90 vert surging problem
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Pro
Joined: Jun 2004
Posts: 646
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From: Santee Ca
90 vert surging problem
My 90 vert has a problem with surging. It seems to be ok under load but as soon as I let off the gas to come to a stop or if I am coasting down a hill the car surges. Sometimes when I am coming to a stop it surges so badly it dies. Would a bad tps cause this?
Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
Has the minimum air screw on the TB been adjusted before? If it has the setting may be to low. The IAC could be out of range for the ecm to compensate.
Last edited by mseven; Feb 17, 2006 at 07:30 AM.
Thread Starter
Pro
Joined: Jun 2004
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From: Santee Ca
I have noticed that it only does it after the car is hot. It runs fine when the car is first started. I just checked the TPS and it is sitting at .60 volts. This is a non-adjustable TPS. Checked my fuel pressure again and I have 36 psi cold idle and it goes up to about 41 when I rev the motor up.
Drifting
Joined: Aug 2002
Posts: 1,774
Likes: 125
From: Birmingham AL
It definitely sounds like either a bad sensor or maybe a bad injector. If it runs fine before warm, then maybe oxygen sensor is bad? The motor runs on preset values until warm while in open loop. Then, at a certain temperature, it goes into closed loop and reads the sensors for values. Oxygen sensor comes to mind.
Or maybe the injectors are breaking down and show early warnings of failure when hot. Those L98 injectors are prone to failure. Unplug each one and the resistance should be around 16 or 17 ohms, or at least consitent with each other. I had a bad one on my '89 and I went crazy trying to figure that out. One of my injectors read like 3 ohms while the rest were at 17. It ran like crap at idle sometimes. While idling like crap, I unplugged that one injector and it ran smoothly- instantly like magic. New injectors fixed that problem.
Or maybe the injectors are breaking down and show early warnings of failure when hot. Those L98 injectors are prone to failure. Unplug each one and the resistance should be around 16 or 17 ohms, or at least consitent with each other. I had a bad one on my '89 and I went crazy trying to figure that out. One of my injectors read like 3 ohms while the rest were at 17. It ran like crap at idle sometimes. While idling like crap, I unplugged that one injector and it ran smoothly- instantly like magic. New injectors fixed that problem.
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Advanced
Joined: Dec 1999
Posts: 95
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From: Harrison Twp MI
I went through similiar issues with our 91. It also stalled and was through an egr code.
In the end it got a complete tune, new injectors, egr, iac clean and fuel pump
My surging was at idle.
Jeff
In the end it got a complete tune, new injectors, egr, iac clean and fuel pump
My surging was at idle.
Jeff
Advanced
Joined: Dec 2004
Posts: 66
Likes: 0
From: Glen Rock PA.
Had the same problem on my 85 spent lots of $ at 2 different shops,sensors, ecm, you name it, turned out to be a bad harm. bal. Bring # 1 up too TDC check and see where your pointer is at, good luck.
Last edited by 46snake; Feb 18, 2006 at 09:06 AM.
Racer
Joined: Mar 2004
Posts: 305
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From: Houston Texas
Originally Posted by Siveck
Unplug each one and the resistance should be around 16 or 17 ohms, or at least consitent with each other.
Originally Posted by Siveck
While idling like crap, I unplugged that one injector and it ran smoothly- instantly like magic.
FYI (to all) -
I sprayed a throttle body cleaner into the triangle hole in the front of the TB (getting it into the IAC). Still may have a long way to go, but it idled a little bit better. (It raised my idle speed to 1300 rpm, with my engine warmed up.) I guess it's time to adjust my idle speed, then the TPS again.
Either I am going to get the IAC cleaned up, or it will be replaced. If that isn't the problem, then at least, I will have eliminated it from the equation. It hasn't been replaced in the three years that I have had the car. So it wouldn't hurt to replace it.
Last edited by Moxxi; Feb 21, 2006 at 01:18 PM.