1986 Ford Ranger / 2.9L Intermittant Bad Performance

Specific repair issues for RWD trucks, SUVs & vans
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Tim Martin
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1986 Ford Ranger / 2.9L Intermittant Bad Performance

Post by Tim Martin »

Ok. This customer just purchased an 86 Ford Ranger, 65,000 miles, 2.9L engine, manual transmission and two wheel drive. The issue is this. You start it up cold, it may or may not run fine till it is shut off. The next time you start the engine, cold or hot, it will barely run, will misfire out the intake, and barely get out of its own way. It will be like that till you shut it off and the next time you start it, it may or may not be fine. It has new plugs, wires, cap, rotor, distributor, mass air flow sensor, throttle position sensor, and oxygen sensor. Fuel pressure is right on the money as is timing. When it runs ok, it is a pleasure to drive but when it is not running ok, it is like a bucking bronco, rough, unpredictable, and undependable. I know this is the first year for this 2.9L engine and the multiport injection system. Its fairly simple, or so I thought cause I worked on many of these through the years but this one has me stumped, very much so. Oh, and by the way, there is no codes in the computer, and I have disconnected the EGR with no difference when it was running bad. What am I missing?
benny
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Re: 1986 Ford Ranger / 2.9L Intermittant Bad Performance

Post by benny »

ran in to this a wile ago hook up your scaner and watch evap sol. evap may be full of fuel and when it opens its drawing in raw fuel
Tim Martin
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Re: 1986 Ford Ranger / 2.9L Intermittant Bad Performance

Post by Tim Martin »

benny wrote:ran in to this a wile ago hook up your scaner and watch evap sol. evap may be full of fuel and when it opens its drawing in raw fuel
Being a 86, data cannot be read by scan tool, at least not by either of the two that I have. Could data be read, it could potentially make this job alot easier.
benny
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Re: 1986 Ford Ranger / 2.9L Intermittant Bad Performance

Post by benny »

sorry miss read your post thought it said 96 i will beat my brain a little harder
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steven kiser
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Re: 1986 Ford Ranger / 2.9L Intermittant Bad Performance

Post by steven kiser »

O.K. so here is what I have for you. I would check the Air Bypass Valve and ports for sludge. Also another huge issue with these was that the finish on the inside of the throttle body would get tacky and wash off if carburetor cleaner was used to clean it. This caused issues with the plate seating and some "techs" would drill the bleed hole in the plate bigger to allow more air to pass through trying to compensate for a stuck throttle plate. There also were those that would screw with the set idle causing occasional idle roll or surging because the T.P.S. and throttle plate were out of whack. I ran into issues with improper vacuum routing on these. Some would cause the E.G.R. to open and stay open. The issue of remaining open could be caused by the bleed port being plugged off because someone thought it was a vacuum port. I would look towards a bad coolant temp switch if everything else looks good. Another thing that just popped into my vast echo chamber was the Intake sensor that screwed into the intake next to the plenum mount. It would gunk up with crapolla and not read properly. If this came into my shop with the symptoms you have I would replace the Mass Air Flow and wouldn't assume the replacement was any good. I suffered through more than a few where the replacement wasn't worth the box it was in causing hours of unneeded work. I did a bit of on line looking and there were a few T.S.B's. on this. One was an Octane issue, another a By Pass Valve, and this one caught my attention, it has to do with a bad timing spout. Test it by attaching a timing light and pulling the spout while watching the timing. This should be done only after the truck reaches operational temperature. If it doesn't change it could be a bad spout, broken wire, ad connector in the harness or a bad P.C.M. After all this babble I would lean towards a bad Air Vale. This messing up could also take the EGR on a little ride also. Good Luck.
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