1988 Ford LTD Crown Victoria - Vibrations & Gas Issue

So here’s the deal. About a month ago, my car, a 1988 LTD Crown Vic (Automatic Transmission), started doing something strange. When I’m on the highway, and I go about 70 mph, everything is fine until I start releasing the gas pedal a little to make sure I don’t gain too much speed. When I ease off the pedal a little while going about 70, there’s a very strong vibration that can be felt and heard throughout the car. If I go faster than 70, for example 75mph, that vibration gets so much more stronger and louder. I have no idea what it could be. Could it be the transmission fluid? The fluid is very old and possibly very dirty (30yr old fluid is still in there, along with new fluid i’ve been adding)
If anyone has any pointers or suggestions, it’d help a lot.

The second problem I’m having is fairly new. It’s only happened 3 times the past week. What happened was if I were stopped, or going a very slow speed, like 5mph, when I’d give my car gas, it just wouldn’t go or pick up speed till after a few seconds. So far, this has only happened in the beginning of my journies; the first 5 minutes of driving.

I’m not sure if both these problems are related or not, but any help would be appreciated


You need to check for codes and that will require an analog DVOM or a test light and some instruction on how to connect it. Hopefully there is an EEC forum out there somewhere. If you get the codes post them here to compare opinions here to the EEC forum.

Check this link


it might get you started

nah, can’t be 30 year old fluid. I am sure you can make it another 30 years without a fluid change:grin:

Have the driveshaft u-joints and the rear axle pinion bearings checked. Sounds a bit like the rear axle pinion bearings are going away.

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I agree with @Mustangman sounds like a bad u-joint in the driveshaft.

Typical u-joint symptom. If this has the 5.8 engine, it has a carb and and probably needs an accelerator pump diaphragm.

So it’s been a while since I wrote about this problem, and at that time I’ve been working on this. First, after reading replies I’ve gotten on this post, I checked the u-joints and tried to jiggle the driveshaft around. Nothing budged, so it seemed that things were pretty tight. the u-joints seemed fine. I heard that another cause for the vibration issue could be that the wheels are misaligned. It would also be cheaper than dealing with the U-joints. so I decided to get that done first. After that, I took the car out for a spin and the problem still persisted. Since the vibrations happen when I press the gas at a certain point, I thought that maybe it was something going on with the fuel system, so I bought a fuel system cleaner and poured it into the gas tank. after driving about 50 miles, of course, there was no change. After that, I took a look at the u-joints again. This time I noticed that there were 2 bolts that were loose that connected the flange to the differential. They were more unscrewed than the others.

But yeah. the bolts are a special kind of bolt and I don’t have the specific tool to tighten them up. I would’ve gone out today to get it, but it was Christmas today and stores were closed. So tomorrow, I’m going to tighten those bolts and take it for a drive and see if that solves the issue. I’ll come back it to confirm whether or not it was the solution.

If the attachment of the driveshaft to the differential input flange is loose, that’s very likely the issue. Good idea to remove those bolts completely and check for damaged threads, rather than just tightening them up. Best of luck.

If not, there’s other possibilities, post back.

Turns out that was the issue; loose bolts. All 4 were loose, but 2 were more loose than the others. I tightened them the best i could, and sure enough, after driving it on the highway, the vibrations has stopped.

The important take away from this would be that if you have a similar problem, check the u-joints, the driveshaft, and the bolts around those joins to make sure they’re as tight as they can be.

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