Help! 4.0L Fuel? Problems -
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Unread 05-30-2012, 08:59 AM   #1
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Join Date: Aug 2002
Posts: 19
Help! 4.0L Fuel? Problems

Alright, so I'm nearly at my wits end trying to figure out my fuel problems.

Vehicle - 91 Comanche. 4.0L. 170k mi.

Problem - Jeep starts and idles fine. Drive OK while cold, warms up pretty quick. After warm, when starting from a dead stop, the Jeep stumbles heavily under throttle. (Very delicate throttle application does not cause a problem). If i stay on the gas, she'll die. If i let off it'll stumble for 15 seconds before coming back around (at which point i'll be at a dead stop).

I've replaced -
Fuel Pump (Bosch)
Fuel Filter
Threw in newer (cleaner) injectors from my old 97 XJ (I assumed their compatible).

Before I went to the Bosch Pump, I had some buzzing coming from a cheap-o pump. I checked the pressures at that time and it was 29 and 37 with the vacuum plugged and unplugged, but I haven't checked it since I replaced the pump.
The Jeep had been cutting out under throttle but not nearly as bad, and died on a hot day (only had problems at temp again). So I had gone ahead and replaced the pump. Figured the cheap pump was still causing problems since it was buzzing, so I replaced it with a Bosch.

Could it be the FPR, even though previously my pressures were in range? I can't think of anything else that I could be.
From what I can tell, everything else on the Jeep is stock, most of it may be original. I had driven it for maybe 10k miles before it ever gave me any problems (aside from leaky injector delayed starting).

Thanks for any help,


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