1987Comanche

I put a steel valve cover from a '96 on my '90 in an effort to reduce the amount of oil dumping into the air filter. The '96 (and newer I assume) has a one piece baffle that runs the entire length of the cover. It reduced the oil by about 50% but didn't stop it entirely. If you don't have blow by soaking the air filter there's probably no advantage to swapping valve covers. But, since I'm on the subject, What else can I do to reduce the amount of oil dumping in my air filter?

So really the only direction to go from here is to pull the rear window and reseal. It does make sense that the seal could be compromised at any point on the window and, from that point on, the gasket channels the water to the lower edge of the window. I replaced the rear window on my old Isuzu pickup once upon a time but it was a rubber gasket and no sealant. How hard is this one to pull? DJM do they use both a rubber gasket and urethane? That may be a project for later this spring/summer.

So any thoughts as to which part of the rear windows is leaking? The water is split evenly from Dr to Pass and comes through at the lower corner on each side. I can run a bead of black rubber sealant around the entire window perimeter but that would prob look pretty messy.

The idle speed is computer controlled and automatically adjusts if the ISC is working properly. It's a stepper motor on the Throttle body that physically pushes the throttle open when cold and you can adjust the length of the screw if you loosen the locknut. I'm guessing it's seized and was adjusted so the idle is right when hot. Try this. Unplug the ISC (a 4 pin connector if I remember correctly) and see if the truck runs differently. I bet you won't see any change at all.

I'd say 90% chance your Idle speed controller is messed up or inoperative. My '87 2.5 had identical symptoms.

I've done a lot of research on water leaks (the old '87 had one, the new '90 has multiple leaks) and I've plugged a few so far. It rained a lot this weekend so I tried to track a few others down. I was able to track them a lot farther back than before but am still trying to get to the source. Here's what I have: 1. Water on both Dr & pass side of the floor pooling behind the support bracket under the seat. The trail leads past the lower seatbelt bolts and seems to end where the body makes it's 90 degree bend from the back of the cab to the side of the cab. I'd guess rear window but the gasket seems to be in good shape. What specifically do I check for here? 2. 2 separate trickles of water apparently coming from the fuse panel?? One trickle is from the center of the block and the other is from the RH side. I replaced the clutch master cyl and sealed it to the firewall when I installed it so it shouldn't be that. I also sealed the hood release grommet and accelerator cable grommet when I had the master cyl out. What else is up there to leak?? 3. A very small trickle on the driver's side where the leading edge of the door makes it's 90 degree bend. My water deflectors are in place but may need to be resealed. It has to be either that or the door gasket.

The radiator on my '90 4.0 sprung a leak and I'm seriously considering this conversion. I did some research and I have 2 questions I didn't see addressed: 1. Is the header panel/radiator support different between closed & open systems in order to accommodate the filler neck and pressure cap on the open system? It looks like the newer trucks have a bend in them at the filler neck to accommodate the neck. 2. What do you use for an overflow tank and where do you mount it? It looks like the new style overflow tank wouldn't work as it would interfere with the ignition wire going from the coil to the distributor. It looks like a later model washer fluid tank might be a decent substitute as a coolant overflow tank.

Anybody??

I came across the build sheet for my '90 and it's in pretty good shape considering it was printed on 1/30/90. I called Chrysler and they gave me all the info they had and, while useful, it wasn't exactly what I was looking for. I'd like to decode my entire build sheet, if possible. I've done a fair amount of research and haven't found anything that gives me what I'm looking for. For example how do I decode these? Sales codes: line S, steering and suspension. BA, CB, FA, GA, UA Billing/Track: 4XA, 5KK Dr/Qtr Trim Panel: F/LT=E57, F/RT=E56 There is a list of abbreviations on the back of the build sheet but it only has alpha character codes (ex XEA=tow hooks). Is there a comprehensive list or good site I can check out?

Which Wix? Is it the basic one with the black anti-drainback or the more expensive one with the red anti-drainback and spring in the center?

Purolator and Bosch so far. I looked at the Carquest (Wix) filters and the expensive ones have a spring inside. I asked the guy what pressure it takes to overcome the spring (I only have 10psi at hot idle) and he didn't know. Also the Carquest filter was $7.25 so I thought I'd get a 2nd opinion and more info first.

As you know the Renix 4.0s have the oil filter mounted vertically & the predictable result is that the oil drains out of the filter when you shut the truck down. My '90 doesn't particularly like that and rattles, etc for about 5 sec when you restart. I'd like to find a filter with a good anti drainback valve to combat that as I can't imagine it's good for the motor. Suggestions? My 2nd option would be to put a later HO adapter on and mount the filter 90 degrees.

Is it possible to access the cab sheet metal behind the doors (for dent removal) from the inside of the truck? I was able to access the inside of the lower rocker and straighten that out, the area I'm wondering about is the area that lines up with the fuel filler door. There's a long dent in the center panel, between the air extractor and rocker that I'd like to work on but I don't necessarily want to drill the sheet metal if I can help it.

This one is a bit odd. I finally got the '90 on the road and have noticed an odd quirk that's a bit baffling. When driving around town the truck idles at what I would consider to be a normal 1000RPM or so. It hunts around a bit but by and large idles ok. I'll ride a few miles on the highway at 70mph or so and, upon exiting the freeway, the idle speed sits at 1500 RPM and will do so until I shut the truck off for a few minutes. I cleaned the throttle body out with TB and air intake cleaner, cleaned the Idle Air control valve and even swapped in my spare IAC. Absolutely no change. Any thoughts/suggestions? The '90 is a Renix 4.0, AX-15, 4WD.

