What should I expect from my 2.5?

[rnobles]

Hey guys,

got an 86 2.5L 2wd with 151,000 on the odo. automatic. truck had been sitting up for 3 or 4 years so it is pretty gummed up.

changed fuel pump and filter and started the cleanup process of the engine. it seems to idol pretty well, maybe a little high, and it runs down the road ok although pretty weak.

The motor boggs for a second when you step on the throttle then will pick up, is this just something i have to deal with with the 2.5? or will futher cleaning and tuning will this improve? (no lag when you apply gradual pressure to the throttle). havent check my gearing yet but from what i have felt, they are probably 3.55.

i just need to know what the best case scenario would be from someone with a good 2.5 so i will know what to work towards. any input will be greatly appreciated, thanks

[Pete M]

is the old gas still in the tank?

[Squeegy410]

My '82 dart does that, but its just because i havent put my four barrell edlebrock on there yet :dunno: The dart is carburated so it doesnt relate very much to fuel injection, but it may have something to do with your passing gear linkage :dunno:

[rcturgeon]

all i can say is mine ran okay when i got it was a fight to start becasue i had to play with the throttle to keep it running till it warmed up and it lacked power, all i can say though is as i slowly replace sensors it keeps getting better and better, oxygen sensor in mine made it pull alot harder all the time just check to see if its still working with an ohmeter, i suggest doing that with all the sensors

 

if you need the values ill send them just ask

[dasbulliwagen]

I got my 2.5 under similar circumstances... been sitting mostly for several years. I tuned it up, put several bottles of fuel system cleaner through it, and it helped little by little. The thing that helped it most was a new O2 sensor, and its run great ever since, realtively speaking. As for what to expect.... don't expect too much and you won't be dissappointed. Anything you do for performance ains are going to be marginal at best, but your best bet would be to go to 4:10 axle gearing assuming you are going to stay stock height. Your auto may have better gearing already.... I think car-part.com listed 4:10 as an axle choice for 86... that should have come on the 5 speed manuals, but it could be under the auto as well, youll need to confirm this though. There a several ways to do it. But ways to pick up a little peformance are to do away with the engine driven cooling fan and replace it with an electric unit and controller, some say throttle body spacers work, cold air intake, Gut the cat converter..... but this could cause problems with loss of backpressure though I have experienced no problems with it myself, high flow muffler, header- from various sources, cam- if you can find one, Clifford performance make an intake for it for an aftermarket fuel injection setup or a carb, port and polish head...... if you REALLY REALLY want to keep the 2.5 those are your options, but for the low cost of a donor cherokee, you could have a complete 4.0 driveline... but wheres the fun in that??? Jeep ran 2.5 equipped Comanches in SCCA sucessfully for many years, so theres got to be some good to hopping them up. Feel free to ask any questions here, and ignore all the naysayer that just tell you to swap to a 4.0... unless you really want to!

[rnobles]

is the old gas still in the tank?

no, i pulled the tank and cleaned it out and gave it a fresh coat of paint when i had to change the fuel pump.

[rnobles]

I got my 2.5 under similar circumstances... been sitting mostly for several years. I tuned it up, put several bottles of fuel system cleaner through it, and it helped little by little. The thing that helped it most was a new O2 sensor, and its run great ever since, realtively speaking. As for what to expect.... don't expect too much and you won't be dissappointed. Anything you do for performance ains are going to be marginal at best, but your best bet would be to go to 4:10 axle gearing assuming you are going to stay stock height. Your auto may have better gearing already.... I think car-part.com listed 4:10 as an axle choice for 86... that should have come on the 5 speed manuals, but it could be under the auto as well, youll need to confirm this though. There a several ways to do it. But ways to pick up a little peformance are to do away with the engine driven cooling fan and replace it with an electric unit and controller, some say throttle body spacers work, cold air intake, Gut the cat converter..... but this could cause problems with loss of backpressure though I have experienced no problems with it myself, high flow muffler, header- from various sources, cam- if you can find one, Clifford performance make an intake for it for an aftermarket fuel injection setup or a carb, port and polish head...... if you REALLY REALLY want to keep the 2.5 those are your options, but for the low cost of a donor cherokee, you could have a complete 4.0 driveline... but wheres the fun in that??? Jeep ran 2.5 equipped Comanches in SCCA sucessfully for many years, so theres got to be some good to hopping them up. Feel free to ask any questions here, and ignore all the naysayer that just tell you to swap to a 4.0... unless you really want to!

 

Thanks for the info!

i actually had alot of those modifications in mind, just didnt want to have my hopes set a little to high for the little 4-banger, lol I'm going to try to slowly change out all the sensors, and DRIVE, DRIVE, DRIVE her as much as possible. hopefully that will get her back in shape.

 

I have to admit though, when i bought it i had all intentions of doing the 4.0 swap. After spending a little time on it i think i want to see what i can get out of the little 2.5.....

[jimoshel]

I have 3 MJ's and 2 XJ'S I drive often. All have the 2.5 engines. I also have 8-10 (not sure how many ) 4.0 motors. I am very satisfied with the performance of the 2.5 or I would be swapping a 4.0 into them. None of them bogs on acceleration. They're not killer power houses but they are reliable and will get the job done. I did have a '88 MJ with 3.53 axles that was a little limpid but after swapping to 4.11 it perked right up.

JimOshel

Defender of the underdog

Protector of the picked on.

Guardian of 2.5

Etc., Etc.

[dasbulliwagen]

Guardian of 2.5

Etc., Etc.

 

 

You and me both!

[kro10000]

A turbo would help with the bogging :brows:

[jimoshel]

I don't think so. Turbos need to be wound up to work and the engine needs to be up to speed for that to happen. When a motor bogs on acceleration it is because of a sudden influx of air and a lack of fuel. Just clean the TBI and check the sensors and TPS.

[kro10000]

Was kidding, but for the sake of sake itself... a small turbo would wind up at low revs and give some kick

[jimoshel]

Yep. I.m still working on my turbo adaption to a 2.5. Got together and made a test run the other day. Worked great when first fired up but as the motor warmed up it began leaking around the intake adapter and head. I think it's a stress weld, good when cold but warps when hot. I'm still working on it.

[kro10000]

Sweet, I was planning on doing a Turbo 2.5 on several MJs I had found before I met Red

[rnobles]

didnt have much time to look at things today, but i did notice that the wires to the map sensor plug (according to the diagram under the hood) were kinda rigged up and one had even fallen out. so i unplugged the sensor and fired it up and the throttle bog was gone, but it was running rich. (bare with me guys, I'm learning as i go with this stuff) going to try and get what i need to fix the plug tomorrow and maybe it will fix my little problem.