Question about 2003 Jeep Grand Cherokee

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2003 Jeep grand cherokee, 6 cyl; Had a slew of problems. My transmission was slipping, shuddering when you got to 51 to 54 mph, and speedometer was haywire causing me to use my gps to check speed. Check engine light was on, codes 306 and 123. Checked the tps voltages, found that the Haynes manual had me checking the wrong pins for voltages. Got that squared away and found I had to replace the TPS again. Erased codes, now no check engine light. Wasn't aware that the TPS could cause so much...Replaced the oil, filter, transmission oil and filter, adjusted the bands per the book. (Man, that front band screw and bolt is a bear to get at!!!) Still had a little slipping in lower gears and it would at times rev up past 3500rpm then catch itself and run normally. While driving, the engine shuddered and just felt like it was out of balance, got the check engine light, checked and it was code 306 again. Checked oil levels again, seems like I didn't add enough trans fluid. Book said capacity of trans is 4 qts, thats what I put in. level is just barely at bottom of dip stick, getting 2 more quarts, maybe will fix rest of problems. If after this dissertation, you think I should check something else, please let me know. I did checks in accordance with Haynes book for my 2003 Jeep grand cherokee for vacuum leaks, fuel system, etc......

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  • juan433 Sep 03, 2010

    Thank you for the reply. Filled the tranny to level took it out for a spin and now I have another issue along with the p306, the shudder was a little worse, the check engine light was flashing, pulled over, stopped flashing, when I checked; a new code P0155 O2 sensor issue.????? Will it never end from now on....seems like the TCM and PCM are competing for my attentions:(

  • juan433 Sep 03, 2010

    Thanks for the additional comments. I changed the fuel filter and checked the vacuum hoses, but I'll check them again using your method, Great idea! Will let you know about the IAC when I'm done, won't be til next week though. Tahnks again...

  • juan433 Sep 28, 2010

    Did all of the above. Found a few cracked vacuum hoses and replaced them. I have not checked the fuel pump pressure yet. Hopefully that will be the propblem causing the rough idle and shuddering between 52 and 54 mph. Thanks for the help.



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I don't know why they put in the book that it takes 4 quarts if it takes 5 to fill it to specs.

Well, it seems that you did all the hard work already. the only thing left to do is add a bottle of Rislone Transmission Stop Slip and Sealant. $10 at AutoZone or similar autoparts store. This stuff works great on slipping transmissions.
You would see the difference after just 10-15 miles, and it seems the more you drive it, the better it feels. The wife says it saves $$ on gas. She must know. : - )

If you haven't fill the tranny to level, add the additive first and then top it up with fluid. Do not overfill. If it is leveled, use a pump to get some fluid out thru the dipstick tube, add the Rislone and top it up with fluid.

Good luck!! Don't forget to rate this post!!!

Posted on Sep 03, 2010

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  • Rene J Solis Sep 03, 2010

    Very carefully check for vacuum leaks, hoses can be cracked, loose or disconnected. What I do is unplug every single one of them and cut about 1/8" off, this will make the connection tighter and at the same time check for toasted hoses.

    Also, remove the two screws holding the IAC (Idle Air Control) Solenoid, located on the Throttle Body, use a rag wet with fuel injector cleaner and wipe it clean, it is going to be dirty, then wrap the rag on a pen or pencil and clean the solenoid's housing, particularly the far end, where the solenoid seats. DO NOT APPLY FUEL INJECTOR CLEANER DIRECTLY INTO THE SOLENOID OR THE HOUSING.

    Compress the solenoid with a twisting motion before installation, do not use too much force. No need!!

    Keep me posted!!

  • Rene J Solis Sep 03, 2010

    Replace fuel filter if you haven't done so and check fuel pump pressure, you can borrow a tester from AutoZone or similar Autoparts, no need to buy one.

    Integrated with the fuel pump assembly is a fuel pressure sensor, when faulty, it gives you all kinds of codes. Make sure the fuel tank cap is tight

  • Rene J Solis Sep 03, 2010

    Don't forget to check the fuel pump pressure!!!!!



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