airspeed

Be sure you can feel vacuum on the small line going to the throttle body. The rubber grommet that goes into the valve cover needs a 2.2mm through hole in it. I used an .092 drill bit by hand and cleared the hole in the grommet.

I had a similar situation with my 2.5 when I was putting it together. The distributor post is a 4:00 and the rotor needs to be set at 6:00. I kept looking at that and thinking this can’t be right, I had two different manuals and they both said the same thing. You stop and think the engine actually fires ~ 10-15 BTDC, that rotor is probably in the right place.

Here are the photos of the floor liners. These liners would fall in-between the hard plastic and the soft rubber. They are stiff enought to hold their shape around the edges but compliant where they will follow the contour of the floor. I ordered them from Baseline 4x4 Outfitters for $61 plus shipping.

I just bought a set of Rugged Ridge #12920.25, for my 88 MJ, I think they fit really nice. They are a bit pricey, I see them going from $59 to $79. I can take a photo tomorrow if you want to see an actual picture of the mat in place.

The exhaust valves will be the first thing to fail if the engine is running too lean. You will need to pull the valves out of the head to see if the seating surface is burned. How high are the valves sitting in the head? Is the valve surface a little above the head chamber, even or below? This is another indicator of how bad they are worn. If the exhaust valve is leaking it won't put pressure in the valve cover, it will leak to the exhaust system. The leak down test would have to go by the piston rings to put pressure in the valve cover. The CCV on the 2.5 TBI is the 2.2mm grommet on the back of the valve cover, make sure that is open, I used an .092 drill bit on mine. How many miles are on this engine? If you rebuild the head and put it back on then you might find that now you have bad rings.

There is no vacuum to the pressure regulator on the TBI system. There is a diaphram, spring and a adjustment screw on the throttle body assembly. I'm not sure where the pressure gauge would connect to. The leak down tester is a good tool, you can learn a lot about the condition of the engine. Be sure that engine is TDC #1 and don't leave the socket wrench on the crank, that motor will spin real fast with 100psi in the cylinder if you are off TDC ever so slightly. I use a plastic stick through the plug hole to feel the piston at TDC and just keep going around 1, 4, 3, 2.

I think they are M12-1.75 x 50mm length. There maybe a couple that are longer, ~60 - 70mm

I used the 94 Taurus 3.8 fan and purchased a two speed fan relay from dccontrol.com. I had to move the radiator forward about 1.0". That fan can move some air! The fan control has a small temp probe that you press into the radiator fins and has an adjustable pot for temperature on low speed.The fan fit the radiator so well I didn't even have to make brackets. You can see the fan relay mounted on the fender well

There are not a lot of performance parts for the 2.5's. Clifford makes a header for it but at $300 not sure there would be a ROI. My 2.5 in Colorado is probably putting 90HP to the wheels, not bad around town but when you get on the highway at 75 it has a hard time keeping up. The trade off is the mileage, ~20-23 in town and ~28-29 on the road at 65 mph.

I would think as long as the 90 head had the TBI you should be OK.

There were some variations in the blocks with the oil pumps and bypass valves. Not sure what the deatails are. They seem to reference a casting number, not sure what that is about.

I believe the 86-87 had the carburetor, 88-94 had the TBI and then they went to multi-point injection for the remaining years. I’m pretty sure they would have different heads and different cams with other variations regarding sensors and ECU's. I recently ordered a complete rebuild through AutoZone built by Proformance for ~$1500. That is a nice motor, it came complete with all tin installed and has a 3 year 100k warranty. The new engine shows up in a shipping pod, swap the motors and ship the old one back. Built in the USA with American parts. They have a good tech support line and answer all questions.

I have been chasing a "horn not working" problem for a while. My first problem was a bad ignition switch, no voltage to the horn relay, fixed that. I have continuity with the relay ground wire all the way up the column to the slip ring. When you push on the horn button there is no ground? I can use test leads and go from the slip ring to any other piece of metal on the car and the horn will honk. All the rotating mass inside the column is isolated? You would think that all that steel running in metal bearings would have some grounding continuity. :dunno:

I can understand the vacuum leak at the booster but I'm not sure what the ground on the taillight would have to so with the EGR valve. I know there is a EGR / Evaporator Canister solenoid that should activate the EGR valve. My thought is when the EGR solenoid activates it turns into a vacuum leak at the EGR valve and kills the engine.

