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Author Topic: popping in intake  (Read 5450 times)

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Offline afb

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popping in intake
« on: September 10, 2013, 06:37:25 PM »
I'm at a loss... I took the head off to get at a lifter back in put it all back together and drove for 2 days. this sterted when it was raining like crazy last weekend. My yj 2.5 idles fine but when i rev it in neutral it has a popping sound to it. In gear it sputters almost raspy sound starting at 2000rpm and a loss of power happens but it does rev up. Its popping codes 21 24 and 25. Aic, tps, and o2 sensor. All were replaced 5k to 15k ago. The parts guy instantly said with all those 3 codes he bets the pcm. Any ideas on what it could be?

Thanks in advance.
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'93 yj 2.5 with all the engine mods done so I can beat a kid on a tricycle in a race.

Offline hps4evr

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Re: popping in intake
« Reply #1 on: September 10, 2013, 09:03:35 PM »
Timing?
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Offline afb

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Re: popping in intake
« Reply #2 on: September 11, 2013, 05:44:53 PM »
It seems fine.
The jeep idles smooth and revs with a hiccup in neutral and under load it revs smooth to 2000 then the popping happens as you gain rpm. 
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'93 yj 2.5 with all the engine mods done so I can beat a kid on a tricycle in a race.

Offline CiaMonkey

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Re: popping in intake
« Reply #3 on: September 11, 2013, 09:30:08 PM »
Vacuum lines?
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Offline apeman

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Re: popping in intake
« Reply #4 on: September 11, 2013, 10:13:57 PM »
Probably a funky 02 sensor. My 4.0l did the same thing.
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Offline afb

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Re: popping in intake
« Reply #5 on: September 12, 2013, 07:05:08 AM »
Vacuum is good and I unplugged the o2 but no change.
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'93 yj 2.5 with all the engine mods done so I can beat a kid on a tricycle in a race.

Offline jkrubi

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Re: popping in intake
« Reply #6 on: September 12, 2013, 02:49:05 PM »
Have you checked the plugs/wires yet? I had a car do that, it turned out when I removed the wires I broke one and it only showed up under load and when wet.
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Offline afb

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Re: popping in intake
« Reply #7 on: September 12, 2013, 05:26:05 PM »
Cap rotor and wires are good. Unplugged the tps and she died for a second and ran again.  All sensors are working.  An one know how to check the ecm?
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'93 yj 2.5 with all the engine mods done so I can beat a kid on a tricycle in a race.

Offline mike s

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Re: popping in intake
« Reply #8 on: September 12, 2013, 10:46:04 PM »
Vacuum leaks tend to only show at idle. Wide open throttle there is no vacuum. Lean mixtures cause popping out intake esp under load. Leave o2 unplugged and clear codes. Drive it for awhile and see if its better. Only check for PCM is try a different one. Don't have a spare but drive a '94 two fiver... Might be the same to try

Double check ignition. When in doubt, throw it out and put in new stuff. Chased cracked plug/poor wire/bad cap misfires way too ma y times
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Offline afb

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Re: popping in intake
« Reply #9 on: September 13, 2013, 02:22:27 PM »
I erased the memory and unplugged the o2, same.  Tps unplugged,  ran but low idle and engine changed for worser checked connections and wires,  all good. Craaaaaaaaaap.
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'93 yj 2.5 with all the engine mods done so I can beat a kid on a tricycle in a race.

Offline jkrubi

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Re: popping in intake
« Reply #10 on: September 13, 2013, 02:46:11 PM »
Since you've had your head off, you checked the timing?
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Offline Evil-Jeep

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Re: popping in intake
« Reply #11 on: September 13, 2013, 04:20:57 PM »
I spent a few days chasing similar issues........ after going thru all the sensors, vacuum leaks, gaskets, it ended up being a plugged cat.

If you can drive it see if it will "bottom" out under load and limit your revs and speed to ridiculously low amounts.
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Offline afb

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Re: popping in intake
« Reply #12 on: September 13, 2013, 08:30:01 PM »
It has a new banks header and new 2.5" pipe to the back with no cat. Lots of pressure coming through her. Timing is good and the idle up to 2k is real smooth then goes to crap.  The codes now are 21, 23, 24, 25. I've been popping off every electrical plug I can find.
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'93 yj 2.5 with all the engine mods done so I can beat a kid on a tricycle in a race.

Offline vantagetes

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Re: popping in intake
« Reply #13 on: September 24, 2013, 08:14:17 PM »
Check your ground  ::)
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Offline vantagetes

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Re: popping in intake
« Reply #14 on: September 24, 2013, 08:16:42 PM »
Also what voltage are you getting at idle vs high rev from the alternator? Still think it's a ground.
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