I have a 1980 F100, straight 6, one barrel carb and 3 on the tree manual transmission. I recently replaced the EGR valve. Why? I noticed the 'pin' or needle therein stuck in the 'erect' position and I live in CA which requires a SMOG test every two years. Mind you my truck was running fine too (?). So, I bought one from Rock Auto (Standard brand). Now, my truck runs worse with it on? It stammers, exhaust 'popping' and is not as easy to start even once hot? I smell excessive gas fumes too. Anyway, I had enough today and pulled the vacuum hose and plugged it with a screw. Truck runs 100% better.

So, my question is why would the truck run worse with a new EGR than with a dysfuctional one or without one at all? Is this a symptom of vacuum issues and/or other emissions related component issues?

I'm confused?

 

I'm just learning myself but it sounds like you may have it on manifold vacuum instead of ported.

Have you checked to make sure there is no vacuum at idle?

If it's constantly receiving vacuum then you basically have created a vacuum leak. At least that's the way I have it figure.

I'm sure someone will correct me if I'm wrong.

Good luck

 

If it stays like that longer than 4 hours I think you're supposed to call a doctor!

Sorry...I couldn't resist. LOL.

Two theories jump to mind.

One is your old EGR wasn't working, and when you installed the new one you weren't tuned for it.

The other is all new parts are suspect. Sadly, they just don't make things like they used to. Where your old one may have been stuck shut, the new one might be stuck open, or leak or something. And a stuck open EGR will cause problems. I was once told to spray carb cleaner in the EGR and if the fluid leaks out past the valve its not good.

But since it runs okay with the vacuum disconnected the ERG must be closing well enough.

Don't know a lot about EGR but I think Carolina is right. I don't think the EGR should have vacuum (be open) at idle or full throttle. I think it's only supposed to open under cruise conditions. Hopefully you still have a vacuum diagram sticker somewhere under the hood that may offer some EGR vacuum routing clues.

 

A very good post on EGR.

https://www.ford-trucks.com/forums/1...-line-faq.html

 

If the egr is open all the time, and the exhaust ports under it are open, the engine will not idle period. So your old egr could not have been stuck open unless one of the pipes or passages were blocked with carbon and junk.

But apparently it was not working, since the new one makes a difference. If you want to test it with the vacuum line off, get the engine started, and with the engine running reach under the valve and push up on it. If everything is open, when you push up on the egr the engine will run rough and quit.

Get the engine going again, and with it idling, take the vacuum line you plugged off that is supposed to go to the egr, and take the plug out and put your finger over the end of the line. If it sucks on your finger, then that's a problem. Like the others said, this line should only have vacuum when you rev the engine, when the engine is idling, there should be no suction on this line. This line also should no suction on it till the engine warms up.

 

In terms of running worse now than before, it could be a few things. Depending on the state of the original EGR. If it was stuck closed vs this one being open, etc.
The bottom line is that the new EGR valve could be bad or it's a control (vacuum) issue.

But first a quick blurb on EGR..

EGR is supposed to recirculate the exhaust gas only when the engine is warm enough AND above idle. On older, non-computer controlled vehicles (I think 1980 may qualify but in CA I'm not sure), it's controlled by a ported vacuum switch. On computer controlled vehicles, it's controlled by the solenoids which are in turn told when to turn on by the computer. The computer get's it's data from a temperature sensor and throttle position sensor.

If the valve is stuck closed, no big deal in terms of engine running although you won't pass emissions and you may get some pinging. If the valve is stuck open, you'll get too much exhaust gas mixed in too early and run rich. That would cause the rough running and most likely the gas smell you talked about. Gas smell could also be caused by a problem with the EVAP system (which is also controlled either by ported vacuum and a thermal valve or the computer and solenoids)

So...

You could have a bad EGR valve, A bad vacuum connection, a wrong vacuum connection, or a bad ported vacuum switch. In any case, it sounds to me like the valve is OPEN when it shouldn't be.

If you have the wrong vacuum source (manifold instead of ported) that would cause the problem. If the ported vacuum switch is bad - ditto.

Simple to test. Disconnect the vacuum line at the EGR valve. Engine at idle and warm or cold you should have no vacuum at that hose. Engine above idle and cold - same deal. Engine above idle and warm = vacuum.switch.

If you have vacuum at idle, check the switch source. Sounds like manifold vacuum instead of ported. If you have ANY vacuum with a cold engine, you have a bad ported vacuum switch (assuming it's not computer controlled..). Again - you should only have vacuum at the EGR above idle with a warm engine.

Now if it's computer controlled, you can check vacuum at the valve as well and if it's there at the wrong time, I'd be looking at temp sender for the computer or a bad solenoid.

Happy Hunting. Once you understand how the system works, it's just a matter of process of elimination

 

Kscop wish I could rep on mobile. Nice post.

 

Thanks. I've done a lot of work with my EGR, EVAP, etc. during my conversion from feedback carb to regular carb / DUI distributor. Had to do a lot of research to get all the details.

I put a FAQ and HOW TO out there as well

Now if only I could get the straight scoop on the timing marks..

 

I was just mentioning in another thread that I'm going system by system trying to figure things out. Its a journey not a destination I guess. Best of luck!

 

1980 wouldn't have computer controlled vacuum would it?
There should be a thermal switch and a delay valve in line to the EGR.
EGR should be color coded green if any of the original hard plastic vacuum lines still exist.

Have a look on the radiator support for an emissions sticker.
There should be a simple vacuum routing diagram.

 

I would think that a 1980 would be vacuum controlled via a thermal ported vacuum switch. Not sure why you would need a thermal valve, since that is the purpose more or less of the ported vacuum switch.

There would be a thermal valve in the evap line but that's a whole other topic..

 

Vacuum Delay Valve is not thermal.

Let me see if I can find a 1980 I-6 routing label on the net.

KScop, what is the problem with your timing pointer?

 

I wish Ralph were still here... IIRC California trucks began computer controls in 1980 but I'm not at all sure what they entail or what they controlled....

 

I found this 1981 diagram in another thread.
It doesn't show any valves, it's just connected to the WOT port of the carb.



https://www.ford-trucks.com/forums/9...questions.html

 

I know that some systems used a restriction in the vacuum line, but most that I've seen that are not computer controlled just used the thermal vacuum switch. In terms of computer control, all I know is that CA started using some of that earlier than others.

In my 85 (from Montana) it had a computer that managed the emissions components as well as the carburetor mix and timing.

To answer the timing mark question, and not meaning to hijack, I need to time my I6 and couldn't find any timing marks. Finally figured out that the notch and 'peep sight' were used for a crank sensor (mine doesn't have a sensor but does have the notch and such) to indicated #1 TDC. Based on that, I can make my own marks and time my engine.. (I have a thread in the engine forum on it)

Hijack complete..