IAT Sensor for an 86 2.5

[I_s2k]

Hey guys, finally worked up some courage and motivation to jump back into my Comanche project. 1986 2.5, 4 speed and long story short I’ve been chasing an issue where the Jeep will start and run(horribly at that, incredibly rich, sputters etc) only with the MAP vacuum line unplugged. Verified voltages on all sensors in and around the throttle body, rebuilt the throttle body, cleaned all grounds front to back, replaced MAP 3 times,replaced 4 small vac lines going to the throttle body, adjusted new TPS, new gasket on EGR, good vacuum coming from the MAP vac line, ECU appears to be fine visually and I’m getting 5v to the sensors tested. I'm now wanting to maybe replace the IAT, CTS, and maybe the o2 sensor. I haven’t really checked the latter but I know the IAT is smoked as I remember pulling it out and the end of it being busted to $#!&. Anyone have a line on a new sensor and if not, a conversion? It’s my understanding that these sensors no longer exist but I cannot for the life of me find a conversion thread. TIA!

[eaglescout526]

How bad does it look? As long as it has the bulb on the end of it, it should be fine. Should test it to see if it Ωhms out to spec on both cold and hot air. Same with CTS. 

 

Look at the O2 as well. Do you happen to have a REM? 

 

Does the heater relay for the O2 work? 

 

I am not aware of a conversion for the 2.5L. There is one for the 4.0L. BUT! The two sensors are different in thread size. 2.5L looks smaller than the 4.0 and I have a 4.0L one thats been converted. I also have heard of a relocation for the IAT as well. 

 

This kind of issue would drive me mad. Are all vac lines verified to be good and crack free? 

 

While its running, have you looked at the spray pattern of the injector? Maybe the seals around the injector are bad and causing it to leak more fuel in and its running rich and like garbage because of such.

 

Do you know how long it has been since that MJ ran and drove before your ownership? I went and did some homework on your MJ just to get caught up on what were gonna deal with.

[I_s2k]

8 hours ago, eaglescout526 said:

How bad does it look? As long as it has the bulb on the end of it, it should be fine. Should test it to see if it Ωhms out to spec on both cold and hot air. Same with CTS. 

 

Look at the O2 as well. Do you happen to have a REM? 

 

Does the heater relay for the O2 work? 

 

I am not aware of a conversion for the 2.5L. There is one for the 4.0L. BUT! The two sensors are different in thread size. 2.5L looks smaller than the 4.0 and I have a 4.0L one thats been converted. I also have heard of a relocation for the IAT as well. 

 

This kind of issue would drive me mad. Are all vac lines verified to be good and crack free? 

 

While its running, have you looked at the spray pattern of the injector? Maybe the seals around the injector are bad and causing it to leak more fuel in and its running rich and like garbage because of such.

 

Do you know how long it has been since that MJ ran and drove before your ownership? I went and did some homework on your MJ just to get caught up on what were gonna deal with.

Haha thanks for coming back after a few months and merry early Christmas to you! I abandoned this thing to work on my XJ but I’m getting tired of DDing my CCLB 7.3 but I never lost hope, just got tired of fiddling with the Comanche with no progress.

 

I'm hoping after work today I can spend some time with it. From what I recall, the bulb is intact but cracked, I believe it’s still connected to the sensor itself just a little worse for wear. As stated before, ofc being almost 40 years old, the vac liked are pretty dry rotted and also worse for wear but I do know that it is getting good vacuum but I do wanna try and replace some lines if I can get some hose. I haven’t bothered with the o2 sensor or the CTS other than trying to see if unplugging the o2 would make any difference and it did not.

 

I haven’t looked at the injector while the Jeep is running but I assumed(I know I know, never assume) it was doing what it needed to do just based off the incredible richness when the map is unplugged. In the event that I need to replace the injector and these few sensors, would you have any recommendations for brand? I know how these things are picky for their sensors and unfortunately I do not have a REM.

 

The PO for this unit was kind of spotty but and didn’t own the Jeep for very long before I got it but I do know that the original owner did a bunch of shade tree mechanic repairs ie: wire nuts, shelving for speakers, missing fuses, shotty taillight wiring etc. So the history of when it last ran and drove is pretty vague.

