4.0 EGR Question

[oldfaithful]

Hello All,

Thanks for taking the time to read & reply! I've got a problem & a question for you. My 97 B4000 4x4 has the 4.0, manual trans, 180k miles and a "slightly" rough idle. Earlier this year I did the manifold gasket and that was a big improvement in all related areas.

Since then I've been wondering about the idle's "slight" roughness. I replaced the spark plugs and that did improve it a bit. My CEL is on, and the only code is for EGR flow...I can't remember for sure right now whether it was high or low. I've applied vacuum to the ECR while idleing and the engine did stumble, so I suspect that the problem could be the DPFE. However I've also started the motor cold with the ECR vacuum hose disconnected/plugged and noticed that the EGR still heated to the point I couldn't touch it within 30 sec. That tells me that exhaust is still passing through the EGR tube & valve even though the vacuum hose is plugged. I'm under the impression that the EGR should permit no flow if the hose is plugged. Given the distance from the exhaust manifold to the valve, I can't imagine the valve's body heating up this quickly due to heat conduction alone. I'm thinking that the valve is stuck slightly open and can't close completely. (BTW...I've tried to remove the EGR to bench test & clean, but road salt has made this very difficult...AKA the wrench flats are rusted away.)

Should the EGR heat up this quickly, if there is no flow permitted with the hose plugged? Am I incorrect in this understanding of the EGR system? Thanks a lot!

 

[oldfaithful]

Bump.

Anyone have any ideas? Should the EGR valve heat up so much in 30 sec that you can't touch it, when the vacuum hose is plugged? Does this mean the valve isn't closing? Thanks.

 

[oldfaithful]

All right, I'll answer my own question and close the thread.

The EGR valve was indeed leaking. I couldn't get the large hex on the inlet to break loose so I removed the tube between the EGR and the intake manifold. Then I took the suggestion of 'Yellowsplash' and put a rubber expandable freeze plug in the manifold hole. Then started the motor and could feel a noticeable exhaust flow through the EGR even though the vacuum hose was disconnected & plugged. That explains why it would heat up so much in just 30 sec. Quickly noticed that the idle was much smoother too!

So that's it. Made a plate to close off the exit of the EGR and problem solved.

Thread with Yellowsplash's suggestion...
http://www.therangerstation.com/forums/showthread.php?t=64692&highlight=freeze+plug+egr

 

[Yellowsplash]

Glad to hear it fixed your problem...hopefully the check engine light wont prevent you from passing state inspection or anything of that matter. If so, a simple bamachip tune with emissions removed will fix that.