High idle and start problems

Tiny
DAVRIN COETZER
  • MEMBER
  • 1996 VOLKSWAGEN VANAGON
  • 2.5L
  • 5 CYL
  • 2WD
  • MANUAL
  • 185,000 MILES
Hello. My Micro-bus 2.5i starts but idles at 3,000 rpm's constantly and I cannot get it to come down. Then if I turn it off or it stalls it will not start again, but if it stands for about five minutes it starts right up again and idles at 3,000 rpm's again. I have checked all the vacuum pipes and found that one was off. After I attached it again the idling came down but fluctuates terribly. Please help me!
Tuesday, February 5th, 2019 AT 2:05 AM

3 Replies

Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello,

This still sounds to me like you have a vacuum leak. Check that all hoses are not cracked and all of them are hooked up properly. Here is a link that you might find helpful:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Thanks,
Alex,
2CarPros
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Tuesday, February 5th, 2019 AT 7:19 PM
Tiny
DAVRIN COETZER
  • MEMBER
  • 2 POSTS
Thank you. I checked all the vacuum pipes and there are no leaks. Could it maby be sticky injectors or that strange diaphram at the airbox perhaps?
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Wednesday, February 6th, 2019 AT 8:26 AM
Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello again,

Well a vacuum leak or unmetered air leak is any air leak entering the engine before the combustion chamber. A good way to check for a vacuum leak is to get a small propane torch. Please use extreme caution and proper safety gear when doing this troubleshooting. Barely crack open the nozzle on your propane torch, making sure not to light it. You just want the propane to be coming out. Have an assistant start your vehicle. With the engine running, pass the propane torch around the air-box, air intake ducting, throttle body, intake manifold, and all vacuum lines and pipes. If there is a leak, when the propane torch passes by it, the engine rpm's should momentarily pick up as the propane is ingested into the cylinders and consumed in the combustion process. Let us know what you find out.

Thanks,
Alex,
2CarPros
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Wednesday, February 6th, 2019 AT 9:32 AM

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