Anyone know much about the 2.5 liter?

[Hammloaderman]

I recently bought an 86 with the 2.5 auto 4x4, ran great for about 3 weeks now is running crazy rich and won't start about half the time before I just start replacing things hoping it works does anyone have any ideas?

[Eagle]

The '86 2.5L uses throttle body injection, with an ignition and injection control system by Renix, so the electronics are very similar to the 4.0L. Some piossibilities to check out:

 

* Oxygen sensor

* Oxygen sensor wiring (is the ECU getting the signal from the O2 sensor?)

* ECU

* Temp sensor (there should be two -- the one that sends data to the ECU should be on the lower left side of the block if it's located similar to the 4.0L)

[Hammloaderman]

In the process of refreshing all the grounds and changing the valve cover gasket as Chilton's told me my problem was a vacuum leak, is there any way to test the ECU or O2 sensor?

[Hammloaderman]

So, I'm not much of a mechanic but I figured a valve cover gasket was well within my scope, what exactly do I do with all the $#!& built up in there? I'm surprised the poor thing was even running, the valve cover was half full of gooey gunk

[87Warrior]

You cannot test the O2 sensor with a multimeter like the other sensors. If you suspect it hasn't been changed in recent history, go ahead and replace it with a NGK/NTK sensor. I believe NGK supplies Mopar O2 sensors.

 

If you are still hunting for vacuum leaks, take a closer look at the cluster of 4 vacuum lines connected to the throttle body between the throttle body and valve cover. The rubber connector is known to leak at the throttle body. Best course of action to repair it is to remove the block and replace it with 4 individual vacuum lines. IIRC, there are two sizes.

[dasbulliwagen]

For tons of 2.5 info you can check out www.4bangerjp.com lot of 2.5 specific info there.

[cruiser54]

Did you screw up the vacuum line to the MAP sensor on the firewall during this fix?

[87Warrior]

For tons of 2.5 info you can check out www.4bangerjp.com lot of 2.5 specific info there.

LOL. Been trying to join that site for 4 years. I gave up.

[mnkyboy]

Just join the Facebook page then message Jeff Yokomura,you will probably be on the 4bangerJP forums the same day.

[yxmj]

not to highjack the thread but....if you don't have a face book....you can't join???

 

For original poster I have the same motor and it sounds vac related to me...check all the lines....extra look at ones that rub up against anything

[87Warrior]

Just join the Facebook page then message Jeff Yokomura,you will probably be on the 4bangerJP forums the same day.

Seriously, I have tried with no success. I've managed to keep the 2.5 running great without the forum so I stopped wasting time trying to join.

[mnkyboy]

Most of it applies to The MPI engine anyway,if you contact Jeff he will add you but for most stuff the Facebook group is fine.

 

The forum itself usually doesn't have a whole lot of activity.

[Hammloaderman]

Finally had time to finish putting the valve cover back on, the pcv valve was packed completely full of oil sludge as was everything else, beginning to wonder if this poor thing ever had an oil change before, seems to run better now with a new pcv valve and replaced the rubber hose connected to it, cleaned probably 2 pounds of gunk out of the rockers and pushrod holes

[Hammloaderman]

On a side note, if I was to swap heads on this what years will fit? And someone on another thread mentioned that the block on the Dodge Dakota 2.5 was the same as the AMC 2.5, is the head the same too?

[Eagle]

Most of it applies to The MPI engine anyway,if you contact Jeff he will add you but for most stuff the Facebook group is fine.

It's fine ... if you have facebook.

[jmderyke]

 I've learned the 2.5 TBI very well and I keep wanting to post a complete guide to keeping it going and diagnostic repairs with pictures.... Time is a problem for me.  Anyway here's something that might help for now.

http://www.4wdmechanix.com/Tuning-and-Troubleshooting-the-2.5L-Jeep-TBI-Four?r=1

 

  If the vacuum lines are old replace them all, especially the map sensor vacuum line.

[Hammloaderman]

Thought I had the old girl running alright so I decided to make a run to the lake since the weather was so nice today. Discovered rather quickly that once she gets warmed up all the way, half hour or so, she's back to spluttering and running super rich, all the important vacuum lines look to be in good shape and I noticed that the fuel pump is making alot more noise than before, possibly because it's pumping so much fuel?

[cruiser54]

Thought I had the old girl running alright so I decided to make a run to the lake since the weather was so nice today. Discovered rather quickly that once she gets warmed up all the way, half hour or so, she's back to spluttering and running super rich, all the important vacuum lines look to be in good shape and I noticed that the fuel pump is making alot more noise than before, possibly because it's pumping so much fuel?

Super rich generally leads to the MAP sensor and/or it's vacuum source being wonky. 

[Hammloaderman]

 

 

Thought I had the old girl running alright so I decided to make a run to the lake since the weather was so nice today. Discovered rather quickly that once she gets warmed up all the way, half hour or so, she's back to spluttering and running super rich, all the important vacuum lines look to be in good shape and I noticed that the fuel pump is making alot more noise than before, possibly because it's pumping so much fuel?

Super rich generally leads to the MAP sensor and/or it's vacuum source being wonky.

I pulled the electronic plug off the map sensor and it immediately died, restarted it and pulled the vacuum line off which made it run like I'd pulled a plug wire off, the vacuum line had crazy suction on it too

[jmderyke]

Don't ignore the obvious, if the fuel pump is all the sudden making a funny noise I'd check the fuel pressure. Running should be between 14-15 psi. If thats good Check the intake air temperature sensor resistance and coolant temperature sensor when at operating temp, must below 1000 ohms, mine is usually around 250ohms. If way higher resistance is read that would be telling the computer the engine is cold when it really isn't making it rich.

[Hammloaderman]

Update on the comanche, I've been driving it back and forth to work long as I don't shut it off I'm usually ok, it's not running rich anymore, went from 8 mpg to around 33, then back to the mid 20's, haven't had access to a fuel pressure gauge yet but I did find out that when it's all the way warmed up when it starts running bad and won't restart for several hours I'm losing spark, going to pull the cps tomorrow and clean it, and I plan on checking the ICU and the cps with a meter to see what they read

[dasbulliwagen]

don't forget the O2 sensor. I chased issues on mine after I got it that all went away after putting a new O2sensor on it.

[Hammloaderman]

Ok guys so ive changed the cps, fuel injector, tps, map and about half the vacuum lines now and still having problems. I'm completely stumped at this point, she's down to only running about 10 minutes before it cuts fuel and dies any other suggestions? Currently working on finding an o2 sensor to try