1998 ranger 4.0 shaking
 

i am new to this forum (first post) so forgive me if this is post is out of place. I have a 98 ranger xlt 4.0 v6 automatic 2wd with almost 158k miles. I recently replaced spark plug wires (planning on replacing plugs soon) put in a new fuel pump and filter, had a basic service done, (all fluids are good incl. transmission) fixed an injector wire, fixed a cylinder #3 misifire and a few other tlc deeds.

I have been experiencing a bit of shaking, feels like its coming from the engine compartment, but my incling is that its transmission related. the shaking occurs once i get up around 30-35mph and also around 40-50mph. it goes away when i let of the gas and also goes away when i accelerate. it does not happen all the time. and happens more often than not when im on an incline. I heard from a friend that the transmission in this truck is not one of its strong points and with 158k miles i know its getting up there. Looking for some direction, do i start with trans. service? could it be a faulty tps? perhaps changing the spark plugs will help?

thanks in advance, im new to the world of working on cars and am grateful for any wisdom that is shared.

I've seen a car behave that way, and it WAS a TP sensor, so it is a possibility. That sensor is cheap enough to replace just to try. If it wasn't the problem, you have a spare sensor.

I have a Ranger 2.9L, with 175K miles. I have it running great, but it has taken quite a bit of maintenance. These engines were some of the first with EFI. I have found that most of the EFI components can be heat sensitive. Lately I was having the same running problem as yours, and sometimes with the shaking. It was the TPS again this time. From a cold start it ran well enough but after 10 or 15 miles on a highway, it would not want to accelerate in 1st, 2nd, or 3rd, but if I could get up to speed in 4th or 5th it would run O.K. This went on for a while until it just quit altogether. After it cooled off, it started and I got it home, but it was not certain I would make it. The Ignition module, the coil, plus the distributor cap, and rotor can also give you the same symptoms. It can get confusing at times, for sure. I had a name brand plug go bad with 27K miles on it and I was surprised that the engine was not that rough running, but of course the power was down. One more point is that I installed a new timing gear set, 5 pieces in all. This gave my engine a second life. I also use synthetic oil, which must help, because it doesn't burn oil at all. It does leak oil from the dam valve covers, that's a battle. Lots of people don't think to replace timing chains, they think all you need to do to correct the timing is to adjust the timing because of wear, with the distributor, and that is correct, BUT that doesn't correct the problem of the valves and ignition timing being out of sync. Remember, the valves need to be in time with the pistons, and the ignition timing has to be synced with both. This could be why you are getting the shakes from the engine. Your 98 4.0L, I think is similar to the 2.9L in that in 98 the 4.0L didn't have the overhead cams yet?, so my chain comments should apply? I see I had your year wrong, but it seems to me the much longer chains on OHC engines should be more susceptible to causing valve timing problems, by having a lot more chain links to stretch? I haven't worked on one, so I am going to ask someone about that point myself. I doubt the shaking is because of the transmission? but it probably is not impossible.
One last suggestion, Wells Mfg. Corp. has a nice EFI servicing manual which applies to working on these early Ford EFI systems, that you can download and print out, for free. I think this manual will help you understand your Ford's EFI system.
Hope all this helps.

I didn't think about the TFI module overheating, as my 4.0 has EDIS mounted on the inner fender, and no distributor. But the engine problems that come when the engine is warmed up is common with an overheating TFI module that's bolted to the distributor.

Even though I didn't have a problem with it, I did take a pre-emptive measure on my 302 v8 by moving the active TFI module from its distributor to the inner fender and adding a heat sink:

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