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Unread 06-11-2012, 05:13 PM   #1
Michaelgoesrawr
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Failed smog: 4.2 Carb to 4.2 FI advice

So I took my Jeep to get smogged on the 9th and these were the results

Idle at 1048, co2 meas 11.00, o2 meas .50, (HC(PPM) GP=270, meas 1351 max=120), (CO% GP=2.50 meas 5.25, max=1)
2500 RPM, co2 meas 13.80, o2 meas .60, (HC(PPM) GP=330, meas 436, max=180), (CO% GP=2.50 meas .67, max=1)

I have no idea what all that means really. The mechanic said that it's burning oil really bad, which I knew it burns oil because I went through what seemed like less than a quart of oil every semester for school. I don't know though. As it was getting tested I could hear a knock from the waiting area of the shop. He comes in and starts shaking his head and tells me about the knock in the back two cylinders. I don't know what exactly is knocking but when asked what would be the best solution his reply was "rebuild or replace the motor" and that if I "baby it and don't romp it or drive the piss out of it, the motor may last another year". (I trust him and have no reason to believe that he is trying to get me to pay him for a motor because he only offered to go through the carb and see whats wrong with that for $90 bucks).

So I am currently out of a vehicle with only about 600 dollars to spend to fix it. At first I started thinking "this would be a perfect opportunity to build a stroker and drop it in" but that idea was short lived because a crate stroker is over 3k and as stated above I don't have the money to buy a 4.0 and all of the needed parts. My uncles dad offered to help me pull the head and go through the valves and pistons but again, a lot of money that needs to be spent in order to get it back on the road.

Anyways, here is my question, I have an '89 Jeep with a 4.2(rebuilt I think less than 10k miles ago) that has had the fuel injection conversion done mated to the TF999. I rolled it so driving that isn't an option. I understand that I will need the wiring harness(and I will need to rig the neutral safety switch) and I will need to install an electrical fuel pump but do the mounting points line up or will I run into problems with how long the transmissions(TF999 compared to the BA 10/5) are for some reason?

Sorry for the long winded post, I felt like I needed to tell you where I'm coming from. Any other advice or ideas would be greatly appreciated.

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Unread 06-11-2012, 08:42 PM   #2
Old4X
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$600 won't buy much as far as your failed engine. Best bet is go with the good engine. Why not just put it behind your 5 sp tranny?
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Unread 06-11-2012, 09:14 PM   #3
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Quote:
Originally Posted by Old4X
$600 won't buy much as far as your failed engine. Best bet is go with the good engine. Why not just put it behind your 5 sp tranny?
I was trying to ask if the two transmissions had the same mounting points on my frame or skid( I'm not sure where to start measuring). My plan right now is to take the good engine and put it in my jeep which has the 5 sp already.
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Unread 06-26-2012, 07:02 PM   #4
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I was really unclear in my first post but basically an engine swap is going to happen. What I am asking now is what would be better, taking my carb set up from my current engine and put it in the motor that has fuel injection so I do not have to swap my computer, or would it be worth it to take the computer and leave the fuel injection on the motor I am going to put into my Jeep?
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Unread 06-26-2012, 07:28 PM   #5
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Both trannys bolt up the same on the skid plate keep searching on Craigslist for 4.0's. and computers I found a 4.0 with computer ax15 and transfer case for $300
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Unread 06-28-2012, 01:46 PM   #6
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Quote:
Originally Posted by jhartley View Post
Both trannys bolt up the same on the skid plate keep searching on Craigslist for 4.0's. and computers I found a 4.0 with computer ax15 and transfer case for $300
That's what I'd like to do, but can't find any that don't cost way more. As stated above, I have maybe $600 to spend, hence the swap Jeeping on a budget sucks.

I'm not worried about the fitment issues anymore, but I am worried about the computers because I have never done this before. My question now is, can I just swap the computer boxes that are located under the dash(right?) and jumper the pin to deactivate the neutral safety switch(because I have a manual in the jeep the motor will be going into) or will I have to swap all of the wiring?

I apologize for the stupid questions. I'm not very good with the more complicated engine stuff yet.
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Unread 06-28-2012, 03:25 PM   #7
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You'll have to swap wiring for the computer, the harnesses aren't the same. The rest of the wiring will remain untouched.

Does the good 4.2L have the Howell TBI or does it have the Mopar MPFI?
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Unread 06-28-2012, 03:37 PM   #8
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Quote:
Originally Posted by NonRubicon
You'll have to swap wiring for the computer, the harnesses aren't the same. The rest of the wiring will remain untouched.

Does the good 4.2L have the Howell TBI or does it have the Mopar MPFI?
I think it's the TBI but I am unsure because the kit was bought used and installed several year ago.

Regarding the computer, I will have to pull the wiring through the firewall and replace it with the good 4.2 wiring and reinstall the good 4.2 computer in the cab? Or is the computer in the engine bay?
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Unread 06-28-2012, 04:10 PM   #9
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i am not sure but i would put hte fuel injection on the jeep. just swap everything over exactly as it sits in the 89 to the 88. then you will be ok
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Unread 06-28-2012, 07:12 PM   #10
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Thanks super. I've never done anything like this so I wanted to be prepared as possible. What I said about swapping the computer would correct as to where it's located and taking the wires out through the fire wall into the engine bay?

Edit: The 89 hasn't been on the road and hasn't been driven much since June of 2009 so is there anything I should do when I swap it/before I get it smogged that will help with a pass. It passed fine before but I don't know if siting has anything to do with it.
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Unread 06-28-2012, 07:28 PM   #11
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you will need to clean out the old fuel in the lines and maybe let the pump sit in carb cleaner over night as it might have varnished up. also, sit the one or two injectors in cleaner over night also. other then that, as long as you cat is good and the o2 sensor is reading right, you should be ok.

as far as the copmuter and wiring, i guess that is right. i don;t know much about that system in particular but i know if you follow that harness from the injectors and sensors, it will take you to the ecu and then you can unhook the harness and pull it through the firewall and then unbolt the ecu and pull it off the firewall
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Unread 06-28-2012, 08:14 PM   #12
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It runs fine when I drive it but I will when it's out. Will I need to change the flywheels from my bad '88 4.2 with the standard to the good '89 4.2 when I put it in? It's a good thing my girlfriends father is helping me do it, every time I look at all of the wires I get dumbfounded lol.

Also I will most likely take the exhaust from the '89 and put it on mine because I was gonna do that anyways before i found out my motor was bad.
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Unread 07-07-2012, 12:51 AM   #13
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Also, it seems like there is a tranny leak on my '88 with the bad motor. It looks like it's coming from right behind the oil pan where the trans meets the engine. What kind of seal would I be looking to get to fix that? Rear main or a trans seal?
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Unread 07-07-2012, 02:41 PM   #14
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Anyone?
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4.2l , engine swap , failed smog , tf999

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