Engine revving on its own? - GM Forum - Buick, Cadillac, 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.

Engine revving on its own?

Reply

 
 
 
Old 05-09-2010, 04:49 AM
  #1  
Senior Member
Posts like a Turbo
Thread Starter
 
Join Date: Oct 2009
Posts: 291
Thanks: 0
Thanked 0 Times in 0 Posts
jdaniels is on a distinguished road
Default Engine revving on its own?

Tonight, when I started her up, (97 SSE), the engine revved and the rpms shot up to 3000 for about 2 or 3 seconds. Happened 2/3 times I started it. No drivability problems and no check engine light.

Throttle position sensor? Or what? Haven't done anything to it recently.
jdaniels is offline  
Reply With Quote
Old 05-09-2010, 09:08 AM
  #2  
Senior Administrator



Certified Car Nut
 
Join Date: Jul 2003
Location: Dark Side, NY
Posts: 16,308
Thanked 1,249 Times in 938 Posts
Mike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond repute
Default

IAC stuck open more than it should be???
__________________
2002 S10 V8
Please do NOT PM technical questions
Please do not reply to posts older than 6 months
Mike is offline  
Reply With Quote
Old 05-09-2010, 10:29 AM
  #3  
Senior Member
Posts like a Supercharger
 
Mad_Coachman's Avatar
 
Join Date: Dec 2003
Location: Baldwin,New York
Posts: 185
Thanked 23 Times in 16 Posts
Mad_Coachman will become famous soon enoughMad_Coachman will become famous soon enough
Default

Originally Posted by jdaniels View Post
Tonight, when I started her up, (97 SSE), the engine revved and the rpms shot up to 3000 for about 2 or 3 seconds. Happened 2/3 times I started it. No drivability problems and no check engine light.

Throttle position sensor? Or what? Haven't done anything to it recently.
The same thing happens with my 97 SE.I'm going to replace the IAC today and check my fuel pressure due to the fact that I've been getting P0171 codes and I'm suspecting a weak fuel pump.I'll let you know if the IAC fixes the revving.
Mad_Coachman is offline  
Reply With Quote
Old 05-09-2010, 11:20 AM
  #4  
Retired Senior Admin

Expert Gearhead
 
Danthurs's Avatar
 
Join Date: May 2006
Location: Sheboygan Wisconsin
Posts: 29,661
Thanks: 0
Thanked 20 Times in 16 Posts
Danthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to all
Default

Surging RPM can be a vacuum leak, stuck IAC, dirty throttle body. Check each of those and I'm sure the problem will be found.
Danthurs is offline  
Reply With Quote
Old 05-09-2010, 11:21 AM
  #5  
Senior Administrator



Certified Car Nut
 
Join Date: Jul 2003
Location: Dark Side, NY
Posts: 16,308
Thanked 1,249 Times in 938 Posts
Mike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond repute
Default

Try cleaning the IAC pintle with carb & choke cleaner first. The P0171 could be a dirty MAF sensor, or a vac leak somewhere.
https://www.gmforum.com/showthread.p...ighlight=p0171
__________________
2002 S10 V8
Please do NOT PM technical questions
Please do not reply to posts older than 6 months
Mike is offline  
Reply With Quote
Old 05-09-2010, 11:29 AM
  #6  
Retired Senior Admin

Expert Gearhead
 
Danthurs's Avatar
 
Join Date: May 2006
Location: Sheboygan Wisconsin
Posts: 29,661
Thanks: 0
Thanked 20 Times in 16 Posts
Danthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to all
Default

I just added another check to the P0171 code, check for loose MAF and IAC sensors. Both are open to the vacuum, and the IAC has a O ring that should be checked.
Danthurs is offline  
Reply With Quote
Old 05-12-2010, 01:55 AM
  #7  
Senior Member
Posts like a Turbo
Thread Starter
 
Join Date: Oct 2009
Posts: 291
Thanks: 0
Thanked 0 Times in 0 Posts
jdaniels is on a distinguished road
Default

Got an engine light tonight, will run it tomorrow and see what'* up.
Where is the IAC?
jdaniels is offline  
Reply With Quote
Old 05-12-2010, 07:05 AM
  #8  
Senior Administrator



Certified Car Nut
 
Join Date: Jul 2003
Location: Dark Side, NY
Posts: 16,308
Thanked 1,249 Times in 938 Posts
Mike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond repute
Default

Here is your IAC. Just to the left of your MAF sensor.


__________________
2002 S10 V8
Please do NOT PM technical questions
Please do not reply to posts older than 6 months
Mike is offline  
Reply With Quote
Old 05-12-2010, 11:15 AM
  #9  
Senior Member
Posts like a Turbo
Thread Starter
 
Join Date: Oct 2009
Posts: 291
Thanks: 0
Thanked 0 Times in 0 Posts
jdaniels is on a distinguished road
Default

This is going to be the most oblivious and ridiculous post ever, I know, and I haven't gone out and tried, so it may very well be easy..

But I'm assuming all of this (MAF, IAC) requires me to take the engine cover off, correct? (The grey plastic piece labelled 3800) How would I do this?
jdaniels is offline  
Reply With Quote
Old 05-12-2010, 11:26 AM
  #10  
Member
Posts like a V-Tak
 
ChibiBlackSheep's Avatar
 
Join Date: May 2010
Location: Philadelphia, PA
Posts: 81
Thanks: 0
Thanked 0 Times in 0 Posts
ChibiBlackSheep is on a distinguished road
Default

Originally Posted by jdaniels View Post
This is going to be the most oblivious and ridiculous post ever, I know, and I haven't gone out and tried, so it may very well be easy..

But I'm assuming all of this (MAF, IAC) requires me to take the engine cover off, correct? (The grey plastic piece labelled 3800) How would I do this?
Remove oil cap, pull upwards.
ChibiBlackSheep is offline  
Reply With Quote

Thread Tools
Search this Thread
Quick Reply: Engine revving on its own?


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.