Idle Problems

Tiramisu · Tiramisu's Garage

I got a problem with the idle on my '74 914. I just recently got it running again (thanks to many people here) and set the timing to the 27 BTDC mark. Now the car idles at about 1800. I tried to adjust the idle screw but it is turned all the way in. I am assuming it is the big screw on the side of the throttle body (driver side). Retarding the timing back near TDC does not seem to make any difference either. I was thinking it might be a TPS adjustment but I'm not sure. Any help would be appreciated.

Bleyseng · Bleyseng's Garage

Usually high idle is caused by a vaccum leak, a stuck open AAR valve or the hoses are misplaced.
First check the AAR valve, does it fully close after 5 minutes, meaning no air passes through it.
Second, check that all the hoses are to Dave Darling hose layout located elsewhere on this site.
Lastly, check that the intakes are bolted down tight and the runner seals are in good condition. You can spray carb cleaner to see if these leak also.
My bet is you have the hoses set up wrong, its easy to do, so check them out.
How is the weather in Friday Harbor? I love going up there it's so beautiful in the fall.
Geoff

Wayne 962 · Wayne 962's Garage

We have all the hose diagrams on the site in our 914 tech section, if you need to check your hose arrangement...

-Wayne

Tiramisu · Tiramisu's Garage

Dave,

I used your 2.0 diagram here to setup the hoses (which have all been replaced, including the throttle body, injector, and manifold seals). One question I have is about the vacuum advance hoses. I have the two hoses connected coming off the throttle body..I have heard that one come off the side of the dizzy is not needed?

Tiramisu · Tiramisu's Garage

Wayne I mean..not Dave

Bleyseng..hello! Weather up here has been awful..rain constantly..it has been difficult to take the sailboat out. Its a good thing I guess as I have been working on the 914...its been a garage queen since last spring.

Bleyseng · Bleyseng's Garage

You have a 74 914 so only one hose should be connected to the TB and to the dizzy. The one at the dizzy should be the retard hose located on the bottom of the vac can. The other is for the vac advance which is NOT used. The retard hose should be connected to the Port at the TB which is located below the TB plated and pointed to the dizzy. If you have a 73 TB then you would hook up the vac advance too. The retard hose is the important one as it retards the timming, lowering the idle.
Re check all the hoses as it's very easy to misplace them resulting in high idle. This is a common problem when you replace the hoses one or two get plugged in wrong.
Geoff

Tiramisu · Tiramisu's Garage

Ok..now that is opposite of what Daves Hose Diagram shows. The hose from the top of vac can (pointing up) is connected to the TB pipe that is pointing to the dizzy. The other hose goes from the bottom of the vac can (pointing the pass side) to the TB pipe that is pointing to the rear trunk. So I should connect the bottom vac can hose to the TB pipe pointing to the dizzy?

Bleyseng · Bleyseng's Garage

The vaccum retard port is located next to the idle screw and the hose should be green in color. I think the other vaccum advance hose is smaller. The engine rev's should drop when you plug the retard hose in, but if it's a large vac leak it won't make much difference. Usually the problem is a misplaced hose for that kind of idle or the timming is waay off.
Geoff