Hey, I blew the engine out of my 94 Yj and found a replacement. A few things confuse me about the new engine though. It is a 4.0L just like the original but it was rebuilt and has roughly 65,000 miles on it. also the casting number indicates that it was no older than 1991 but had been fitted with throttle body injection which confused me, why would the previous owner get rid of the MPI fuel rail system that came out in that year for a less efficient TBI system. so i had the engine installed and fitted with a Manifold with MPI but now that it has been swapped out the, new engine runs gutless with hardly any horsepower and idles low with an occasional jump in Rpm. On the highway i can't even use 5th gear as it just boggs and drops in speed. Any insight helps.
I think my first move would be a compression test just to be sure it isn't a failed rebuild. A gent on another forum only has 50K on his and one cylinder has dropped out to 60 psi with real low 120's compression in the rest.
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
There are a bunch of things it could be. Fuel, sensors, etc. It has no essential difference if it had the 91 with the HO engine. I would bet something got screwed up in the swap. Mike has the right idea in starting with compression, but I would hope who ever swapped it in for you would have checked before doing it.
Well initially i had hoped it was something as simple as fuel because what was left in the tank had been sitting for a while, so i added some supreme fuel and drove it with little improvement, also today I started it and noticed that the oil pressure gage was maxing out. Super disappointing.
Hey, so my mechanic checked the timing and at top dead center the engine ran like crap. so he had the idea to set it ahead a little bit and th eengine now runs awesome! It runs nice and torqy as it should, my only concern now is what might come from running my engine with the timing chain slightly out of adjustment?? Also the oil pressure guage is still maxed out when i start the jeep, whats the best process of elimination to identify that problem??