Jeep acting weird in cold weather.

TapouT

Well-Known Member
Joined
Oct 5, 2008
Location
Hickory nc
I just bought a 1994 Jeep Grand Cherokee with the 4.0 in it. In the mornings when it's cold outside on the way to work the Jeep stumbles pretty bad and surges while I'm driving..if i start to give it more gas it will stumble and pop through the exhaust. I live literally 5 minutes from my work and I'd say that halfway there the Jeep will stop stumbling and run fine. It only does it in cold weather though. I can start the Jeep up in the afternoon when it's warm and just hop in it and go, no problems whatsoever. What could be causing this?
 
On a serious not though, when an EFI behicle is cold, in runs in what you call 'open loop', this means its taking no readings from the o2 sensor and running the vehicle pretty rich, it also operates in open loop during WOT. Then when it goes into closed loop it leans out the mixture. The above response would be the most likely, worn ignition components would make it run crappy while in open loop.
 
I let the Jeep warm up for close to 20 minutes this morning then drove it to work and it did absolutely fine..weird!
 
mattb6679 said:
Have you checked the cap/rotor and plugs. Sounds like ya need a tune up.
Click to expand...

My money is on bad spark plug wires and/or moisture/corrosion in the cap. Try this, tonight after dark grab a spray bottle with some water and spray down the engine with no lights on. You may see a lightning storm under the hood if your wires' insulation has aged out. The engine will stumble too. If the cap is pretty old you will have corrosion deposits on the contacts inside the cap. Filing these clean will help short-term but replacing the cap is the fix.
 
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