1988 jeep cherokee Laredo 4.0
12-30-2016, 05:44 PM
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1988 jeep cherokee Laredo 4.0
Hey guys I'm needing help... just bought an 88 cherokee 4.0 and it wasn't running I checked the distributer and the gears were gone so I replaced it and put jeep back in time and it ran. But I'm having a slight problem with it running it idles fine the you give it some throttle and it is spitting and sputtering and back firing I smell fuel coming bout of exhaust. I've replaced the csp sensor, map sensor, new plugs and wires and coil pack, changed injectors and checked fuel pressure running at 34lbs then cut off and pressure drops emidiately to 0lbs any help would be much appreciated!!! Thanks
12-30-2016, 06:22 PM
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Year: 90,84
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Engine: 4.0,2.5
Hi Haden, and welcome! That darn problem pops up and can be tough. Your three wire, (titania), o2 sensor gets a five volt feed from your ECU. How well it grounds that is what the puter uses to figure fuel. Because it's so easy, and just maybe could be illuminating, you could try unplug your 02 and just see.
The puter should make it run OK on default settings, but IF that 5 volt feed is grounded by a faulty sensor the Puter will get an incorrect reading. Check the wires as well, they melt/ground to the hot exhaust manifold.
On top in my sig below is a link to Cruisers tips you will want to see. No doubt he will be along .
"coil packs" are on 00 and 01. There you have the ICU and coil sort of "doing it"
The pressure should not drop that fast. Fuel pump check valve, injectors, or FPR are faulty. The brittle little tube from the TB to the MAP is Crucial. no cracks, blocks, leaks.
The puter should make it run OK on default settings, but IF that 5 volt feed is grounded by a faulty sensor the Puter will get an incorrect reading. Check the wires as well, they melt/ground to the hot exhaust manifold.
On top in my sig below is a link to Cruisers tips you will want to see. No doubt he will be along .
"coil packs" are on 00 and 01. There you have the ICU and coil sort of "doing it"
The pressure should not drop that fast. Fuel pump check valve, injectors, or FPR are faulty. The brittle little tube from the TB to the MAP is Crucial. no cracks, blocks, leaks.
Last edited by DFlintstone; 12-31-2016 at 08:27 PM.
12-31-2016, 08:47 AM
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Year: 1990
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Engine: 4.0
12-31-2016, 12:30 PM
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When I changed 3 injectors I started it up ran fine then turned off to tighten everything up and after that I started it and it went back to doing the same thing...? Any other suggestions @dflinstone
Last edited by Hayden Potter; 12-31-2016 at 12:32 PM.
12-31-2016, 12:57 PM
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I would be very suspicious of any connectors that you coulda jostled while buttoning things up.
01-02-2017, 10:47 AM
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Just looking at what you first posted. If it wasn't running when you bought it, the fuel pump may also be shot. Jeep can run more or less fine at idle with an "about to die" fuel pump but will act up when you give it gas. I'd be tempted to swap the fuel pump but I'd go down the Cruiser list and check the basic RENIX things out like TPS readings, grounds, C101 connector, etc before you get "PSS" (part-swapping-syndrome).
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01-02-2017, 02:52 PM
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Year: 1990
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Just looking at what you first posted. If it wasn't running when you bought it, the fuel pump may also be shot. Jeep can run more or less fine at idle with an "about to die" fuel pump but will act up when you give it gas. I'd be tempted to swap the fuel pump but I'd go down the Cruiser list and check the basic RENIX things out like TPS readings, grounds, C101 connector, etc before you get "PSS" (part-swapping-syndrome).
01-02-2017, 09:57 PM
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Year: 1990
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