parkia86

So here it goes: 1987 Jeep Comanche I have a 4.7L stroker installed, had no issues at all for about a year. I replaced the ECU with an 89 a few days ago Just replaced the CPS (must have gone through 3 or 4 of these things in the last 4 years The exhaust was replaced about a year ago due to rust. And it fires right up and runs very strong, however, once its been running for awhile and i give it gas... it starts bucking a little bit... I smelled some burning and examined under the truck and found the Catalytic converter was RED HOT! I Have never seen this before and i am long time comanche owner (10 years same truck). My question is: Where is the most logical place to go? It worked fine with the 87 ECU prior to CPS replacement, do i need to retune the fuel delivery for the 89 ECU? Is this a sign that the ECU is bad? Has anyone else seen this? Could it be the O2 sensor is bad? It doesnt appear to be anything mechanical... the only symptom i am seeing is the red hot cat. I can test fuel pressure at the rail but all of the injectors were replaced, regulator was replaced, ICM and Coil were replaced with the install of the Stroker. The only thing different is the ECU.

The mechanic I had install it was not registered or certified by ATK... he did have an official business / shop etc... ATK didn't seem to dig too far into "who" installed it. They basically authorized the repair the same day the issue was discovered. If you install yourself however, it might not be covered.

The shop only charged me 500 bucks in labor for the engine swap... the oil pan and all the other stuff i mentioned increased the final number a bit

​I just recently completed swapping out my old 4.0L with a 4.6L Stroker from ATK and I could not be more happy with the results. Prior to purchasing the Engine, I pinged the forums and probed the interwebs for a reputable reman company... all I found were bad reviews and horror stories... It made me feel uneasy but I went with ATK anyway. I figured I would post my experience. Prior to the Swap I had a 1987 4.0L with about 160K on it. The engine was still firing up and running but I felt it was time for a swap. ​The price was / is awesome. I paid 2900 for the stroker. It did not come with a valve cover but all of the gaskets were included. For the swap I also decided to put it a higher flow water pump, a new starter, plugs , wires, CPS, Thermostat, and a flex plate. Once the parts arrived I dropped the manche off at the shop and waiting for the motor to go in. I am told the install was simple... fit as expected ... no issues. HOWEVER.... as soon as the mechanic fired up the engine ... she leaked oil like a bastard! To be sure it was not the oil pan... I put a new oil pan in and replaced the gasket and sure enough it still leaked..... It was obvious it was the Rear Main Seal but we wanted to be sure.... I called ATK prior to authorizing work... and a little up set I explained the situation. Sight Unseen ATK authorized the mechanic to fix the problem and paid for both the parts and the labor. It took a few weeks for the check to finally arrive but never the less it did. It is worth noting that it if you purchase from autozone, the labor is covered by their warranty .... and the parts are paid for by ATK. Now not to throw any stones but the mechanic said the RMS was installed backwards :doh:​ With that said the RMS was replaced and the engine fired up with no leaks!... BUUUUUUT It was running sluggish.... I panicked thinking the engine was truly a dud and I would join the few folks on the internet in bashing ATK... but it turns out I did not upgrade the injectors to 24psi ( which most stroker forums recommend) .. ATK states that it can use the stock stuff... but it just does not run right. I also bought an adjustable fuel pressure regulator as well to dial in the power... it was not necessary but it helps. After all this... the MANCHE is more powerful than ever and runs very strong.. While I was a little disappointed with the quality control of ATK, they came through immediately with a fix.. at no cost to me. Feel free to PM me if you have any questions... I hope this helps some folks on the fence about REMANS...

Interesting. How in the world did you figure that out? Did you have the same sluggish symptoms as mine? The mechanic seems positive that new higher powered injectors with the regulator will solve the problem.

Turns out it is running very very lean. The injectors I bought from Amazon weren't rated to 24 lb/hr and I'm also putting in a hesco adjustable fuel pressure regulator. This should fix the problem!

