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Unread 05-05-2013, 10:41 PM   #1
commodude90
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1992 YJ Wrangler 
 
Join Date: Mar 2012
Location: Jamestown, New York
Posts: 27
YJ 4.2 to 4.0 MFI Need help with finishing touches.

Hello all...... Bought a '92 y with a 4.2 in it last yr. The paperwork, title was obviously screwy as the 4.2's were 1990 and before and the Vin on this was for a 92 but had a 4.2 in it. Anyhow, the body and fratme were in great shape for western New York, so I bought it and went to work. I rebuilt the 4.2 bottom end (psitons, rings, pump.etc..). During this time I bought a 92 junk body and frame Renegade for the motor, tranny and such. I nuttered up the 4.2 and put the refurbished 4.0 head on it with a new distributor(hei).
It ran well with the new DGEV weber, so I took my time until this spring to install the 4.0 EFI. I just got it up and running two weeks ago but still have a few items to finish. I have searched quite a bit, and have lurked on this site in particular to figure out this conversion. Some of the things I have to finish, I can't find definitive answers to and hop that someone can help.

Jeep now: 1992 with a converted to 4.0 multi-port fuel injected engine.
I kept the v-belt driven steering, water pump and alternator which I upgraded to a 125A model. The Alt. upgrade has been great as the charging guage stays rock steady regardless of what lights and accessories are on.
I think the jeep was a combo of several years of jeeps 88-92 and I ended up with the Franken jeep. But alls pretty good now as I've straightened a bit of the mess out.
I need help on.....
1. As the jeep is an automatic with a tf999 auto transmission, the drive selection on the column used rods and linkage to shift, and a kickdown rod linkage also. When converted to a 4.0 throttle body, I do not have the right kickdown cable bracket or lever on the transmission. I do have the 4.2 kickdown bracket on the transmission that used a rod for kickdown purposes. The 4.0 throttle body uses a cable from throttle body to transmission kickdown lever. I need the lever for the transmission kickdown cable duties. I had the 92 transmission rebuilt for use with the still then, carb, operated sytem that used rods and linkage. Like a dumb #ss I cant locate the 92 lever that was on it originally. I've looked locally and online but can't locate one. Has anyone fabbed up this cable link to the kickdown?
2. The original wiring harness inside and out was from the earlier 4.2 yj version... haven't been able to figure out the tach set up. Does signal for the
originate from the computer to feed the original 4.2 tach, or are the two tachs different animals?
3. With the Map sensor plugged in, the engine is sometimes hard to start and sometimes cuts out when warmed up. Would this have something to do with the 4.0 efi being installed on the 4.2 block putting putting the Map sensor readings out of range for a complete 4.0. The engine runs pretty smooth without it, but probably not at its best efficiantcy. Im getting about 12-14 mpg's , the mpg's for a 1992 is listed at 14/15 city/country, that's without the map sensor plugged in. I did disconnect the 4WD vacuum system and installed a posi-lok cable for reliability- would not having a reserve canister no longer in the vacuum system cause a wild running efi system. I have replaced all of the system sensors with new except the VSS. I had installed a new VSS but it's drive stem broke so I re-installed the old one which seems to be working fine.
4. The distributor I installed from the 1992 has the cam sync sensor located at the bottom of the distributor cup whereas most other distributors for the 4.0 have a under the cap, top of the cup, disc shaped sensor. Would this newer style work in place of my older distributor type. The connectors appear the same, but there were differences in the 1991-1992 and other yrs of the YJ Fuel injection systems. The computer I have is for a 1991-1992 MFI system 4.0L system.
Thanks for any help or leads ...... I've learned tons from this site and wouldn't have gotten this far without it.....

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Unread 05-05-2013, 10:58 PM   #2
Fenix85182
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1989 YJ Wrangler 
 
Join Date: Jan 2006
Location: Southeastern CT
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1. I'm not sure about auto-trannys.
2. When I swapped in my 4.0, I left my original gauges out of my '89. To get my tach to work I had to run a lead off the ignition coil to the tach input in the original bulkhead. Worked the first time and has been consistent since.
3. My 4.0 swap gets me on average around 16 mpg. The MAP sensor simply gives the computer info about barometric pressure and allows it to idle correctly with the right info, so I don't believe the 4.2 bottom-end would affect it at all. I would take apart and clean the IAC. Check the intake for any carbon build-up in general.
4. I've had computers from a '91 and a '94 in my motor, which is from a '94. I don't believe the location of the camshaft sensor makes a difference, but I could be wrong.
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Unread 05-07-2013, 04:10 PM   #3
commodude90
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1992 YJ Wrangler 
 
Join Date: Mar 2012
Location: Jamestown, New York
Posts: 27
Found the tach wire.... it works now....!!

