hello my 88 xj has a weird vibration when its in overdrive.......its not there under acceleration only after it goes in to overdrive.....when you let off the gas in overdrive it goes away completely and is as smooth as a new car....when you hit the gas again it comes back.....any ideas

 

Ok I just drove it again maybe vibration is the wrong way to describe it it kinda feels like it is missing.......but only at 40-55ish in overdrive do you guys think it could be a fuel injector problem......can you test the fuel injectors? please any help would be great

 

You can get some injector cleaner or even put some "Sea Foam" in the tank. I would also check the pressure on the fuel rail...Tj

 

Also some simple things.

your sure the tires are balanced some tires will act funny over 50mph. It is easy to lose weights you can drop weights in days after getting a balance.

Are your rotors true?

How is your Transmission oil is it clean or is it gritty?
Have you had your your transmission serviced and the sceened cleaned?

Crankcase and Differential lubricants are at the top of the fill holes? add with a plastic syringe.

 

If it is the injectors, which I dont think it is, you can check the resistance. I believe that they should be around 10-14 ohms.

If it is a drive train problem it could be a torque converter. However, it sounds as if it is a balancing issue. I would look into having the tires balance. It could also be the U-joints. They can cause vibrations as well. Since this vibration is limited to a certain speed I would think that it is a balancing issue.

 

ok the engine is knocking i thing .........the motor runs fine until it changes into overdrive and the rpms drop to 1500 then it runs like crap feels like its missing.....if i hit the trans power button the rpms go up and the motor runs fine again it is only running like crap in overdrive at 1200-1500rpms any suggestions as what is causing this....

 

Check your fuel filter if it's a little plugged up it may let enough fuel through under normal driving but then when you need more it doesn't allow a full flow. I had a similar problem with my old Bronco was fine under normal rpms but if I got on it I got the stumbles similar to what your describing. Turns out it was the fuel filter not the injectors rails or the pump.

 

Ok I changed my fuel filter, put ford 19# injectors and changed my spark plugs while I was at it......This it the best thing I have ever done to my jeep it runs like a dream......there is a huge difference when you go from a bad injector to the ford ones.......it runs so smooth and has more power any body who has not done this upgrade should......the filter was $12 the plugs were $17 (Champion platinum) and the injectors were $59 shipped, tested and with new o-rings from ebay....the only bad thing about this mod is that i broke the plastic thing that holds fuel line in the fuel rail I call all the part stores none had the part so I had to get it from the jeep dealership $18 for a piece of plastic and a o-ring Ouch...any way it is running like new.....thanks for the help