Hi Guys, i recently got a 1999 Jeep Cherokee Sport i love it and all but theirs all kinds of little things wrong with it.. Could anyone try to give me a clue to whats wrong with it? if i dont let it set for like 5 minutes when i start it i can take off down the road and it will sputter and jerk all over the place until i hit the gas hard and it stops.. or i slip it into neutral and rev it a few times and slip it back into drive, Then it drives normal but it gets annoying after awhile.. i have no clue how to figure out the problem my mom took it to her work and hooked it up to one of the high $$ computers that look for issues on your car and mine passed with no errors.. iv put 700-800 dollars into it trying to solve the problem but still their was no luck. iv even had it taken to a guy who took a 2 yr class about working on Jeep/Dodge/Chrysler cars. and he couldent even tell me what was wrong with it.. i dont think its the transmission or anything nor the fuel because iv had the gas tank dropped, new fuel filters and so many more things.. it was wrecked in the past that i know of but in the rear end of it.. any idea's guys? i would really appreciate it

 

No Suggestions?

 

Have u tried replacin the MAP sensor? my jeep was doin that a while back but mines a manual not auto idk if its different or not but it shouldnt be. it should be the sensor on your firewall it has like 3 wires comin from it with a vaccum line that goes to your manifold replace that sensor and clean the line and tell me wat happens

 

#1 (upstream) oxygen sensor. I know exactly what you are talking about. Once I disconnected it (seized in good, also rounded off now ) The bucking stopped.

 

Test your throttle position sensor on the throttle body. Mine had a very similar problem. If I wasn't on my phone I would give you the link to how to test it.

 

*Always review tuneup hardware. Plugs, wires, cap, rotor

*Oxygen sensors have a finite lifespan of between 100k to 150k. If yours is old or original, get them out of there. At least the upstream (pre-cat) one as that contributes to fuel / air mixture

*Coolant temp sensor and map sensor can be tested with a meter and a manual. Has the computer been scanned for any "stored" codes? Should do so, even if the check engine light is not currently on.

*Testing of fuel pressure (with a gauge; looking for 49 psi plus or minus 5 psi) and also testing of the throttle position sensor would be of value here.

TEST your way to a solution. Don't throw parts at this.

 

Also note about the oxygen sensor...a faulty one will not always throw a code. Case in point, mine. My Jeep was sputtering and bucking once started and slamming the gas fixed it for the time being, but no check engine light. I disconnected the sensor's harness and the bucking stopped and check engine light came on.

 

Did you ever figure it out? My 99 is doing the same thing right now 156K miles. Gonna try unplugging the O2 first and see.

 

Hi all,

How about the crank angle sensor? Mine's a '98 and it does it when hot but as soon as it is moving and 'cools' a little problem gone.
A few Jeep folks here have suggested the CAS. My brother's Alfa did the same. The car stopped when hot but leave it for a while it would start and run fine 'till it got hot again.

Bought a new one and having it fitted today.

My 10c

Oliver

 

Unplugging the upstream O2S is an exercise in futility.

I had the same issue years ago and changing the ustream O2S fixed it.

Use only NTK O2S.

 

swapped #1 (upstream) oxygen sensor and its fixed

 

Good work.

 

Could the OP tell the forum what parts have been replaced and or tested? It sounds that possibly a sensor on the 5v circuit is defective or possibly shorted to ground. I would suggest testing the following sensors. The MAP , TPS , B1S1 O2 heater element , Crank and Cam sensors. These sensors should all share the same wiring circuit, also might be a good idea to check the physical condition of the wiring along with the fuses and relays along this circuit.