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my 1988 Jeep chereokee act's like it's out of timing


 
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opeluman
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Joined: 06 Jul 2005

PostPosted: Wed Jul 06, 2005 5:02 pm    Post subject: my 1988 Jeep chereokee act's like it's out of timing Reply with quote

Hi everybody...I have a 88 jeep Cherokee 6 cyl with mpf injection . When the vehicle gets to operating temp, it acts like the timing is off. Just giving it the gas causes it to sputters jerk and it has no power. If I floor the car its takes off like a bat out of hell. Have changed the fuel filter, all injectors and fuel rail, MAP sensor and the fuel regulator, no help. Also the car over heats when I pull a hill. Can anybody help.
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deadonarrival
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Joined: 06 Jul 2005
Location: Spring, TX

PostPosted: Wed Jul 06, 2005 9:05 pm    Post subject: A little help on your problem Reply with quote

I am not sure but jeep XJ on some of the years had a different cooling system, Unsure or the technical name. The fill access port for the system was the overflow bottle and no access to the radiator. They had a problem of overheating. On the missfire check the cam sensor, if it is going bad it will act up when the vehicle is warm but will not set a engine code. 1988 timing is computer controled and the only timing problem you could have is if the timing chain is jumped, old age, 100,000 miles plus
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ThePhantum
Pissed-Off Admin
Pissed-Off Admin


Joined: 23 Jan 2004
Location: I knew it...I'm surrounded by Assholes!

PostPosted: Wed Jul 06, 2005 10:02 pm    Post subject: Reply with quote

The 87-90 XJ's have a closed cooling system. There is no radiator cap and no overflow tank (as in traditional "open" systems). Instead it had a pressure tank, which is where the system is filled. It then needs to be "burped" of air (hence the term "closed"). If there is air in the system it will give you fits. Even the Jeep engineers admitted that the closed system was "a colossal mistake". It can be switched over to an open system fairly easily. Here's a writeup.

I doubt the timing chain has jumped because when you kick it in the guts, it goes. The sputtering could be any number of things. Have you checked fuel pressure at the rail? If it's under 30, my money is on the pump (since you've got a new regulator).

You can also check to see if you have a leaky injector with the gauge. The pressure should be around 35 when you turn the key on (which turns on the pump). When you turn the key off, the pressure should stay for at least 5 min. If it drops before then, you have a leaky injector so pull your spark plugs. The one with the most carbon build-up is the winner...the injector for that cylinder needs to be replaced.

If all that checks out, a vacuum leak could also cause the problem. Spray some carb cleaner on each vacuum line connection point. If the engine pitch goes up...you've found a leak.

Also try the normal gallery of culprtis; TPS, MAP, and CPS sensors.

Have you done a compression test on the cylinders? If something there is not right, you've got bigger problems.
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opeluman
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Joined: 06 Jul 2005

PostPosted: Sat Aug 06, 2005 2:33 am    Post subject: Reply with quote

Hey just want to let anybody who might be interested in finding out the problem with my Cherokee and how I fixed it. Took a fuel pressure reading at the fuel rail and I only had 21 PSI...and when I shut the engine down it dropped to 0 immediately. So I changed the fuel pump and that solved the problem. I also installed a 2 core radiator and now the engine runs at 210 norm and 220 with the A/C on and in traffic. Thanks everybody for your help
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