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crashnburn54 10-29-2009 11:00 AM

Rough Idle and Starting Issue
:banghead:Hey guys first time posting here and lucky me has a fun problem to solve. So I have a 2000 TJ with 2.5 inch lift, 32's, 4.0/auto, subs & amp, and remote start. Truck has 90k on it now and it has just started acting up on me over the past week.

The problem is that sometimes it won't start. I will get in and nothing will happen. The starter will click and I can hear the fuel pump come on but no lights or anything will come one. After either holding it in the start position for 4-5 seconds or retrying to start it 4-5 times it will fire up but then runs rough at idle and then dies. It doesn't matter if I rev the engine up right after I start it or not it still will die when it comes back down to idle. After it acts up I can start it up and it will run fine. It doesn't do this every time and it doesn't do this in certain conditions. Here is the best part, it never ever throws a check engine light when it does any of this.

Looking to see if anyone has had anything like this happen to them or can give me a place to start looking. I have heard the TPS or CPS could be going but im not sure because its happening all the time. Looking for any help if anyone knows where to start or what it could be, I don't wanna just start throwing parts at it becuase that starts to add up pretty quickly. Thanks


rrich 10-29-2009 12:18 PM

If no lights come on, then all the computer sensors are not at fault. The TPS, CPS, O2 sensors etc are not being used.

Sounds like battery related. Cables, connections, even the battery itself. Check them all.
Taking the battery somewhere to test it may not show up the problem. A broken strap or connection inside it can be intermittent. Best way is swap it with another known good battery to see if the trouble still exists.

Seems there's a rash of batteries recently that have internal connection problems, especially the side terminal type.

Jerry Bransford 10-29-2009 12:57 PM

The very first thing I would do is to buy a wire brush battery connector cleaner which has a male and female wire brush. THOROUGHLY clean both the battery posts and connectors and see what happens.

No, you can't just look at them to see if they look "ok" or simply tighten the connectors.

I had a similar problem with my Toyota last month and the connectors looked fine. But when I removed the connectors, I was shocked at how cruddy everything was under the connectors. Cleaning the connectors and battery posts solved my Toyota's starting and dying problems. It actually died on me when I was at a stop light and it would occasionally idle roughly. The reason this can happen is because on both the TJ and Toyota, the alternator requires a good 12 volt "exciter voltage" to produce output. So if the 12 volts from the battery is flakey via a bad connection, it can cause the engine to idle roughly, die, or have starting problems. :)

Loic 10-29-2009 01:07 PM

i just replaced my batterry, it had a bad cell, my iddle was not regular and right before i got to the store i turn the key and nothing, no dash light nothing, weird thing is i just drove the jeep back from work.... changed the battery and the problem went away

s3nt3nc3d 10-29-2009 07:24 PM

Did you have it tested to confirm it was a bad cell or just assume since replacing the battery fixed the problem?

Reason I ask...about a month ago I went to use our backhoe at work and had a similar problem. I'd kick the ignition on sometimes and have full power...and then suddenly when I turned the key, it'd click and all the lights would go out, etc (like it just killed the battery).

I figured it was a bad cell...spent nearly an hour trying to get the battery out of there. Hauled it down to our local battery shop. The guy questioned me on what it was doing...hooked it up...comes back out with a drill and cleans the posts and says, "Your battery's fine. Post needed cleaned."

Sure enough...I cleaned up the terminals on the tractor, put it all back together and the problem went away. A new battery would have solved it too though. lol

Loic 10-29-2009 08:28 PM

the battery was tested by my mechanic a week before, he is the one who told me it had a bad cell and told me to go to a store to get a new one

crashnburn54 10-30-2009 09:11 AM

Thanks for all the info. I tried cleaning cleaning the terminals and so far so good. Thanks

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