[eaglescout526]

25 minutes ago, I_s2k said:

Haha thanks for coming back after a few months and merry early Christmas to you! I abandoned this thing to work on my XJ but I’m getting tired of DDing my CCLB 7.3 but I never lost hope, just got tired of fiddling with the Comanche with no progress.

Haha of course and merry early Christmas to you as well. 
I once heard from a YouTuber, if you’re not having fun, you’re doing it wrong. 
 

Hmmmm. I dont know if you have been to this website but a very good read. 
https://4wdmechanix.com/moses-ludels-4wd-mechanix-magazine-tuning-and-troubleshooting-the-2-5l-jeep-tbi-four/

 

The IAC and CTS basically are more for timing and fuel flow which in a sense if it’s dumping fuel would be fuel flow. 
 

Did we ever talk about the EGR?

As far as brand goes, It’s a crap shoot. I know O2’s we’re made by autolite for AMC. MAPs were GM, injector probably is GM too. As for the others, we’ll it’s a crap shoot. 
 

ohhhhh. I don’t like the sound of that history. Hmmmm well ok then. 

[I_s2k]

5 hours ago, eaglescout526 said:

Haha of course and merry early Christmas to you as well. 
I once heard from a YouTuber, if you’re not having fun, you’re doing it wrong. 
 

Hmmmm. I don't know if you have been to this website but a very good read. 
https://4wdmechanix.com/moses-ludels-4wd-mechanix-magazine-tuning-and-troubleshooting-the-2-5l-jeep-tbi-four/

 

The IAC and CTS basically are more for timing and fuel flow which in a sense if it’s dumping fuel would be fuel flow. 
 

Did we ever talk about the EGR?

As far as brand goes, It’s a crap shoot. I know O2’s we’re made by autolite for AMC. MAPs were GM, injector probably is GM too. As for the others, we’ll it’s a crap shoot. 
 

ohhhhh. I don’t like the sound of that history. Hmmmm well ok then. 

So I went ahead and just for $#!&s n gigs made sure that it was in time and it is, piston 1 TDC, oil pump pointed alight past 3:00 and rotor sits in at 6:00. I pulled the IAC for another look and it is still connected to the sensor but man it’s rough haha, I’ll attach a picture. I’m not seeing a CTS where I thought it would be, I know 4.0’s have one at the back of the head and one on the tstat housing. Any idea of where there on these?

 

EGR seems to be okay, I can manually move the diaphragm in it and one of the things I did months ago was clean it up and put a new gasket on it as the old seemed a lil shot.

 

Looking at the o2 sensor now, that thing looks burn but I don’t know if an o2 sensor would cause this thing to run so bad, I also know they are internally heated. Will attach a picture as well.

[eaglescout526]

IAT doesnt look too bad actually. Better shape that most. That cage is usually melted off. 

To find the CTS, put your finger where the IAT sits, go towards the drivers fender and youll find the CTS bolted into the manifold on the side.

 

That O2 doesnt look happy, or good. Looks a little burnt. 

 

Glad ya checked the timing for giggles and its ok.

[I_s2k]

33 minutes ago, eaglescout526 said:

IAT doesnt look too bad actually. Better shape that most. That cage is usually melted off. 

To find the CTS, put your finger where the IAT sits, go towards the drivers fender and youll find the CTS bolted into the manifold on the side.

 

That O2 doesnt look happy, or good. Looks a little burnt. 

 

Glad ya checked the timing for giggles and its ok.

I just pulled the fuel pump and needless to say, I may have found my issue or least this isn’t helping me any haha. Do you know if there’s anyway I could rob parts off the 89 XJ pump?

[eaglescout526]

You can swap all the parts on the XJ assembly over. Ahhhh yes the 86 sending unit dilemma. So you can swap over parts like the float level and hose and wiring. You can not how ever swap the bigger pump to that unit. You can swap the smaller pump to the bigger one but not the other way around. I am pretty sure you cant as I had an issue where I had to figure out why my fuel level was reading funny on my XJ and it used that smaller unit. Then I ended up having an issue where the pump was dying on me and would only produce enough pressure to last me a 5 min drive. If that. 

