Checking EGR valve

[bigd65]

How do you check the EGR valve. I went to buy one today and thought i was checking it buy sucking on the vacuum stem and i sucked air the same as mine. wen the guy looked it up on the computer, it said ' CANNOT BE CHECKED WITH A VACUUM PUMP"
I wanna make sure mine is bad before i buy a new one, AT 56.00 bucks

[RussTburb]

what kinda rig is it for year make model? I got access to test here at work so let me know.

[swervin ervin]

Jeff,

from all I know, it's supposed to hold vacuum. I checked a old one with my Mityvac. It's got a gauge on it. So when I applied vacuum to it, it would leak down vey slowly. The new held dead on and never leaked. I guess the old one had a tiny pin hole or something.

One way you could check yours without a Mityvac or similar tool is to hook it to manifold vacuum while the engine is running. You can feel under the bottom when it moves up.

[bigd65]

Mike why would the computer at Autozone say you cant check with a vacuum pump. The new one even would not hold air. You think it could be a defective new one

[Cooter_01]

56 bucks that a good price , mine was 90 bucks , EGR valves are useless dont hook it back up

[RussTburb]

IMHO, egr's are not a waste. they allow to run more advance or cheaper gas and not get pinging. Jeff what kind of a problem are you having? is it on your '85? TO the best of my knowledge they should hold vacuum. But what is the symptom? A choppy idle can be caused by the egr. excessive pinging under a load could be an egr valve. Just wanna help man!

[bigd65]

RussTburb,
no symtoms, i had it blocked off before, then when they started the emissions test here, i knew i had to start putting CRAP back on. i know EGR's dont really take any power, but when i put my E-BROCK carb it was to wide till i got a spacer. my emissions test is up in MARCH and i have to start replacing things. Anyways, that is just how i tested it was by sucking of the vacuum hose and i got air. I drove it yesterday and didnt feel any problem in the driveability, in fact it might have felt a little peppyier but that im sure is the cool weather and that i finally got aroung to changing my THERMOSTAT. that was another problem, had a heater hose bust on me and it got a little hot, it seeems i had one of those fail safe THERMO's and it stuck open
I think i will hook it to manifold vacuum today and try it, what would it do if opened at idle?

[Russell]

As far as mine goes, if you start the vehicle up for like 10 seconds then turn it off, the egr shouldn't loose any vacuum due to the check valve on it, at least until you pull the hose off at which point it should make a popping sound as the valve goes back to its original position, and the hose fills back up with air...

These things are suppost to hold air, mine will still have pressure on it the next day.

[Grim Reaper]

Yes some EGR's cannot be checked with a hand operated pump. The way to check them is on the engine (or for that mater you can check it on any engine that has a vac port). If it's on the engine your workin on then hit it with untimed port and it should about stall the truck if it's good.

That style EGR is supose to be on a timed port. Actually ALL EGR's are timed. EGR is off at idle. It will cause a very poor idle and possibly stall the engine if it is on at idle. It doesn't kick in till around 1200-1500 RPM on a V8. 1800 or so on most I6 engines. 4 cylinder about 2k.

[bigd65]

is there suppose to be a check valve in the line. i just hooked it straight to ported vacuum

[PHOENIX]

You should have a vacuum line coming from ported vacuum on the carb and into a TVS switch (opens at 160 degree). The vacuum line from the TVS should go straight to the EGR. Sometimes you need to install a vacuum delay valve in the line between the TVS and the EGR. The VDV can be confused with a check valve. It does work like a check valve too, you can put it on the wrong way. The VDV is needed when the EGR is operating at too low of an engine RPM. If your engine stumbles on takeoff then you might need a new EGR or need to add a VDV.

If you have a sticker under your hood near the hood latch it may show if your truck had a vacuum delay valve. Previous owner didnt have one on my truck. When I went and bought a new EGR from the GM dealer I had a stumble problem off the line. I installed a vacuum delay valve and it went away.

[swervin ervin]

Eddie nailed it to a tee. You need to route it through the TVS so it won't work until the engine gets to operating temp. If it's hook straight to the carb, it will work when the engine is cold and cause stumbles and rough driving until it does get warm. Real irritating.

I don't have a delay valve in the vacuum line. Works great without one. The delay valve is not a check valve. What it does is delay vacuum loss to whatever it is hooked to.

Jeff, don't hook it to manifold vacuum. It will work at idle and not above. This will kill drivability.

Mike

[bigd65]

Well i tried hooked it MANIFOLD just to check it and NO CHANGE in idle or anything. So i guess its time for a new one

As far as the VDV or delay valve, all that stuff is gone so it is hooked straight to the carb (ported) i will just have to deal with the cold drivability, ALTHOUGH NEVER HAD THAT PROBLEM. Anyway, it dont get very cold down here in SOUTH TEXAS, so the trucks warms up pretty quickly. I just gotta get a NEW EGR now.

ARE the ones from gmpartsdirect , actual GM PARTS , as in ACDELCO ? G showed me the link and says its like half price.

[swervin ervin]

Jeff,

sounds as though your EGR has left the building.

Yes, gmpartsdirect is genuine GM parts. They are a GM dealer located in NC.

