94 Yj Engine trouble - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Wrangler Forums > YJ Wrangler Technical Forum > 94 Yj Engine trouble

Spartan Locker's at all time LOW exclusive from ROCKRIDGE FS: Jeep Fog Light LED Bulbs! Several Brightness Options! Bds fox ipf 2.0 racing series shocks now available at rock

Reply
Unread 03-30-2015, 11:35 PM   #1
94Rape-J
Registered User
 
Join Date: Sep 2014
Posts: 8
94 Yj Engine trouble

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.

94Rape-J is offline   Reply With Quote Quick reply to this message
Unread 03-31-2015, 05:18 AM   #2
Mike Romain
Registered User
1986 CJ7 
 
Join Date: Nov 2007
Location: Off the Grid in Chester Grant, Nova Scotia, Canada
Posts: 15,740
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.
__________________
Mike
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)
Mike Romain is offline   Reply With Quote Quick reply to this message
Unread 03-31-2015, 05:30 AM   #3
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 17,246
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.
Que89YJ is offline   Reply With Quote Quick reply to this message
Unread 03-31-2015, 02:41 PM   #4
94Rape-J
Registered User
 
Join Date: Sep 2014
Posts: 8
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.
94Rape-J is offline   Reply With Quote Quick reply to this message
Unread 03-31-2015, 03:39 PM   #5
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 17,246
Check out the sensor and wire to it. You still might be ok.
Que89YJ is offline   Reply With Quote Quick reply to this message
Unread 04-08-2015, 12:58 PM   #6
94Rape-J
Registered User
 
Join Date: Sep 2014
Posts: 8
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??
94Rape-J is offline   Reply With Quote Quick reply to this message
Unread 04-08-2015, 07:05 PM   #7
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 17,246
nothing at all.
Que89YJ is offline   Reply With Quote Quick reply to this message
Unread 04-08-2015, 08:29 PM   #8
Rebel442
Registered User
1989 YJ Wrangler 
 
Join Date: Jul 2008
Location: Chicago
Posts: 635
Quote:
Originally Posted by 94Rape-J View Post
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!
Find a new mechanic, quickly.
__________________
It Wouldn't Be A Project If Everything Worked Right.
Rebel442 is online now   Reply With Quote Quick reply to this message
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Thread Tools






Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.