rough idle - 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 01-27-2010, 07:37 PM   #1
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Default rough idle

ok, 1997 Bonneville SSE

I'll start it up, it will idle rough for 5 to 30 seconds, rev up to around 2500rpm come back to idle and be fine. It has done this since I bought it 6 months ago. I knew about it when I bought it and it never really bothered me until now. What could cause this? It has new plugs and wires as of about 3000 miles ago. (it has 154,000 on it) I really don't wanna go to the dealership and be charged $100 for them to tell me whats wrong.

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I wanna change my fuel filter, O2 Sensors, and clean my MAF but my dad just wants to go to the dealer because I don't know whats wrong with it.
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Old 01-27-2010, 07:41 PM   #2
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Put some injector cleaner in the tank, check for vacuum leaks, check the PCV valve, check the EGR valve, check for a clogged air filter.
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Old 01-27-2010, 07:41 PM   #3
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That sounds wierd. I haven't heard of something like this before. It will be nice to know whats causing it.
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Old 01-27-2010, 07:56 PM   #4
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Quote:
Originally Posted by Danthurs View Post
Put some injector cleaner in the tank, check for vacuum leaks, check the PCV valve, check the EGR valve, check for a clogged air filter.
injector cleaner was done recently, air filter is damn near new, we checked for vacuum leaks the first week of owning the car, and how do i check the other 2?
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Old 01-27-2010, 08:07 PM   #5
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Remove the PCV valve and shake it. If it rattles it'* good. Remove the EGR valve and inspect it. Did you check for vacuum leaks on the EGR tube?
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Old 01-27-2010, 08:09 PM   #6
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im not sure what we did. we checked close to 6 months ago. where are the egr and pcv valves located?

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Old 01-27-2010, 08:10 PM   #7
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The only other thing could be the throttle position sensor.
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Old 01-27-2010, 08:13 PM   #8
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i unplugged that earlier today when it was idling ok and i didnt notice a change. should i unplug it and start it up?
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Old 01-27-2010, 08:16 PM   #9
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No, leave the TPS plugged in. Try unplugging the MAF and start it. It will run rough for a bit and then smooth out. If the problem goes away then your MAF is bad. If there'* no change, the MAF is good.
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Old 01-27-2010, 08:16 PM   #10
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Wait, you unplugged it while it was idling and no change in idle? It'* not showing an engine light is it?
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egr valve, maf, rough idle, tps, vacuum leak

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