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bogging down, missfiring on warm start

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Old Nov 22, 2010 | 06:47 PM
  #1  
EMAXX620's Avatar
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From: Southeast Michigan
Year: 2000
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Engine: i-6 4.0
Default bogging down, missfiring on warm start

Well it seems like it started happening more and more, and just started recently. Went somewhere today, got up to temp (right under 210) turned it off for 10 mins or so and went back to go home. It "started" but sounded like it was firing on only a cylinder or 2 and immediately died. tried again, same thing. after another few times it started enough to run, but was misfiring like crazy on 1-2 cylinders. gave it some gas and the rpms didnt really change much, but after it idled with me giving it some gas, it started running fine again. This happened like 2-3 times today. Once it got going, i opened my door and it was very obviously it was pouring in fuel, it smelt VERY rich.

It only seems to do when its warm, is this the "heat soak" issue i have seen mentioned a few times. Normally when i get back in and go to fire it up, the temps are the line above 210 or close to it.

things it could be that i recently did.
plugs (not to long ago, gapped properly, NGK plugs)
injectors (swapped to ones in my signature)

any one able to identify if this is heatsoak, a sensor, or something else and a possible fix?

ANY help would be much appreciated.
Thanks
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Old Nov 22, 2010 | 09:29 PM
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If you have a fuel pressure gauge you should hook it up and see what the pressure is doing when you shut it off.......I had a hard start problem that turned out to be an injector leaking fuel into the engine.

The pressure shouldnt fall by more then a few pounds.....if it does pinch off the fuel line and if it still dropps it has to be an injector.
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Old Nov 22, 2010 | 09:41 PM
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i dont think theres any fuel in the fuel rail at shutdown because when i swapped my injectors i hit the pressure relief valve and not a whole lot came out, definetly not pressurized. same with the ones at the junkyard that i got the "new" injectors for. ill try to get ahold of a gauge tho
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Old Nov 23, 2010 | 08:13 AM
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You should always have fuel pressure in the rail, if you dont you have something leaking.
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Old Nov 23, 2010 | 12:54 PM
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Sounds like a classic case of heat soak. My 01 XJ does this on warm days, and my only sure-fire solution is to open the hood for 10-15 mins. Then it is fine.
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Old Nov 23, 2010 | 03:29 PM
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Originally Posted by 420blackxj
Sounds like a classic case of heat soak. My 01 XJ does this on warm days, and my only sure-fire solution is to open the hood for 10-15 mins. Then it is fine.

I thought the same thing but he mentioned that he smells gas.
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Old Nov 23, 2010 | 05:18 PM
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you have a faulty injector or injectors. Took me forever to figure this out on my jeep, I replaced all the little sensors, finally put the old injectors back in and all is good. One of my injectors was actually cracked at the tip.
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Old Nov 23, 2010 | 05:39 PM
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would a faulty injector cause it only when its hot though? Repair, the only time i ever smelt it was when it wouldnt start, and finally started. like it was pouring fuel into the cylinders but wasnt firing. Im really thinking its heatsoak because as soon as the temps get down right below 210 it starts up normally. Ive been reading up on heatsoak and it seems like i need to wrap injector 3 with heat tape and that should clear it up. I guess ill give that a shot first and see what happens
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Old Nov 23, 2010 | 08:35 PM
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Originally Posted by EMAXX620
would a faulty injector cause it only when its hot though? Repair, the only time i ever smelt it was when it wouldnt start, and finally started. like it was pouring fuel into the cylinders but wasnt firing. Im really thinking its heatsoak because as soon as the temps get down right below 210 it starts up normally. Ive been reading up on heatsoak and it seems like i need to wrap injector 3 with heat tape and that should clear it up. I guess ill give that a shot first and see what happens
Heat soak will make a weak electrical part fail to function when it is above a certain temp....if it was heat soak I would expect it to be an ignition problem.....pull a plug wire and check for spark.

I dont know why wrapping the #3 injector would help.
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Old Nov 24, 2010 | 05:44 AM
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if the injectors faulty it could flood the one cylinder leading to a flooded start condition, next time it does it see if it stinks from the cat trying to burn off the super rich setting. That was my clue it smelled of rotten eggs while idling. Maybe try some temp tape, that aluminum tape for thermal applications?? I still think it sounds like a bad injector. They are pretty easy to take apart.
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