RPM Issue (Again) - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 10-28-2005, 12:32 PM   #1
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Default RPM Issue (Again)

Hey guys,

For the last 3 or 4 weeks, I've had a recurring RPM issue. Usually the problem resolves itself when I leave the car sitting overnight, however this time around the condition hasn't cleared up.

Almost like the car is hitting the idle RPM limiter while the car is in motion, if I floor the car, or even if I just need extra acceleration to pass someone or maintain speed on a hill, whenever the car gets near 4000 RPMS it literally fights against itself as the engine backs off the RPMS to about 3600-3700, then accelerats again, et cetera. This has occured 4 times now, all after I've taken a trip in excess of 50 miles. Also, I've noticed that this starts happening when the car gets low on gas.

The car really acts weird whenever I get low on gas, so I've been thinking its time to replace the fuel pump. However, I'm not really interested in frivelously spending so I'm looking for other advice. Up to this point, I have replaced (at NEBF): Spark plugs and wires, air intake, oxygen sensor, throttle body gasket, completely cleaned throttle body, cleaned MAF sensor, tstat and both gaskets. Before NEBF, I also replaced the throttle position sensor, and the PCV valve.

I'm really at a loss here as the car isn't throwing any codes either. Thoughts?
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Old 10-28-2005, 12:34 PM   #2
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The 92'* ? were known for loose baffles and problems. When we are together this weekend I'll make sure and have fuel pressure gauge on hand. 7 feet of hose to watch while driving.
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Old 10-28-2005, 12:58 PM   #3
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I'd say either fuel pressure or an exahust system back pressure test...

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Old 10-28-2005, 01:32 PM   #4
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Quote:
Originally Posted by jr's3800
I'd say either fuel pressure or an exahust system back pressure test...
What exactly does the exhaust system test involve?
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Old 10-28-2005, 02:13 PM   #5
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Quote:
Originally Posted by Mortehl
Quote:
Originally Posted by jr's3800
I'd say either fuel pressure or an exahust system back pressure test...
What exactly does the exhaust system test involve?
Unscrew the O2, screw in the adapter for the Exahust system pressure tester, and test the back pressure at idle, 2000 rpms and the like... I wish I had one of those testers... I better not speak too soon... The last time I did I went a bought a fuel pressure tester....LMAO

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Old 10-28-2005, 02:14 PM   #6
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Quote:
Originally Posted by jr's3800
Quote:
Originally Posted by Mortehl
Quote:
Originally Posted by jr's3800
I'd say either fuel pressure or an exahust system back pressure test...
What exactly does the exhaust system test involve?
Unscrew the O2, screw in the adapter for the Exahust system pressure tester, and test the back pressure at idle, 2000 rpms and the like... I wish I had one of those testers... I better not speak too soon... The last time I did I went a bought a fuel pressure tester....LMAO
Exhaust pressure tester huh? I don't have one of those. I suppose as long as the directions don't include putting your lips on the tailpipe and blowing...lol
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Old 10-28-2005, 02:42 PM   #7
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A nasty strainer sock on a fuel pump can produce the same effect as a lack of baffles. Just something to keep in mind. Your FP tester should show if this is a problem in a turn.
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