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Originally Posted by woodsrat
My wife has a '94 Jeep Wrangler. It just turned 70,000 miles and has had to be towed to a repair facility at least three times during this time. I could usually determine whether or not it was a fuel or spark problem but that was about it.
The last time I went over to the dealership after the tow truck came to get it and found a mechanic out back with a pile of boxes of parts plugging them in and trying to start it. He had no idea what the problem was and it was pure guesswork. Like the other two times it turned out to be a sensor of some sort that fed information to the F. I. system.
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1994 is before OBDII. Early FI systems like the one in your Wrangler don't really have self diagnostics. The factory service manual would tell the mechanic how to test those sensors but most just plug and play instead. It also wouldn't surprise me if a Jeep dealer no longer had a manual for a 24 year old Jeep.
Quote:
Originally Posted by woodsrat
Another mechanic told me that while you can put modern cars on a computer for diagnosis it's no guarantee that the problem the magic box says it is will be the problem--and then it's experience and/or guesswork.
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That is true. The scanner tells you where to start looking for the problem not the exact problem For example, my 2004 Chevy Astro Van was throwing a code for the evaporative emission system. The code narrowed the problem down to 2 valves, a sensor, and a bunch of hoses that could have leaks. The valves checked out OK, the hoses held vacuum and it turned out to be the fuel tank pressure sensor. Too bad it was on top of the tank so the tanks had to be dropped to replace it.