Rough idle/dies after starting

Tech topics for the TJ and LJ (Unlimited) models manufactured from 1997 to 2006.
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Fourthwolf
Posts: 54
Joined: Sun Sep 08, 2013 12:00 am
First Name: John
Last Name: Wolf
Jeep Year: 2000
Jeep Model: TJ (1997–2006 Wrangler)

Rough idle/dies after starting

Postby Fourthwolf » Sun Jan 12, 2014 9:29 pm

So for a couple weeks now I have had idle/start problems. It's inconsistent. The main issue is that my jeep will die right after starting, or, if it does start, the idle will be rough/low. Around 500 rpm. But it is off and on, not consistent. No problems when driving normal speeds.

The first thing I did was remove/clean the throttle body. This seemed to fix it for 2 days, then back to crap.

After unplugging the IAC and the TPS it threw a code for a bad TPS. I replaced the TPS with no major improvement.

My battery happened to be bad, so I replaced the battery. This "fixed" it for another few days.

Tonight I checked my fuel pressure and my fuel pressure was good at key-on and idle. Both when the engine started up fine, and when it idled rough. It also didn't drop too much after waiting 30 minutes.

When I unplugged my IAC tonight, for it to run in limp mode, it started fine (but then ran in limp mode).

The only other weird thing is that sometimes I can put it in drive and the car won't die until I'm backed out of my parking spot or pulled forward a few feet. Once it died after I went down my whole street.

I tried listening for air leaks with a stethoscope, and I think I heard air escaping from under the spring that controls my throttle butterfly valve.

Thoughts? Suggestions? Pointers? Maybe just an elimination check to narrow it down?


Fourthwolf
Stock TJ, open diff.
Matt
Posts: 198
Joined: Tue Dec 15, 2009 7:00 pm
Location: Edmond, OK

Re: Rough idle/dies after starting

Postby Matt » Mon Jan 13, 2014 6:13 am

Sounds like a problem I had with my old dodge gas truck. When moving it was fine but wouldn't idle at a stop.

Can you give it gas (high idle it) to keep running when you're stopped? If so, perhaps you got a bad replacement tps or iac? Also have you filled up recently? Could've gotten bad gas. That's what it turned out to be in my truck. After I ran that tank out, it ran fine ever since.

Good luck!
'00 TJ
'78 CJ7
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soonermatt
Posts: 493
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First Name: Matt
Last Name: Luttrell
Jeep Year: 1994
Jeep Model: YJ (1987–1995 Wrangler)

Re: Rough idle/dies after starting

Postby soonermatt » Mon Jan 13, 2014 4:50 pm

Throttle position sensor fits symptoms but you replaced that. Most exhaust and fuel issues present themselves at revs not idle. I still think it is MAF, TPS or CPS.
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Red Jeep
User avatar
Fourthwolf
Posts: 54
Joined: Sun Sep 08, 2013 12:00 am
First Name: John
Last Name: Wolf
Jeep Year: 2000
Jeep Model: TJ (1997–2006 Wrangler)

Rough idle/dies after starting

Postby Fourthwolf » Mon Jan 13, 2014 7:05 pm

I've filled up multiple times and the problem persists. It never does while idling at lights/stop signs, but will dies right after starting. Giving it gas keeps it alive until I stop. Generally, when it's dying after start I can rev it, then throw it into gear and drive off, and then it will just rough idle after that.


Fourthwolf
Stock TJ, open diff.
User avatar
Fourthwolf
Posts: 54
Joined: Sun Sep 08, 2013 12:00 am
First Name: John
Last Name: Wolf
Jeep Year: 2000
Jeep Model: TJ (1997–2006 Wrangler)

Rough idle/dies after starting

Postby Fourthwolf » Mon Jan 13, 2014 9:25 pm

Update: I just found a split where my crank case vent tube contexts to my intake. Autozone and O'Reily's don't carry a spare and the dealership won't have one until Wednesday. I electrical taped the snot out of it, and we are humming along for now. Expect further updates as things develop.
Image


Fourthwolf
Stock TJ, open diff.
User avatar
soonermatt
Posts: 493
Joined: Mon Jan 17, 2011 2:00 pm
First Name: Matt
Last Name: Luttrell
Jeep Year: 1994
Jeep Model: YJ (1987–1995 Wrangler)

Re: Rough idle/dies after starting

Postby soonermatt » Mon Jan 13, 2014 9:27 pm

Hmm. I would have expected oil in the breather or on the ground with a CCV leak. That works though.
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Red Jeep

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