Please help me out here!
Thread Starter
Racer
Joined: Feb 2007
Posts: 290
Likes: 0
From: Winchester CA
Please help me out here!
Here's the problem...
I was driving my '80 (California 305) getting on the freeway from an on-ramp when I noticed a significant lose in power. I pulled her over and she was idling very rough. I replaced the vacuum modulator on the tranny thinking this would correct the problem. It didn't. Today I started looking closer and I removed the EGR valve. I connected a small vacuum hose to the nipple and I applied vacuum. As vacuum is applied I can see the round flat metal disk start to move, but it doesn't go all the way in. Should the valve hold vacuum? Is my valve stuck open or closed? If I need to replace it, where should I go to buy one? I need to pass smog very soon and would like to drive her this summer.
Thanks to all in advance,
C3
I was driving my '80 (California 305) getting on the freeway from an on-ramp when I noticed a significant lose in power. I pulled her over and she was idling very rough. I replaced the vacuum modulator on the tranny thinking this would correct the problem. It didn't. Today I started looking closer and I removed the EGR valve. I connected a small vacuum hose to the nipple and I applied vacuum. As vacuum is applied I can see the round flat metal disk start to move, but it doesn't go all the way in. Should the valve hold vacuum? Is my valve stuck open or closed? If I need to replace it, where should I go to buy one? I need to pass smog very soon and would like to drive her this summer.
Thanks to all in advance,
C3
Thread Starter
Racer
Joined: Feb 2007
Posts: 290
Likes: 0
From: Winchester CA
Thank you for the replies. Well, I looked at the EGR valve closely and it does have a tiny rip on the rubber material. It isn't holding vacuum. So, the valve is in the closed position then. Would a closed EGR valve have the symptoms I described; rough idle, loss of power, shaking a lot...?
Thanks,
C3
Thanks,
C3
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
No. A closed valve would not be noticeable other than some spark ping under heavier throttle. An open, or partially open valve would cause such behavior.
You need to examine the basics. Your ignition and fuel systems.
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
You can run around with the EGR disconnected without much trouble. You have a different issue someplace.
Thread Starter
Racer
Joined: Feb 2007
Posts: 290
Likes: 0
From: Winchester CA
What about a valve that's in the closed position but has a ruptured diaphragm? Would this be a similar situation as a valve that is stuck in the open position with a working diaphragm? The diaphragm on my valve has a small tear. I will be replacing it later today.
Thanks again
C3
Thanks again
C3
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Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
The diaphragm is just part of the vacuum motor. If you really suspect EGR is your problem, you can make (or buy) a block-off plate that takes EGR out of the equation. This would be a lot cheaper, from the trouble shooting perspective, than buying a replacement valve and you'd have your answer. For the EGR to be the issue, in tact diaphragm or not, the pintel would have to be in the unclosed position. This happens, but is an issue separate from the diaphragm itself.
Burning Brakes
Joined: Jul 2008
Posts: 923
Likes: 37
From: Green Bay Wisconsin
Hello all,
The way to check the operation of EGR valve is:
Start car and let idle, reach under diaphram of EGR valve and push the valve open manually. A good idle will get bad and a bad idle will get worse while you hold open the EGR valve. Sometimes they get stuck open and cause a rough idle.
Hope this helps,
Douglas in Green Bay
The way to check the operation of EGR valve is:
Start car and let idle, reach under diaphram of EGR valve and push the valve open manually. A good idle will get bad and a bad idle will get worse while you hold open the EGR valve. Sometimes they get stuck open and cause a rough idle.
Hope this helps,
Douglas in Green Bay
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
Hello all,
The way to check the operation of EGR valve is:
Start car and let idle, reach under diaphram of EGR valve and push the valve open manually. A good idle will get bad and a bad idle will get worse while you hold open the EGR valve. Sometimes they get stuck open and cause a rough idle.
Hope this helps,
Douglas in Green Bay
The way to check the operation of EGR valve is:
Start car and let idle, reach under diaphram of EGR valve and push the valve open manually. A good idle will get bad and a bad idle will get worse while you hold open the EGR valve. Sometimes they get stuck open and cause a rough idle.
Hope this helps,
Douglas in Green Bay
an open EGR will make it idle like crap if it even idles at all.
