88 Cherokee rough idle & rough acceleration
10-22-2013, 06:45 PM
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88 Cherokee rough idle & rough acceleration
Hey everybody, I'm new here but to the point now. I have an 88 4.0 I6 and about a month ago one of my fuel injectors/ fuel pressure regulator started leaking, so I figured time to upgrade and got some all new 4 hole injectors and regulator installed that and started it up, it ran ok untell I put it into drive and it puttered and the idle was rough. Figured I forgot to reset the pcm so I did that and later started it up and it ran smoothly untell a few days ago. I was coming back from an off-roading trip and had to do some four wheeling and I stopped to re-strap some gear and as soon as I got back in and put it in drive it started puttering again and had the rough idle so got it home and checked everything and it looked alright. Also I checked my distributor and rotor and spark plugs and nothing looks wrong and all electrical components work in that system. So does anybody else have this problem or and idea of what it could be. Thanks.
10-23-2013, 06:40 AM
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Good chance you bumped the line from the throttle body to MAP during the injector install.
MAP sensor tube
There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor, behind the valve cover, higher up on the firewall. It has one vacuum line as already mentioned, with a 3-wire plug in the bottom.
CRUCIAL!! The MAP sensor will tell the ECU to dump fuel with little to no vacuum to the MAP. Any crack or blockage and it will be pig-rich. ( black smoke, fouled black plugs, must hold your foot to the floor to keep the engine running). You can pull the line off the MAP sensor and feel for vacuum with your finger. If it runs!
A visual inspection usually reveals any issues with the line from the throttle body to the MAP sensor.
MAP sensor tube
There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor, behind the valve cover, higher up on the firewall. It has one vacuum line as already mentioned, with a 3-wire plug in the bottom.
CRUCIAL!! The MAP sensor will tell the ECU to dump fuel with little to no vacuum to the MAP. Any crack or blockage and it will be pig-rich. ( black smoke, fouled black plugs, must hold your foot to the floor to keep the engine running). You can pull the line off the MAP sensor and feel for vacuum with your finger. If it runs!
A visual inspection usually reveals any issues with the line from the throttle body to the MAP sensor.
10-23-2013, 06:42 AM
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
AND, since you've got an 88 and seem interested in eliminating issues and maintaining your Jeep, click on the pink link in my signature and perform the "fixes" in posts 1 through 4 for starters.
10-26-2013, 12:03 PM
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Good chance you bumped the line from the throttle body to MAP during the injector install.
MAP sensor tube
There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor, behind the valve cover, higher up on the firewall. It has one vacuum line as already mentioned, with a 3-wire plug in the bottom.
CRUCIAL!! The MAP sensor will tell the ECU to dump fuel with little to no vacuum to the MAP. Any crack or blockage and it will be pig-rich. ( black smoke, fouled black plugs, must hold your foot to the floor to keep the engine running). You can pull the line off the MAP sensor and feel for vacuum with your finger. If it runs!
A visual inspection usually reveals any issues with the line from the throttle body to the MAP sensor.
MAP sensor tube
There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor, behind the valve cover, higher up on the firewall. It has one vacuum line as already mentioned, with a 3-wire plug in the bottom.
CRUCIAL!! The MAP sensor will tell the ECU to dump fuel with little to no vacuum to the MAP. Any crack or blockage and it will be pig-rich. ( black smoke, fouled black plugs, must hold your foot to the floor to keep the engine running). You can pull the line off the MAP sensor and feel for vacuum with your finger. If it runs!
A visual inspection usually reveals any issues with the line from the throttle body to the MAP sensor.
10-26-2013, 12:05 PM
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10-26-2013, 12:12 PM
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Year: 1990
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10-26-2013, 12:28 PM
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Year: 1990
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31 @ idle with the vacuum hose connected to the fuel pressure regulator and 39 with the hose unplugged.
10-28-2013, 02:59 AM
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10-28-2013, 06:44 AM
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Year: 1990
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Weak fuel pump or MAYBE clogged up fuel filter.
Could also be that the rubber hose inside the fuel tank that connects to the pump is split.
If you do decide to replace the pump, do not use Airtex brand.
Could also be that the rubber hose inside the fuel tank that connects to the pump is split.
If you do decide to replace the pump, do not use Airtex brand.
10-28-2013, 08:39 AM
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Year: 1990
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10-28-2013, 08:54 AM
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0