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Discussion Starter #1
I was on a trip and after 400 miles i hit the cruise back on and when it downshifted it fell on its face. Eventually could not maintain speed and had to pull over. Air temp was 85. Put fuel filter on went for a drive and it ran fine. Next day after 250 miles it did it again. Air temp was about the same. Only code was for o sensor and changed it. Drove 15 miles to interstate and it did it while accelerating. Pulled over turned engine off for a few minutes and restarted.Air temp 93. Ran about 30 mile before it happened. After several more times it went fifty miles and sun was going down. Drove through the night using ac sparingly as it seemed to help not having it on and had no more trouble.What is the problem?? Please help!
 

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2007 Kia Rio5, manual, roll up windows. 1996 Dodge Ram 1500 4x4, 5.9L V8
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How's the engine temp? Do you ever see it rise when this issue occurs?

The first thing that comes to my mind is a fuel delivery problem. Maybe check out the fuel pressure. Other than that, check cooling system.
 

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Cerato S Hatch Auto
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How was the fuel usage during these episodes? Did you have to fill up more than usual? Strange that you experienced the problem when cruise control was turned on; maybe demand on accelerator input was out of normal range?

2002 losing power often indicates blocked CAT.
 

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Discussion Starter #4
Engine temp never change. Fuel use was fairly steady over the 1400 miles. Not as good as before but no sharp decline.I did change fuel filter and almost changed the pump but do not believe the fuel pump is bad.
 

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Discussion Starter #5
I have had a couple of mechanics suggest catalytic converter may be restricting when hot. The symptoms could be exhaust restriction ,air restriction or lack of fuel when hot. At least in my mind!Do these have sensors in the converters? If so I had no codes for it. I did consider mass air flow but when it happened I unplugged without turning motor off and tried to go. It made no difference but if I shut the engine off and restart it runs. Now I have found it seems like the longer it was shut down the longer it would run with out symptoms. This does support the idea that it could be temp related.
 

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Has this been solved?

I have the exact same issue except that I don't have cruise control.
I'd been driving over 12hrs continuous twice in the past week with OBD / Torque Pro scanner monitoring. What I can see is that when power starts dropping (after 3-4 hours driving), the STFT wobbles all over the place and LTFT starts rising, eventually maxing out at 25%.

My fuel pump & filter are less than 2 years old. Both O2 sensors are also under 1 year old (upsteam is 1 month old). Have tried removing and cooling fuel / main relays when shutdown for 15 mins, waiting for cool down to restart. This didn't help. Tried swapping sides with relays, no change. Will be picking up new relays this afternoon.
Also will be trying to get a measurement on fuel pressure and considering the fuel rail damper as a potential issue.

My issues also go away when driving overnight / cooler outside air temps. Engine is not overheating, there are no cooling issues there. Seems like something is getting "heat soaked" and causing lean fuel condition...
 

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97 sportage 06 forester XT
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Recently changed my damper on the fuel rail, no change there is not much to go wrong in it i would reccomend that as a last step its a pita to change out ( and its 50 bucks =( ). Is yours a 2002 also? believe they have an air temp sensor dunno what it affects. I would get some new relays, clean the Maf sensor, and check the fuel pressure regulator. I had an injector that would not work when hot but that was only on restart. Someone said tps can be faulty when hot might wanna check the sweep when its up to temp.
 
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