Hello....
Found the correct tach wire on the coil. On my 1992 wiring harness connector to the coil it was the yellow with black stripe from the coil to my 89 main fire wall connector which is green with hite stripe.
Thanks a lot. One more check mark.....done!!
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Unread 05-08-2013, 08:37 PM   #4
commodude90
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1992 YJ Wrangler 
 
Join Date: Mar 2012
Location: Jamestown, New York
Posts: 27
One thing leads to another with a Jeep.

Today I troubleshot the Map sensor. I wasn't getting a voltage reading from the center (b) pin while plugged in with the engine on. The resistance range between the pins A and C was ok, but was in the Megaohm range between a and b, C and b on the sensor itself. Changed it out at the parts store and it strted right up, it wouldn't start up before when plugged in. Went for a cruise and ran well except it stalled when coming to a stop a few times. Someone suggested that I reset the computer ( whenever a sensor is changed). I'll do this tomorrow and see how it goes. Will get to the IAC soon also.
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Unread 05-09-2013, 08:41 PM   #5
commodude90
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1992 YJ Wrangler 
 
Join Date: Mar 2012
Location: Jamestown, New York
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Getting closer......

Ok, so today I reset the computer in the yj by discharging the capacitators in the engines computer by disconnecting the battery and holding the Pos and neg leads together for a minute. We went for another 30 mi. ride with a couple stops along the way. It ran even smoother than yesterday after the map sensor change. It did stall out on me twice though during rapid decelerations. When I gradually slow down the engine seems to catch itself in time to bump up the idle speed. It doesn;t seem to be responding quick enough to do this during a rapid deceleration. I am going to change plugs this weekend and oil, plus do a seafoam cleaning. I will also go over the intake manifold to listen for leaks, add the old vacuum reserve canister back into the emissions system. Will keep updating to track this down. Mileage didn't seem to improve btw.
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Unread 05-10-2013, 09:12 PM   #6
commodude90
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1992 YJ Wrangler 
 
Join Date: Mar 2012
Location: Jamestown, New York
Posts: 27
Switchin' to glide...........

Today brought a big improvement in the idle circuit..... Previously the Jeep would stall out at a quick deceleration or quick turn. I changed out the cam position sensor in the distributor. I must have an older distributor as the one I have has the cam sensor in the bottom of the distributor bowl versus later ones that have the disc shaped pick up sandwiched between the cap and bowl. I had remove the drive gear from distr. shaft to remove the sensor, then reassemble. Ireset the computer....... it still stalled on me at a st0p.
I then added seafoam to the tank and oil to begin the cleanout process.
I also directly added some to the intake slowly while still idling. Shut it down and waited five minutes per instructions to start it up again. When they say the fumes generated would be extreme for a short while they weren't kidding. Don't do this while the neighbors are barbequing! I thought my jeep caught fire as I was lost in the exhaust smoke from the sea foam treatment!!
The Idle at startup settled and it ran the smoothest at all speeds I've seen it do in the year I've owned it. Next I'll be figuring out some more wiring to get the CEL back to the dashboard instead of having to use a test light and wiring the 4WD engage switch to the dashboard indicator light. I also need to get the in tank fuel pump wired to the harness provided wire and remove the one I added to get it working. Always something, but it's been fun learning so much and seeing the results. I think my wife is finally becoming a reluctant believer as she has enjoyed all the test rides and seen the resulting improvements.
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Unread 05-14-2013, 05:47 PM   #7
commodude90
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yj is smoothing out