Anyway, if you can get wholesale price at a dealer close to you, you can get it for the same price and maybe even cheaper than gmpartsdirect. By the time they add shipping, the price isn't so great.

For instance. I bought my EGR in July, 2000 at my local Chevy dealer at wholesale price. It was $48.50 and with tax came to $52.16. I just checked at gmpartsdirect and for the same part number, it would be $38.50, plus $7.95 shipping, and $2.70 tax, which is 49.15. They say the list price is $77.01. I looked at my receipt from my dealer and the list price was $70.30 when I bought mine.

Anyway, if you can get wholesale price from a local dealer, check there first. It may suprise you and you won't have to wait until it's shipped.

BTW, I use a GM EGR valve, part number 17113439. It works great. This is a different number than what is called for. I read on the internet somewhere this valve works good for my application and they were right.

[bigd65]

So what is the differennce between the one your using and the one it calls for ?

[Grim Reaper]

Hay make sure that it's a bad EGR. there should be a hole under the vac pot.You can usualy feel the diaphram as it moves when you apply vacuum. If it's moving then it may not be bad.

Pull it off and look down the hole it covers. Some times those passeges will get full of carbon. On of those goes to the heads into the cross over and the other goes into the plennum divider under the carb or TBI and dumps into both sides of the plenum. I had one carbon one side only and gave me some problems till I found that.

[swervin ervin]

Jeff,

I have no idea what the difference is. They both look the same from the outside. I'm by no means a EGR valve professional. Only thing I can tell you about EGR's is there is a N type (Negative backpressure) and a P (Positive backpressure). Now don't ask me what this means. Both of the above part numbers are N types. This is what our trucks came with.

I agree with Grim, check for carbon too. This happens a lot.

[1972C10]

The way i check them is push the diaphram in all the way and hole my finger over the vaccum line hole if they start to seep out there leaking otherwise it woudl be good..

Also you can try this With the engine runnin cap off the line that goes to it locate a full time vaccum hoook a hose to it and put your thumb over it stick it onto the egr valve while it is runnin if it opens it should kill the motor.

[bigd65]

i tried that and it didnt DIE, i think it is bad.

[1972C10]

Yeah if you hook it to wide open vaccum it should kill it

Its supposed to 0pen up at highway rpm not idle so if it opens at idle it will cause it to die. You in an area where smog is requiered?

[bigd65]

YES, all because of HARRIS CO. TNRCC ( what is was formerly know as) i dont know what they are calling themselves now. they seem to think that because of the large mounts of traffic that Houston has they need to enforce the emissions in surounding counties. I think they get paid for STUPID DECISIONS

[silverado_ss03]

hey bigd65 i used to live in angleton but my parents moved down south to the rio grande valley. oh how i miss angleton.

[bigd65]

I kinda like it here to, been here for 19 years. i like it because there just aint traffic, at least now, but HOUSTON is growing. Traffic is bad as far as FM1462 now, and im sure it wont be a few years beforte we have traffic jams in ANGLETON.

[greg0380]

[QUOTE]I have no idea what the difference is. They both look the same from the outside. I'm by no means a EGR valve professional. Only thing I can tell you about EGR's is there is a N type (Negative backpressure) and a P (Positive backpressure). Now don't ask me what this means. Both of the above part numbers are N types. This is what our trucks came with.


I messed around with EGRs awhile ago. They are important and should be kept in the scheme of things. Alot of the carbs are calibrated for them and if you plug the egr it affects them. When the egr works it lets a small amount of inert exhuast gas back into the combustion chamber to reduce NOXs and control pinging by acually cooling the combustion temperatures. Negative and positive backpressure egrs test differently. As i remember it, the stock egr from the factory were negative backpressure and would hold vacuum, but a positive backpressure will not. Pretty much today, as a replacement part, you will always get a positive type. If you look at it closely, on the positive style there is a small pinhole on the opening that is exposed to the exhaust ports. It senses and regulates how much the egr should open based on the amount of backpressure in the ehaust chamber, which is a good indicator of engine loading. The vacuum signal will then opent the valve. The positive type are supposed to be more accurate and effective. They should be used with a TVS.

WHen the egr opens it effectively creates an intake manifold leak, but it leaks burnt exhaust gas (considered inert). This slighlty affects manifold vacuum signals and can affect things in the carb (like the power piston operation). As it was explained to me, this inert gas helps to completely fill the combusion chamber with a gas (other than air) that will not burn, because it has already been burned previously. This contols pinging and emission levels.

[Old Chevy Lover]

So, does the EGR help/hurt/not affect gas mileage? I started driving my suburban a couple weeks ago. Idle was rough, and #8 plug kept fouling out. Messed with it, and messed with it, finally pulled the vacuum line off the EGR one day, just seeing what it was. Full vacuum, all the time. Motor immediately jumped up to about 800 RPM idle, purred like a kitten. I just left it unhooked, as I thought something was bad with it. But, after reading the above posts, sounds like the EGR is functioning pretty well, I just gotta find the right vacuum port to hook it to. Oh yea, #8 plug hasn't fouled out yet. Just pulled it out tonight. You can still tell there is some oil getting by the rings, but, so far, its still firing.