TheSamba.com :: View topic - Can't adjust idle on fuel injected bus????

Tue Jul 19, 2005 7:19 am

75 fuel injected automatic bus.

I've been through this bus from front to back so far this year and in general it's running great. New points, dist cap, condensor, plugs, air filter, fuel lines, fuel filter, injector seals, adjusted valves ect....

It seems to run great on the highway, cruises at 60-65 no problem, but, it is very tempermental at cold start and once it is warm off the line performance is very slow. The idle is just a touch low which is causing some problems at stop lights with the foot on the brake. I usually slip it into neutral to keep the idle smooth until the light turns green.

Problem is that the idle adjustment screw has no effect on the idle. I can back it all the way out or in with hardly any effect on the idle speed. Previously this adjustment has been very sensitive, with a 1/4 turn making a 50 or 100 rpm difference to idle speed.

Has anyone had a similar issue or know this system well enough to give me a clue? A vacum leak seems to be the most plausible explanation to me but I can't find anything obvious. Very frustrating.....

Thanks for your help!!

Tue Jul 19, 2005 7:50 am

I would also guess a vacuum leak.

I know you know this but for the new guys out there, common places to look at are the "S" boot and all of its connections, the 90* boot on the aux air regulator, brake booser line and check valve, intake runner hoses and gaskets at the head, and the seal between the throttle body and air plenum.

Good site for finding vacuum leaks....

http://www.aa1car.com/library/vacleak.htm

Wed Jul 20, 2005 5:04 am

Aux. air valve problems? Is your cold start valve operational? These engines are vacuum critical, so if there's a leak it's going to run poorly as a result.
Good luck!

Wed Jul 20, 2005 6:56 pm

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