help!!!!
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New User
Joined: Jan 2003
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From: hockeytown
help!!!!
i have a 1994 ford bronco with 302 engine with 630000 miles on it. after several hours of testing i gave up and took it to a repitube shop. here is the deal, at idle it runs great no problems, but when driving down the road the tach starts jumping all over the place and once in a while it will feel like it is hitting the rev limiter. and its causing the truck to run terrible. the fuel pressuure is fine thro out the entire rpm range. the compression is good, its pulling 20 inches of vaccum. no engine codes. alternator been tested and is in excellent shape. its got new wires cap and rotor. the shop has an ase 25 year tech working on it and he cant even figure it out. dose any one have any ideas?? it also has long tubes with out cats. also the tech said somthing about the tach getting shorted out. and that he know whats the problem is not, but cant figure out what it is.
thanks
jason
thanks
jason
Posting Guru
Joined: Jul 2003
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From: Independence, MO
is it just the tach acting up or is the motor it self running eratic, if the engine is reving going down the road is the transmision slipping? how can the engine rev if your not accelrating. DW
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From: hockeytown
bronco
the engine will run good and the tach will start jumping around not effecting engine rpm at all. and the engine will start running rough. like a miss and very hesitant and it almost feels like a slipping transmission. once in awhile the rpm gauge will peg and it will feel like the a rev limiter is getting hit. and the check engine light never comes on.
Lead Driver
Joined: Jul 2003
Posts: 7,404
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From: Wheatland, Mo
I know that it may seem like a dumb option, but I did have some wierd probs like that and it was all caused by a bad battery cable. The computers in your truck have to have a specific amount of voltage. A slight drop or fluctuation in the voltage can cause the puter to send out bad signals causing all sorts of wierd things. The same thing happened to my buddies Durango and it was shifting erratically and adjusting itself thinking it was going 300mph. He replaced the battery terminal and all worked great again.....just a thought.
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From: hockeytown
bronco
the engine rpm doesnt bounce around like the tach does. it will feel like it is slipping then bang hard into gear. no trans codes either. and the engine will run rough.
thanks
thanks
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New User
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From: hockeytown
bronco
tps checks out fine. the battery cable are in excellent shape the truck has 63000 miles on it and looks pracically brand new.
thanks
jason
thanks
jason
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Senior User
Joined: Jan 2003
Posts: 392
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From: The South
how on earth did you get 630,000 miles on a 1994 Bronco?! Holy crap man... you would have to make over 10 round trips a year from new york to San Diego to rack up that kind of mileage!!!
Geesh... and I thought i was pushin it with 130K!
McNabb
Geesh... and I thought i was pushin it with 130K!
McNabb
Senior User
Joined: Feb 2002
Posts: 132
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From: South Bend
I had the exact same issue. Drove me nuts, I finally took it to a shop to have it checked. There's a wire that hooks up to the coil that feeds to the tach. All that was wrong with mine was that wire was loose. As soon as that was fixed it started running right again.
Fleet Mechanic
Joined: Aug 2002
Posts: 1,568
Likes: 33
From: Swansea SC
I have a 1992 bronco xlt had similar problems .At certain rpms mine fluctuated, went up/down, it seemed like it was a slipping transmission. What a pain in the a@@ this was, months of posting and testing ,loose ground mabey redid all them connections cleaned the computer terminals, battery connections replaced a few sensors to no avail then had enough to the dealer OUT COME instrument cluster ( 52$$ from a junk yard) it ran like a normal truck should
hope this helps your situaton TR
hope this helps your situaton TR
Senior User
Joined: May 2003
Posts: 132
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That's a nasty problem.
Hey there buddy. I had the exact same problem with my 84 bronco xlt. you problem probably lies in the ignition coil. my truck's tacho would jump up and down and then the motor would go weird then quit, or kick up to normal again. I swapped the GT40-r bosch coil for a mec-717 bosche transformer type coil and everything went fine from there. if that doesnt sort it, it might be a bung plug from coil to dizzy or from battery to coil.
good luck mate.
good luck mate.