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Another Grand Cherokee problem


BrianZ06
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The new PCM fixed the stalling problem. I now have a tranny issue. This is a 97 with the 4.0 and 150,000 miles. If I drive it slow and easy it will go thru all gears fine. Soon as I get on it to go around someone or just want to take off harder it loses power. It seems like it does not want to go when you make it down shift. Does this sound like a torque converter problem. Fluid is good. I don't mind taking it some where for an honest opinion but where ? There are so many little electronic parts on this that is driving me crazy. Who has a a tranny code analyzer ?
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Bogs down and pretty much does nothing. I have owned a few slipping trannys and this is not the same.

 

Granted I've never messed with Jeeps, but this doesn't sound like a trans, it sounds more like a clogged exhaust, fuel pressure dropping off under load, ect. Not ruling out a trans problem, but I'd be looking elseware first.

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Funny you say that Im thinking the tranny is not the real problem also. The cat converter is new but the muffler is very old. I checked the air flow out the pipe using the official redneck method with my hand when someone gave it a little gas and and more pressure did come out. Im sure this method is not very accurate. Is there way to test air flow out an exhaust. Fuel related problem did not come to mind. Dirty fuel filter ?
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Funny you say that Im thinking the tranny is not the real problem also. The cat converter is new but the muffler is very old. I checked the air flow out the pipe using the official redneck method with my hand when someone gave it a little gas and and more pressure did come out. Im sure this method is not very accurate. Is there way to test air flow out an exhaust. Fuel related problem did not come to mind. Dirty fuel filter ?

 

There are back pressure gauges out there, but if I thought that was a real problem I'd pull one of the O2 sensors and go try it. This method doesn't hurt anything if you just do it to see if it makes a difference. Mufflers don't usually clog up, it's usually the cat if it is, but since its new I'd look into other things first. Get you a fuel pressure gauge and see what happens when the vehicle is under a load. Then I'd be looking into some live data on a scan tool, any misfires under load, what are the fuel trims doing, stuff like that.

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Thanks for the input. I actually took the o2 sensor out of the converter and drove it and it was the same. I read some where that dirty injectors can cause a bad bog down and I guess the fuel filter is in the tank only. I will look into it more tomorrow.
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Does it slow down, stay the same, or what. The GC's don't like to downshift much while going between say 15-40mph and not a lot can be done to fix this from what I've read.

You can always use the shift lever though.

 

If the throttle position sensor hasn't ever been changed it could be bad, I replaced mine to fix some intermittent fast idle conditions. Also the trans gov pressure sensor, gov pressure solenoid, and O/D / TC lockup solenoids are easy to change and go bad. I've changed them all in mine and it works much better. Tip don't bother trying to change the harness that comes with the O/D / TC solenoid assembly, you'll spend another hour and decide to just reuse the old one thats halfway built into the transmission.

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Also I did two treatments of marvel mystery oil + STP super concentrated gas treatment in mine and it did make a notable difference in performance. Though I'm at 170K and I bet no ones ever tried cleaning the injectors like that. I also sea foam the crap out of all my vehicles oil every few months and it keeps the oil nice and clean. Mine is my DD and it sees +1000miles per week though.

 

The fuel pump is also something that goes out, but more often its an o-ring on the fuel pump assembly that fails and causes backflow into the tank which causes the side effect of lower fuel pressure. If you run into the problem of having to try to start it more than once to get it going that is an indication of the problem.

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