Help for cold start-up stumbling issue
03-15-2005, 09:31 AM
#1
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Help for cold start-up stumbling issue
89 951 w/ 40k miles:
On cold start the car will idle fine, then as I drive away there is a comprehensive stumbling and hesitation, low in the rev-range, almost no forward motion. It's as if there is a huge vacuum leak and engine mgmt is way confused. All gauges showing normal. No obvious disconnections under-hood.
This issue seems to work itself out as the car warms. When the issue is evident there will be a nice puff of black exhaust. When the the car "catches" it then runs perfectly.
Any thoughts; TPS? vacuum leaks?
This issue's symptoms was/is very similar to one that was traced 6 mos. ago to an arcing coil wire that confused the engine mgmt and caused very rough, underpowered idle and thick black exhaust. That issue obviously didn't go away as the car warmed.
Has anyone experienced this set of symptoms? Suggestions greatly appreciated!
On cold start the car will idle fine, then as I drive away there is a comprehensive stumbling and hesitation, low in the rev-range, almost no forward motion. It's as if there is a huge vacuum leak and engine mgmt is way confused. All gauges showing normal. No obvious disconnections under-hood.
This issue seems to work itself out as the car warms. When the issue is evident there will be a nice puff of black exhaust. When the the car "catches" it then runs perfectly.
Any thoughts; TPS? vacuum leaks?
This issue's symptoms was/is very similar to one that was traced 6 mos. ago to an arcing coil wire that confused the engine mgmt and caused very rough, underpowered idle and thick black exhaust. That issue obviously didn't go away as the car warmed.
Has anyone experienced this set of symptoms? Suggestions greatly appreciated!
03-15-2005, 11:13 AM
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03-15-2005, 01:09 PM
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Drive-by provocation guy
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I have that sometimes as well. Only on cold start up and/or cold climate. I just let it idle a bit before driving.
03-15-2005, 01:52 PM
#5
Just had all of this kind of stuff with mine....get yourself a vacuum leak tester and unplug lines at the valves, etc, fuel pressure regulator, dmaper, bypass valve, etc. and see if they all will hold a vacuum. All were shot on mine and am in the process of replacing, and my resident "experts" tell me this should sove all the problems.
I should have all the stuff in the mail today, and will try and get the work done this afternoon...if so I'll post pics, etc and tell you how it runs....but you're describing all the symptoms of my car, and I KNOW I was having a bad vacuum leak (among other things) and my gauges, etc didn't show anything.
I should have all the stuff in the mail today, and will try and get the work done this afternoon...if so I'll post pics, etc and tell you how it runs....but you're describing all the symptoms of my car, and I KNOW I was having a bad vacuum leak (among other things) and my gauges, etc didn't show anything.
03-15-2005, 04:55 PM
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Same problem.
I thought it was temp related so I tested DME temp sensor and AFM temp sensor.... all checked out close to spec. Hoses and vac lines are newer. Tested vacuum at fuel regulator and got 17.. not great, but not bad enough. New idle screw, and ICV.
Starting to wonder if my GURU chips are to blame? As I have heard of this symptom occurring on 18psi chips, Ive even had the DME resoldered. I guess I will replace the temp senor anyways and see.
Good luck and please post when you find the culprit...I will
I thought it was temp related so I tested DME temp sensor and AFM temp sensor.... all checked out close to spec. Hoses and vac lines are newer. Tested vacuum at fuel regulator and got 17.. not great, but not bad enough. New idle screw, and ICV.
Starting to wonder if my GURU chips are to blame? As I have heard of this symptom occurring on 18psi chips, Ive even had the DME resoldered. I guess I will replace the temp senor anyways and see.
Good luck and please post when you find the culprit...I will
