Modérateur : valJeep
ça me parait correspondre.Symptom: Engine idles poorly or is hard to start when hot, but clears up after a few minutes and acts completely normal.
Description: "It's 90 degrees outside and I just got off the highway to get gas. I got to talking with someone else about XJ's and when I got back in mine 10 minutes or so later, it wouldn't start/it started and idled VERY poorly, like it was missing on a couple cylinders. After a few minutes it started and ran like normal."
Cause: The later year 4.0 engines tend to have this problem a lot. Due to the design of the exhaust and intake manifolds, the fuel injectors can get very, very hot, and the fuel inside them will boil and turn to vapor. This often happens after a long(ish) drive on a hot day. You park your Jeep at the store, and with the engine off, there is no air flow to keep things cool. The under-hood temp climbs, and the hot spots tend to be the fuel injectors for whatever reason - specifically, Injector #3 gets the worst of it. Then when you get back in about 10 minutes later, when the temperature has risen as high as it's going to get, you get the rough idle/no start symptoms. Eventually the vaporized fuel will be pushed through the injectors and fresh fuel will be injected, and the engine will run like normal.
Another possible factor that contributes to this issue is when the plastic housing of the injectors has cracked, exposing the metal inside of the injector directly to the heat. If your injectors are old, the plastic has likely cracked, and they are not more susceptible to heat. Replacing the old injectors with new/upgraded ones will HELP with this issue, but not solve it entirely.
Fix: Chrysler released two Technical Service Bulletins on this issue. One suggests a reprogramming of the ECU to engage the electric fan at lower temperatures in an effort to keep the under-hood temp down, but this generally proves to be ineffective as the problem occurs with an engine-off heat soak.
The other TSB recommends the installation of "heat sleeves", little pieces of fire proof shielding that slip around each of the injectors. The part can be ordered through any Chrysler dealership, or you can use basically any type of heat shielding to deflect heat away from the fuel injectors.
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