Perpendicular

The truck is a 94 22RE automatic.

I am having idling problems and have tracked it down to the EGR valve getting a vacuum at idle.

Anyone ever run into this and have an idea as to what I should be looking at?

I have diconnected the line to the EGR and it will run fine but eventually set off a Code 71 as expected so I would like to fix the problem and make the truck run the way it was designed.

Any help is greatly appreciated!

scope103

meaning: you get no vacuum to the valve when the truck is warm and throttle open?

I'd suggest you start here: http://personal.utulsa.edu/~nathan-b...18egrsyste.pdf. This gives a diagram of the system and a description of what you're supposed to find when.

I, for one, appreciate someone who wants all the parts of the truck to run as the boys in Japan expected. Particularly on the emissions end.

Perpendicular

I have been going over that sheet but not sure I understand what I am trying to figure out

I get a vacuum once the truck has gott4en warm at all. I.E. first thing in the AM it starts and runs great. About 60 - 90 seconds I start to get a vacuum to the EGR and it will no longer idle. It will continue to give a vacuum no mater what the trottle is at, for whatever reason.

Any ideas?

sinneDBTB

search egr mod. i have read that it is benificial to plug or remove it and to fix the code problem you need to stick a 10k ohm resistor in the female plug end to trick the ecm into thinking it is still operating.
i will be removing mine later today.

sb5walker

Check the routing of all egr vacuum lines, especially the ones that go from the throttle body to the modulator, and run the tests of the vacuum modulator as described in the manual.

If the two hoses between the throttle body and modulator have been swapped either at the throttle body end, or on the modulator, that could cause your difficulty, as could an internal problem in the modulator, such as missing filter or torn diaphragm.

It's hard to tell from the vacuum diagram in the factory manual which port on the throttle body each hose is supposed to go to. You might look for a pic showing the throttle body and modulator on a motor with known good vacuum routing - I have the 3vze so can't help you there.

Your egr vsv is probably fine since it prevents vacuum from going to the egr when the motor's cold.

sinneDBTB

the egr could be malfunctioning and staying open allowing too much exhaust into your engine.

sinneDBTB

i'll save you some time...
https://www.yotatech.com/forums/f116/egr-106749/
https://www.yotatech.com/forums/f116...my-egr-108005/
these threads talk about the egr.

scope103

sb5walker has it right. It sounds like your vsv is doing what it supposed to do (holding off vacuum until warm). It sounds like the EGR valve is doing what it is supposed to do (messing up the idle once it gets premature vacuum, but not before). But the modulator, etc. is not. You shouldn't get vacuum (even when warm) with the throttle closed. The easy part is to check the vacuum routing as suggested. You should have a label under the hood with 95% of the routing.

If that doesn't do it, invest in a vacuum gauge http://www.harborfreight.com/cpi/cta...emnumber=93547 and just follow the procedure in the manual. (and don't assume that it is a bad modulator; it might be a $.15 hose split.)

Perpendicular

FIXED - I think.... Will know if I get another check engine light in a day or two.

OK, so you won't belive this but I figured I would share what _really_ happened and what fixed it.

I washed the engine a couple of weeks ago so I could get ready to replace the timing chain. After washing it, the truck ran crappy. I thought it was likely the cap, rotor, wires, plugs so did a full tune up. No change, could not make the truck idle after 60 - 90 seconds off a cold start. My buddy figured out the EGR was getting a vacuum so just disconnected it for now so I could get through the timing chain and then work on it again.

Fast forward to today. With everyones help on here and the FSM we went about to check all the valves, etc. NOTHING looked right according to the diagrams. I mean, the hoses appeard all wrong but yet the truck ran well before the eninge wash. Truck runs well now without the EGR hooked up.

After 30 minutes of looking and scratching heads my buddy says lets start from the beginning and make everything the way the diagram shows.

Bingo, it works!

No idea why it ran so well before it was washed, but once things were back in the correct places the truck runs strong and correctly wiht all of it's EGR system function well.

Thank you to all that helped. This board is a great community!

scope103

The truck will run (as many on this list will point out) with no working EGR - you're just poisoning the atmosphere. It is possible that crud kept your mis-connected EGR from working at all, and when you accidentally knocked off the dirt it started "working" again - the wrong way.

I hope you learned a lesson -- don't ever wash that truck again! ;^)