TFitzPat87

Hi Guys,

I'm currently talking to a guy in my area who has a pretty nice comanche for sale. I have yet to check it out, but it looks good (don't see any rust in picture). The only thing is, it has a fresh rebuilt motor, which can be a plus as according to the guy... the shop that did the work is reputable and built his 4.7L stroker that has been solid. That being said, he says it misses around 1700 to 1900 rpm.

It's a 1990, 4.0L, 4x4, auto. Everything has 170k on it except the motor. Considering it's a 1990, that makes it a Renix, correct? If that's the case, do you guys have any idea what causes a miss like that? He said he thinks its a cold air sensor?

I'd appreciate any recommendations for things to look at when/if I go check it out. He was asking $4,600 but already got him down to $3,800 through email, and I'm sure I can get him even lower than that if I go check it out. This guys is clearly a jeep guy, so he seems to be pretty reasonable.

Thanks in advance!

88whitecomanche

Map sensor is probably what he is talking about,
A miss around that rpm could be anything, you would have to diagnose it yourself to figure out the problem, it's renix era so a multimeter, cruisers renix tips and cruiser himself can help you diagnose it...
Id still bring him down to 3k just to figure out the problem...

TFitzPat87

Appreciate the response! If the motor sounds good, runs good, and everything else seems good, would a miss at 1700 to 1900 rpm sway you from buying it? I'm achin to get my hands on a comanche, but I don't want to buy it just to have one.

I'll be honest, rebuilt motors worry me, but I hate to pass it up if it was a quality rebuild.

88whitecomanche

Then I would walk away, Comanches can be had under 3k
Depending on your tastes

TFitzPat87

Yeah, the problem is finding a good one in my area. I've started my search in other states. I still may go check this one out if I get more pictures from the guy, but we'll see.

If anyone else has anything, it's much appreciated. I'm always willing to learn new stuff anyway.

Spydie

Just an update about that truck, he took $2800 and I'm currently working on getting everything on it corrected.

TFitzPat87

Nice! Good luck to ya. I got shipped outa town for work for a couple weeks, so I was never able to go look at it. The day I got sent outa town, he told me he'd take $2800. I was pretty bummed, but oh well.

Let us know what the problem was.

Spydie

Man! I wish I would have known he'd take $2800 from moment one. Oh well, IMO it was worth it. I've been looking over everything the last couple of days and here is what it was doing

1.) Backfiring like crazy. Couldn't get on the gas without it popping.
2.) Stuttering. When I'd get on the throttle at any speed it would stutter or shutter kind of hard to explain. It wouldn't even go up my driveway without doing it.
3.) Had the miss at 1700rpmish.

Here's what I have found and fixed

1.) The spark plugs were not replaced when the engine was done and man were they bad. 4 of them were fouled.
2.) TPS Sensor had one wire not reading. The pigtail on the wire harness was absolutely destroyed and the C output wasn't reading anything. Once i got it replaced and connected right, i was getting .03v when it needed .83, so that was an issue as well.
3.) The biggest, and honestly most mind boggling problem was the vacuum lines were all sorts of messed up, despite him having the hose diagram on the hood! He had the Map sensor running to a vacuum port on the fuel rail so both the map sensor and this port were sucking while nothing was blowing The fuel rail vacuum was needing air so bad that if you covered it with your finger it would shut off the truck. So i connected the Map sensor to the throttle body and ran a new hose for the fuel rail vacuum to the air box and got that squared away. Then I was looking some more and found that the line for the vacuum canister wasn't even hooked up so I reconnected that.

So, now the MJ is running "smoothly" Idle is 100x better, I can now drive it up my driveway with no shuttering what so ever. Haven't had it backfire on me yet. Going to get it plated today so I can see how it handles on the road. It used to bog down around 45mph and not want to continue without backfiring. I'm hoping most of that will be solved with this. We're all honestly surprised it made it the journey from Flint to New Baltimore.

Oh, and I was sure we were going to be shot at driving through Flint just because of how much it was backfiring. I'm sure if you looked on their web page there were plenty of calls about it

TFitzPat87

Awesome! So when you get it all finished up, I'll come and give you 3500 for it. Hahaha!

Spydie

Haha! You and one of my buddies can fight it out! Took me way too long to give it up that easy

TFitzPat87

Ok fine, I'll give you $3750!