I've got the midrange hesitation blues

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Postby spyder_xlch » Wed Jan 30, 2008 10:36 pm

You can also test for vacuum leaks by spraying carb cleaner, brake cleaner, WD40, or whatever you have. Propane even works. Just spray it anywhere vacuum can leak. Hoses, carb base gasket, intake gaskets, vacuum controled devices, etc. If the idle changes when you spray something, that's where it's leaking.
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Postby res0o7eb » Wed Jan 30, 2008 11:27 pm

I concur with Paul. I read something somewhere that a lean condition causes a part-throttle hesitation.

Good troubleshooting info in this thread.

Probably should move it to Carb/Intake/EFI Induction Tech.
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Postby Mastiffen » Thu Jan 31, 2008 9:55 am

Thanks, guys! I will do a full search of this when the weather allows for it. But one thing: I'm not convinced that the acc pump matters because it will only give an extra round of gas when I first press the pedal all the way down. When if I hold the pedal there (no movement up and down to pump more) it will still accelerate steadily as far as I have tried (which is around 140 kmh, the max of the speedometer, and that was up a slight hill). As long as I don't let up the pedal, it will go on until there's nothing more to get out of the engine.
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Postby acstestinc » Mon Feb 04, 2008 9:53 am

The accelerator pump will supply extra gas anytime that the throttle is moved "quickly". Be it at idle or doing 100 KPH.

You won't feel the hesitation, when the throttle is wide open, because the air introduced through the vacuum leak becomes a much smaller percentage of the total air being drawn into the engine through the carb and doesn't change the air fuel ratio much. The strength of the vacuum signal also drops down to almost zero thus minimizing the leak. The leak will have most of it's detrimental effect when your only applying a little throttle.

Paul
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Postby Mastiffen » Sat Feb 09, 2008 2:04 pm

Well, today I finally got the chance to work a bit on it. I started the checklist, and I spent a full can of starting spray without finding anything. I removed a few units as well, but nothing changed. I tried to adjust the ignition timing as well, but that only got me a partially skinned left little finger. It's been a while since I hurt myself working on a car, so I guess it was that time again... Anyway, I have deicided that this is probably above me, so I'm gonna let the neigbour's 20 year old son (freshly educated car mechanic and dirt track racer) have a good look at it next week. Thanks for all the kind help, I guess I just suck at this! ;)
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