I've done the ign. upgrade with the ford stuff, the carb replaced with a carter from a 80CJ, computer bypass, all suggested by this board. my jeep was running great for two days then IT happened the ruff idle came back just suddenly. the jeep runs great till its wormed up. I'm suspecting the EGR, anyone have any suggestions on diognosing this dohicky I'm not to familyer with this system How can I be sure this is the problem?

[img]/wwwthreads_images/icons/cool.gif[/img]http://members.home.net/paul5696[img]/wwwthreads_images/icons/cool.gif[/img]

As I understand it, most common failure mode of an EGR valve is not opening - the diaphragm goes bad. EGR valve typically doesn't open until motor warms up, at least with the standard CTO (coolant temp operated) setup.

Sounds like some items are still controlled by your CTO. You could simply unplug the EGR and plug the vac line going to it, and see if it helps - that would prevent the EGR from opening, and pinpoint the EGR if it is the culprit. What the EGR does, is let a fixed amount of exhaust gas into the intake. When mine was bad, it simply didn't open. This results in higher NOx emissions, but I can't see how it would make the motor idle poorly.

If I recall correctly, I think the CTO also controls how much, or which, vacuum (manifold or ported) gets to the vac advance on the distributor - not exactly sure on that one, but I think it (the CTO) plays some role. I would look more at this, in my opinion, than the EGR. Maybe when it switches over something is not working correctly, or your CTO is bad.

Could be choke, too, of course. ??

I'm not the all-knowing by any means, these are just my thoughts. [img]/wwwthreads_images/icons/smile.gif[/img] You can also remove these 2 funtions (vac advance and EGR) from the CTO - my weber/GM HEI setup doesn't use a CTO. I think this would just make the motor warm up slower, but the difference is likely minimal.

Good luck
Pete

88 YJ - trails/beach trips only![img]/wwwthreads_images/icons/smile.gif[/img]
79 4WD F250-hauler/tower of my toys
70 Jaguar E-type - the best car England ever made. [img]/wwwthreads_images/icons/cool.gif[/img]
90 Honda CRX - Daily pavement-pounder. 42 MPG. [img]/wwwthreads_images/icons/cool.gif[/img]

If you've scanned the board, you've probably already found this, but just in case....
BTW, this was a BIG help before I went to my Weber.

http://www.off-road.com/jeep/tech/engine/carter.html
http://www.off-road.com/jeep/tech/258bbd/

BTW,
You can easily check it its related to your EGR by pinching-closed the vacumme line that goes to the EGR w/ a pair of pliers. You shouldn't have any change in idle-speed since the EGR isn't supposed to operate at idle.

If the idle-speed/sound changes when pinching, the problem is the vacuume's existance and is NOT a 'failure' in the actual EGR valve. Track down why vacuume is there. (use the URLs I posted).

Good luck, let me know if this helps,

Sam88Jeep


'88 YJ, 4.2L, 32/36 Weber, Jacobs Ign.

I had the same problem for a while. Removed the EGR completely on my CJ and it still didnt help. Then I discovered that the choke spring had gone bad, and hooked up a manual choke cable and havent had any problems since then.

cjcrawler
"The Beast"
74CJ/304/33's/dana30&44wlockright/3.15:1case
fullcage/woods'shafts

I talked to a local jeep expert and he told me that I should spray the egr will carb cleaner and listen for a change in sound from the engine. Guess what There was a change so I'm guessing that my egr is leaking

[img]/wwwthreads_images/icons/cool.gif[/img]http://members.home.net/paul5696[img]/wwwthreads_images/icons/cool.gif[/img]