Disconnected EGR Valve?

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Disconnected EGR Valve?

July 16, 2005, 04:05:19 PM

I went to replace my EGR valve today because I suspected it may be responsible for a knock my engine makes when the weather is hot. The Chilton manual was typically unhelpful and didn't even point out where this thing was so I had gone like 2 months thinking this other component was the EGR valve but today with the new valve in hand I discovered the real one and found to my surprise it wasn't broken (probably), it was disconnected. There was a stray vacuum line nearby capped off with a bolt, I'm including a picture of that and I'm willing to bet that's the missing connection. I could reconnect it but first I need to know if there's a reason I shouldn't. We established in another post my 83 5.0 was retrofitted with a carb, is there some reason that the EGR system would interfere with that arrangement? Or did the last owner just decide the car was better off without it?

Re: Disconnected EGR Valve?

Reply #1 – July 16, 2005, 04:14:11 PM

Scratch that there are actually 2 stray vacuum lines. Is the EGR Solenoid about the size of a can of Red Bull? Because if so then this is the one. Only question is whether I should connect it.

Re: Disconnected EGR Valve?

Reply #2 – July 16, 2005, 05:27:46 PM

K I know I'm talking to myself but I have a theory now. Since EGR systems are often computer controlled whoever swapped off my throttle body system may have gotten sloppy and disconnected my EGR when he didn't have to. As far as I can see my EGR never used computer control.

Re: Disconnected EGR Valve?

Reply #3 – July 16, 2005, 05:53:04 PM

According to my '84 shop manual:
5.0L T-Bird and Cougar for sale in Canada came with a 2150 2V carburetor.
Does the distributor have a vacuum advance on it?

Re: Disconnected EGR Valve?

Reply #4 – July 16, 2005, 06:04:08 PM

Don't know exactly what that is but there is a vacuum activated diagphram of some sort mounted to the distributor shaft.

Re: Disconnected EGR Valve?

Reply #5 – July 16, 2005, 06:16:58 PM

That's it. Sounds to me like your car was built with a carb. You don't have a computer.

Re: Disconnected EGR Valve?

Reply #6 – July 16, 2005, 06:26:41 PM

Is the vacuum distribution decal still on the car?
You probably have a vacuum gizmo with 3 or 4 vacuum lines to it that compares venturi vacuum from the carb with manifold vacuum and operates the EGR valve.

Re: Disconnected EGR Valve?

Reply #7 – July 16, 2005, 06:30:36 PM

Interesting. That answers a question I've been wondering about for a while. Means the specs I have are out the window. And seemingly there's no reason the EGR should be disconnected except maybe out of a misguided attempt to improve performance, I just saw a guy on ebay the other day trying to peddle EGR bypassers or something.

Re: Disconnected EGR Valve?

Reply #8 – July 16, 2005, 06:32:56 PM

I think that's the solenoid, it has a connection to the exhaust manifold and a really big vacuum hose seems to run straight through the thing as well.

Re: Disconnected EGR Valve?

Reply #9 – July 16, 2005, 08:13:38 PM

There so many variations of these EGR systems it's hard to tell exactly what you have.
What you seem to be discribing is something called a Back-Pressure Transducer. One of the big hoses is the vacuum supply and the other big hose goes to the EGR valve. The EGR valve is mounted on a spacer that goes under the carb.
The transducer senses the back pressure of the exhaust and controls the vacuum to the EGR valve.

Re: Disconnected EGR Valve?

Reply #10 – July 16, 2005, 09:30:33 PM

I was mistaken earlier when I described the solenoid (again a decent diagram from Chilton would be nice). The valve is connected directly to a device planted in the manifold which is also connected to the carb and to the other device I described with the major vacuum hose running throuh it. In any case I reconnected the valve and I'll see how the car runs on a decent drive tomorrow. Depending on that I may run some tests to see if the system is working.

Re: Disconnected EGR Valve?

Reply #11 – July 17, 2005, 05:26:54 PM

I drove the car on my usual route today and I got my usual knocking sound. Afterwards I pulled the vacuum line to the EGR again and verified there was vacuum though I have no means of measuring it. I reconnected it and watched the valve while I worked the throttle and sure enough it did move though I somehow expected more. Just how much does an EGR valve move anyway? I tried connecting the new valve I had to the vacuum hose but strangely enough it didn't react at all to the change in throttle. Does the valve need to be actually mounted to the engine to work??? Is this valve likely defective?

Re: Disconnected EGR Valve?

Reply #12 – July 17, 2005, 07:22:20 PM

I just got a piece of vacuum hose and activated the valve at idle by sucking on the hose. From what I gather that should have impaired the car's idle if not stalled it. Nothing. Though once again the valve moved a little. I checked the new valve in the same fashion and I could hear the air whistling through it so I guess it needs to be sealed onto the manifold for it to work. If the existing valve is operating the way it's supposed to then where do I go from there?

Re: Disconnected EGR Valve?

Reply #13 – July 18, 2005, 08:22:06 PM

Uhhh...I took off the valve to clean the EGR passageways and....yeah...isn't there supposed to be something in there to contact the valve?? Or does the gas pass through the base of the valve itself in this case? I guess that would make sense. Bah. Forget I said anything. I'll see if the valve works now that it's got a quart of carb cleaner in there.

Re: Disconnected EGR Valve?

Reply #14 – July 20, 2005, 12:14:41 PM

I bought the Chilton manual too and it was a big ole pile of $4!7. :flip: I purchased the HAynes manual and it is better written.

Sorry I have no advice on the EGR dilema, but I saw those EGR bypass things too and wondered if they really work. Any thoughts anyone?