Unknown Fuel Delivery Problem????

[DonMarine]

HELP!!! We have a 1997 Jeep Grand Cherokee Limited V-8, 4x4 AT with about 104k on it. We were in the process of giving the car to our daughter and prior to doing so took it to the dealer and spent $1300 for a variety of repairs/maintenance such as detailed tune up, replacing transfer case gasket, PS and cooling system flush, cleaning injectors and cleaning adjusting throttle body, just the whole nine yards! As she drove off happy with her new car, it began to buck and jerk violently one she was on the interstate when accelerating. I drove out to where she was and picked up the car and it did the same to me (not right away, but within an hour or so). I got the feeling that it was either a bad fuel pump or a fuel filter (both of which I undertand are positioned inside the gas tank). I have a pretty good aftermarket warranty and took it to the dealer. He has had it now for a week and has driven it extensively and it just won't do it again (ain't that always the way it is?). Service personnel seems willing to properly diagnose it and repair it (and even thinks himself that it might be the fuel pump) Don't want to give her the car in this condition and don't want to pay for a pump (without the warranty if that isn't the problem). Engine tach reflects acceleration, but car doesn't speed up....is this indicative of some other problem like transmission (they serviced this as well), or transfer case problems? Warranty runs out in December and I can envision problem showing up right after the warranty runs out if I give up. Does it do any good to ensure the warranty company knowqs the problem, or will they ignore when warranty runs out/ I know I am asking a lot of questions, but I think you will understand my anxiety!

[dksob81]

Does the CHECK ENGINE light come on?

[DonMarine]

Originally Posted by dksob81

Does the CHECK ENGINE light come on?

No. No indictations that anything is wrong except for the jerking and bucking.

[dksob81]

well then I would say it could be a couple possible problems, Fuel Pump, Throttle position Sensor, or maybe Crankshaft Position Sensor,

I am going to point more toward the TPS to start. if u email me I can send u a test for the TPS.

Joe [email protected]

[Cam7]

I had this problem with another make but it was a bad coolant temp sensor short. Dont think it could be yours it would throw a code, service engine light would light up. Could be fuel related such as fuel pump. Try to elminate as much as possible without buying all new parts. Could be a CPS or Cam sensor , PCM and even a bad coil. Ive heard of coils going bad shorting out when the vechile is driven for a while and the coil gets warm enough to short out. One thing is that you said that it started right after work was done. Could be the Transmission trying to lock up. What speed was she going when the trouble started?

[erictlewis]

it sounds like the camshaft possition sensor, I had my jeep in the shop several times because i thought it was the trans, I had suspected the overdrive module, because it did that right at 50-55, and right around 80-85. Trans is the only thing I don't work on.

I never got it to code, until finally it broke big time then the engine shut off and would not stay cranked. Then I suspected the O2 sensors, so i replaced them myself, only to find out it was the camshaft possition sensor. This is a regular occurance on the 5.2 engine right around 100K.

[ChadEbert]

<Whewwwww> got my 5.2 to 115,000 without any issues and sold it, to think of the excitement I missed...LOL