Ideas for Upgrades

Hello everyone,

I am Judas, from Northern Wisconsin. Recently bought a 1994 Wrangler YJ, and have been sorely disappointed with my decision. The jeep itself is very clean and has almost no rust, have nice 31" tires with wider rims and is quite clean. However, the 4 banger in it is tired and on its way out. At the same time, it suffers from the infamous 2nd gear grind. I am at the point where I am thinking of either selling it, or changing the drivetrain to something more powerful and robust.

I have come here after being let down by the negative comments on other forums about my decision to buy a YJ with a 2.5 in it. I understand that this is the lowest of the low in the world of Jeeps, but I am certain that its not the end of the world.

I have a very limited budget for an upgrade and wonder what would be the (a) cheapest option other than to continue with the drivetrain, or to swap out with the same stuff (2.5L with an AX5), and (b) the easiest option for an upgrade. Some say it is the 350 V8 (GM), and others say that it is better to switch to a 4.0 HO I6 engine with an AX15. I know the AX15 is the way to go, but I cannot find one for cheap anywhere near me.

Secondly, of the two options I listed above, which is more straightforward to do? For the 4.0 option, do I need to stick to a drivetrain from a Wrangler or can I go for one out of a Cherokee? I have found some out of 1996 Cherokees.

The issue of modifications to the chassis and other components is also a matter of concern to me, as once again, reading through various posts and forums, I have come to realize that while a 350 swap might be more straightforward, it is much more expensive. And the 4.0 swap is cheaper, but more difficult. Is that true?

What route would you advise a newbie to take?

 

KISS most important Skill level and Budget.

Figuring a DIYer and a low budget, KISS, fix what you have, Learn and make a nice DD (daily driver) .
Those people badmouthng the engine are giving light to their dreams coulda woulda shoulda, it is what it is a nice 2.5L YJ.
Now lets get to work - how does it run? What Issues are there? oh yeah what is your skill level?

 

Thanks. Finally with a voice of reason!!

I will start by saying that I am moderately mechanical. Have worked on some JDM cars, doing basic tuning work and have done a few engine swaps. No experience whatsoever on a Jeep.

As regards the jeep, the body is great, no rust, no issues with suspension or brakes. No coolant leaks. Engine is weak - takes time to get up to speed and the maximum I have gone is 68 mph. There is an exhaust manifold leak somewhere, which one can recognize. It is severely under-powered. The transmission is an AX5. Grinds when going into 2nd. The shifter is all over the place, but that is normal. Leaks fluid from somewhere on the underside, and you cant see it, because the skidplate is in the way. Clutch is fine, and fuel consumption is good. I can smell gas in the oil, but with 180,000 miles, what else can one expect? The engine revs fine, but idles with a rattle, which goes away when you rev it. I bought it a few days ago, and haven't done any oil change or plugs or wires. Previous owner said that the plugs were changed a few years ago and I will be doing an oil change. I just added some STP oil treatment to quieten the engine, and it helped a bit. But I am not sure if there is low compression (gas smell in the oil). PS pump and power-steering is fine. No cracks, and no dents on the jeep. It has a 3" body lift, which I hate, so I will be getting rid of it once I figure out how to loosen the rusted out bolts.

I have never ridden a jeep before, and my only experience with vehicles is with faster RWD cars and V8 trucks (ford, dodge). Seems more like a truck where the first gear only goes up to 10 mph and then you have to grind your way into 2nd and then third. It starts to struggle after 50 mph and takes a while to get to 68 mph.

That is where it's at right now.

 

Welcome @Judasentinel ,my first jeep was an '89 YJ 2.5 MT back in the day. Best $8995 I ever spent and unfortunately lost my mind trading it in...regrets . Somewhat under powered when new but it kept me out of speeding trouble. Performed admirably off-road in 4H or 4Low where it counts on trails or beach sand. Fun vehicle that averaged 20mpg on road trips. Don't be too sad as your YJ has a solid frame and body for 25 year old vehicle based off your post. The 2.5 is probably tired but it sounds like the trans needs a rebuild. Keep mods and expenses in check in order to enjoy the off-road capability that can be made better which is what this forum and jeeps are all about. Huge aftermarket support that's just waiting for your jeep bucks. Post a pic or two via upload a file tab.

 

make a plan

Identify the exhaust leak.
If possible check for codes even if CEL is off. You tube has tutorials if unsure.
Get fluids and filters. Every week target something Trans, Eng oil, Coolant.
Get a manual - local library?
Ask before buying parts yeah it matters.
Do you have -
a Compression gauge?
Fuel pressure gauge?

Might want to start with - a bottle of seafoam for fuel system, a bottle of RISOLONE' to address any sludge/varnish. Get some miles to this week asses the new ride.

 

Welcome from Texas

 

Thank you for such a warm welcome. Seafoam is already in the system. All fluids are good, except for the leak from the transmission. Will stop leak of some sort work on that?

There is only one code - 33, which is for the AC circuit - I dont have an AC, so it shows up. Other than that, there are no codes at all. The Jeep runs clean.

I also wanted to ask you guys something else about my intended engine swap. I have found a used 4.0 engine and ECU plus harness from a 1996 Cherokee XJ with an automatic transmission. Should I buy this engine/ECU/harness combo and then connect it to an AX15 that I get separately? Will my stock transfer case work with this combo or do I need that too? In addition, are there any issues relating to the OBD II ECU on a 1996 XJ that will not allow me to run it on my Jeep? Finally, if I do go the 4.0 engine upgrade route (eventually - right now I am just enjoying the jeep as it is), will I need to get different driveshafts?

