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Dr. Hamman
Dr. Hamman, Automotive Engineer
Category: Car
Satisfied Customers: 6286
Experience:  30 years experience, Repairing, building, & designing, automobiles.
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what causes the engine rpm to run extremely high at start ...

Resolved Question:

what causes the engine rpm to run extremely high at start up then die ,have checked TPS and repaired vacumn leaks. Also this occurs without any movement of throttle cable.
Submitted: 8 years ago.
Category: Car
Expert:  Dr. Hamman replied 8 years ago.
Hi, I will do my best to assist you. When you are finished please click on accept. I don't get paid unless you do. I don't know if you are a pro or a novice so we may have to fine tune the answer.

Lots of things could do this normally it will be a combination of trouble. One making it run fast and another shutting it down. Do you have a check engine light on. If you do the vehicle has stored some trouble codes in its onboard diagnostic system. These codes can lead you right to the problems many times. If you have them you should get the codes read. I would check the throttle cable and the IAM to find the fast run problem. For the problem of the engine shutting off, I would attach a fuel pressure gage and put an extra spark plug in one of the wires . Then I would watch the fuel pressure and the spark. One of the is probably going to quit when the engine dies. That will give you and idea of where to go. If you have any more questions I am here to help. Good luck, and Thanks for using Just Answer.

I hope this helps, 100% satisfaction is my goal. If the answer is not clear, please reply and I will assist you more. When you're satisfied, click on accept. I don't get paid unless you do. A bonus and positive feedback are always appreciated, good luck and Thanks.
Customer: replied 8 years ago.
There is no light on which only adds to the confusion.Let me elaborate more, this car belongs to a friend so I'm not totally up on whats going on. So   today I started it up & ran extremely rich I also heard vacumn leaks which I repaired drove the car around the block it ran fine shut it off & re started only to run at half throttle and begin to surge. Shut it down again checked all linkage & lines all ok. upon restart runs between extreemly rich & wants to max out no movement at the cables or butterfly. What can cause such climb in rpm without the throttle being opened?
Expert:  Dr. Hamman replied 8 years ago.
I bet you have a bad MAP sensor. There is a device that is meant to control the idle speed the IAM, it can rev the engine.
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