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Rb25det Idle Rev Move Up And Down :(

perzn_34

By perzn_34,
in Engines & Forced Induction

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perzn_34 Experienced

perzn_34

Posted
Posted

Hey guys i have a r33 rb25det motor in my r34 gtt. Its a build motor has been in there almost a year and it has always been fine.

I have a td06h 25g setup putting out 322rwkw on 20PSI with haltech p1000. I run a Greddy copy inlet plenum with a BM 80m throttle body.

Recently i changed my wastegate to a new turbosmart. I got confused with which hoses goes to the top of the gate and whiten goes to the bottom of the gate, a few trial and error caused a few runs down the freeway over boosting to about 30psi maybe a bit more.

I have fixed the issue of overboosting but now it idles at 1400rpm to 1800rpm, and once the engine is WARM the idle bounces between 1400 to 1900rpm, up and down.. all the time once warm. Driving and boosting is fine.

I thought maybe I'm leaking air, or blew hoses off, but i checked them all and seem to be fine. Also had a look at the inlet manifold gasket up close with a torch and the didn't seem like any pieces of it has blown out. i can see the gasket also has silicon on it too.

SO can anyone tell me whats the cause of the high idle rpm and the revs bouncing???

Any help would be greatly appreciated thanks

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scotty nm35 Grand Master

scotty nm35

Posted
Posted

30psi sounds good Andrew. Why were you trying to fix it? :P

Sounds like there is a leak as I said, causing the idle air control valve to open and close while trying to lower the idle to it's preset revs.

If there are no visible leaks, a pressure test may be the best option...

Blackkers Experienced

Blackkers

Posted
Posted

While it's idling you can spray some throttle body cleaner or degreaser or wd40 on the suspect areas and listen to the idle.

It just helps to rule out things like gaskets which are hard to visually diagnose

perzn_34 Experienced

perzn_34

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  • Author
Posted

I did spray some degreaser on the inlet plenum gasket and the revs droped a bit like its going to stall. It was along the whole gasket. So could it be the whole gasket leaking? :s

Also what replacement gasket should i use? What silicon? And should u machine the freking greedy fake manifold? Its like $200 to machine them ffs

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