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Engine Hesitation/Stutter/Miss
I have a weird problem. When backing off the throttle and when feathering to maintain a constant speed, there is occasionally a stutter that feels like a momentary loss of power. Sort of like the ignition system turned itself off for a split second. Everything is great when accelerating. I cannot duplicate this condition in the driveway. With no load on the engine, it backs off smoothly and runs smoothly at constant rpm. This problem just started last October and seems to be getting slowly worse. I've checked the timing and looked for vacuum leaks. Looking for ideas on things to check. 418W, MSD 6AL ignition, Holley 4150 HP. Many thanks.
Jerry |
Check the condition of the cap and rotor. It sounds like a hiccup in the MSD box, but there is no reason why it does not happen during acceleration.
Hook it up to a smog tester that analyzes the spark. |
Read your plugs..
Get on a side road where you can shut it down and pull off the road at a moment's notice. Try and duplicate the problem and as soon as it starts shift to nuetral and shut the engine dowm immediately. Pull the plugs and check their condition. Wet? carboned up? Sooty? It could be a fuel problem and/or spark. That will give you a base line on where to go from there.. Dave |
I had a similar problem on my 427 , dual quad Galaxie at very light loads and small throttle openings . Turned out that my air fuel ratio was off at cruise ( too lean ) and the issue cleared up when I richened it up a little . However , I may have an advantage on you as my carbs are highly modified and there isn`t one circuit that I can`t adjust.
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Bobcat is correct. Too lean at part throttle.
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Thanks to all for the suggestions. I'm going to check the distributer cap and rotor and then have it dynoed. Hopefully that will resolve any fuel mixture issues.
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FYI, the distributor cap contacts were in pretty bad shape, so I replaced it and the rotor. Problem fixed! Presumably it was happening during acceleration, but I didn't notice it then.
Thanks again for the input. Jerry |
What do I win for guessing the cause of your problem? Does the fact that the same thing happened to me 2 years ago decrease the award? :o:JEKYLHYDE**)
Congrats on a smooth running Cobra! |
Yep mine did the same thing. The center contact in the cap was worn flat.
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Warren asked: What do I win for guessing the cause of your problem?
You get my sincere thanks and a gold star. And if I ever meet you, at least one beer. Jerry |
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