P0456 Evap Small Leak P0303 Cylinder 3 misfire 2001 XJ

[Talyn]

The TSB by the way is a joke. Everything else out there that does that gets a new injector. Problem is Jeep decided some insulation was a cost effective (warranty pricing here) way to bandaid the problem which is crap injectors incapable of sealing at high temps. I'd just replace the culprits instead of wrapping junk around them- IF you verify first that they're leaking.

Its not the problem with the injector. Its the problem with excessive heat directed at the #3 injector. Even using a new injector, or different injector won't help. Its also not from the injector leaking, but the fuel vaporizing in the injector.

Also, there are two TSBs here. One is for the hot soak #3 misfire, which is the heat shield mentioned. The other one is for a cold start misfire, which is for the cold start issue.

 

[Talyn]

I've gotten cylinders 1 and 2 to misfire as well as 3 on occasion. Which NGK plugs do they recommend? I have standard champions in right now.

The stock application for the NGK will be fine.

When do the misfires happen? I know you said hot and cold starts, but you didn't mention the 1 and 2 misfire previously, so the TSB may not be 100% relevant here.

 

[LazersGoPEWPEW]

Yea the number 1 and 2 have happened on separate occasions and I want to say it was a cold start. I clear the codes and then they pop up maybe a week or a few days later. So I've stopped checking the codes over and over again. Sometimes my CEL turns itself off after I haven't had the issue for awhile.

I'd say most of the misfires happen on cold start but I did have a blinking CEL once after a hot start.

 

[Talyn]

The cold start issue could be the PCM reprogram TSB.

But I would rule out everything else before that. The NGKs will kelp with the misfires too.

 

[LazersGoPEWPEW]

I've heard that in the late models they used the platinum spark plugs as a stock feature. Should I get NGK plats?

 

[Talyn]

You heard wrong, the 4.0L never had stock plat plugs, and you shouldn't use them in it. Standard v-groove NGK plugs are fine. ZFR5N is the pn.