ping or miss fire at 3000 rpm - JeepForum.com
 
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post #1 of 12 Old 04-29-2013, 06:29 AM Thread Starter
Nate_nev
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1997 XJ Cherokee 
 
Join Date: Jun 2012
Location: Sault Ste. Marie
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ping or miss fire at 3000 rpm

I've done almost everything to this jeep and now after it heats up or driven for 20 min, as soon as I hit 2900 RPM this the jeep miss fires and "jerks".

refer to:

https://www.jeepforum.com/forum/f11/s...-hand-1386981/

and

https://www.jeepforum.com/forum/f11/f...spark-1463440/


needless to say I am at the end of patience (and budget) with this thing and ready to scrap a decent 97 XJ with no rust and many new parts.

any thoughts? I've changed the CPS 3 times in the past year.

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post #2 of 12 Old 04-29-2013, 08:26 AM
EvolutionXJ
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You check basic stuff like head gasket leaks or anything? Do you have funky colored emissions when it starts to sputter? If so then something could be leaking into the cylinders causing misfire. If the exhaust gas is white then you could have a coolant leak into the cylinders. Could be caused by a blown head gasket or a cracked cylinder head.
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post #3 of 12 Old 04-29-2013, 08:41 AM Thread Starter
Nate_nev
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no funky colors in the exhaust or strange smells. I think I may turn it over to the dealership to trouble shoot from here if I cannot get any recommendations that make sense. I do not want to give up on this machine as it is in great shape.
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post #4 of 12 Old 05-01-2013, 11:25 AM Thread Starter
Nate_nev
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after bringing this machine to the dealership for them to troubleshoot, we still have no clue on what is causing this issue.
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post #5 of 12 Old 05-01-2013, 12:25 PM
mayeni
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I once had a problem very similar to yours. When the engine was hot and it excited 2300 rpm, it started to back fire and loss power. It turned out to be the fuelpump, which didn't deliver enough fuel, which meant that the fuel in the fuelrail boiled, because the flow was to low. So I don't know the flow rate, but try to find it somewhere and then test it, because it really sounds like my case. Also mine fuelpump had to run for awhile before the flow dropped.
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post #6 of 12 Old 05-01-2013, 01:28 PM Thread Starter
Nate_nev
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I am willing to give anything a try... by flow rate, you mean "volume per minute" correct?
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post #7 of 12 Old 05-01-2013, 02:30 PM
mayeni
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Yes, volume per time. It is easy to check and almost free. Good Luck.
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post #8 of 12 Old 05-02-2013, 06:27 AM Thread Starter
Nate_nev
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well, upon further investigation. even through I am not throwing codes... when it "stalls" it is showing rich on the high bank 02 sensor. am I getting too much gas or not enough spark?
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post #9 of 12 Old 05-02-2013, 07:23 AM
831xj
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Check for cracks in your header. Can almost guarantee that is it. Chased my missfire for 6 months. Same problem as you.
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post #10 of 12 Old 05-02-2013, 09:19 AM Thread Starter
Nate_nev
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will do, thanks for the info. I will update after I check for exhaust leaks and re-verify the injectors.
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post #11 of 12 Old 05-03-2013, 01:11 PM Thread Starter
Nate_nev
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new symptom.. have to do the poor mans prime for cold start.. i would say the fuel check valve but isn't that in the filter/regulator? if so I just replaced it on Sunday. maybe leaky injector? any ideas?
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post #12 of 12 Old 05-08-2013, 08:09 PM
EvolutionXJ
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Yea I have to do thst to mine as well :/ and I'm pretty sure mine is the check valve. And I don't wanna replace the pump so I'm gunna get over it till it gets worse. But as for you I'm stumped man. Sorry I can't be of more help. Ill try to do some research and see if I can help out though. However if you do find the cause then post it in here so I can know how you fixed. You can never know too much
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