My 88 Comanche has an intermittent stall when coming to a stop. I put my vacuum pump on the EGR valve and it is zero, no vacuum. I went and picked up a new EGR valve and on the bench it reads zero, no vacuum? Does this valve need to be at operating temperature to hold vacuum?

My 88 Comanche 2.5 TBI needs the gasket that goes between the EGR tube and the exhaust header. I have checked Rock Auto, NAPA, Autozone, no luck.

I have been tracing a "horn not working" problem. The brown wire from the horn relay goes back to a slide switch located down on the steering column. This switch is operated by a push-rod from the ignition swith up on the steering coulmn. The sliding contacts in that switch are just worn out, I took it apart and cleaned the contacts and reseated but that didn't help. What is the technical discription of this switch and where can I find a new one? 88 Comanche, 2.5, 4 spd.

Is the Taurus fan running backwards? I had the same problem on mine, with all the air and noise it is hard to tell the direction of the or air flow.

My horn doesn't work at all, no power from the brown 14g wire. According to the schematic there is a 12ga brown that come off the ignition switch and leads to a power distribution "E" location, then turns into a 14ga brown wire that goes to the horn relay. Does anybody know where the power distribution location "E". I'm thinking it is a connector down on the steering column? I'm going to install a set of gauges so the dash will come apart in the future, then I will dig around and find it.

Don't go to Sears!!

I had the same problem on my son's XJ. On the NAXJA website they have a good illustration how to place a small 3" long 1/2" socket extension behind the hub and into the steering knuckle. Start the engine and carefully crank the wheel, the hubs pops right out. Please note this is a dangerous operation to do on jack stands, you do this at your own risk. It does work very well.

Update: I talked to the service writer and tried to explain to him that the work was not done properly, he went and got the tech that did the work and the conversation went down hill from there. The technician had severe OD, opposition disorder. What ever you said to him he would take an immediate opposing view and then want to argue the point. I finally got to the service manager and he agreed they would take it back in and look at it. In talking with all three people I heard several times, "why would you worry, it has a lifetime gurantee". I dropped it off and stopped by the next day. They replace both ball joints on the right side and managed to get 3 of the 4 zerk fittings installed. I think they are using the wrong tool for that ball joint and not getting them installed straight, then they have to beat on them with a hammer to try and square them up. The tool they use presses from the top of the ball joint. It does not hold the part perpendicular to the steering knuckle. The tool I saw at another shop had a sleeve that went over the OD and pressed on the outer flange. It steers good and tracks down the road nice. I’m not going back, I have learned my lesson. That was a $489 lesson. You turn 25 and spend the rest of your life learning what you don't know.

I had the Comanche in for a set of tires and front end alignment, they gave me the ball joint routine. I went out with the tech and felt the play in the upper right and there was a little bit of movement, I would say about .028". They would not gurantee the tires or the alignment unless I fixed the ball joints. I thought I will take this home and do it, then I though let Sears do it. This is not a complicated task, what could they do wrong. I brought it home and it drove real nice, tracked straight down the road. 200 miles later I decided to take a look at their work, my heart skipped a beat. There were no zirk fittings in any of the ball joints and the upper right, a picture is worth a thousand words.

Had a simular problem with my sons XJ, just bleeding air out of the slave cylinder? I found the rubber boot from the inside of the cap that goes on the clutch master cylinder had fallen down in the bottom of the resivoir. The resevior was full of fluid and you could bleed all day long and get no fluid out of the slave! I kept looking in the resevior and thought something wasn't right, reach in there with a small screw driver and sure enough the little rubber boot was on the bottom restricting the flow of fluid. It's an easy check.

MAT/ IAT / ACT what ever it is called, I did find it at RockAuto. They call it Air Charge Temperature sensor. I have this problem where the engine goes rich after warm up. The more I think about it this may not be the problem. I pinned up a 60 ohm resistor, I'm going to put that in place of the sensor and see what it does.