slathrum

I just bought a 2001 XJ. It's my first Jeep and I'm discovering this lovely heat soak issue in the hot weather. Codes I'm getting are P0205 and P0305 - cylinder 5 misfire and cylinder 5 open circuit. Only happens when restarting the engine warm. It does not clear itself up though with driving. It will continue to misfire until you stop and let the engine cool down. So far I've insulated the injectors and fuel rail and switched to a 180 Tstat, and while it has helped, it's obviously not fixing the problem of heat from the exhaust to intake manifold. My next idea is to just go for it and replace the exhaust with a new header and catback, while making sure I wrap the header up real well. Sound like a good plan? Anyone else have any thoughts or luck with this? It sucks dealing with the misfire, when otherwise the engine will run as smooth as butter for as long as you want, as long as you don't start it hot!

95Cherokee

Install some hood vents, they will reduce under hood temp by 20 degrees or more.

Not saying this will solve your problem but it can't hurt.

KTMrider

There are many different approaches poeple have had tot his issue. None are full proof. But the two that seemed the best and had the best results (from what i've seen) are hood vents and a E fan relay by pass. I think that spending the money on new headers would be a waste. Look into hood vents(cheaper) and there is a by pass for the E fan to have it on at all times the key is in. I will see if I can't find the link. I am lucky enough to have only read about the problems on heat soak and not expirence them. knock on wood. Hope i helped!

KTMrider

I couldn't find the thread on how to rig the E fan on, but if you wanna heat wrap your header go for it! Just be a PIA.

ReblTeen84

I had this problem a year and a half back or so before I learned what I was doing - I got code P0303 out of it. After a craptastic amount of money spent trying to fix it, the dealer finally did their job. Per Chrysler, an insulator on the cyl 3 injector and an upgrade to the PCM to make the e-fan kick on earlier fixed it. I've had a rough idle on the hottest days, but only lasts a minute or two until the fans cool it down.

Vegas

your misfire in cylinder 5 due to heat soak is a bit new/unusual to me. on the newer Cherokee I6 HO you would get your problem but it is usually cylinder 3 that misfires like ReblTeen84 said. its the way they designed the new intake that sits cylinder 3 fuel injector too close to the exhaust that would heat up and cause this. i live in Vegas desert and during summer after extended drives with the AC on it would restart real rough and misfire. at first i thought it was a coil pack problem but found it was the injector getting too hot. i went and got a spark plug insulator wrap, a $10 part from Jeep, and used it to wrap the injector. this was early last summer and have had no problems yet. i would say try this before spending any unnecessary money like i would have. good luck.

slathrum

Thanks for all the replies. So far I've wrapped every injector and the entire fuel line under the hood with spark plug wire insulation. I'm thinking my next immediate plan will be to install hood vents. I still want to get an aftermarket header like this one - http://www.ineedparts.com/auto-parts...-manifold.html and upgrade the rest of the exhaust too. I'm thinking a basic catback with a Borla muffler should sound pretty good. Hopefully by attacking this from all angles I can cut down on the underhood heat.

slathrum

Interesting new development - Since I insulated the fuel injectors and rails, sometimes when I start the jeep hot and it cools off with some driving around, I can get it to stop misfiring by stopping at a stop light and restarting the engine. I'm not so sure this is just heat soak. It's obviously a part of it because it only happens on hot starts, but could I be having a problem with the actual injector, or the ECU? Its like once it recognizes a misfire, the ECU just ignores that cylinder even though the problem may no longer exist.

Vegas

what are the specs of your Jeep? year, model, engine, drivetrain... its not in your profile info.

slathrum

Sorry, I'll get that updated. Basically a 2001 Cherokee Sport 2wd with 4.0 and automatic.