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Discussion Starter #1
This morning when I went out to steal I mean get a Christmas tree I had a problem I can't figure out with my 1992 Carry pickup.

I started and ran fine, but when I apply the brakes, the engine revs to full throttle. I had to use the handbrake . At first I thought it may be vacuum related, but when I turned the heater fan on the engine reved to full again. This is with my foot off the throttle pedal.

Any suggestions ?

Thanks:

John
 

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Discussion Starter #2
This morning , I was able to look at the truck. It still puzzles me.

The heater fan switch only revs the engine when turned to high. Since low and medium speeds have no effect on the throttle I can live with that.

I took the brake light fuse out and the problem went away. The problem must be electrical . I don't want to work on wiring in a Nova Scotian winter but I'll have to do something.

Once again, any suggestions where I should look first.

Thanks:

John
 

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There is an "idle-up" system that increases the engine idle to compensate for the alternator load when there is increased electrical load - this is most likely what's causing your problem.

Unfortunately, since I'm not familiar with the Carry you have (which I suspect is a used JDM import), I have no idea how the idle-up works - on carbureted engines it's usually a vacuum actuated linkage, if it's EFI, it could be either an airbleed, or whatever idle control mechanism the EFI system uses.
 

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Discussion Starter #4
Fordem: Thanks.

Its a 1992 DD51T with a F6A carbureted engine, imported from Japan Partners..
I just discovered that it revs when the lights are turned on too. This does not happen when I remove the brake light fuse.

It revs to 4000+ ( I shut it off before it revs too high ) so I doubt it's a high idle. I will try to find the control though. Any hints about where it might be or what it looks like. I can't see any solenoids, pots or shafts move when the brake is applied and the engine races.

Right now I think I should look for a bad wire between the brake light switch and the tail-lights.

John
 

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Discussion Starter #5
Yesterday I found that taking the vacuum hose off the Fast Idle solenoid on the carb solved the problem of the engine racing when the brakes were applied. Before I did that, I found that turning the lights on made the engine race so I'm still confused as to why this would happen.

Today, I took it for a drive and it only ran at about half throttle. After it warms up it idles high and the throttle pedal does not go all the way to the stop. There's a bit of wet snow today so I'll wait until it's drier to look for that problem.

One thing at a time.

John
 

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Discussion Starter #6
Found the problem. There are two levers on the throttle shaft . One for the throttle cable and one for the link to the fast idle solenoid. They were seized together but need to operate independently. After I cleaned them and freed them up the truck worked fine. I reinstalled the vacuum tube and it still works fine.

That doesn't explain the racing engine when the throttle/lights/heater fan were used but hey the truck works.

Thanks:
John
 
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