Mechanics

DID GM PUT RPM LIMITER IN ECM TO PREVENT TOO MUCH ENGINE RPM WHILE IN PARK?

1995 Oldsmobile 88 • 189,000 miles

95 olds 88 royale has surging problems while driving with diminished response to throttle. I asked similar question just recently but now have another question. I have tried 2 different maf sensors with the same results. The original and a (reman like new) both make the rpm surge from approx. 5000 rpm back down to approx. 1500 rpm constantly up and down as long as I dare hold the throttle down. If I let up on the throttle to about 2/3 the engine levels out and runs smooth. Did Gm put a rev limiter in the ECM control module to prevent the rpm from going too high while in Park? My other GM vehicles do not react like this car does. I have changed almot everything except ECM. What about having the ECM reflashed?
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Herb1948
September 6, 2012.



A rev limiter will not affect it while driving down the road. Do you have any codes in the computer?

Saturntech9
Sep 6, 2012.
There are no codes. Have had it checked with GM Tech II and everything checks OK. All sensors, injectors, fuel pressure and timing issues appear to be ok. While driving down the road I have a slight surging and thought that maybe this surging up and down while in park could somehow be causing the driving issue. Throttle body has been cleaned; 2 different maf but not a brand new one; monitored fuel pressure with gauge on windshield while driving; new IAC and TPS. Voltage and grounds have been checked

Tiny
Herb1948
Sep 6, 2012.
Have you performed a back pressure test on the exhaust?To see if you have a plugged cat?

Saturntech9
Sep 6, 2012.
There is less than 1 psi back pressure. I would buy new MAF if I thought it would solve the surging problem. I have freq. Tested the MAF but not at high rpm when the engine is surging up and down as it would just send a surging freq. Back to the ECM.

Tiny
Herb1948
Sep 7, 2012.