There seems to be some debate about what the easiest vs. cheapest engine swap is on a YJ. Some say it is better to do a Chevy 350/LS swap and others say the 4.0 is better. I don't know which is better. One would think that since a YJ came with both 2.5 and 4.0 options, the two would be quite interchangeable, with minor changes required. Seems that is not the case and this swap cou;ld be more difficult and expensive than a Chevy V8 swap.

Based on that, I have the following two options:

1. 1996 XJ 4.0 engine, automatic transmission ECU (OBD II) and harness, an AX15 transmission from some other vehicle, and my stock transfer case
2. An LS 5.3L V8 Chevy engine with its own auto ECU and harness, an AX15 transmission from some other vehicle and and my stock transfer case

Can you guys please educate me on what one would need to get it going for each of the options and pros and cons of each? I am unable to find an OBD I ECU that is from a Jeep with a manual transmission, as most people prefer Automatics (we prefer Manual). Hopefully I can spend the next few months gathering the parts I need for the swap while I enjoy the Jeep as it is.

 

I totally agree with awrench and aggrex. The 4cyl should easily be able to handle the 31s even with stock gear ratio. By the way your stock gear ratio for the 2.5L should be 4.10s. It should not be struggling at 50mph. Check your compression first, and make sure you are starting with a good power plant. I bet you could use a new catalytic converter or even delete it if you are allowed to in Wisconsin. Check you air filter. Second gear grind comes from all the other POs skipping first gear. Sounds like the synchronizer is on its way out for second gear. Look for a complete Dealer Service Manual. They have excellent diagnostic pathways in them for hunting down problems that might give symptoms like lugging or under powered etc. The 4cyl and AX15 are incompatible, and everything is incompatible with AX5. If you decide to do a 350 swap, the cheapest way would be to find a late 80s to early 90s TBI 305 or 350 chevy 1500 4x4 with a 5spd that is all rusted out but runs good for cheap. transplant the The motor and trans and tcase, or find an adapter for your tcase. I believe Novak makes motor mounts for the 350 that bolt into the exhisting jeep motor mount holes on the frame. They also make adapters for motors to trannys to tcases. They have a ton of research information on their site too. When I first got into jeeps I spent hours on their site. If you do a 4.0 swap, again find a wrecked or useless jeep with good parts and swap over the motor, tranny, and tcase. For yor front axle you may want to look into a posi-lock for it if the vacuum actuater has quit.

Dealer service manual below. There are 3 supplements to this manual. I paid about $100 for all of them, but this is the main one you need.

https://www.ebay.com/itm/1994-Jeep-...ir-Manual-Book-S-SE-Sport-Sahara/253581556458

Posi-lock https://www.quadratec.com/products/52435_0X_PG.htm

https://www.novak-adapt.com/

Here is a great donor truck for your swap $800 somewhat near you by Texas standards.

https://chicago.craigslist.org/sox/cto/d/beecher-1988-chevy-silverado-pickup/6878596161.html

 

So if I do find a 4.0 from an XJ that is 1996 or newer with auto transmission, can I still use that engine and ECU with an AX15 from another vehicle? Is my understanding correct that I can use my stock harness as it is, and just add two more wires for the two additional injectors to receive the pulse signal?

In my area, Jeeps are like rare diamonds - very very very few available, and people who have them either dont sell them or want a good chunk of change for them. All I can find is Cherokees with 4.0s in them. Most are automatics, so I want to know if an auto engine and ecu will work once mated to an AX15 in my jeep. Since OBD II was introduced from 1996 onwards, I hope its not an issue.

 

A cherokee 4.0 is the same motor. You will need the ECU for sure. I would get the harness to be safe. I'm not sure on the auto trans options for YJ vs Cherokee. You can make almost anything work with a little elbow grease.

 

1st does NOT matter where you are you cannot remove the Catalytic converter. Not a state law*.
Always before engine swaps check with state for any issues, some states have draconian regulations.
ie a 94 4cylinder jeep needs a same year 4cyl jeep. Best to check NOW.

The 4.0L being a jeep eng would make this swap easier, alot to change BUT the jeep had that engine SO we can likely find a part. You will need a PCM for a manual trans - something to consider BEFORE getting the 4.0L auto set up mentioned, yes you will need the harness - there are 2 more cylinders.

* cannot remove or render inop an emission device. Thats a Federal reg. Only unregistered off road as racing, competition use.

 

WI has emission laws, but only in certain counties and areas in the south. Hell, we dont even have helmet laws in our area. So I am not worried about emissions. As regards modifications, there is no restriction on that. Thousands of modified cars are on the road, with various Frankenstein setups, and there are no restrictions governing engine swaps.

I just learned today that an ECU from an auto jeep will also work, since the automatic transmission has its own TCM (Transmission Control Module), which only gets signal from the engine ECU to operate. The main ECU/PCM does not control the transmission. The harness in my jeep will also work, but it does need a slight bit of work, in terms of adding two more wires to provide the pulse signal to the extra two injectors. Most everything else is the same. All these engines came with the same EGR systems, and I am not going to remove them.

 

EGR valves are over rated

 

I might mention I lived in the Wisconsin (Waukesha) GREAT people !! But emissions laws IDK but added Before someone spends..