Since seafoaming the engine, it has been running very well. It still takes a couple seconds to start, not the catch and immediate start Im shooting for, but it runs and idles well. We used a tank of fuel this past weekend driving route 62 in Pennsylvania in the Allegany National Forest in Northeast Pa. Of course we did take some off the beaten tracks into the forest and up some pretty steep camp trails. Doing the math, I got about 14mpg which I,m happy with for the type of driving we did. Im still looking for the correct transmission kickdown lever and may head to the autoyard this weekend.
I re-installed my factory yj foglights and noticed my headlights dim with them on, I will be changing the wiring on that to hopefully fix that. I also wired in the 4wd dash light to work with the end switch on the Posi-lok 4wd engagement cable I installed previously. I still have to find where under the dash my fuel pump wire ends up. It was never used previously as I had the carbed 4.2, but its in the harness in the rear. Im using the temporary wire I ran back to the pump when I converted the 4.2 with the 4.0 head and mfi.
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Unread 05-15-2013, 10:29 PM   #8
clintrivera
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1998 TJ Wrangler 
 
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Do you have a VSS? Not having one could explain your stalling when coming to a stop. What did you do about your CPS? Did the TF999 have a spot for it?
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Unread 05-17-2013, 06:12 PM   #9
commodude90
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1992 YJ Wrangler 
 
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Location: Jamestown, New York
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cps and kickdown

Yes,,,, I did replace my VSS with a better quality than the cheapie I originally used. The cheapie broke a drive element within its housing. The engine hasn;t stalled at all since replacing my cam position sensor a week or two ago. As for the CPS,,, the tf999 I used out of a 1992 parts wrangler has a hole in the top of the bellhousing. Once I applied a little pressure to the top of the sensor while tightening its holding bolt, it's worked fine. My idle circuit seems to be running very well now.
Today I installed a kickdown cable the throttlevalve of the transmission. I made a bracket and installed the cable to pull the existing lever to the rear of jeep. It now shifts at 18mph and about 28mph.... just a hair low, but Im looking at 31s for tires so just may leave it adjusted here for now. It now shifts well and the increase in hydraulic pressure at open throttle and mid=range improved nicely. I really shouldnt have driven it without the kickdown off, the tf999 and 32 rhs are pretty tough trannys though, but still.....had I known.
Im happy that Im getting at least 14 mpg's now and maybe it'll get a bit better with the shifting cleared up.
The mpfi conversion has been a long road, but has been worth it as far as smoothing out the engine and driveability. the old nuttered 4.2 ran well also, but I definately gained a bit of power with the 4.2 mpfi conversion with the 4.0 head set up.
next... finding that dang fuel pump wire up front under the dash... and am considering a limited slip differential or locker for the rear.
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Unread 06-20-2013, 10:42 PM   #10
commodude90
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1992 YJ Wrangler 
 
Join Date: Mar 2012
Location: Jamestown, New York
Posts: 27
Is it ever going to be DONE...

Since my last posting Iv'e added 31 inch wrangle a/t's. Not my first choice, but I got them for 200 bucks at a auto yard off a jeep that they just got in. They were like new so I couldn't beat the deal. I also replaced the posi-lok cable to my front axle lock. I had installed the old cable incorrectly. It had been touching the intake manifold and although I didn't see any obvious signs of melting, there were marks on it. The cable was stuck . I ldid finally get it to move after a couple of hours working it back and forth, but not very well as it was still to hard to operate. It was also way too long and made for a extremely lifted jeep in my opinion. I routed and tie wrapped the new shorter cable, and it now shifts in and out of 4 wheel nicely. I also soldered new leads to the 4wd indicator light switch on the front axle lock housing where the old vacuum motor used to be. This was supplied with the original posi-lok cable kit (#900) that I originally installed. The leads on the switch were very short and unprotected at the switch solder joint. I covered my new solder job with heat shrink over the new solder joints and then one larger one over them, followed up by spiral wrap. I left enough to allow for axle flex. So now my 4wd posi-lok cable works again and so does my dash light.... It's almost to the point where the wifey said she'd give it a go driving it the next time we hit a trail.
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Unread 03-02-2014, 10:26 AM   #11
commodude90
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Join Date: Mar 2012
Location: Jamestown, New York
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Okay.... 9 months since posting update....
The Jeep had been running great (until this week). It ran as if not on all 6 cylinders. Investigated and found the rear two cylinder spark plugs fouled out and more than normal blow by in the air filter. Changed out plugs and they almost fouled out immediately again. Checked engine codes and got a running lean code 51, Checked o2 sensor and it was pretty dirty, so I changed it. I cleared out the codes and reset the computer memory. Clearing out the memory and put the computer back into adaptive learning mode by switching the headlights on and off after discharging the capacitors. Still running poorly. I next checked the intake and exhaust manifolds without the fan belt on and viola... a steady column of exhaust pumped up between the collector point for the exhaust tubes. I also had a leak at the manifold donut connection. This I think has been causing the jeep to sense a lean condition, dump extra fuel and cause fouling and poor driveability. I removed the headers and checked it for leaks by spraying carb cleaner at the welds, and sure enough, I had several streams running inside the tube. I just ordered an APN exhaust manifold and will install that when it comes in. The manifold I replaced was an ebay cheapie I put on last year during my 4.0 head swap. The one I removed is leaking at the collector welds where two of the tubes almost touch and there doesn't appear to be much if any weld there.
Let ya' know what happens.........
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Unread 03-11-2014, 01:54 PM   #12
commodude90
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1992 YJ Wrangler 
 
