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Random rough idle

Mitchs07explorer

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Joined
August 14, 2015
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Location
Idaho
City, State
Meridian, Idaho
Year, Model & Trim Level
97 XLT V8 AWD
07 XLT V6
Just got my Ex back yesterday, it now has a Remann transmission and I plan on keeping it for the long haul. Everything else for the most part is in pretty good shape and lots of other new parts. I’m trying to figure out this rough idle I get on occasion when I start my vehicle. I’ve noticed that I seem to get the rough idle after I’ve filled my tank up with gas and it also happens if I’m parked on an incline but can happen on flat ground too. After 10 seconds it clears itself up and runs smooth. Every now and then my cel will turn on and throw the code P0442 (small evap leak). I replaced my evap canister purge valve, gas cap and I also replaced my EGR valve. Not sure yet if I got rid of the p0442 but I definitely still have that weird ocassional idle. Anyone have any ideas as to what might be causing the weird idle?
 



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I had a kinda similar thing. I would start it and the idle would seem "off" I guess you could describe it as rough. I never waited to see if it would go away, I just shut it down and restarted, and 9/10 times it wasnt there on the second start, 1/10 I had to try a third time before it was good. Never got a CEL, so I just lived with it. Then one day at work I couldn't get it to go away with multiple restarts, so I just drove home, and finally got a CEL, Cant remember the exact code but it was misfire on cyl 1. So I cleared the code and swapped plugs in cyl 1 and 3, and the code followed the plug. Replaced plugs and have not had an issue since.

Of course, I remember another thread on here with a similar story and it turned out to be the ignition coil.....
 






I had a kinda similar thing. I would start it and the idle would seem "off" I guess you could describe it as rough. I never waited to see if it would go away, I just shut it down and restarted, and 9/10 times it wasnt there on the second start, 1/10 I had to try a third time before it was good. Never got a CEL, so I just lived with it. Then one day at work I couldn't get it to go away with multiple restarts, so I just drove home, and finally got a CEL, Cant remember the exact code but it was misfire on cyl 1. So I cleared the code and swapped plugs in cyl 1 and 3, and the code followed the plug. Replaced plugs and have not had an issue since.

Of course, I remember another thread on here with a similar story and it turned out to be the ignition coil.....
I think it w
May have been another post of mine because I remember reading this before. I think it was about my other ex which turned out to be a burnt sparkplug wire. On this (07 4.0) ex it’s about as random as you described in your situation butvthe rough idle clears itself within 10-20 seconds and then idles smooth. I thought I’d read somewhere that those symptoms could have to do with evap system but I can find anymore info in regards to anyone having similar issues to mine. It’s just so random it makes it impossible for me to pinpoint and I hate to take it to someone because they’ll hang onto for a few days and probably won’t be able to replicate it :(
 






If they had the battery off for a while doing the transmission, there is a throttle body adaptation cycle that takes about 10 minutes from cold start through warm up. There are some good video on this topic, I did it after replacing my radiator and it made a big difference.
Also maybe a good time to clean the throttle body.

 






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