Vacuum line and EGR valve issues on 90 Comanche, Please help

[NewtoMJ]

This issue is on a 1990 MJ 4.0 l6 automatic with just under 165k miles. I went to do my emissions test today for Colorado and the truck failed due to high NOx levels. After researching what causes high NOx levels I found that the EGR is supposed to reduce them and that may be my problem. Upon inspection of my vehicle I noticed that my EGR valve is not hooked up to any vacuum lines, the solenoid is no where to be found and most of my vacuum lines appear to be misplaced or missing. I was using the diagram on the firewall for reference on how the lines are supposed to be run. Has anyone else run into this with their Comanche? Where would I start to try to restore the vacuum system to its original state? I included a crude drawing I did to illustrate how the vacuum lines are currently run in the truck. I would greatly appreciate any help I can get. Thank you in advance.

 

 

 

This is the diagram on the firewall.

 

This is my illustration of how the vacuum hoses are currently connected

 

I have a few more photos, here is a link to the slide show of all the photos I have: I can take more of specific parts if need be. Thank you again!

[Marine1Texas]

Your lines are ran fine just make sure they are not leaking. Where you have the red nipple that is capped that is where your going to run your line to the solenoid valve.

The EGR solenoid valve will be located on the driver side fender next to the fuel baluster. you should see a plug there for it near. The solenoid valve is controlled by the ECU. basically that capped vacuum from the intake go's straight to the front of the solenoid valve and on the back of the solenoid valve you will have a blow off breather and the main that go's right to the EGR.  

 

this is what your going to need http://www.factorychryslerparts.com/products/JEEP/1990/40L-I6-MPI-GAS--5-Speed-Manual/SOLENOID--EGR-Vacuum--SOLENOID--Vacuum-Switch/4520241/33002298.html

you should be able to find one off a jeep in the junk yard. from what I can see on the parts write up the 1986 to 1990 CHEROKEE, WAGONEER, COMANCHE 2.5, 4.0 share the same valve.

 

located here

Up-close looks like this

[fiatslug87]

If I were you I would buy the whole vacuum harness and replace what's there. All the hookups would be almost obvious. The NAPA numbers are:

7151367 from valve cover to connector/intake/pressure regulator/EGR pressure transducer

7151366 from connector to airbox/EGR solenoid

7151365 from valve cover to manifold

 

Dorman also makes them.

 

It looks like you also need the EGR pressure transducer (I'm on mobile and can't enlarge your pics). I can take more pictures of mine tomorrow in the daylight if you want.

 

[NewtoMJ]

fiatslug87

I was thinking I'd need to replace the entire harness, if you could take more pictures for me so I know what all I'm missing and how it all connects that would be greatly appreciated. The wife has a 99 cherokee so I have nothing to compare it to.

[SVPete]

The line labeled "orifice" in the diagram is supposed to go where your drawing (red line) shows the MAP sensor connected to.

 

The MAP sensor is supposed to be connected to the throttle body. Look on the base of the throttle body where the diagram shows it running to. You can make it out in fiatslug's photo of a remarkably clean engine.

 

Buy both harnesses as fiatslug recommends.

 

The transducer comes with a new EGR valve (75-ish bucks). I am pretty sure you can't get just the transducer.

[SVPete]

As an update to my previous post....it looks like you are missing the bracket that holds the two pieces of the vacuum harness (mentioned by fiatslug and in the photo) securely together and in position. Without it, you run the chance of your brand-new harness(es) vibrating around the engine area and breaking. So if you buy the new harnesses, you will need to either get a bracket from the junkyard or figure something out to hold the assembly securely in place. In fiatslug's photo, the bracket I am writing about is right above the cable loop behind the power steering pump.

 

Also, I wonder if you have a high idle with the MAP connected where it is in your drawing. Unless someone plugged the port in the throttle body where it is supposed to connect to, you have got to be sucking air there. Search on the site, other club members have used steel brake line to run from the throttle body to the MAP sensor....but that may be a future project to undertake.

[fiatslug87]

Here are some pics that should point you in the right direction. I'm including the parts list so you can see all the parts and the bracket SVPete is talking about. If you cannot find the bracket, the harness halves have orifices where they connect that zip ties can be passed through to hold the two together better. Also, the rear valve cover line should go into the intake manifold in front of the throttle body. Let me know if you need specific views.