Hello everyone. I have a stock 2001 Jeep Cherokee Sport. I have owned it since day 1. My check engine light has been on for about a year now. The Jeep runs just fine. I had my mechanic pull the codes today. They are as follows:
He said usually with all of these errors, the Jeep would be running rough, if running at all. Here is what I have done so far: Replaced all spark plugs, new coil boots, had a new computer installed around 2002 for code errors, and replaced the gas cap. The evap leak probably just needs the smoke test. The misfires are what concerns me. The only time the Jeep will run rough is if I have been driving it (usually on hot days) for any length of time, I turn it off and let it sit for about 20 minutes and restart it. It usually shakes and the accelerator won't respond very well. After I get going, it runs fine again. Help?
I seemed to have the same issue. Couldn't get the engine light to stay off and the misfire codes kept showing up. The vehicle still ran great. I used Lucas oil fuel treatment and behold I haven't had any codes come up for months. Appears to have better gas mileage and only came on once recently when I was crawling around in the heat of the day, then my results were the same as yours. (It shakes and the accelerator won't respond very well. After I get going, it runs fine again.)
Summer heat vapor lock issues started to come into play, but my temps are running high. The vapor lock problem I believe is the overheating when the engine shuts off, causing a vapor lock. One thing I've had to do until I make the changes is lift the hood right away when shutting it off if I intend to not sit very long. Along with parking in the shade and never going where I will sit in traffic.
Going to put in a new t-stat, with a CSF 3 core and likely a new clutch fan. I'm also going to drop in hood louvers from gen-right. Positive this will take care of any problem with overheating. I also replaced the gas cap at the same time I started adding the Lucas oil fuel treatment.
You have the dreaded heat soak issue. I've been dealing with this since I bought it 2.5 years ago (and I had the same codes, plus more). Nothing I did would fix it, and I replaced literally everything related to it and nothing changed. I even went overboard with heat shielding stuff. The misfire would happen every single time I shut it down and restarted it while it was hot. There is a technical service bulletin for this problem and it consists of wrapping injector 3 with heat shield but this did not do anything for my issue, and for others as well.
I heard about rigging up the e-fan to run after shutdown so I gave in on this last attempt to fix it and to my amazement, it worked. Running the e-fan after shut down blows cool air right on the fuel rail/intake manifold and drastically reduces the temps, preventing the misfire. Since this fix, about two months, I have not experienced the misfire, even in 85 degree weather.
Some threads on me complaining about it and possible fixes:
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