Brett777

After being with my Comanche for over 11 years, it's time for the ol truck to be restored. She was tired when I got her but ran well for all the time I have had her and now she's going in. Will be posting picks almost daily and of course, any help will be much appreciated.

Well........the numbers are in!!!!!! Cause for the problem? Exhaustious pipeous interruptus.......or in layman terms.....the damn exhaust was delaminating approx 3 inches prior to the flange where the cat bolts too!!!!!!! After about 4 hours of labor and a brand spankin new custom exhaust system, she pulls like never before! The pipe clogged like a artery just prior to a massive heart attack. Additionally, there were bigger flaps of metal acting like valves further restricting the flow under acceleration. Boys.........its Miller time!

The fuel pump flow and pressures have been checked from idle to running at 55 mph and so has the timing as I replaced all the plugs, harness, cap, rotor, and coil. The ignition parts were replaced to to fix this problem but simply because I had these parts in my shop and figure what the hell.............I have darn near replaced everything else! The cockpit of my truck now looks like a rolling laboratory because almost everything has a probe or gauge attached to it that leads back to my test computer that I use when test flying aircraft. This has now become personal! I just drilled some holes in the exhaust system and installed some homemade piccolo tubes attached to pressure transducers as well as installing some aircraft EGT probes at the exhaust ports to see the pressure changes and the EGT changes when she runs out of steam. I also installed some piccolo tubes fore and aft the air filter to get some idea of what happens when she starts losing power on the intake side beyond 25% throttle. Sounds like a rolling dyno but like I said.......it is personal now! Actually, it only took me about an hour to install all these probes and I am very curious about what the data will show.

This is where I started going from head scratching to going bald! Flow rates were checked from the pump tot the rail to each injector, just like I would with an aircraft FI system. Voltage levels at the computer were all good and I even calculated parameters for voltage drop based on wire size and length......................results= nothing wrong here either. Who wants to join me in going bald now?

117841 original but only 17564 on the engine which is 4 years old.

This truck has a 5 speed manual transmission and the TPI voltage starts at .512 volts and tops out at 4.776 volts wide open.

All of that has been checked and or replaced. Let's put it this way.......I am eyeballing one of my 406 small block Chevy engines to put in it like in my CJ5!!!!! I don't want to but this problem Is making no sense to me

Unfortunately no. I took it off an installed a "test" pipe and the same thing is still happening.

Hello guys! I have a 1991 Jeep Comanche 4 wheel drive with the 4.0 HO MPI engine.............. This is a new occurrence within the last 3 days. When I press down the accelerator the engine takes a very long time to accelerate. It is as if I am hauling a very heavily loaded trailer. I have checked everything I can from dragging brakes to see if a boat anchor for an aircraft carrier has been hooked to the rear bumper, replaced the MAP sensor, TPS, idle mixture controller, O2 sensor, checked the vacuum at idle and when driving, fuel pressure at the rail and pump at idle and driving, etc, and still I have this problem. I cannot climb a hill even at a 1% grade without losing speed. It is as if the the effective throttle range is only the first 25% of throttle and after that it has no effect. I also notice that if I press the throttle half way or even fully depressed the engine coolant temp rises about 25-30 degrees. Spark plug check showed that the crease in coolant temps. I have checked everything I could including valve lift at the rockers to see if a cam lobe has been worn out and everything seems to be within spec. Any help would be greatly appreciated.