I picked up the gauge set at Harbor Freight and hooked it in place of the oil press sending unit. I agree that the RMS isn't related to low oil pressure...rather I have one that seems fairly leaky and was going to replace it while I had the pan off. Do you think it's possible I have bearings going bad after 117K miles? The inside of the valve cover is pretty dirty b/c the PCV system doesn't appear to have worked correctly in years. The oil I drained out didn't have anything abnormal in it though. When I changed the oil pump on my Beretta I saw a 20psi increase across the board, which is why I was thinking it might help out here. If the bearings were worn would I be able to affect the oil pressure while revving during warmup? In that case how difficult are the bearings to change with the engine in the truck? I'm assuming I'd get standard bearings since I wouldn't be doing anything else.

For what it's worth I put pads, rotors, calipers, & hoses on my new '90 4L 4WD last Fri. Pads are Wearever gold GMKD477, rotors are Wearever YH141602, Calipers are Cardone 184340 and 184339, and hoses are Trutorque H38895 and H38894

I put a mechanical gauge on it last night and here's what I saw. On cold startup I'll hit 40psi and, as she warms up I'll drop down below 20psi. I'll bottom out at around 13-15psi and, at this point, bringing it from idle to 2000RPM doesn't affect oil pressure at all. I'm thinking the pickup screen is clogged and the next logical step is to drop the pan and put in the high vol pump. Any other ideas? Also how hard is it to change the rear main on the 4.0? I was going to do that while I have the pan off.

Other than noisy lifters I didn't experience any odd sounds, smells, overheating, etc. To be fair the lifters have been noisy since day one. I did notice the oil was surprisingly clean. When I bought the truck the oil was filthy, which is why I changed it before I limped her home. After driving 5 miles home the new oil looked almost as dirty as the old oil. After driving on the highway yesterday the oil is now quite clean and the color I'd expect it to be, considering it only has 60 or so miles on it. Could it be the Purolator filter did it's job and is now completely plugged with garbage, forcing the bypass to open and, in the process, bypassing the sending unit?

Since the truck sat for 6-9 months I could definitely see that. The pressure relief is integral with the pump on these, correct? Would there be any reason to pull the oil filter adapter? Other than pulling the sending unit and cleaning it I hadn't planned on pulling the adapter, just the pan and pump.

Both the cluster and oil pressure sending unit were transferred from my '87 (sold today...) where they worked perfectly. I won't say the wiring in the new truck isn't to blame but I know the cluster works pretty well. I changed the oil as soon as I got it home from the PO's house (it was nasty). I used a Purolator filter on it. This is, however, the first day the truck had seen the highway and 30+ miles of driving in probably 6-9 months...based on when the inspection ran out. I'm thinking the safest course is a high vol oil pump, new pickup, clean the pan out and see what happens. Since the engine oil seems clean the bearings should be ok, correct?

I was running errands in the '90 that I picked up last week and I noticed the oil pressure gauge acting a bit odd. I just swapped the cluster and put in the used sending unit from the '87, which always read fine with that gauge. Anyway I noticed right off the bat that the gauge wasn't nearly as active as it was in the '87 (lower pressure at a stoplight, increasing with revs). It read around 40psi at cold start up and dropped to about 17psi as it warmed up, with no difference in pressure reading whether stopped or moving at 45mph. At the last errand (Auto Zone appropriately) I started the truck and the gauge was at zero psi, with no change. I drove about 0.3 mile, saw it was still at zero. I pulled over, shut her down, and checked everything. Oil was clean, everything looked ok. I got back in and went another mile or so and still had no reading on the gauge. At this point I stopped and had her towed back home. Fortunately the oil looked clean when I stopped the 2nd time. Once I got home I pulled it from the wrecker to the driveway and the gauge read 20psi. Perhaps I was being overly cautious getting her towed but my question is WTF? Bad sending unit, clogged pickup screen, electrical problem, or was it actually at 0 PSI? Thoughts?

What year did Jeep change from the old school font on the gauges to the newer style red/white lettering? Also was it possible to get a 4.0L truck with the bare bones idiot light cluster (old style font) in 90? I'm wondering how accurate the mileage is on the truck I'm looking at purchasing and I hadn't seen any '90+ models with the old style cluster except this one.

What kind of driveability problems did the truck have when you bought it? Any indications the compression was that low? I'm assuming you had some issues as you replaced the fuel pump and rail. I'm wondering because I'm going to look at a '90 4.0 on Tues.

That makes sense. I'll have to disregard the numbers they quote in the Jeep Bible as they list 120-130psi min for the AMC 150. I was trying to figure out the discrepancy between that and the FSM. I'll do the compression test keeping 155psi in mind as the min.

Here's the story. Earlier today I came across a '90 Sportruck, 4.0L, 5 speed, 4WD with 118K for sale. The truck definitely needs some TLC but seemed to run ok (couldn't drive it as it had no tags). Other than high oil consumption the '87 2.5L runs pretty well and doesn't need anything but the oil consumption is kind of worrisome. Also she's about 25 miles from 198K. If I bought the '90 I'd have to sell the '87 so it seems a thorough checkout is in order. The FSM lists adequate compression as 155-185psi/cyl. A few of the books I have say +-10% is the max variation, other say up to +-20% is acceptable. I want to use a compression test of the '87 to help me decide whether or not to go after the '90. What is the min acceptable compression on the AMC 150? Based on the FSM it seems 140 psi is the min. Any thoughts?