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Drivability problem, XR7

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Apr 5, 2017, 11:36 AM

Post #1 of 2 (645 views)
Drivability problem, XR7 Sign In

1990 Mercury Cougar, X jerkinR7. 3.8 supercharged engine, 43000 miles. All of a sudden stars missing, jerking, bucking, dying at stops. undrivable. Will suddnely clear up and drive fine for undetermined time. Been to Ford dealer 3 times. Won't repeat problem there. Replaced fuel pump. no change. I can't find anything wrong doing key on-engine off, key on-engine running, and wiggle tests. HELP! Car was my wifes(deceased) and immaculate classic.

Tom Greenleaf
Ultimate Carjunky / Moderator
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Apr 5, 2017, 1:36 PM

Post #2 of 2 (635 views)
Re: Drivability problem, XR7 Sign In

Bucks and can die out at stops then clear up?
Low mile but old. I think I'd check distributor for how clean it is inside and how much if any transfer of stuff from rotor to cap. You can just blow those out with air. Why could it be that is low mile lack of warming up frequents moisture may have messed up pick up coil inside with junk.

Other test is spray wires with slightly salted water on wires slowly area by area looking for arcing then on to spray distributor cap all this while just at idle for changes to the speed or make it stall out.

This seems more like a high voltage leak out to me than a fuel problem because it's intermittent and can go without the problem. You really can't see carbon traces of leaks from cracks in cap or weak spots in wires by eye too well but when wet they'll act up if weak and shouldn't ever.

If it seems like picking on one or two cylinders only the sparks plugs would show it if it does it enough and long enough. They too can be bed new or old almost always from mishandling them or a poor socket angle without proper ratchet for angle straight on a plug not crooked at all hard to do on some without an assortment of sockets and or using a wrench on socket instead of ratchet at all. Just ideas as I think this is just a spark issue,


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