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trekvana
User
Dec 2, 2011, 10:00 AM
Post #1 of 6
(1785 views)
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Weird engine RPM issues
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I have an Automatic 98 2.2L GMC Sonoma 2WD with 160,000 miles that exhibits some weird rpm issues. When I have the car in park, and I rev up the engine to 3500rpm the engine rpms starts pulsating up and down from 3500rpm to 4000rpm and back (you can hear the engine rev up so its not a tachometer issue). Also as the car goes up to the 4000rpm my speedometer reads 2-3mph (although the car is in park!) and then back down to 0mph at 3500rpm and then back up to 2-3mph at 4000rpm, etc.. What is going on!?
Just installed New OEM plugs and wires. Ignition packs check out as well.
(This post was edited by trekvana on Dec 2, 2011, 10:05 AM)
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Discretesignals
Ultimate Carjunky
/ Moderator
Dec 2, 2011, 12:17 PM
Post #2 of 6
(1764 views)
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Re: Weird engine RPM issues
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Your hitting the rev limiter. The vehicle is operating as intended.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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trekvana
User
Dec 2, 2011, 12:24 PM
Post #3 of 6
(1757 views)
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Re: Weird engine RPM issues
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I'm a little unfamiliar with the concept of the rev limiter. So pretty much 3500rpm is the limit for this engine in park? Also would a limiter affect the speedometer as well?
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 2, 2011, 1:23 PM
Post #4 of 6
(1752 views)
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Re: Weird engine RPM issues
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The manufacturer is trying to prevent you from blowing uop your motor even though you are trying like hell.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
Ultimate Carjunky
/ Moderator
Dec 2, 2011, 4:20 PM
Post #5 of 6
(1743 views)
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Re: Weird engine RPM issues
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Not exactly sure on why the speedo would show mileage when you hit the rev limiter. I have seen it do that on quite a few GM automobiles. Just a theory, but the speedometer is an air core gauge and may be getting electromagnet induction from the RPM gauge. Not something to be concerned with honestly.
The manufacture added some coding into the PCM programming to limit the engine speed, when the transmission is in park or neutral, by cutting off fuel injectors. It's there to protect the engine from excessive engine speed. Excessive engine speed can cause catastrophic engine damage.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Dec 2, 2011, 4:50 PM)
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trekvana
User
Dec 2, 2011, 5:53 PM
Post #6 of 6
(1726 views)
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Re: Weird engine RPM issues
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awesome. thanks guys!
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