bad running f150
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bad running f150
I have an 85 f150 4x4 with a 5.0 ltr fi engine. problem is that it has a miss/hesitation when under load. when it warms up it idles rough. i hvew checked the firing order and it is good. i replaced the spark plugs, wires, dist. cap, rotor and coil. still no good. a buddy of mine tried something where he poked a test light into the top of the wires on the cap. all of them changed the engine except cylinder 7. he suggested swapping the injectors to see if it would follow the number 7 injecto or stay there. i swapped it witth number six and it followed. so i replaced the injector. again no luck. this thing is drivinf me nuts. i have also replaced teh throttle position sensor, map sensor, cleaned the throttle body and iac. it has a new fuel pump. any help would be very appreciated. could it be a burnt valve or worn cam. possibly a fuel pressure regulator?
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Do a compression check and see if #7 is low. If it is, then you can pursue the possiblity of a cracked ring, burnt valve, broken valve spring, etc.
Als make sure your #7 and #8 sparkplug wires are as far away from each other as possible. This is not a natural thing to do since they are right beside each other, but they are also next to each other in the firing order, and 302's are famous for crossfire between #7 and #8 cylinders.
Als make sure your #7 and #8 sparkplug wires are as far away from each other as possible. This is not a natural thing to do since they are right beside each other, but they are also next to each other in the firing order, and 302's are famous for crossfire between #7 and #8 cylinders.
Last edited by Franklin2; Sep 16, 2007 at 08:43 PM.
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When you replaced the injector, was it still #6 that was bad or did it move back to #7? I'd also check for a vacuum leak, easy way to check if that's the problem is to let it warm up and when it starts running rough, move the tps sensor (and NOT the throttle) as it'll shoot more fuel in with the same amount of air. If the idle increases/smooths out, you have a vac leak somewhere or you could have an idle air control valve issue (but it looks like you already replaced it). It could also be a clogged cat converter.
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I got it finally. it was a bad injector on number 7, I went to autozone and got a new injector, installed it and no good. So my shop foreman told me that the guys over at the ford shop owe hima favor so we went and one of the techs had an injector. i put the injector in and BAM!!!!!!!!!!!! she runs great. no thanks to autozone for selling me a crappy injector. I returned it for a refund and no questions asked. thanks for all the advice on this one i really appreciate it!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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