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TOPIC: high revving?

high revving? 4 months 1 week ago #38030

hi all,
took the X for a short spin last night, no more than a couple of miles as I have just moved house and was brining the Fiat over top the new place.

I backed her out of the garage and let her idle for 2-3 mins so she could warm up slightly, which she did as usual. Set off driving and pushed the choke in, but noticed that the revs are staying at 2000rpm. I blipped the throttle a couple of times (this usually has the effect of dropping the revs) but they remained above 2000rpm.

I didn't have a chance to have a look last night but wondered if there is anything I should look for before I start digging deeper/

For info, the car is an '82 1500, with the standard carb and auto choke. It has had a manual choke conversion added at some time in it's history and the two choke's have always seemed to work in quite happily together, hence my leaving them alone!

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high revving? 4 months 1 week ago #38032

Had you left the car running long enough for the auto choke to cut out.
Blipping the throttle normally brings it down to normal revs.

Is the throttle cable moving ok? It hasn't perhaps got a bit stuck open? A squirt of WD40 might just help.

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Blue Gran Finale F100FAW
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Lido ALF 704S

high revving? 4 months 6 days ago #38041

It's a manual choke then?

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1986 'BAD' Turbo Bertone X1/9
1977 1300 Special Series
1999 Toyota MR2 3.0 V6 vvti daily driver

high revving? 4 months 6 days ago #38042

I didn't know you could have an automatic,water, choke and a manual one. Are you sure you have both, i thought they fitted in the same place on the carb, one or the other.

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high revving? 4 months 5 days ago #38043

Just to clarify. It has had a manual choke conversion, but appears to have the original auto choke still fitted. Although from David's comment, that may not be physically possible! It certainly acts like it has an auto choke in use, the revs staying high but dropping off when you 'blip' the throttle.

I'm moving house at present, so I'll have a look over the weekend when I see the car, and get some pictures to clear up the confusion I have caused!

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high revving? 4 months 5 days ago #38045

I'd have a look at the waterpipes on the choke. It sounds like it the copper spring might not be getting warm enough to unravel. Check you have a constant flow of water in and out of the choke piece. Then check the 90 degree fixing where one of the choke pipes connects to the inlet manifold. These parts do block up with muck.

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1986 'BAD' Turbo Bertone X1/9
1977 1300 Special Series
1999 Toyota MR2 3.0 V6 vvti daily driver

high revving? 4 months 5 days ago #38046

"the revs staying high but dropping off when you 'blip' the throttle."

That is exactly how my car which is fitted with a manual choke behaves. Until you blip the throttle after pushing in the choke knob the mechanism inside remains in the "choke on " position.

I would say its quite normal.

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Last Edit: by Pete Pearson.

high revving? 4 months 4 days ago #38049

You don't need much air getting past the choke butterfly to cause a high idle. This can be caused by dirt getting into the spindle, a worn spindle, a cable that's starting to stick, a carb out of adjustment. In your case you may have the added complication of a possibly not to clever choke conversion. When the engine is warm but idling too high physically turn the butterfly mechanism back against the stop to see if that settles the idle. If it does then you know that the carb is okay. Then try again disconnecting the choke and then the accelerator cable to find out which one is causing the problem. Pete is right in saying that some chokes not only enrich the mixture but set the throttle part open, which after you have pushed the choke in you then unset by pushing/blipping the pedal

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high revving? 4 months 2 days ago #38052

I found half an hour to have a look at it this weekend, started her up and left her to idle for ten minutes to warm through. Everything went as usual, and she had exactly the same symptoms, i.e. with the engine at operating temp the idle was up around 3000rpm.

So I switched off and started to take the air filter off, so I could see a bit better





That safety pin which is replacing a split pin or R clip had found it's way over the lip directly in front of it, and was wedging the butterfly open. I flicked it back into place and she is right as rain.

Aplogies for the time wasting,
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