smokey

Here is the manual for 1988

Ok, finally got around to swapping ECU back to Org 1988. Almost no difference in 0-60 times. So I don't think there is any topend realworld hp diff in the 1989-90 ecus. Most of my gain was the injectors. (best mod for the money). Now that I have stop drag racing it, I will run a tank a gas through and see mpg changes. But, two things I have noticed are better 25-50 mph run times and one of the things I think is weird is way cooler engine temps. On the two different sensors (bottom and top of engine) I am seeing 20-25 degrees cooler temps on warmup. With the 1988 ecu I see 210 warm and with the 1990 ecu I see 185 warm I wonder if the calibration for the sensors is different for the different model years ecu? I think the Nickintime cpu reads the raw data not the ecu data but I don't know. I do know the heater does not blow as hot with the 1990 ecu, so I would think the engine is running cooler. Maybe not as lean. Keith

Good call. I will try that. First I am gonna run the new ECU for a week and do some more runs and see if there are any changes. I will then swap back to the factory and post the results.

I would like to give my experience with a few mods to my 1988 Comanchewith AW4. 1988 Long bed with 31 bfgs and 4.10 gears weight at truck scales of 4,300lbs. About 150K on the stock motor(k&N filter). After a tune up (plugs and wires and dist) I did 10 0-60 runs using nickintime engine monitor. Best run was 13.28s at 5,000 feet 65f. Using a HP calculator that's about 118 hp at the wheels. Not to bad at 5,000ft and about 500lbs over stock. Stock time would be 10.9s or about 140 hp at wheels.(Published by 4 wheel drive mag in 1988 : )) SO, the fun part the mods. $75 ebay First 1990 auto engine ECU. NO change. Well maybe a little worse the best 0-60 time was 13.31 (maybe could be driver error?) Where is the 7 hp everyone says you get with the ecu swap???? I do think it shifts a little different but that should be controlled by the TCU so if anyone knows if the newer ecu really does anything different I would like to know. I also noticed no change in A/F ratios or duycycle of the injectors at 5,000 rpm. Second mod. $135 Jeff Liegh 62MM throttle body. BOOM 2 HP gain. Best time of 10 runs was 13.22s. My old throttle body was is rough shape. Also the grommet with the MAP hose was pretty bad too. New throttle body and MAP grommet did help a lot with the idle too. Third mod. $62 Amazon Volvo 746 injectors. BOOMMMM 5 HP gain . Best time of 10 runs 12.77s WOW my old injectors were crap 4 where org and 2 had different nozzles on them. So for $272 I got 7 real world HP gain. I am going to drive it for a couple of weeks to see if the ECU learns anything and do some more runs. I will post up if I see any other improvements like cold starts or mpg (I think it will go down because I will be hammering it all the time, I got 16mpg avg on 10 fillups before) I also wonder if I did the injectors first would that of change the other mods?

I replaced the rubber seal on the bottom of the driver window, the water was running down the window straight in the door then into the door jam.

Another issue is the fan clutch, I did the test with cardboard to see if it was working and it passed. The engine would run at 220 all the time. I swap in a new clutch and runs 195 normal and 205 running uphill with the AC on.

Another water issue is the wiring that runs along the driver door kick panel, if water sits in there too long you will be chasing electrical issues. I had a major leak from the driver window and corroded all of these wires.

If you can weld. https://www.ebay.com/p/DIY-Front-Winch-Bumper-Bare-Metal-for-1984-2001-Jeep-Cherokee-XJ/14026003340?iid=192725993086

Just a tip, I had a bad pump issue and bypassed the ballast resistor on the fender well to get the truck home. It raises the the running voltage to 14 from 10 volts. It was just enough to get me home.

I would grab the oil pressure and temp sending unit from the donor vehicle, I had a problem with the temp sending unit on my 88 using an 87 full gauge package. I even bought a new temp sender from autozone and it did not work but the factory one from the donor vehicle works fine. All the factory wiring is the same so when you plug the new cluster in the tach will work. I had an issue with the speedo and odometer and ended up resetting the donor vehicle odometer to match my miles. Also the speed is off but aren't they all. There is a swap over year for the speedo cable from plastic to metal so I would grab the donor vehicle speedo cable too.

Just got back from 1600 mile round trip with the Comanche. The truck ran great got 14.2 MPG flat towing a 3600lbs CJ5. Ran a little hot in the pan handle of Texas put it was uphill climb to Raton, NM and it was 94 outside.

Anyone want to take the trucks out? I live in Denver.

Here is a link. https://www.tfltruck.com/2019/05/this-sucks-our-jeep-comanche-is-very-broken-the-budget-is-blown-cheap-jeep-challenge-s2-ep-2-video/

Ok, update on my 16 gal fuel tank. So after all the testing, I decided to cut a hole in a perfectly good fuel tank. Then I cut the filler neck and overflow inside the tank and resealed the hole I cut. I finally got to the gas station and filled up with 23.6 gallons and the auto stop on the fuel pump didn't puke fuel on the side of the truck. If you look at the over flow tube it was bent at a 90 degree angle and was halfway into the tank. So it looks like the only difference between the 16 and 23 gallon tanks are the filler and overflow in the tank.

I love posting to old threads. So I just bought a 1988 Long bed Comanche from the original owner and drove it 1500 miles home. Have to say why in the world would they make a 16 gallon tank? When I got home I pulled the tank and stamped on the side is 16 gallons. It has three straps and the measurements are 33.5 inches by 12.8 inches by 12.2 inches. The math comes out to 2.978 cubic feet which is 22.3 gallons of space. So I filled it with water and low and behold it held 23.8 gallons of water. It is the filler next that extends into the middle of the tank almost half way that limits the space. Also on fillups it causes the auto stop on the pump to blow gas out over the side. Has anyone cut the filler neck? And the most important question of the day what were they thinking making a tank the exact same size as the 23.5 tank but make it only hold 16 gallons? If you want less weight just don't fill it up. Sorry for the rant was thinking about it for 1500 miles.