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Discussion Starter · #1 ·
Greetings all. New jeep owner (read very little mechanical ability) with a couple questions: my jeep is a 91 with a 4.2L engine. I thought 90 was the last year was the last for the 4.2 (i think the VIN decodes to 6cyl). Is this correct and is there any way to tell (without pulling it apart) if it was rebuilt. It also has fuel injection-any idea of the HP and any special considerations for a jeep with FI? Much appreciated.
 

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91 should be 4.0L not 4.2.
 

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They had both that year.

Edit:
I went and checked and the 4.0 was the only I6 that year. You must have a late 1990 that was badged a 1991.
 

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The later productions numbers in 90 had the 4.0. They are very rare. Jeep decided to take the 4.0 from the Cherokee lines and use them in the Wrangler platform. All 91-on had the 2.5s or the 4.0s. HP around 180 horses in 91.:thumb:

FYI, the 4.2 was an optional engine in the YJ line from 87 to 90. The 2.5 was the standard.:eek:
 

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Discussion Starter · #10 ·
I thought the 91 had the 4.0L. Mine is defiantly a 4.2L. Also the fuel injection must have been an addition. Does the FI make more HP? I've never had a jeep so I really have nothing to compare it to. Looking forward to warm weather. Thanks to all for the quick feedback. More questions to follow.
 

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My 91 has a 4.0 with fuel injection. The fuel injection was on my list when I was shopping for a jeep. My last cj-5 had a carb and it would die on every hill.
 

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What, exactly, makes you think you have a 4.2? If you have MPFI, there is only two ways that can be on a 4.2. First, is to swap the entire head, intake fuel rail, wiring and some sort of crank position sensor. Second, is to have this Mopar Multi Port Injection Conversion Kit. real pricy.:confused:
 

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Discussion Starter · #13 ·
I'm sure you're right. I realized it by way of an oil change. The second day I had the jeep I attempted to change the oil and replace the filter. However, the new filter for the 4.0 wouldn't line up with the threads. After 20 min of trying (once again I'm a mechanical nube) to get the filter on I called the auto parts place and asked them to check it for me. They said I had the right filter (for the 4.0). When I told them it wouldn't line up they asked me to read them the number off the original filter. Turns out the original filter matched the 4.2L. Does this sound plausible?
 

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a previous owner my have swapped the 4.2 block in for a bad 4.0

got any pics of the motor? (fuel injection sys, oil filter adptr, wiring harnesss etc)
 

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Does it have a mounting place on the right side of the block for the mechanical fuel pump?
 

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Discussion Starter · #17 ·
Sorry it's been a while folks. Once again thanks for the feedback. Pics have been slow in coming due to computer issues. I'll try to get some on ASAP. Like most old jeeps I've got some work to do. Oil pan gasket leak, slow on the start (probably internal fuel pump), and I've got a one to two drop (after driving) leak after shut down around the yolk - although no apparent leak around the transfer case seal - any ideas. It shows up right at the U-joint. Could it leak from the seal and because the yolk is spinning so fast, manifest itself at the U-joint? I just don't want to end up draining the transfer case. BTW did I mention I love my jeep...
 

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Does it have a carb now? You say it has internal fuel pump so it may have come with a fuel injected 4.0 and someone replaced it with 4.2. If it doesnt have fuel pump back at fuel tank I think someone went through alot more then the usual engine switch and/or maybe it was Jeep-Jacked and someone did some VIN # replacement, LOL. Also does the title show it was ever totaled? Good Luck
 
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