usetaboost

iTrader: (1)

This is on the el camino I purchased early this summer that has the lg4. I decided to start a new thread for others that are looking for egr info. Since I purchased this car I've been battling a tip-in stumble when the car gets up to temp. Been driving me nuts and I was at my wits end and assumed it was the carb. Some more checking today, I pushed the egr valve in when it was up to temp, it started to lower rpm and wanted to die. Ok, obviously the egr valve itself is doing what it's supposed to do. So I pop the vac hose off going to the egr and rev the motor, no vacuum. I plug the vac hose and brake load the engine, no tip in stumble. I went back and forth 3 times, tip in stumble with hose connected, no tip instumble with hose disconnected. I have vacuum going to the solenoid, but no vacuum coming from the port going to the egr when I rev to 2k. This obviously points to a bad egr vacuum solenoid. If this is true, why is the tip in stumble present with the vac hose hooked up but not when it's unhooked if there's no vacuum present?

usetaboost

iTrader: (1)

No one has anything huh? Can't even tell me how the egr valve works?

Jeffs82TA

iTrader: (1)

Is it a normally closed or normally open egr valve?

usetaboost

iTrader: (1)

Don't know. I would think they're all the same on the lg4s. I think it's a backpressure type since the solenoid provides vacuum to the egr. I think what's going on is when the vac hose is hooked up it's preventing the egr valve from moving since the solenoid is stuck closed.

ZF6camaroZZ4

That doesnt make any sense. If theres no vacuum on the other side of the solenoid connected or not....... your results should be the same.
I think the ecm only activates the egr in cruise 4th gear. Thats the only time you get a code with it plugged.

usetaboost

iTrader: (1)

Theres no egr code but yeah youre right it doesn't make sense. That's why I'm trying to figure out exactly how it all works, when and why. I plan on spending more time on it tomorrow so if anyone comes up with something lmk

Damon

EGR is commanded to open proportional to throttle and being in gear (I think it is called for in all forward gears, not just OD). This is done by altering the "duty cycle" of the EGR solenoid. At 0% all vacuum is vented to atmosphere. At 100% it is all going to open the EGR valve.

To know what's supposed to be happing would require looking at the chip programming to be sure.

But you can test it without looking at the programming. Hook up a vacuum gague somewhere you can see it while driving- like duck taped to the outside of the windshield (my personal favorite- I do it all the time). Hook it to the vacuum line that would normally feed the EGR valve. When you drive it around you'll get a pretty good idea under what conditions vacuum is being applied to the EGR valve. It doesn't take much vacuum to open it- maybe 4-5" will get it full-open.

usetaboost

iTrader: (1)

ok if I get time I'll try it out. Based off the description I've given, anyone got a clue of what could be wrong?

bestracing

The solenoid could be leaking and letting some vacuum through and partially opening the EGR causing the stumble. You might not feel the vacuum on the hose right away but it can build up over time. You should do what is suggested and look at it with a vacuum gauge. I would use a Tee fitting so you can see the vacuum readings with the EGR hooked up.

Fast355

iTrader: (2)

Here is one thing to remember, like on my 1983 G20 van with the M4ME, the E4ME setup often uses an EGR BLEED solenoid connected to the ECM. What this does is eliminates the EGR at periods of heavier loading and tip-in.

usetaboost

iTrader: (1)

I got a few days off, my friend has a vac pump I'm gonna check the egr and the solenoid. and report back. Also, what is everyone running for timing on these lg4 engines? Seems like 6* is a good starting point from what I've read. I bumped it 2* and installed the dual snorkel air cleaner and it felt like a whole different car just by doing that.

Damon

4* over stock timing setting (of 0* in the case of the LG4) has always been a safe starting point in my experience. Some can take more, some can't. It's try-it-and-see beyond that point.

naf

iTrader: (7)

If you're running an LG4 with the KS, keep track of your mileage. Too much timing may cause it to over retard and you won't notice detonation or knock.

bestracing

That's a good base timing number for a stock or very mild cam.

usetaboost

iTrader: (1)

I'm also been wondering if the egr even affects anything if its inop. From what I've read it just lowers combustion temps at part throttle, other than that it does nothing. The idle seems to be slightly rough, I'm wondering if the egr is nothing but a big vacuum leak. I pushed the valve up and put my finger over the vacuum inlet and it went back into it's normal position right away. Yeah I know it isn't very technical but the air cleaner was off so I figured I'd give it a try.

Damon

Some EGR valves have a "bleed" built into them. Not sure if the LG4 valve does, but it's possible.

usetaboost

iTrader: (1)

Yeah I think I remember reading that in the haynes manual. I think it's supposed to bleed down after 5 seconds or something. Mine doesn't hold anything at all. I'm gonna try getting a vacv pump this weekend. Had a house full of sickies last week, now i'm sick

naf

iTrader: (7)

A properly functioning EGR will allow you to run slightly more timing advance. EGR will help reduce pinging at throttle tip in from low cruise. In this sense it will allow more power and better mileage.