HELP! 02 4.7L running way to rich. Rough idle and dying. - JeepForum.com
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Go Back JeepForum.com > Models > Jeep Cherokee & Comanche Forums > XJ Cherokee Technical Forum > HELP! 02 4.7L running way to rich. Rough idle and dying.

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Unread 03-27-2009, 09:31 PM   #1
totalchaos
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Join Date: Mar 2009
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HELP! 02 4.7L running way to rich. Rough idle and dying.

Hello,

I donít know if anyone can offer any help or advice but if you have an idea, I would be very grateful to hear it. I dealing with a 2002 Jeep Grand Cherokee Laredo 2WD with a 4.7L and automatic trans. The problem is mostly a rough idle to the point that you have to drive with both feet to try and keep it running at stops. When accelerating it will run ok and has decent takeoff but you can still feel a miss. I took it over to the local parts store and had them pull the codes and they told me that it had an open circuit on injector #1 as well as a misfire for cyl #1 (no surprise to get those 2 together). They also told me that they got a code for a faulty speed sensor and misfire on Cyl 2,4 and 8 as well. It running so rough I wasnít surprised about the misfire codes. They told me I may need to replace the 4 coils that were misfiring along with the speed sensor, and either the #1 injector or harness. I ohm tested the #1 injector and found that if you moved one of the prongs that the ohms would go from about 12 to well over 150 and sometimes OL. I also found that it was well past due for plugs since they were so worn the gap was well over .080Ē. #1 plug was really bad fouled and didnít look like it had been firing well for quit some time now. #2 and 4 plugs were a little oil fouled but not that bad. The rest were normal other than being really worn. I put a new injector, coil (cyl #1) and plugs in. After this it seemed to run a little better but not enough to idle in gear. I checked all the injector harness with a noid light and they all were getting a good signal. I also checked the fuel pressure cause it seems to be using more gas. I wasnít sure if it was from driving with both feet at stops or maybe a leak in the fuel system. The pressure seems to be holding good at about 50 lbs with the key in the on position. I though maybe bad fuel so I added some treatment to the tank and topped off with good fuel about a week ago and still no change. I have only had this jeep about 6 months and the problem started as an intermittent problem that would only happen every now and then but a couple of weeks ago it just started doing it all the time. All the other coils are getting good fire from them. I pulled the IAC and cleaned it and the bore in the throttle body for it. I also tried to see if valve for the IAC would move back and forth out side the engine and it seemed to move freely. I put it back and the engine ran better on first start up after reinstalling it but only for a few seconds. Then it went right back to the rough idle. It sounds like Iím getting some spark knock as well from time to time on accel. After the first work I done with replacing the Injector, plugs, and coil, I took it back to have store clear code and ran it for a few mins and had them check again. They still got a code of an open circuit to injector #1. Does anyone have any advice for me that might help? I cant see anything wrong in injector #1 or any others. I tried to spray some carb cleaner looking for a vacuum leak but didn't find anything. The only time it seemed to run any smoother was when I fired it up with the IAC uninstalled and plugged in. I was looking to see if it was making adjustments and it was. I tried to spray around the intake and all Vac lines as well. Nothing seemed to make any difference. It seems like I'm getting to much fuel but if I was certain about this, I wouldn't be here asking for right..LOL I did notice what seemed like more than normal carbon build up in the throttle body to. I cleaned some of it out with the carb cleaner but didn't know if this info might help any. I was hoping a different perspective might shine some light on this. The information display inside is telling me that my MPG is about 8 MPG roughly. I hope this helps cause I'm not getting anywhere. Would the speed sensor be able to cause this problem? I haven't ever had an experience where it did but maybe I just haven't been so lucky..LOL
Thanks for any help and Iím sorry about the long post. I wanted to try and give as much detail as I could.

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Unread 03-27-2009, 09:40 PM   #2
xjfever
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You should repost this in the ZJ/WJ section. They will be able to help you more. Welcome to the forum though.
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