MAF pluged ECM looks at O2, Temp, and amount of air entering engine if MAF is sending low air flow ECM will lean then O2 reports lean ECM richens thuis block goes up engine stays running lean.
Was this
answer
helpful?
Yes
No
Friday, March 12th, 2010 AT 2:47 PM

Please login or register to post a reply.

Recommended Guides