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do ALL 4.0s run like crap until they warm up?

X

xj88superjeep

NAXJA Forum User
Location
NJ
Just curious if everyone's 4.0 runs really crappy in cold weather until they reach operating temp, or if it is just the 2 I own? They both run GREAT, but when it's cold out, they are really sluggish run like crap to the point that I have to drive like an old lady until they warm up. Could it be because I run 15w40 oil?
 
X3, summer I run 10-30 but winter i run 5-30, but it runs fairly well when cold.
 
The only thing that mine does when its cold is if i put in the throttle too quickly it stutters and sometimes dies. Besides that it runs perfectly.
 
when cold mine will bog until the temp comes up alittle i herd it`s common
 
I run 15w50 in mine, it runs great when its cold.

Of course, it takes my transmission three minutes to grab any forward gear when its cold out, so it may just be warm before I'm moving.. ;)
 
PurpleCherokee said:
If it runs that badly cold then you might wanna look at your computer :shiver:
Click to expand...
How is looking at his computer going to help?

2u7ubs0.jpg
 
My red Jeep with it's modified HO throttle body (and Renix ECU) thinks it's carbureted, it idles rough if it's stone cold (sitting overnight cold). After about 30 seconds to one minute it smooths out and idles well. (and it just runs well anytime, it only acts weird on idle)


I don't really care, it's much better than having to wait five minutes before driving my '71 Ford with a 390 because it hates being cold!
 
GSequoia said:
My red Jeep with it's modified HO throttle body (and Renix ECU) thinks it's carbureted, it idles rough if it's stone cold (sitting overnight cold). After about 30 seconds to one minute it smooths out and idles well. (and it just runs well anytime, it only acts weird on idle)


I don't really care, it's much better than having to wait five minutes before driving my '71 Ford with a 390 because it hates being cold!
Click to expand...

My '62 F100 runs like its warm after 15 seconds, no matter what the outside temp is. You need to adjust your choke.
 
Well, at this point, both of my Jeeps are mechanically sound as far as engine and sensors are concerned, and the 97 has a brand new reman and reprogrammed PCM. In the summer, when I got into the whole oil debate, I found through a few different oil changes that my 88 ran better with higher oil pressure, better compression, and less leakage on 15w40 diesel oil. (that was before the felpro VC gasket) I also like that the diesel oil endures high operating temps without burnoff (the 88 was a hot head until I overhauled the cooling system) and has extended drain intervals and lots of zddp. A few other guys swear by diesel oil too, and since it worked well for me, and I bought my 97 with almost the same amount of miles I went with it. Both my trucks run great, they just make a LOT of comotion over 2500 RPM, and they seem like they are being held back when it is cold out and the engine temp is below 200*... Once they are up to temp, they run perfect and love the go pedal!
 
I'm sorry, but in the Winter (especially on the '97) I'd run a 5w30. I know there's a lot of Internet forum talk about running diesel oil in vehicles that don't call for it, but I put much more faith in the engineers at Chrysler than forum talk.
 
My 2000 runs good all the time. As long as you can crank it enough to start it, I don't think the oil makes any difference in how it runs. (At least until right before it seizes up.) But running a motor hard before it warms up always causes accelerated wear on the piston rings and cylinder bores, so you shouldn't even try to see how good it runs cold.:nono:
 
winterbeater said:
My 2000 runs good all the time. As long as you can crank it enough to start it, I don't think the oil makes any difference in how it runs. (At least until right before it seizes up.) But running a motor hard before it warms up always causes accelerated wear on the piston rings and cylinder bores, so you shouldn't even try to see how good it runs cold.:nono:
Click to expand...

This is my train of thought also... I try to keep the RPMs under 2000 until I reach operating temps (and I actually warm up the engine BEFORE I drive as often as possible) simply because I KNOW it's much healthier for the motor and extends engine life... But even with that in mind, I've never seen a difference between pre operating temp performance and normal operating temp performance as big as I have in these 4.0s
 
robert2008 said:
I'm sorry, but in the Winter (especially on the '97) I'd run a 5w30. I know there's a lot of Internet forum talk about running diesel oil in vehicles that don't call for it, but I put much more faith in the engineers at Chrysler than forum talk.
Click to expand...

To be fair, I based my choice on personal experience with high mileage motors, knowledge that mechanics have used diesel oil to extend engine life in gasoline engines, and as I said, the fact that the 88 performed better with it than the 5w30, or 10w40 high mileage oil. This had nothing to do with internet lore, I actually chose the diesel oil over the "mobile synth" that everyone on the internet pushes because I've had a car that never leaked a drop, and the second I put a synth in it, it leaked like a sieve (and no, it was not gunked up with dirty oil that was keeping it from leaking) and it also started tapping that disappeared once I switched back to higher viscosity dino oil... but the oil debate will rage on, I'm sure.
 
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