 

Do you just need to swap the hose over?

[I_s2k]

3 minutes ago, eaglescout526 said:

You can swap all the parts on the XJ assembly over. Ahhhh yes the 86 sending unit dilemma. So you can swap over parts like the float level and hose and wiring. You can not how ever swap the bigger pump to that unit. You can swap the smaller pump to the bigger one but not the other way around. I am pretty sure you can't as I had an issue where I had to figure out why my fuel level was reading funny on my XJ and it used that smaller unit. Then I ended up having an issue where the pump was dying on me and would only produce enough pressure to last me a 5 min drive. If that. 

 

Do you just need to swap the hose over?

Just what I needed to hear haha, if this doesn’t work I’m debating going down and buying an inline and throwing it in there. I’m not sure if it’s just the hose that’s the problem just based off the general condition of the gaskets and what not and it looks like the pick up could be partially clogged. Is there supposed to be a sock or anything at the bottom that fell off? I found it exactly how it is in the pictures.

[eaglescout526]

That hose looks pretty damn awful actually. That would cause the engine to run like trash and creating a rich condition cause its struggling to stay running. 

There should be a sock on the bottom of your pump like that XJ pump you have there. Luckily the socks interchange. What does the inside of the tank look like to really tarnish everything?

[I_s2k]

4 minutes ago, eaglescout526 said:

That hose looks pretty damn awful actually. That would cause the engine to run like trash and creating a rich condition cause its struggling to stay running. 

There should be a sock on the bottom of your pump like that XJ pump you have there. Luckily the socks interchange. What does the inside of the tank look like to really tarnish everything?

Well…..I found the sock, and the rest of those gaskets😂

[eaglescout526]

Clean tank! If that sock fell off from whoever last toyed with it as they put it in, I can see it getting clogged up.

[I_s2k]

32 minutes ago, eaglescout526 said:

Clean tank! If that sock fell off from whoever last toyed with it as they put it in, I can see it getting clogged up.

So upon further investigation, I don’t think anyone’s messed with it. All of it looks oe and it appears that rubber isolator at the bottom of the pump rotted away and the sock fell off. It won’t stay on since there’s nothing holding it

[eaglescout526]

Yeah the socks are one of those it either fits nicely or it doesn’t. Zip ties come in clutch here. But that could be your problem along with a rotting hose. Combine the two and you’ll have that pump struggling to send fuel up with the sock creating a clog, the junk and that line just being almost rope again. 

[I_s2k]

26 minutes ago, eaglescout526 said:

Yeah the socks are one of those it either fits nicely or it doesn’t. Zip ties come in clutch here. But that could be your problem along with a rotting hose. Combine the two and you’ll have that pump struggling to send fuel up with the sock creating a clog, the junk and that line just being almost rope again. 

I’ll be damned, it’s running!!! I can’t believe it took me damn near a year to figure that out, I thought to myself I’d never fall victim to “it needs a fuel pump”😂

[eaglescout526]

Hahahaha hell yeah!! Love it when it’s that simple. You should’ve seen me trying to figure out my issue on a running yet dying fuel pump. 

[I_s2k]

35 minutes ago, eaglescout526 said:

Hahahaha hell yeah!! Love it when it’s that simple. You should’ve seen me trying to figure out my issue on a running yet dying fuel pump. 

Hahaha dude I told myself when I was troubleshooting this months ago “I’m not gonna fall victim to the ol oh it’s just a fuel pump”. Thanks for all your help over the year man, I greatly appreciate it! Now to get this thing road worthy! By chance would you happen to know how I could bypass that rear adjusting brake system? I have axles out of my XJ that I’m throwing under this thing for a 4wd swap and need to ditch that.

[eaglescout526]

Lol!

 

As for the brake system bypass, I’ve heard it’s as simple as connecting the lines together. But don’t quote me as I still have mine operating. 

[I_s2k]

19 minutes ago, eaglescout526 said:

Lol!

 

As for the brake system bypass, I’ve heard it’s as simple as connecting the lines together. But don’t quote me as I still have mine operating. 

Oh okay right on! Thanks again man!

[eaglescout526]

No problem!