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99 HO 4.0 into 91 Comanche


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I have a 91 Comanche, 4x4, 5 spd ax15, that I'm trying to replace the engine on. It originally had a I6 HO in it. I bought an engine from a friend out work that is out of his 99 Wrangler, also a I6. I had it at a shop locally that I trust but they said I was pretty much SOL. I tweaked my motor mounts to get the engine dropped in and mated up to my tranny. power steering pump and alternator wouldn't mount onto the new (read 99) engine block. apparently it takes a different water pump as well, although the new one i bought for the old(read 91) fit perfectly. 99 also had what I believe is a magneto set up as opposed to the Distributor Cap my 91 had originally had; hooked up my Distributor and wires to my plugs. To make a long story short I had already purchased a new radiator and had everything minus the p/s and alternator wired up when I conceded and took it to said shop. The told me it ran, albeit rough and then took another couple of months to tell me they had done all they could. Now it is in different stages of disarray and come to find out they broke one of my plugs off in my block. I've been toying with this off and on for a year but with diesel down here at over $4.75 a gallon, driving my 84 Chevy CUCV M1008 is getting pretty pricey and I would like to sort my engine swamp fiasco out.

 

I have no qualms with welding up my own bracket for power steering and or alternator. My Old (off of the 91)exhaust manifold and intake rail with MFI fit perfectly onto the new (99) engine. I still have all the parts (IE exhaust rail, fuel rail, alternators, P/S pump) from both engines. I just need help if anyone has dropped a newer I6 into an older Comanche or Cherokee. Feel free to email me @ obby787@yahoo.com with any help or advice (other than get a reman 91 block).

 

Thank you,

Bobby

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Which computer (PCM) and which throttle body are you using? The 91 and 99 parts are not compatible.

 

The 91 was OBD-compliant. The 99 is OBD-II compliant. The sensors are different, the PCMs (powertrain control modules) are different, the ijectors are different, and the fuel system runs at a different fuel pressure.

 

Basically, you need to decide if you want to re-use your 91 externals, or update EVERYTHING to the 99 spec.

 

The 99 doesn't have a magneto. It uses coil-on-rail ignition, basically a small individual coil for each spark plug. No big deal -- you can yank the little sender for that and plug in your 91 distributor if you're going to stay with the 91 parts.

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I have the throttle body off of the 91 on there. i haven't done anything to the computer and would prefer not to. . .

 

I know that one of the sensors on the truck won't hook up to the 99 engine block, but I think its just oil temp. I figured switching engines within the same family was a common thing but all I could find info on was dropping a GM v6/v8 or upgrading from a 4banger to the straight six.

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you need to put EVERYTHING from the 91 motor on to that motor.

 

including the intake manifold.

 

it WILL bolt up. i've got a 2001 4.0 sitting in my barn out of a wrangler, and compared to a renix all mounting was the same.

Not necessarily, the problem is, if he uses the 99+ intake manifold he's going to have to match a newer (96+) power steering pump with it. The older OBD-I sensors will need to be used in the 99+ manifold as well. I would highly suggest going that route, it's good for a few hp anyway. Also to what Eagle said, most 99s still use the dizzy, I have a 99 XJ that I bought just because of that since I don't like the 00-01s that use coil packs. A lot of things seem fishy about what the shop told you, could you take some pictures of what you're working with so we could help you? 91 and 99 alternators I know for a fact mount the same way as well.

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you need to put EVERYTHING from the 91 motor on to that motor.

 

including the intake manifold.

 

it WILL bolt up. i've got a 2001 4.0 sitting in my barn out of a wrangler, and compared to a renix all mounting was the same.

Not necessarily, the problem is, if he uses the 99+ intake manifold he's going to have to match a newer (96+) power steering pump with it. The older OBD-I sensors will need to be used in the 99+ manifold as well. I would highly suggest going that route, it's good for a few hp anyway. Also to what Eagle said, most 99s still use the dizzy, I have a 99 XJ that I bought just because of that since I don't like the 00-01s that use coil packs.

 

true. i forgot that scorpio_vette did this on his wife's early TJ.

 

the 00-01's have a sensor in place of the dizzy...a distributor bolts directly in to the hole from what I've been able to gather on my motor.

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