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Unread 07-19-2010, 09:39 AM   #1
YouStupidBunny
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What is the highest engine operating temperature?

2001 2.5L
Automatic

What is the highest ambient operating temperature for the Wrangler?

In the mornings and in cooler seasons, my Wrangler runs perfectly but these past few weeks our high temperatures here in Vegas are around 110+ degrees with zero humidity.

My idle began running rough, but runs fine when moving. I noticed the idle gets rough in extreme temperatures only. The guage doesn't go up much. Just around 215-220. Doesn't sound too alarming, but when the themostat opens and the guage reads around 210 and lower, the rough idle goes away. The issue seems to be associated with heat or it's a symptom of something else.

Known to be good:
IAC
TPS
Upstream O2 sensor
Battery
Water pump
Coolant temperature sensor
No leaks
Coolant is new
No coolant in oil

Against the good advice on this board, I replaced the thermostat with a 180 degree one. When the ambient temp went up, it just stayed open all the time, the temps stayed up all the time and didn't help at all.

Went back to stock degree thermostat and it helped a bit. Mostly, it delayed the rough idle.

Other than the high ambient temperatures, I can't associate anything else with my problem. 105 degrees, the Jeep runs fine. 108 seems to be the cutoff point and starts to intermittently idle rough. 110+ and the Jeep is an idling mess.

This isn't something new. I chase this same problem every summer when the temps get this high. When it cools a little, the problem goes away and I stop looking. The rest of the year, it runs perfectly. These extreme temperatures only last a month and a half.

Could the ambient air temperature be the problem and if so, does anyone know what the highest operating ambient temp is for the Jeep?

What could I do to help if that is the problem? Larger radiator? Electric fan? Hood vents?

Thanks, in advance, for the help, men.


Last edited by YouStupidBunny; 07-19-2010 at 09:50 AM..
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Unread 07-19-2010, 03:37 PM   #2
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It did it again. Another 110 degree day.

I probably drove about 50 miles in a mix of highway and stop and go city traffic without problems. It was fine all morning with heavy driving and only started this afternoon when the ambient temps went up. It has to be the heat, right?
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Unread 07-19-2010, 08:00 PM   #3
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Now it gets more confusing. It did it again this evening, but the guage never reached 210. I think the temperature just may be a coincidence or something triggering another problem. I'm stumped.
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Unread 07-19-2010, 08:02 PM   #4
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Vapor lock?
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Unread 07-19-2010, 08:16 PM   #5
gilg2533
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I would suspect that you have an electrical component that is failing. Temperature differences such as you are describing can often cause parts that are beginning to fail to cause intermittent problems. When i used to work as a tech when we had intermittent problems like this we would trace down the problem and then use a heat gun to heat the component up to duplicate the issue. Aditionally if you ever have a problem with something in cold wether take the part off wrap it in a paper towel, place it in the freezer for a few hours and then re-test.
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Unread 07-20-2010, 07:05 AM   #6
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Quote:
Originally Posted by gilg2533 View Post
I would suspect that you have an electrical component that is failing.
Which component would be your first guess? I've replaced everything I could think of that would cause a bad idle.

I took my hood off this morning to see if the heat is a contributing issue. If a part is going bad because of the heat, I know taking the hood off to fix will only mask the real issue, but at this point that will be good enough for me.
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Unread 07-20-2010, 07:09 AM   #7
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Quote:
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Vapor lock?
I considered vapor lock, but I thought it was less likely since it's a fuel injected, pressurized fuel system. Am I wrong in thinking this?
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Unread 07-20-2010, 03:08 PM   #8
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Figured it out. It was the Jet Stage II chip. Had it for about a year. Was about to put the PCM into fast learn mode, saw the Jet chip and thought I'd see if that was the problem. Pulled it, then reset the PCM.

All is well now. In fact, all the positive effects that I thought were from the Jet chip were still there after I removed it. I fell for the ads and convinced myself it worked. Placebo effect sure is powerful if you want something bad enough.
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Unread 07-20-2010, 03:57 PM   #9
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Those chips advance timing. As intake temps increase you need the less advanced timing in order to compensate and prevent knock, ping and detonation.
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Unread 07-20-2010, 04:45 PM   #10
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Quote:
Originally Posted by YouStupidBunny View Post
Figured it out. It was the Jet Stage II chip. Had it for about a year. Was about to put the PCM into fast learn mode, saw the Jet chip and thought I'd see if that was the problem. Pulled it, then reset the PCM.

All is well now. In fact, all the positive effects that I thought were from the Jet chip were still there after I removed it. I fell for the ads and convinced myself it worked. Placebo effect sure is powerful if you want something bad enough.
Another smarter person on the forum...
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Unread 07-20-2010, 08:17 PM   #11
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Ok, removing the Jet chip helped, but the problem came back again. I put the hood back on thinking I fixed it. I took it off tonight and will drive it the next few days without to see if that helps. I still believe the problem is somehow related to high ambient heat.

The temp gauge doesn't go up much, but it only idles rough in extreme heat.
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Unread 07-20-2010, 09:08 PM   #12
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There has to be something not right bc I live in the burning desert and have those issues, there are a few guys here from Saudi and Lebanon and such and those of us who were lucky enough to visit those great sandboxes know what real heat is!! 125 in the day can be the norm and those TJ take it so something isn't quite right. Nothing else to suggest but the can and do run in extreme heat so...
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Unread 07-21-2010, 01:41 AM   #13
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I live in Georgia and it has been hot here the past 3 months, so i feel ya on the heat. Check the fan clutch and see if it is worn out. Also I would not swap the E-fan in your Jeep. I put one in my Jeep last summer and it gave more problems than it helped.
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Unread 07-21-2010, 07:07 AM   #14
Zen
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Quote:
Originally Posted by gilg2533 View Post
I would suspect that you have an electrical component that is failing.
I'm with this guy now...

When the engine is warm knock on the PCM and see if the engine stumbles. Is the Jeep throwing any codes? Even if the light is off check if there are any pending codes.
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Unread 07-21-2010, 08:21 AM   #15
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No codes. I'm sure it is something electrical. I just can't figure out which piece.

When it does idle rough, as soon as I tap the accelerator, the engine is smoother than ever.

What would tapping the PCM do? I used to do that do old TV's growing up. Sometimes it worked.
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