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Truck skipping under a load

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Old 05-08-2014, 05:58 PM
Dixiesweep Dixiesweep is offline
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Truck skipping under a load

Ok guys hope you can help. I have tried everything. My truck skips when in OD and pulling a hill or with the A/C on. I have changed the plugs..have the hottest you an use, and then largest wires you can use. Its a 91 f150 with the 302 with OD. I changed the rotor button and distributor cap. I also changed the distributor pick up coil. Speaking of the coil i have also changed the coil. I checkd for vacuum leaksand did find one small hose with a split.

Is there a way to check for leaks other than using starting fluid or WD40? Its driving me nuts. I completely rebuilt this engine about 50,000 miles ago.It doesnt seem to skip until i get into OD. I work with this truck every day and go thru about three tanks a week. Im sure the skip is killing me.

Any ideas would be appreciated..thanks guys!
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Old 05-08-2014, 07:40 PM
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Conanski Conanski is offline
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What you describe sounds like a lean stumble. On an EFI motor there cannot be any leaks in the exhaust system upstream of the O2 sensor and that includes the smog systems( EGR and AIR injection), if there is a leak the engine will run lean. If the O2 sensor is original or even old looking change it, they can drift off spec with age, but also check codes and post up what you find.
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Old 05-08-2014, 09:07 PM
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Well, for starters, put the correct plugs in the thing. A "hotter" plug holds the heat at the tip longer, which could cause preignition. If it calls for autolite 25s then you can use 26s, but if you're using 27-28s you're asking for issues. This isn't winter in the arctic.
Next, what wires do you have. 10mm Taylor's or just an expensive set you think was good quality. You need wire separators no matter what wires you have, they can't be zip tied into a bundle. Cross fire is common on these trucks and causes a skip.
O2 sensor liks suggested, and check fuel pressure. If your pumps are weak, you'll get a lean condition under load, which od is a decent load.
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