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General Forums => The Mess Hall => Topic started by: fireman411 on July 13, 2011, 09:08:48 PM
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its been a while but I need some help. My 90 yj after running for a little bit will drop idle and stall out. I have changed the plugs,wires,cap,rotor, fuel filter. It will only do it if it has th hose on it going from the air box to the TB. I can not figure it out to save my life.
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not sure which hose you are referring but have a look at the air filter (just because you mentioned the airbox)
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Think the MAP Sensor is getting a false reading because the hose is off.
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you must be talking about the vacuum line for the hot air vacuum operated door in the air box. it applies vacuum to open the door and if the tube from the air box to the exhaust manifold is still there would start partial shutting ounce the exhaust manifold heats up and gets the air hot... don't really see how that vacuum door system could kill the jeep. would only see it leaking and causing a high idle.
(http://i164.photobucket.com/albums/u25/chardrc/vacumediagramcolor.png)
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Think the MAP Sensor is getting a false reading because the hose is off.
only if the line going to the MAP sensor is off, damaged or plugged will cause false readings, having another line off or a leak does not cause false reading, it just reads the correct (less) vacuum and the idle would be higher due to more air entering the engine. If it was a MAF sensor then you'd be correct (the additional air entering the engine would bypass the MAF sensor), with MAP the vac leak theory does not apply.
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It will only do it if it has th hose on it going from the air box to the TB.
So it runs ok with the hose disconnected? This sounds like the hose gets blocked off when attached.
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so if it runs with it off and not on i would think the idle control actuator motor is closing the throttle too much and needs the extra air from the open vacuum line to run.. seems odd... if it is as described i would take a volt meter and test the tps adjustment.
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OK well I have changed the coolant temp sensor and map sensor. Still doing the same thing also replaced the hose coming off the map sensor. I am lost. :brick:
Does anyone think it might be a timing issue? Im shooting in the dark now
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could it possibly be the egr being opened at idle (which shouldn't happen but would kill the engine, easy enough to check also without spending any money).double check you lines and try capping off the egr and see if it still cuts out.
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OK well I have changed the coolant temp sensor and map sensor. Still doing the same thing also replaced the hose coming off the map sensor. I am lost. :brick:
Does anyone think it might be a timing issue? Im shooting in the dark now
Do you have a scan tool? What DTC codes are you getting: Stored before you start it and once it dies?
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Do you have a scan tool? What DTC codes are you getting: Stored before you start it and once it dies?
this is 1990 tbi, doesn't store codes and scan tools are few and far between.