93 JGC looses power under accel.

[J&J56]

Hey, I have Grand cherokee that I have recently purchased. I was on my way home this evening and while driving up my hill it started to surge. I then pushed on the throttle and It fell on it's face (total loss of power). It never died. The loss of power under heavy acceleration could be explained as a clogged fuel filter but the surgging while trying to maintain speed has me confused. 0Any help that you might be able to give would be greatful. Thanks.

[oljeeptek]

You should check the fuel pressure and volume first. If its going down, you could get a lean surge at steady speeds, and fall flat trying to accel especially up a hill.

You could also have an issue with the map sensor circuit and/or vacuum hose to it. It is the main load input to the pcm.

I would also check that the ign coil , cap and rotor are up to snuff.

[dksob81]

It sounds like you have a bad Throttle POsition Sensor.

[J&J56]

Thank you for the suggestions. I will check the fuel pressure, MAP, and TPS sensors as soon as I get another day off. I drove it today and all was fine. Thanks again for the response.

[hoofan]

Did you get anywhere with this?

I am having some similar problems and will probably check my fuel presure this week. But if I have something to go on from someone else, it would be great.

Thanks,

Bryan

[wpatters1229]

Sounds almost like my problem. Here is mine. Full tank of gas. Started to lose power like the gas pedal turned to mush and then the car died. Started up again and went a half mile and then died again and could not keep running. Was bucking and acting like mis-fires. Had it towed home. In the morning it started great and I drove it about 2 miles and it started doing the same thing. I replaced the fuel filter since I don't think it was ever replaced. Filter seemed OK...but who knows. Sprayed some starter fluid in the throat of the manifold to help it start and it ran long enough to use up the starter fluid and then died. Had it towed home again. Rolled it into the driveway and hit the key and it started just fine again and then after about 2 minutes of idling it started surging and then died. I then replaced the plugs, wiring, cap and rotor just because and it didn't change a thing. I suspect the fuel pump but I do not know how to check it and if it is bad how to change it out. This is a 6 cyc engine. All the hose etc. look fine. Don't see anything pulled loose or tweaked. My friend said to maybe drain all the gas out and put in a fresh tank since it could have water. I put two bottles of water remover in the tank and that also didn't change anything. Any ideas or explainations of how to test fuel pump pressure etc.?

[J&J56]

I checked the fuel pressure, changed the filter and did an intake system cleaning with sea foam. I then cleaned the Idle Air Control Valve. Haven't had the problem come back untill today. It runs great until you get on it. But I can put-put around town all day with no problems. Takes about two hours of city driving before it starts to act up. It's very possible that it's the TPS. I will probably buy a new TPS, MAP, and IAC then see where that leads me. I'll let you know what I find. (wpatters1229, Your problem definetly sounds like the fuel pump is gone to me. To check the fuel pressure you should go to your local parts store and buy a fuel pressure tester for fuel injected vehicles. It's about $30.00. It screws on to the rail that the injectors are conected to. There should be a cap on the valve that you will need to screw it onto. If you need more help let me know.)
Joe

[J&J56]

I changed the TPS and the IAC last friday and I havn't had had the prob. return since. Pretty sure that this fixed it. Thanks again for all the help.

[2BitJive]

Originally Posted by J&J56

I changed the TPS and the IAC last friday and I havn't had had the prob. return since. Pretty sure that this fixed it. Thanks again for all the help.

Is it still running good? I have the exact same problem with my 93 Limited (6cyl).

[protozee]

The jeep shake or shudder, misfire may occur when the vehicle is operated between 50 - 70 MPH Loss of power too

I tried 2 jeep dealers and they could not fix this, one said it was the coil, replaced it no help, and tune up, injectors cleaned too no help. The other on said it was the torque converter and pump it was under warranty, no help. So I think they just want to sell you something or they don’t know any more then we do, or maybe they throw the service bulletins away. So I did some research on the internet and this is what I found the trouble. So far
I have paid a lot of money at the dealers.

Late closure of an exhaust valve may be the result of no valve rotation and associated build up of carbon on the exhaust valve stem.

So I bought a 16 oz. bottle of Marvel Mystery Oil, put half in the gas tank and the other half in the oil. No more jeep shake or shudder or misfires.

By the way the $500 at the dealer for decarburizing



4.0L MULTIPLE CYLINDER MISFIRE
Date: 08/01/03
Model Year(s): 1999-2004

Description: NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A 4.0L ENGINE. This bulletin involves inspection of all engine exhaust valves and a decarbonizing procedure if necessary.

Details: The customer may experience an incident of engine misfire during certain vehicle operating conditions. The misfire may occur when the vehicle is operated between 50 - 70 MPH and under light loading conditions, e.g. slight uphill road grades. This condition may occur at all ambient conditions, but is more noticeable when ambient conditions are less than 0 C (32 F).

If the vehicle is equipped with On-Board Diagnostic (OBD), a MIL illumination may also have occurred due to Diagnostic Trouble Code (DTC) P0300 - Multiple Cylinder Misfire. Various single cylinder misfire DTC?s may also be present. If the frequency of misfire is high the Powertrain Control Module (PCM) may place the engine in ?Limp-In? mode.

The misfire condition may be caused by one or more engine exhaust valves that are slow to close. Late closure of an exhaust valve may be the result of no valve rotation and associated build up of carbon on the exhaust valve stem.

This condition may occur when the engine is not allowed to run at engine RPM?s that are greater than 3,200 RPM. At 3,200 RPM or higher the engine exhaust valves will rotate if not impeded by high carbon deposits. Low engine RPM?s and high carbon deposits are associated with short trip driving where the vehicle engine is not allowed to fully warm to normal engine operating temperatures. Cold ambient temperatures will increase engine warm-up time and add to the opportunity of carbon deposit build-up on the stem of the engine exhaust valve.