2003 TJ Engine issues - JeepForum.com
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post #1 of 5 Old 08-14-2017, 01:30 PM Thread Starter
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2003 TJ Engine issues

Hey all, Iím hoping someone with more knowledge than myself might be able to help me solve this. Iíve owned this 2003 Wrangler for a little less than a year and it has ~80,000 miles on it. It has a 4 cylinder manual transmission and is currently stuck in southern Utah, unable to get above 30 mph. About 6 months ago, the CEL came on for the first time, when I read the code, it said there was a problem with an air line but could possibly be a leaky gas cap. This didnít seem to affect performance at all, so I didnít make it a priority to diagnose right away.

At the beginning of June, I was on a fly fishing trip and on our way off the mountain my jeep got stuck after sliding down a dry wash into the ditch. It took almost all the engine had to get up and out, and when it was back on the road it stopped running. Initially we thought this was an overheating issue from running the engine so hard. But soon realized even when the engine was cold it could not idle without giving it lots of gas. Eventually the engine wouldnít even start, so we had it towed off the mountain and into a shop. We found that the fuel injection fuse was blown, and replaced it right away; this got the engine started so we excitedly tried to drive away. Unfortunately, the car wouldnít get over 30 MPH and didnít sound like it was running well at all (maybe a cylinder or 2 wasnít firing?), so we took it back into the shop. There we found that the coil was sending 2 strong sparks and 2 weak sparks, so we tried replacing that and it didnít have any effect. Spark plugs look new, and arenít flooded at all. Throughout this, we started the jeep maybe 12 times and blew through 5 fuel injector fuses. So looking at the wiring diagram for the fuses the mechanic decided to begin looking at wiring/ECM. We found a wire that was very frayed and possibly grounding on the chassis. Repairing that didnít help so we replaced the ECM, thinking that all the blown fuses might have shot the computer by introducing high voltages. The ECM was also not the cause of the problem because the engine still isnít running well. Interestingly, the shop went out of business while working on my vehicle so they dropped it with the Jeep dealer to finish the job. Iím already in over $600 with these guys and would like to save some time and money by getting some of your expert advise. (This is my second time putting money into a car in the desert without getting anywhere) Thanks for reading and thinking about this! Forever grateful.


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Last edited by HunterHill; 08-15-2017 at 12:27 PM.
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post #2 of 5 Old 08-17-2017, 04:39 PM
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Did you check fuel pressure? Voltage to fuel pump?
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post #3 of 5 Old 09-02-2017, 07:20 PM Thread Starter
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Hi, thanks for the reply! I just towed the jeep back to my house to try and work on it myself. The fuel pump turns on for ~1 second when the key is turned on, but pressure seems to build slowly. It takes 3-4 on/off cycles (about 20 seconds each) with the key before pressure 45 psi is reached. Then when the engine is turned on it stays at 45 psi I thought the pressure was supposed to jump immediately to there? It seems like the pump is working okay though, flow is clean for that 1 second it is on, and it is a solid stream while cranking the engine. Any idea where to go next? Thanks again, Hunter.
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post #4 of 5 Old 09-02-2017, 07:27 PM Thread Starter
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Also, the jeep dealer guys helped me off of shop time which was cool, they said compression was good and the timing belt was on time. Also the wiring at the ECM was fixed up a bit. I have replaced the spark plugs because they looked pretty rough. The codes I have from the old ECM all say different cylinders were misfiring.
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post #5 of 5 Old 09-02-2017, 07:54 PM
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Something is causing the fuses to blow. Possibly O2 sensor wiring?

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