F150 missing between 50 and 60 mph


Old 01-27-10, 03:39 PM
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Location: Pillager Minnesota
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Unhappy F150 missing between 50 and 60 mph

I have 1997 F150 that shakes or is miss firing when I excelerate while Im going 50mph or faster. It happens when Im trying to increase my speed or going up a hill. If I cancel the overdrive button it is ok running at higher rpms. My check engine light starts blinking for awhile when this happens, any ideas what this might be?
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Old 01-27-10, 03:44 PM
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Not a pro on this, but I had one that had a bad module that locked up the torque converter. Your symptoms seem the same as I had. The truck is trying to downshift from lock up to high gear and it can't make up its mind.
Old 01-27-10, 05:13 PM
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If your check engine light is coming on take it to autozone and have them read the codes for you. That wont tell you exactly what the issue is but it will give you an idea and then you can go from there. Like Chandler said, it could be a module but their are a lot of things it could be.
Old 01-28-10, 07:45 AM
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On OBDII cars when the MIL light starts to blink it means that it has detected a miss fire condition. Follow JPR advice and take it to Autozone and have the codes read. If it continues to blink it can destroy the emissions system, and melt the catalyst in the catalytic converter, or even destroy the engine itself. It could be your coil pack, or cam position sensor. Cars today have way too many computer systems on them. I may only be 29, but I liked carbureted cars much better.

Last edited by crazycory22; 01-28-10 at 07:50 AM. Reason: Spelling errors corrected but there are probably more
Old 01-28-10, 12:49 PM
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cory, 29? Heck, I've got socks that old. You really want to dive into a '56 Chevy with a 348 with 3 deuces, and an Oldsmobile turbo hydromatic tranny. You can sit on the radiator and work on the engine. Tape a $5 bill to the dashboard and tell your passenger, when you launch, if they can reach the bill, it's theirs. Can't do it. Too many G's. Not like today....too many hoses, wires, sensors, and other little black boxes that may or may not have a purpose. You're right!! And you are probably "righter" on the blinking light thingy.
Old 01-29-10, 04:21 PM
Join Date: Jul 2009
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I don't know why you can't find the problem they wrote it on the front of the truck and circled it.
Old 01-31-10, 10:26 AM
Join Date: Jan 2006
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This may sound weird but, when was last tune-up, wires etc.,and have you by any chance pulled spark plugs and see what they look like? We had about 6 or 7 of those at work, in the late 80's early 90's, with 5.0L that would act similar from time to time, only to find out we had carbon on a couple of plugs. or even one, as well as the odd bad plug wire, and even had to spray combustion chamber cleaner into throttle body, and follow directions on can. What it boiled down to was that a weak spark while under load, was causing overdrive to kick in and out to overcome it. We also found that the trucks that were having the problems the most, were the ones driven by the older staff members who actually drove the speed limit, so carboning up was more common on those particular trucks. On a few occasions, I ran the truck out a back road and did a little cleaning myself, (if you know what I mean) but if that failed, we simply pulled plugs, and the one(s) that were showing carbon deposits were replaced, wire checked, or replaced, and back on the road, running good again. I guess Ford never anticipated that when they added the overdrive for better mileage, when at normal (cruising) highway speeds, the engine wasn't revving enough to clean itself out good, thus some cylinders would carbon up. Here's what I would do:
Pull all plugs and have a look at them, and note those that show any signs of carbon build up. Check the wires to them and replace if necessary. Then I'd check and adjust gap and put them all back in. Then go get a spray can of combustion chamber spray cleaner, if not from Ford, get the Chrysler brand. I'd also get a new set of Motorcraft plugs. Follow directions on can, then shut it off, and let it sit overnight, or at least for 3-4 hours. Start engine and rev in safe limits as directions advise. When cooled down, check gap and install new plugs. If you don't put in new plugs, at least pull old ones out and check again that they are still in good shape and gapped properly, due to the fact that I've seen carbon come loose in cylinders and break off porcelain on plugs before, causing a major misfire. That's one of the reason for having new plugs ready to go in after. I'm not ruling out lock-up converter problem 100%, but in all the cases we had same problem, it was never the lock-up, even though it felt like a transmission problem, it was always what is described above.

Good Luck, keep us posted.

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