Help, I have been having problem(s) with my 2002 Wrangler X 6 cylinder 4.0 litre automatic for about a year now. First was it was difficult to start, it would crank and crank for 5 or more seconds before starting.
I took it to a garage locally and they said i neede a new fuel pump. Well this didn't fix the problem and they initially didn't replace all the hoses correctly when they installed the pump. Obviously I marked them off of my list as places to get service. Since then I have found a person who does work in his own shop and has saved me a ton of $$ on all of my vehicles. I have been very happy with his work. Now back to my issue.
After the fuel pump didn't fix it I figured it was time for a tune-up and my new guy did this. It had a miss when idling before the tune-up, but noticeably was reduced after the tune-up. Drove it like this for 6 months. Then started to notice drastic loss of MPG. After a month of the MPG loss, my check engine light came on and was throwing the P0302 code for a misfire in the 2nd cylinder. We have tried everything as you can see from the list that follows, but still haven't fixed it. Mine is different from other posts in that I can drive the Jeep and for the most part it drives fine no loss of horsepower on the highway. Except for the loss of MPG, a miss when idling at a light, very hard to start, and when starting getting a strong fuel smell, it runs good. List of things we have tried or checked.
Troy this is the list of what has been done
Replaced Crank Sensor
Replaced fuel pump
Replaced Fuel pump Relay and Auto Shutdown Relay
Replaced spark plugs
Replaced ignition coil
Replaced coolant temp sensor
Repaired evap. hose on fuel tank
Did an ohms test on all injectors
Checked for injector pulse on start up
Check for vacuum leaks
We also heard that the Crank Sensor can be bad out of the box, so we took the first sensor back and replaced with a different one to no avail. Again the Jeep does run and doesn't cut out at high horsepower like many of the other posts describe. my check engine light has gone back off. However it smells like fuel when starting, takes well over 5 seconds to start, has a miss when idling, and sucks gas like crazy even for a Jeep. LOL Any suggestions would be greatly appreciated. I am not a mechanic, but I will pass them on to my guy that does my mechanical work. Thanks Troy
May want to look at your O2 sensors. Mine had a slight miss when throttling up then no more. It was also using a little more gas than it does now. Make sure that you use ONLY NTK brand O2 sensors. Mine had a bosch (from PO) and they do not perform well in our Jeeps at all. I paid something like $35 for my sensor from rockauto.com. Here is a discount code if you decide to go that route.
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UPDATE: Well after all of that it was something stupid. My mechanic was able to do a spray test on the injector before we started to replace it, and it seemed fine. We had replaced the Crank Sensor with an aftermarket sensor. We took it back out and noticed the spacer or tab that was on it didn't burn or come off. So we manually removed the tab, made sure the spacing was correct and replaced it back in the Jeep. Yoo Hoo!! It worked, the rough idle/misfire was gone, the starting of the Jeep is almost imediate to the first crank, and I have driven a tank of gas, and my MPG is back where I was used to.
Thanks to all of your suggestion, but I thought I would post my fix since it was a little strange. As a note, I wished I'd read more on this forum before having some of the repairs started as when it comes to the sensors on these Wranglers, it appears the smart play is buying OE parts. Seems like the aftermarket stuff just doesn't cut it. I am going to use this sensor while it is working, but next time, I will buy OE patrts for them.