csmart Posted December 12, 2017 Share Posted December 12, 2017 I have purchased an 87 yj tbi 2.5. With help from this site I have been tinkering with this thing trying to get it to run as its suppose to especially in this cold weather. I was looking at my egr valve while I was replacing the vacuum lines and noticed it was unhooked and the line feeding it is plugged. I did notice that the vacuum port on the egr was facing the front of the jeep, that seems to be the wrong direction to me. Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted December 13, 2017 Administrators Share Posted December 13, 2017 There are no dumb questions, csmart! The vacuum port location would not be as important as the alignment of the exhaust gas recirculation ports at the base of the valve. The valve's ports at the gasket must be aligned with the correct exhaust/intake ports. This could be an aftermarket EGR valve. If you're suspect that the exhaust recirculation ports are wrong, remove the valve and verify the port locations. Here is a PDF parts identification diagram for your emissions system and EGR valve. Note that the valve is triangle shaped and should only fit one way. The ports at the gasket should match the flange ports: Jeep 2.5L TBI Emission Controls Parts.pdf. An aftermarket replacement EGR valve might have the vacuum port facing in a different direction, but regardless, the important factors would be 1) proper flange port layout, 2) the in/hg of vacuum that opens the valve, 3) the proper routing of all emissions and other vacuum lines and 4) all devices in place and functioning properly. EGR should not apply at an engine idle, and the valve tapers closed at higher engine speeds/throttle openings when both the manifold and ported (TBI or carburetor sourced) vacuum drop. EGR opening is just off idle (strong ported vacuum signal) and stays open through the lower throttle settings. Ported vacuum drops off as the throttle valve opens up. Use the diagram and parts list to see what you have and what is missing from the system. EGR, as a point of interest, is a passive emissions device. When functioning properly, it simply dilutes intake stream gases to reduce NOx emissions. This has a benefit: The aim is to lower the upper cylinder temperatures, which can reach as high as 4800 degrees F without EGR. EGR drops the upper cylinder temperatures below 2500 degrees F for NOx emissions control. I always restore the EGR system if it is missing or there are signs of tampering like in your engine's case. Moses Quote Link to comment Share on other sites More sharing options...
csmart Posted December 13, 2017 Author Share Posted December 13, 2017 Thanks for the reply, i didnt figure it was part of my idle problem (unless its leaking vacum), Ive been on the hunt to solve this issue. In the process of checking my tps setting i broke one of the aluminum screws that hold it in place. So off with the throttle body to try and drill and tap it out. Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted December 14, 2017 Administrators Share Posted December 14, 2017 csmart...Sometimes an EGR valve can be stuck open and affect the idle due to dilution/leakage into the manifold at idle setting. A quick check is to idle the engine; with finger protection from the heat, pull upward on the EGR diaphragm from the bottom of the diaphragm canister. If the valve was seated, you will hear a distinct roughness in the idle as the diaphragm and plunger open. Ugh on the screw damage... Moses Quote Link to comment Share on other sites More sharing options...
csmart Posted December 14, 2017 Author Share Posted December 14, 2017 I did try that and did get that rough idle result so I was confident it was seated. Another question, I replaced the isa motor but can't figure out how to set it without the special tool to fully extend it. Do I jumper to the back of the isa where the plug goes? If so what terminals do i make contact with? I seen one of your attachmen's had negative to the front and fully retract the 2nd one in. Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted December 14, 2017 Administrators Share Posted December 14, 2017 Can be done with jumpers as described...Others have worked around the factory tool that is now obsolete. Use your volt-ohm meter to determine the Key-On hot lead and check the ground side for continuity. Use an inline fuse if you're concerned about shorting with the jumpers. Should be easy to determine which leads actuate the ISA motor. Follow the guidelines at the forum discussions and PDFs that I included in replies...Avoid hyper-extending the ISA actuator. Damage can occur. Quote Link to comment Share on other sites More sharing options...
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