Too fast idle

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beep
MegaSquirt Newbie
Posts: 4
Joined: Thu Dec 20, 2007 3:20 pm
Location: Brisbane, Australia

Too fast idle

Post by beep »

Hi everyone. I started my car for the first time on MS today and I am very excited. I raise my glass to B&G and everyone involved for this fantastic thing.

Its early stages but my immediate problem is that the engine idles way too fast.. like 1500-2000 rpm. I have had a good check for vacuum leaks and I don't think that's the problem. When I put my hand over the throttle body I can reduce the revs to idle speed (in fact stall the engine) and it sucks pretty hard (I'm seeing maybe 30 kPa), but then the throttle is totally ineffective. So from what I can figure, there is too much air going past the throttle plate when its closed. The idle speed screw is all the way in and as I said I don't think air is getting in anywhere else.

I have the throttle body off the car now, and when I look at the plate there are some small gaps, especially near the idle speed screw. Also, there's a seal on the shaft that is suspect but I really doubt that thats where all this air is coming through.

Image

So do you think my TB is stuffed? Or am I way off? Any advice appreciated.

For background info, the car is a 74 VW bus, originally carbed (yesterday) and with intake etc off one that had factory efi (today). Its MS II v3 and I am using an Innovative WB O2 sensor. Ignition is an old centrifugal advance only dizzy (for now).

cheers
Chris.
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beep
MegaSquirt Newbie
Posts: 4
Joined: Thu Dec 20, 2007 3:20 pm
Location: Brisbane, Australia

Re: Too fast idle

Post by beep »

Thanks for the reply Lance. May I say I really appreciate your support on this forum.

I'm less sure about the problem the more I think about it. Do you think I would be able to slow and stop the engine by blocking up the TB with my hand if it had a leak somewhere else in the intake? It sucks really hard and I can't hear air going in anywhere else.

I guess I was asking if other people's TBs are as gappy as mine? Its a bit hard to tell from the photo, but the plate can't really be any more closed. How much gap is usually in a TB? My efi has a whole big electric powered device to leak air when cold to raise the idle and now I'm wondering what kind of actual area would be used for that. I'm starting to think there is a leak somewhere else.. but it will have to wait until the weekend when I can get some daylight.

cheers
c.
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beep
MegaSquirt Newbie
Posts: 4
Joined: Thu Dec 20, 2007 3:20 pm
Location: Brisbane, Australia

Re: Too fast idle

Post by beep »

Thanks Lance.

I took it to my veedub guy today and the verdict is: TB is shagged.

I did get another one though so I'll give it a whirl on the weekend.

Thanks again
c.
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