Thread Starter
Racer
Joined: Feb 2007
Posts: 290
Likes: 0
From: Winchester CA
I want to thank you all for the replies and pointers. Well, I replaced the EGR valve, and she is still missing throughout the RPM range. The old EGR had a ruptured diaphragm and was not stuck open. Today I started looking at the ignition system at discovered that the spark plugs at number 5 and 7 cylinders were very loose. I adjusted them and test drove the car. The car still misses. 
What to do...
C3
What to do...
C3
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
If it misses while idling, pull off plug wires while it's running and note the rpm difference. When you pull one off and see little or no difference in rpm change that'll be your bad cyl. From there you can investigate a bad wire possibly, check that cyl for low compression as someone already stated, pull the spark plug and inspect it, pull the valve cover and look for an unusual rocker travel etc.
Thread Starter
Racer
Joined: Feb 2007
Posts: 290
Likes: 0
From: Winchester CA
If it misses while idling, pull off plug wires while it's running and note the rpm difference. When you pull one off and see little or no difference in rpm change that'll be your bad cyl. From there you can investigate a bad wire possibly, check that cyl for low compression as someone already stated, pull the spark plug and inspect it, pull the valve cover and look for an unusual rocker travel etc.
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
Spark plugs can also give you a clue as to what cyls are not doing their jobs. Look at them closely and note the color and deposit differences.
Race Director
Joined: Feb 2005
Posts: 16,100
Likes: 17
Do this: Open your hood tonight after dark...start engine and look under hood and check if your spark plug wires are arcing....that may be the issue....(and you should replace the EGR in any case..)
BTW: Got your PM...great hearing from you....maybe we need another C3 clinic....remember this one...???
Just noticed you are now up in Winchester...otherwise I'd drop by and help you out....
Rich
BTW: Got your PM...great hearing from you....maybe we need another C3 clinic....remember this one...???
Just noticed you are now up in Winchester...otherwise I'd drop by and help you out....
Rich
Last edited by rihwoods; May 15, 2009 at 10:58 AM.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Race Director
Joined: Feb 2005
Posts: 16,100
Likes: 17
Another thing to do after checking your wires, is to pull # 8 plug...EGR's can cause intake manifold gaskets to cook/leak oil fouling #8 plug.....this happened to me at 95,000 miles on my 78 with a miss/loss of power...like to drove me nuts...that is a simple check before getting into more detailed checks others have suggested...then pull rest of the plugs and don't lose track of which cylinder they came from...BTW:can you post pics of your plugs...???
Thread Starter
Racer
Joined: Feb 2007
Posts: 290
Likes: 0
From: Winchester CA
Wow! Those pics do bring back some really cool memories.
I just finished replacing the cap & rotor on the dizzy. No results. It's still missing constantly. While the engine was running, I disconnected the plug wire at cylinder number#1 and there was no change in the RPM. I reconnected the plug wire and this time I disconnected it from the dizzy cover and there was a change in the RPM. I'm a bit confused as to what that might mean.
I need some help here. What should I do next?
C3
I just finished replacing the cap & rotor on the dizzy. No results. It's still missing constantly. While the engine was running, I disconnected the plug wire at cylinder number#1 and there was no change in the RPM. I reconnected the plug wire and this time I disconnected it from the dizzy cover and there was a change in the RPM. I'm a bit confused as to what that might mean.
I need some help here. What should I do next?
C3
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Wow! Those pics do bring back some really cool memories.
I just finished replacing the cap & rotor on the dizzy. No results. It's still missing constantly. While the engine was running, I disconnected the plug wire at cylinder number#1 and there was no change in the RPM. I reconnected the plug wire and this time I disconnected it from the dizzy cover and there was a change in the RPM. I'm a bit confused as to what that might mean.
I need some help here. What should I do next?
C3
I just finished replacing the cap & rotor on the dizzy. No results. It's still missing constantly. While the engine was running, I disconnected the plug wire at cylinder number#1 and there was no change in the RPM. I reconnected the plug wire and this time I disconnected it from the dizzy cover and there was a change in the RPM. I'm a bit confused as to what that might mean.
I need some help here. What should I do next?
C3
Pulling wires on an HEI is not a real good idea IMO because the HEI has enough power to jump inside the cap which can put a permanent carbon track on the inside of the cap. If you dont have an infra red heat gun try taking a crayon and touching the manifold at each exhaust outlet and watch the difference in the heat,or use whatever method you can think of (spit works also). All your trying to do is find the cylinder that is not producing as much heat as the rest.