Jumping/Hopping/vibrating when Cold

[BryanG]

Sorry for such a poor description in the title but I don't know how else to explain it. My son's 2000 4.0 Ranger with 118k miles is now jumping, hopping or vibrating when put in gear when cold. By the time he is leaving our edition it stops doing it. It did it with me tonight while in reverse. Any ideas where to start? Tranny I'm assuming but not really sure. If I can come up with a better way to explain it I will. Thanks in advance.

 

[97RangerXLT]

Check your rear brakes. They might be sticking. (I am reading this as the rear end is hopping/ vibrating for a bit until it frees irself, and that the engine itself is running fine. If it is the engine, disregard...)

AJ

Sent from my Samsung Galaxy Note 4 while sitting in my underwear

 

[BryanG]

Check your rear brakes. They might be sticking. (I am reading this as the rear end is hopping/ vibrating for a bit until it frees irself, and that the engine itself is running fine. If it is the engine, disregard...)

AJ

Sent from my Samsung Galaxy Note 4 while sitting in my underwear

I will do that. We installed all new rear breaks about 1000 miles ago but that makes sense. The engine seems to be running just fine. Thanks I will post the fix as soon as I figure it out.

 

[BryanG]

Well got a code P0303 which means cylinder 3 is misfiring. Trying a few things to diagnose this but I'm guessing it is the cause. Hope it's something easy I can fix. Will let you know.

 

[BryanG]

Well tried injector cleaner and a new gas cap with no luck. There is spark from the coil to the cylinder as well. It's crazy how it seems to be happening mostly when the engine is cold. Also didn't start till the weather cooled off here and has been better since it has heated back up. Could be a vacuum leak I guess. It's getting beyond my ability so probably going to have to have a professional diagnosis it next.

 

[97RangerXLT]

The injector itself may not be firing, or intermittently sticking open and drowning the plug with gas.

Check the wire harness and plug to the injector as well

AJ

Sent from my Samsung Galaxy Note 4 while sitting in my underwear

 

[ratdude747]

The injector itself may not be firing, or intermittently sticking open and drowning the plug with gas.

Check the wire harness and plug to the injector as well

AJ

Sent from my Samsung Galaxy Note 4 while sitting in my underwear

Easy test: Run it for a short bit, then pull the plug. If it's dry, no fuel, if it's wet, no spark (ruled out), no compression, or flooding with gas.

 

[Blown]

I would do a compression test as well. You can get a gauge relatively cheap or borrow one.

 

[BryanG]

Cylinder 3 had a bad spark plug. All 6 have been replaced with Motorcraft and problem is solved.