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Location: Jamestown, New York
Posts: 27
Time to outsource...

If you read my last post, you know thet I've been trying to figure out what's going on with the 4.2/4.o MPFI . The engine is running rough, idling out of specs, spewing oil laden crankcase vented mist, fouling out plugs, the works.
I had just replaced the exhaust header which was cracked
The jeep and all is going to my mechanics shop Monday as I think it's going to need a rebuild. When I originally got the jeep, I re-ringed, repistoned the lower end and put a weber on top- that was when it was still a 4.2 carbed engine. Last year I put a 4.0 head and Fuel injected intake on it with new header. It ran really well until this last episode.

I'll be having him rebuild the lower end this time doing the following....
A new cam, grind crank if needed, machine work the block with new pistons as needed. He's owned his own garage and built many-many engines over the past 26+ years I've know him, and I trust him and his opinion.

It's going out this coming Monday to his shop where he'll evaluate it and we'll come up with a plan for what I want. As I know I won't have the time in the immediate future nor the equipment to pull an engine I think this will work out for the best. He says he's been down the crate motor route but as he said... " I've learned in my 35 yrs of business to build my own". He was burned twice using crate rebuilds.... he said one engine was missing a piston and crank and the second had the valve rockers on so tight they wouldnt "rock". Good enough for me.... I gave him 1500 beans up front and will keep you all updated as this rework progresses work and money wise.
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Unread 03-16-2014, 10:15 PM   #13
commodude90
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1992 YJ Wrangler 
 
Join Date: Mar 2012
Location: Jamestown, New York
Posts: 27
getting there....

As I couldn't keep my hands off the jeep until it goes to the mechanics tomorrow, I just had to try to figure out what is going on with my engine. One reported problem... excessive blowby..... may be solved. I had my oil changed last month and didn't think to check the level after.....duh. It was over a quart full, I drained it and am not seeing the blow by that I was before. time will tell.
Right now its running at a real high idle. I get a code 13;Manifold air pressure not changed since start up. Changed out sensor...same code and problem. I think is the intake manifold gasket on the manifold I put on is leaking. Still going to my buddies garage tomorrow so we'll see. At least its back to running with power again.
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Unread 06-11-2014, 06:19 PM   #14
commodude90
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1992 YJ Wrangler 
 
Join Date: Mar 2012
Location: Jamestown, New York
Posts: 27
We finally pulled my engine and opened her up. The first four cylinders have formed ridges on the cylinder walls to the front of the engine. The biggest being about .020 deep at the #1 cylinder. Before pulling the engine, we ran her for a minute and found #1 and #2 pistons sporadically or not even firing. Once we took the head off we found the ovaled cylinders.
It's going in the shop next week to be bored. Once we get to the crank and cam we'll decide then whether to replace or grind.The top end head and valves looked good although they were pretty dirty from the nasty combustion taking place. With the engine out, I'll be cleaning out the bay and re wrapping my wiring harness as it had been patched in when I put a 4.0 head and fuel injection set up on my 4.2 block. So my original "refresh" lasted 20,000 miles. I'm okay with that. Now that the Jeep is family now, we'll go the distance and get her back to like new. Will post as progress continues. I have to agree with most people who have done the fuel injection conversion, that its the best mod to do.
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Unread 06-11-2014, 06:22 PM   #15
commodude90
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1992 YJ Wrangler 
 
Join Date: Mar 2012
Location: Jamestown, New York
Posts: 27
Fuel washed...

When my mechanic buddy mentioned that the cylinders were fuel washed it occurred to me that the reason my oil level seemed overfull all the time was probably because of all the fuel being dumped into the pan from bypassing the rings, and ofcourse the excessive blow-by..
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1992 yj , distributor , MAP sensor

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