I had it delivered to the mechanic I will swing by and check tomorrow.

So kind of a silly question... But if the compression is good then the engine itself can be considered to be in good shape? I paid by credit so I can dispute etc... Although I might be out the install cost. They did warrant the RMS fix so it might not come to that but the mechanic is almost at a loss for why it's running like $#!&.

The first question I asked him was whether or not he checked compression. He said it all checks out and he doesn't think it's an engine issue. I was paranoid because the engine arrived with the RMS installed backwards. But if every sensor works etc.... I'm nervous the motor is a dud.

well the mechanic didnt tell me the specifics on how he reset it... i am assuming he connected the battery wires together....the symptoms as he stated were : engine would fire right up but it had very little power... and felt very weak. He didn't provide any other symptoms... they swapped the ecu with one from another jeep and it did the same thing..........

The engine was manufactured by ATK it is their HP25.. no dyno sheet on hand (the mechanic might have it)...my jeep is a 1987 Comanche... from what ive read the renix should adapt to the stroker pretty well... but it just isnt running right..it feels worse than my old 4.0L. I should note that the ECU has been reset... multiple sensors replaced or swapped out with working sensors.. compression and fuel pressure is good....

Gentleman I just installed a 4.7L stroker engine in my 1987 jeep comanche and she is running very sluggish... seems like an old worn out jeep. My mechanic that did the install has tested every sensor, replaced the bad sensors... fuel pressure is in spec... etc... I called the tech service of the engine manufacturer and he suggested having the jeep tuned... Does anyone have any advice on how to go about this?

Please post that engine cleaning regimen .. that would be helpful. I'm mostly worried about a piston skirt being broken but i hear those are not as common in the older jeep

its the jeep 4.0L in a 1987 Comanche... all of the other cylinders were 120psi ... so about a 20% difference. Sorry for not including that!

Lol looks like the post didn't go through... again ... the issue is i have low compression on 3 cylinders ( all at 100psi)... I put in a tbsp of motor oil in each cylinder and the engine fired right up... stronger than ever... while it was running i put a bottle of restorer in the engine and i ran it about 100 miles or so... it still starts right up... I am assuming that my piston rings are shot... I still have a "Valve Tapping" noise coming from the engine... How much longer do you think this baby will run?

I have been unable to achieve >.245 VAC on any of the replacement CPSs I've put into the truck... the ohms always come out correct... does anyone have a brand they trust? Ive tried napa, mopar (got the high altitude version)... and I will be soon purchasing one from the dealer...

Thank you!

I just realized my topic didn't post my request.... I am looking for what else I can replace while the engine is out or at least what "Should" i replace? So far I'm thinking water pump, starter, CPS, Flex Plate, Thermostat... mechanic won't charge me for stuff he has to pull off anyway.... alternator is in great shape so I'm not sure ill replace that.... does anyone have any suggestions? Adam

Unfortunately I'm now having some minor troubles starting it up... it was working fine until last night.... ughhh

I think broke a piston skirt but I don't exactly know how to confirm this. Do I have to pull the oil pan to see if there is anything inside? The noise the comanche makes is similar to what others have posted on youtube... engine only has 155 k on it... and i don't do any hard driving with it. It is a 1987 4.0L.... on a side note... if it is the piston skirt.. I'm thinking about doing a stroker :)

Interesting. Not sure how I would drill out the upper mounting hole. Maybe I could adjust the mounting bracket so it sits closer to the fly wheel. Anyways I have NAPAordering another part so I will just exchange it and try again. Has anyone ever done this to their CPS?

I just installed a new CPS this morning because my engine was cranking hard and sometimes wouldn't start. My old cps passed the resistance test but failed the voltage test. It was only putting out .225 VAC. When I ran the same test on the newly installed unit it is out putting .265 VAC. I read on here that the output voltage should be .5. I got the part from NAPA.... Is it possible that the new part is faulty? Anyone know of a better brand?

Also thanks for the correction on the transmission heh!