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Unread 07-12-2013, 11:04 AM   #1
patroskam
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2.5 Fuel Issues...I think

Hello...I am looking for some help on an issue that is eluding me. I have a '90 YJ with the 2.5... It will fire up and run great for a while (approximately 10-15 minutes) and then it will start to stall under load. If I let off the gas it will idle, but then any pressure on the accelerator will cause it to seemingly choke out again. I have found that if I turn the key off and then start it again (while rolling) I will get another couple of minutes of everything working fine. So before dropping the tank to swap the fuel pump I figured I would ask those more in the know than me and see if I can confirm some of this.

Any help is greatly appreciated.

Thanks all.

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Unread 07-12-2013, 04:19 PM   #2
jokerchief462
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One of your sensors is giving the ecu wrong info. Vacuum leaks, exhaust leaks bad O2 sensor etc. Any codes????
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Unread 07-12-2013, 04:31 PM   #3
patroskam
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no check engine light...could it throw a code without the light coming on? I know the light works...
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Unread 07-12-2013, 06:19 PM   #4
laybackman
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Quote:
Originally Posted by patroskam View Post
Hello...I am looking for some help on an issue that is eluding me. I have a '90 YJ with the 2.5... It will fire up and run great for a while (approximately 10-15 minutes) and then it will start to stall under load. If I let off the gas it will idle, but then any pressure on the accelerator will cause it to seemingly choke out again. I have found that if I turn the key off and then start it again (while rolling) I will get another couple of minutes of everything working fine. So before dropping the tank to swap the fuel pump I figured I would ask those more in the know than me and see if I can confirm some of this.

Any help is greatly appreciated.

Thanks all.
I am fairly sure that it is not your fuel pump.

I agree. with jokerchieff462 since it does not act up until the engine heats up and your emissions system goes into closed loop mode and runs off of learned memory. Your sensor send signals back to our ECM which measures what they are sent with what they have learned AAND what the factory defaults are. If the ECM finds something out of range and it is a monitored circuit the ECM sets a DTC and the CEL lights up.

As a rule if I do not know when the fuel filter was replaced I would replace it as a matter of maintenance. Why? I bought a brand new '87 Chevy El Camino and it did the exact same thing to me and it ended up being the fuel filter. It gave me grief every so often for the first two years I owned it.

Next does your CEL light up when you start your engine? If not get the bulb replaced.

If it does light up, does it stay lit? Pull any trouble codes that might be stored in the ECM.
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Unread 07-12-2013, 06:29 PM   #5
patroskam
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Thanks for the direction...I was not looking forward to dropping the tank...the CEL does light on start and then goes off...I have not replaced the fuel filter and that is on the list to get done so I will start with that...I was thinking it was electrical or vacuum...but difficult to troubleshoot...
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Unread 07-12-2013, 06:39 PM   #6
laybackman
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Quote:
Originally Posted by patroskam View Post
Thanks for the direction...I was not looking forward to dropping the tank...the CEL does light on start and then goes off...I have not replaced the fuel filter and that is on the list to get done so I will start with that...I was thinking it was electrical or vacuum...but difficult to troubleshoot...
Do the easy stuff first! The fuel filter is never thought of. Will it fix your problem...probably not BUT it could. If not it can be taken off the list of possibilities and the money wasn't wasted which was only a couple of bucks anyway.

Another distinct possibility it you have a failing cat converter BUT I would not advocate replacing it without some evidence that it is NG. They are not as cheap as a fuel filter!!
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Unread 07-12-2013, 06:42 PM   #7
patroskam
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I agree with that for sure...I don't think its the cat...its relatively new, I mean I guess it could be but wouldn't it throw a CEL if that was it?
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Unread 07-12-2013, 07:27 PM   #8
laybackman
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Quote:
Originally Posted by patroskam View Post
I agree with that for sure...I don't think its the cat...its relatively new, I mean I guess it could be but wouldn't it throw a CEL if that was it?
If the cat is fairly new it is more than likely OK.

IF the cat was bad/clogged/missing you would not get a lit CEL. BUT an old failing cat could cause issues once it gets real hot. The ECM would not even know if it was missing on your OBD1 vehicle.

I would get a hair drier and heat up the ignition module mounted on your firewall real well. Then fire it up and see if it runs bad. IF it does you found your problem.
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