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Old 08-03-2011, 01:02 PM   #1
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Lightbulb Loss of power in hot afternoons? HELP!!

Just bought a used 2001 Wrangler SE covertible, 2.5l, 5 speed Manual With A/C. Nice ride but having a few problems. 1st problem: Has power in the mornings and I get it up to 70 (Speedo is probably off due to large tires), and in the hot afternoons, it struggles to reach any kind of cruising speed (Usually around 50 - 55 MPH). Just had a complete tune-up. Thermostat maybe? Too big of tires? It has 32 X 11.5's on 15' rim 5 - 4.5 bolt pattern.

Also, AC / Heater dial only works for AC...No heat.....

suggestions, thoughts?

Thanks Folks.

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Old 08-03-2011, 02:22 PM   #2
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The 2.5 is never gonna be speedy. Running bigger tires adds to the problem and running the A/C will make it even worse. Are you running the A/C in morning when you say it has power? What makes you think its the thermostat?

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Old 08-03-2011, 10:04 PM   #3
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Are you going downhill in the morning and UPHILL in the afternoon>????
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Old 08-04-2011, 01:07 AM   #4
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Have someone scan it and view your IAT. There is a chance that its picking up too much heat. I know for a fact that mine did this with the 4 banger. The pig would not get over 55 in 4th gear on the highway.
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Old 08-04-2011, 06:29 AM   #5
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Buddha, yes, running AC in the AM and PM. I thought Thermostat as when I got it home, popped radiator cap off, gave it some juice, hardly any water flow as if thermostat is partially opened. Enough to keep engine from overheating, yet not enough to keep it running as cool as it should. In addition, the heater in vehicle isn't working when I turn the control knob from Blue to red....I figure no water is getting to heater core. I know the big tires will slow it down somewhat, but it only drags in the hot afternoons so I'm kind of ruling that out, unless they're melting and sticking to the roads. I drive up hillls and down hills both ways to work (LOL). Not sure what an IAT is outside of codes, which was just accomplished at dealer, no codes popped up.
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Old 08-04-2011, 02:57 PM   #6
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I don't know what IAT is either (unless it's internal air temp).

Did you pop off the radiator cap when you got to work in the a.m. to see if it was acting the same way? What temp does it seem to be running at? Mine runs between 195-210 almost all the time.

A thermostat is not a hard fix so if you think that's it it might be worth a try. Here are a few other things I've found while doing a little research. See if any of them seem related to your issue.

low engine power when hot out - JeepForum.com

Low Power - JeepForum.com

Vapor lock now that weathers gettin warm - JeepForum.com

How long since your last tune-up? It doesn't make sense that it would run fine in he a.m. but not in the p.m. because it needs a tune-up, but it IS A JEEP.
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Old 09-19-2011, 03:14 PM   #7
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U ain't in Texas are u buddah?
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Old 09-27-2011, 08:38 AM   #8
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Please don't remove the radiator cap while it's hot. I also loose noticeable power once the intake air temp gets high enough in my 4.0L (monitored with a scanguage II). I've read somewhere that the computer pulls timing once that temp reaches a certain level, but I don't remember that magical limit. I don't doubt someone has tried relocating the sensor from the metal intake to the plastic duct work like other mfg do, but I wonder if they cratered their engine to detonation.

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