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Unread 12-18-2009, 12:04 PM   #1
cosmo_j
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1997 TJ Wrangler 
 
Join Date: Feb 2009
Location: ontario
Posts: 87
engine pulsing

so i got my heep back from mister transmission last week.i start it up and start driving and notice its sounds really weird.kinda like its running on choke.so i pull over and let it warm up some more and check everything over.made sure all my vacuum lines werent frozen or anything.everythings normal.
i start driving down the high way and its worse.it feels like the engines pulsing.so yesterday i put a piece of card board in front of the grill because i thought maybe it was getting to much cold air and the throttle body was freezing like some of the snowthrowers we get in at work sometimes do.
that actually made it worse. it actually backfired 3 times going down the highway.atleast i think thats what the loud noises were.
now it only usaully happens when its at higher speeds.
top of third gear and threw 4th and 5th.
just wondering if anyone had any ideas.
its nerve wrecking driving down the highway in the mornings and the thing is pretty much cutting out on me.
any idears? thanks

oh and the engine is a 4L out of a cherokee and haas a ba10/5 tranny.

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Unread 12-18-2009, 12:16 PM   #2
mcmud
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Quite possibly an air leak at the intake.
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Unread 12-18-2009, 12:23 PM   #3
dbikers
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yeah, sounds like a vac leak of sorts... you said that you put a piece of cardboard in front of the rad and it got worse but didn't mention if it overheated (or if your temp gage works)...
it could even be that it's overheating (worse when you covered the rad) causing it to run like that.

do you know how hot it's running?
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Unread 12-18-2009, 05:53 PM   #4
cosmo_j
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oh sorry forgot about that.no it didnt over heat.normal temperature.it is winter and very cold where i live, making it almost impossible for it to over heat.

also i brought it back to the transmission place to see if the screwed something up and they SAID they checked the vacuum lines and everything was okay.
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Unread 12-19-2009, 02:28 AM   #5
SDGBASSE
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Backfires at higher temperature sound to me like a fuel delivery problem........but I could be wrong.
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Unread 12-19-2009, 07:07 AM   #6
Raindem
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Fuel delivery was my thought also. I've had this happen before (different vehicle, not a Jeep). Every 15-30 seconds it would lose power for a second then come back to life. I guess you could describe that as pulsing. Turned out to be a very small leak in one of the fuel lines. FI engines need high fuel pressure to work and even a small drop could affect it.

Make sure to let us know what it finally turns out to be.
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Unread 12-19-2009, 08:04 AM   #7
cosmo_j
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thanks, ill check my lines.maybe they pinched one some how taking the tranny out?
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Unread 12-19-2009, 11:21 AM   #8
Boanerges
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So I'm taking it's fuel injected if it's a 4.0L. Check map sensor, o2 sensor? These can screw with your air/ fuel mixture which can result in leaning out/burning rich, power loss and backfire. 02 sesnor should be replaced every 30k or so anyways. Also if it sounds like it's running on choke you will need to check the AIC(automatic Idle Controller)located on back of throttle body. It could have gummed up which also relates to these problems. You can usually clean AIC by soaking them and scrubbing without replacing. The 02 could be bad and sending false reading to ECU which regulates through AIC adjusting fuel/air mixture. I just went through a similar situation of losing power/cutting out(Surging) in higher gears. Took check fuel pressure, If EFI look along fuel bar on top of engine for a valve cap cover(looks like tire valve cap). Turn key on, take cap off and press valve in and see if gas shoot out. Keep your eyes away or covered. I'm not a mechanic, I just slept in a holiday inn last night!

Last edited by Boanerges; 12-19-2009 at 11:37 AM..
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Unread 12-19-2009, 11:59 AM   #9
cosmo_j
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update. tried a cap and rotor.did nothing
also problem just got worse. now runs like its on choke all the time now.barely made it to work

^^^^ill try the o2 sensor and above mentioned things now.and which ones the o2 sensor?
would you be able to put a pic?pic of the AIC also.

Last edited by cosmo_j; 12-19-2009 at 12:19 PM..
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Unread 12-19-2009, 01:58 PM   #10
Boanerges
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Unable to post pics due to not having enough posts. Start with O2 sensor which is located on the exhaust manifold. Follow exhaust from engine block and look for a plug connected to the exhuast. it will unscrew with a socket or wrench. after replacing you should reset your ECU by loosening your positive battery cable and holding it to the negative side for 30 seconds to dump memory. Put positive back on and crank/test. After resetting ECU it will take approx 50 key switch starts or 500 miles of driving to recalibrate. Post back and let us know... What yr is your motor?
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Unread 12-19-2009, 02:24 PM   #11
cosmo_j
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i checked the AIC and boy was it bad.it was definitly stuck.but problem still exists.
il try the o2 sensor now.itll have to wait till monday though.so ill have to start the engine 50 friggen times before the problem will go away if i change the sensor????
and i have no idea what year of engine.PO, PO, PO installed it lol.it originally had a 4.2 from factory but now its a 4 fuely
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Unread 12-19-2009, 10:26 PM   #12
Boanerges
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No you won't have to wait after the reset. What that does is dump the memory bank of what it was doing before. Yeah.. Change the 02 and post back.
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Unread 12-20-2009, 12:09 AM   #13
SDGBASSE
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When I got mine, it backfired at higher temperatures because the gas tank was full of corrosion dust, even after a fuel filter change it wasn't enough, I had to drop the tank to scoop out the half gallon of sand at the bottom and change the strainer on the fuel pump.
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Unread 12-23-2009, 11:29 AM   #14
cosmo_j
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i installed a new o2 sensor, fuel filter and plug wires yesterday. still runs like ****.
what sesor or w.e is beside the AIC??maybe i need to clean it too?
its going into the club shop come monday.
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Unread 12-23-2009, 04:50 PM   #15
Boanerges
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Did you reset the ecu after replacing the 02?? You need to check your map sensor too. It's located up against the fire wall about dead center. After you replace any electrical sensors you should reset your bank
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