EGR Leak

[Achilles]

Ok, I've had this rough idle problem for quite awhile and since I did the intake R&R it hasn't gotten any better. But I thought it may be due to a dirty TB and IAC. Cleaned all that up and got only a slight improvement. Now this morning I noticed a hissing sound comming from the plenum area, possibly from the EGR valve. My question is, can the EGR make a hissing sound if it goes bad?.... Assuming it is sucking air. I know I can spray WD40 or starting fluid to find vacuum leaks, but I realy don't want to do that since I've got the engine all cleaned and dressed up. So does anyone elses TPI hiss when it's idling?

This car acts like it has a vacuum leak just the way it hunts for idle RPM.

BTW, I have no codes.

Thanks

 

[tigmaned]

yeah i think if the rubber diaphram gets a whole or crack in it, you'll lose vacuum which could cause idle problems. and i sprayed mine one time and the engine rpms went up so i thought the same as you, but to make sure i have tried again and it hasn't done it???? if it were easier to just R&R i would but i don't feel up to pulling the pelinum for a what if on mine anyway?

 

[Louis Bartay]

If you can borrow a vacuum tester hook up the vacuum hose from the tester and pump up the EGR to about 10 inches of vaccum and see if it holds it for a minute or so. If it is ok then start the engine and put your finger under neath where the diaphram moves the shaft(if your model is where you can get to it) and see if it moves when you speed up the idle of the engine. If it does not move the shaft it has a carbon build up on it, use some carb cleaner after you remove it and clean the hole and the shaft but not let the cleaner touch the diaphram. Or just buy a new one. I did this to my wifes Altima and saved $110.00 for a new EGR. So far my LT4 is OK. Good luck, hope this helped.

 

[Achilles]

If you can borrow a vacuum tester hook up the vacuum hose from the tester and pump up the EGR to about 10 inches of vaccum and see if it holds it for a minute or so. If it is ok then start the engine and put your finger under neath where the diaphram moves the shaft(if your model is where you can get to it) and see if it moves when you speed up the idle of the engine. If it does not move the shaft it has a carbon build up on it, use some carb cleaner after you remove it and clean the hole and the shaft but not let the cleaner touch the diaphram. Or just buy a new one. I did this to my wifes Altima and saved $110.00 for a new EGR. So far my LT4 is OK. Good luck, hope this helped.

Thanks for the suggestions, I will try this out over the weekend. I'll have to pick up a vacuum tester. I should have one anyway.

BTW Louis, what part of FW are you from?

 

[tigmaned]

yes its a good idea but to get to the EGR on a L98 you have to remove the pelnum.

 

[Louis Bartay]

Thanks for the suggestions, I will try this out over the weekend. I'll have to pick up a vacuum tester. I should have one anyway.

BTW Louis, what part of FW are you from?

North Richland Hills/Watauga area.

 

[Achilles]

North Richland Hills/Watauga area.

Sorry, not familiar with that area. More so around Azle, Weatherford, White Settlement, Lakeside, etc.

 

[Louis Bartay]

Sorry, not familiar with that area. More so around Azle, Weatherford, White Settlement, Lakeside, etc.

My Mom has a lake hose in Azle off Steward St on Eagle Mountain Lake. We live west of Azle off Loop 820 past 35 going west like you were heading to Dallas. Exit Ruff Snow (Jean Snow Funny Car in 70s and 80s, the Drag Racer's Dad was Ruff) that is North Richland Hills then Hurst, Euless, Bedford, then Irving where the Dallas Cowboy stadium is. Lived here all my life (55) now but look and act much younger as my son and I Drag Race Motorcycles. I was sales Manager at D&D Performance Exhaust for motorcycles for several years. eimail me if you are ever in town and we will have lunch and bench race, swap lies about how fast are Corvette's are.
SYL
Louis

 

[Achilles]

I don't get that way much since my daughter moved from Weatherford to Phoenix. But I liked it there never the less. If I get that way again, I'll sure look you up.

Anyway, I put a vacuum test to the EGR valve and it's junk. It holds exactly 0 psi.

Thanks for the input!

 

[Louis Bartay]

I don't get that way much since my daughter moved from Weatherford to Phoenix. But I liked it there never the less. If I get that way again, I'll sure look you up.

Anyway, I put a vacuum test to the EGR valve and it's junk. It holds exactly 0 psi.

Thanks for the input!

No problem, glad I could help. Be carefull when you scrape off the old gasket as not to let any fall down into the opening. Make sure the opening of the tube where the EGR bolts to is not clogged up with carbon.Have fun and Happy Holidays

 

[Achilles]

Got the new EGR on yesterday, and reset the timing once again. It seemed to have helped my rough idle problem to some degree. It doesn't hunt as much as it did. Now it holds at about 800 rpm, occassionaly drops to 700, then back to 800. But still seems rough.

So I'm not discouraged, since everything I've done so far is helping. The thing is, the car runs really strong. It's just the idle.

But I noticed the plug is off the mixture screw on the TB. And I'm sure "Bubba" must have fooled with it.

Next course of action, check TPS and try resetting the idle mixture.

I cleaned the IAC when I did the TB, but I don't really know if it works. When I disconnect the harness from the IAC, I have great idle!