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Old 06-12-2014, 05:22 PM   #1
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Bumps = engine cuts out

Hey guys!

My 97 TJ 2.5L 5-speed cuts out when I hit bumps. Just for a second, but completely and totally. Pretty much all the time, or at least after it's properly warmed up. The Odometer drops to zero, fuel stops pumping to the engine, it's like an instantaneous mini stall. This used to happen before I changed out the entirely-rusted-out exhaust system (now I have a clean one from an '00 TJ in there) because both points where the O2 sensors were connected were totally rusted through and I'm assuming that wasn't good. So I had the exhaust system replaced, and the problem was solved (and the thing sounded better and ran WAY better as part of the bargain).

Well, now the problem's back. I just replaced the gas tank (had it replaced, actually - I couldn't drill out the rusty bolts to remove the tank) and the symptoms are back. It's a tiny bit different, but basically, it's the same problem. The dude at Jeep Depot says it's probably one of the three wire bundles that connect to the computer shorting on something, but I'm not sure how to check those without having the Jeep running and burning myself to a crisp in the process. Also, I don't even know where 2 of the three are. There's a wiring harness under the hood near the firewall that looks pretty precarious, but doesn't seem to be loose, and when I wiggled it a little, nothing happened. I think the other O2 sensor is near the Catalytic Converter? I don't even know what the third thing is. Maybe there are three?

Anyway, I thought it'd be a good place to come for advice on this absurd topic. I know electrical issues are awful and impossible to diagnose, but I figured I'd check in to see if anyone had experience chasing this one down.

Thanks!

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Old 06-12-2014, 06:33 PM   #2
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Welcome to the forum. I would start by unplugging and replugging connectors at the ECM and sensors, particularly the crank position sensor and cam postion sensor. Also, check you battery terminals, cables and connections. Make sure there are no loose fuses or relays in the block under the hood.

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Old 06-12-2014, 06:43 PM   #3
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Thanks! I'll look at the Crank Position Sensor and the Cam Position Sensor - a quick check of Google makes me think that the Crank Position is the one I've already checked, although that MAY be something else - I'll have to look again. The battery and cables are good - I just was working with the battery yesterday (putting in a CKMA12 - more on that in another post when it's actually finished), but I haven't checked the fuses - that actually hasn't occurred to me.

Thanks again!
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Old 06-12-2014, 07:07 PM   #4
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Also, there are several grounds on the engine and body. Ensure that they are all tight and in good condition.
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Old 06-15-2014, 11:46 AM   #5
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I had a similar problem in my 97 2.5 tj..it would cut out into a stall sometimes..one day I hit a speed bump and jeep died..it turned out to be the throttle position sensor..it a $60 dollar part and from the way it sounds it's a good chance it may be that..
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Old 06-15-2014, 12:37 PM   #6
Knows a couple things...

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When I had that problem with an old GMC Jimmy, it turned out the battery's main positive cable had a worn spot on it that was intermittently shorting to ground and killing everything. I'd sure be looking at the main power cables, both + and -.
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Old 06-16-2014, 08:34 AM   #7
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Its a harness issue somewhere.
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Old 06-17-2014, 01:15 PM   #8
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Fuses are good, Battery cables are good. I'm going to pretty much start tracing all the wires I can find and wiggling every connection I can find in the hope that I can stall the thing when it's not moving. The problem is worse when it's hot, but that's just usually. Yesterday, putting the thing in second gear for the first time all day caused a weird bog-down that seemed similar-but-maybe-unrelated to the issue at hand.

I comfort myself that I, too, will someday be able to blithely throw around terms like "position sensor," "harness," and "O2 sensor" and confidently know where all those things are and how to diagnose, address, and solve problems related to them. If I just take it all apart, eventually I'll understand it. Kind of the early natural philosophers' approach to anatomy, only with way fewer cadavers.
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Old 06-17-2014, 01:39 PM   #9
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Could be PCM related if it dies easier when hot.
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Old 06-17-2014, 04:45 PM   #10
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I just replaced my tps sensor but I'm still losing power & my rpm is dropping won't reply to the pedal why is it that I'm losing acceleration ? I've replace the fuel pump & filter twice. I'm tired if putting money into it & it's not fixing the problem please HELP
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Old 06-17-2014, 04:47 PM   #11
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Quote:
Originally Posted by Old Man Hatch View Post
Could be PCM related if it dies easier when hot.
I've replaced the water pump the radiator the thermostat all brand new
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Old 06-18-2014, 01:13 AM   #12
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Check your tachometer wires!
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Old 06-18-2014, 09:36 AM   #13
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Changing those parts will not help if your PCM has a cracked board or bad solder joint.
Not saying your PCM is bad. Just saying its a possibility.
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Old 06-19-2014, 10:17 AM   #14
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Prob be best to take it to a shop for diagnosis..what I ended up doing when I had similar problem..I would lose power when shifting from 2nd to 3rd(bogged down)also it died completely after hitting a speed bump..
It turned out to be upstream o2 sensor and throttle position sensor.
After replacement I've had no problems what's so ever..

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