pizzaman09 Posted June 24, 2022 Share Posted June 24, 2022 I have a 90 Eliminator with the Renix 4.0L, AX15 and 4x4. Since purchasing it two months ago I have made great improvements to the power it makes catching up on maintenance and following Cruiser's excellent tips. It runs well but I can tell it just isn't as fast as the 88 SporTruck with the 4.0L I had and just the other day I drove an 01 Cherokee which felt like a rocket in comparison. I'm looking for suggestions on things to look into. The truck has 253k miles What I've done: Tightened loose header bolts Fixed sensor grounds Calibrated TPS Indexed Distributor New distributor, plug wires, plugs Checked compression, ranged between 120 and 135psi New Bosch O2 sensor Fixed coolant leaks New air filter Cleaned throttle body and idle control valve, adjusted gap Upgraded injectors, probably Chinese knock offs of the recommend Volvo injectors. What I know I should do: Clean CPS, possibly advance it and check signal strength Clean coil connections What else? Link to comment Share on other sites More sharing options...
Pete M Posted June 24, 2022 Share Posted June 24, 2022 what size tires? Link to comment Share on other sites More sharing options...
pizzaman09 Posted June 24, 2022 Author Share Posted June 24, 2022 235 75 r15, the 88 SporTruck had the same. Link to comment Share on other sites More sharing options...
Pete M Posted June 24, 2022 Share Posted June 24, 2022 were the other Jeeps automatics? Link to comment Share on other sites More sharing options...
jdog Posted June 24, 2022 Share Posted June 24, 2022 bored throttle body Link to comment Share on other sites More sharing options...
cruiser54 Posted June 24, 2022 Share Posted June 24, 2022 Automatics had 3.55 gears. Manuals 3.07s. I always felt the manuals were slower than the autos. Link to comment Share on other sites More sharing options...
pizzaman09 Posted June 24, 2022 Author Share Posted June 24, 2022 The 88 SporTruck was a manual, the Cherokee an auto. So the diff ratio could make sense for the auto difference. Exhaust looks to be all new behind the cat with a Magnaflow muffler. The cat might be original, it certainly doesn't look very new. Come to think of it, the 88 SporTruck had a set of Banks headers and a new cat, likely needed to pass CA inspection where I purchased it. Link to comment Share on other sites More sharing options...
Pete M Posted June 24, 2022 Share Posted June 24, 2022 3.07 gears suuuuuuuuuuuuuuck.... Link to comment Share on other sites More sharing options...
JMO413 Posted June 24, 2022 Share Posted June 24, 2022 48 minutes ago, Pete M said: 3.07 gears suuuuuuuuuuuuuuck.... Link to comment Share on other sites More sharing options...
Eagle Posted June 25, 2022 Share Posted June 25, 2022 5 hours ago, pizzaman09 said: Come to think of it, the 88 SporTruck had a set of Banks headers and a new cat, likely needed to pass CA inspection where I purchased it. There's your answer. Nobody knows how to get power out of a Jeep engine like Banks. (Banks also makes the only exhaust I have ever heard that makes a 4.0L I-6 sound sexy. Usually they just sound like an old Maine lobster boat, and the aftermarket mufflers just make the lobster boat sound louder.) Oh -- and you shouldn't compare a 90 to a 2001 -- they are the same basic block, but the intake and exhaust manifolds are totally different, the injection is different, the ignition is different, and the cam timing is different. The late model XJ 4.0L has a very different torque and horsepower curve than the Renix 4.0L. Link to comment Share on other sites More sharing options...
pizzaman09 Posted June 25, 2022 Author Share Posted June 25, 2022 A lot of this makes sense. Particularly the diff ratio. Given the power to weight ratio of these trucks, I expected to be able to get to 60mph in under 10 seconds, it's more like 13 seconds. I did like the sound of the Banks header, someday when I have the time I'd love to pick one up and put it in. Are there any sensor outputs I can check? I have been searching and can't find a master list of output voltages or resistances, I just feel the engine isn't running optimally yet. Link to comment Share on other sites More sharing options...
Pete M Posted June 25, 2022 Share Posted June 25, 2022 the link in my signature has some of the sensor test procedures. Link to comment Share on other sites More sharing options...
cruiser54 Posted June 25, 2022 Share Posted June 25, 2022 Have you performed/completed Tips 1 through 5 at www.cruiser54.com? Sensors provide bad info if their ground circuits are marginal. You should do the Tips first. I have a bunch of the sensor values I could provide. Link to comment Share on other sites More sharing options...
cruiser54 Posted June 25, 2022 Share Posted June 25, 2022 A little back story. I was Service Manager at a Jeep dealer from 1980 through 1992. During that time, I was able to order and use 13 Comanches as a perk. First one, 4 cylinder 4 speed. Second one, 4 cylinder 5 speed short bed. Third one 4.0 5 speed, 5th one was 4.0 auto. The 8 I ordered and used after that were 4.0 with the auto. Never looked back!!! Link to comment Share on other sites More sharing options...
pizzaman09 Posted June 26, 2022 Author Share Posted June 26, 2022 12 hours ago, cruiser54 said: Have you performed/completed Tips 1 through 5 at www.cruiser54.com? Sensors provide bad info if their ground circuits are marginal. You should do the Tips first. I have a bunch of the sensor values I could provide. I've done 1,3,5-8, 11-14, 18, 22, 28, and 37. Been meaning to do 4 and 2 doesn't apply as mine is a 1990. The sensor ground tip with number 6 definitely made a difference, I performed the TPS adjustment at the same time. Biggest improvement thus far has been tightening manifold bolts. Link to comment Share on other sites More sharing options...
pizzaman09 Posted June 26, 2022 Author Share Posted June 26, 2022 13 hours ago, Pete M said: the link in my signature has some of the sensor test procedures. Thanks! This is the sort of link I was looking for: http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now