apshively

Hey guys,

My room mate has an 02 Grand Cherokee 4.7 with just over 100,000 miles on it. The last few winters she's been having issues with it stalling when its cold out. What we've noticed is that when its cold the Jeep will start up and run fine but at times when you are driving it from a cold start for the first time of the day it will die when giving it gas or too much gas. It will eventually warm up and will not stall out when giving it gas after she lets it warm up for a while or slowly drives it around the neighborhood. Although, if you come to a stop and idle long enough after it has warmed up, you can hear a fan come on and sounds fairly loud. If you get up to speed (say 40-60) and come to a stop you will notice it stops. It will start again if you idle long enough (3 minutes or so probably). One other thing we noticed is the Jeep takes a while for it to heat up and will only blow hot air when you are revving the engine or driving. Not sure if this is related at all.

Unsure of what to do I started searching and a few people were mentioning the IAC possibly. I cleaned the IAC but the issue persists.

Other things I heard mentioned were possible water pump failing, thermostat, water in gas lines, PCM issue but want to make sure I'm not spending money on unnecessary parts. Again, it ONLY happens when it is cold out.

Any help would be very appreciated!

apshively

By the way just to mention.

After cleaning the IAC last night, this morning she drove it to work and said it almost stalled out but didn't actually stall. So it did help a little it seemed but definitely still has an issue. It took about 10 miles for it to warm up and actually blow hot air. Also, the loud fan noise does still occur. She worded it as "a loud airplane noise".

Thanks!

CherokeeHoonigan

Yea my zj just started that blowing 0 air until i start driving then it lightly blows warm air, but the stalling at higher RPS seems like a fuel related issue to me. does it jerk and shove? could possibly be fuel pump?

apshively

It doesn't jerk or shake at all, it seems to be running fine it just cuts out when you give it gas after a cold start. It can be driven for a little bit after it's first started but I guess its when you give it too much gas, which isn't really all that much. It's not like she's pedal to the metal haha. Then it seems once you allow the engine to heat up some, it will not cut out and runs completely normal, minus the loud fan noise when idling for too long. The fuel pump and filter were both replaced within the past 6 months.

dave1123

If her 4.7 has an electric fan, the noise is normal. My 2000 4.0 has an electric fan and it doesn't start running until the engine reaches 210* at which time it turns on high with her "loud airplane noise", then cuts to low when the temp drops to 195* and runs at low until you shut off the engine. If the temp goes back up, it will shift to high again. If you stop, airflow thru the radiator slows enough for the temp to rise again.

The thing about the heater, I've found that when the air outside is REALLY cold, it doesn't have enough time for heat transfer with the blower on high. Try switching to "recirculate" and see if it heats up better, or switch to a lower blower speed.

About the stalling and stumbling. Check or replace the IAT or intake air temperature sensor. It's a variable resistor that changes with intake air temp and helps the PCM control mixture settings.

I always shift to neutral after starting and allow the engine and transmission to warm a while before moving the jeep. Immediate driving after cold startup is hard on ANY vehicle.

CherokeeHoonigan

^ once again dave nailed it. just figured out on my way home from work lower fan speeds do indeed work better for heat wish i would have found your comment quicker dave.

dave1123

Yeah, I figured that out driving around at -15*F with my window open delivering newspapers, freezing my *** off! I stopped, rolled up the window, and switched to recirculate. When I started to sweat, I lowered the fan speed, rolled down the window, and finished my route only slightly cold.

It's sort of like running no thermostat in a racing engine. The coolant is going thru the radiator too fast to get rid of it's heat.

CherokeeHoonigan

Yeah but it worked for my defrost this morning which is all i really need i have a coat so cold isnt to big of an issue its when im stuck scraping my windows in -15 degree weather that gets to be a pain.

dave1123

As long as we're on the subject of cold weather and coats, My Old Man once told me, "Dress like you had to walk. You may have to! You can peel off layers in the car, but at least have it with you." After spending time in a snow bank, I was glad he taught me that lesson. I even kept a comforter in a space bag behind the seat of my truck.

Most people don't realize the trans cooler in the radiator warms the trans as well. Jeep transmissions won't shift to 4th gear (O/D) until the transmission warms to above 32*F. That's one of the functions of the fluid temp sensor in it. By shifting to neutral and allowing the fluid to flow thru the cooler, it helps warm the trans as well.

CherokeeHoonigan

I have been taught the same thing ever since my father found a lady half frozen to death on the side of the road. she thought it was a good idea to get out of here car and try walking 4 miles to the nearest town since she ran out of gas. i always keep a coat and my welding hoody in my jeep and a nice set of gloves. Been stuck for 6 hours before luckily in the spring with no cell signal and its scary.