I have an '83 F150 with a 300 l6 with a Carter 1BBL carb and am trying to diagnose an idle/ missing problem.

The previous owner of my vehicle had unhooked the vacuum line to the EGR, presumably to fix a vacuum leak??? Upon inspection I found that the EGR valve (mounted in the front of the carb/intake spacer) is "stopped up" and wont open. The diaphram fails to actuate with vacuum applied and does not hold vacuum either. This being the case, the spacer and intake are filled with baked-on sooty deposits, which are proving impossible to remove.

My question is this: what are the negative effects, if any, of removing the EGR valve and plugging the EGR line from the exhaust manifold to the spacer? Also, what is the positive gained by leaving the EGR line and replacing the over-priced EGR valve?

Thank you.

 

>I have an '83 F150 with a 300 l6 with a Carter 1BBL carb and
>am trying to diagnose an idle/ missing problem.
>
>The previous owner of my vehicle had unhooked the vacuum
>line to the EGR, presumably to fix a vacuum leak??? Upon
>inspection I found that the EGR valve (mounted in the front
>of the carb/intake spacer) is "stopped up" and wont open.
>The diaphram fails to actuate with vacuum applied and does
>not hold vacuum either. This being the case, the spacer and
>intake are filled with baked-on sooty deposits, which are
>proving impossible to remove.
>
>My question is this: what are the negative effects, if any,
>of removing the EGR valve and plugging the EGR line from the
>exhaust manifold to the spacer? Also, what is the positive
>gained by leaving the EGR line and replacing the over-priced
>EGR valve?
>
>Thank you
I can't remember for sure if the egr should hold vacuum. I don't think it does. I do know that vacuum alone will not get the egr valve to actuate. The EGR valve requires backpressure from the exhaust to open up -in addition to the ported vacuum signal. Unplugging the vacuum line won't do much other than deactivate the valve. You should cap the line to keep other items plumbed in working correclty. A vacuum leak associated with the valve would be at the gasket surfaces -it's ported, you wouldn't notice it much anyway. You could have the spacer and intake hot-tanked to clean them up, that's a seperate job all together. Other than increased pollution, you won't see much difference plugging your manifold and removing the valve. Many people disable there valves, or make the orifices smaller to improve performance. It sounds like yours has been done already. There is a chance that the valve is not seated shut, or opens w/o vacuum (this would be a defective valve) then you'd see a really bad idle. Start the motor, put a vacuum pump on the valve, and pump away -you may need to do it quickly to keep the valve open for any length of time, but you should see / feel a difference in how the motor idles. If there is no change, I'd suspect the valve is defective. A crude way I found to check these valves (removed from engine) is to get a helper, a vacuum pump, and a bicycle air pump. Hold the nozzle from the air up to the inlet hole of the valve (firmly) and try pumping air..then do the same with the helper pumping the vacuum pump at the same time. If it works right, it should not pass air without vacuum.

 

Thank you Tetraruby, I'll try that.

 

 

the 86 carb is electronically controlled....the computer is looking for a certain air/fuel mixture that includes the EGR function. without this function it may run lean, or it may not actually run lean, but the computer will think it is without the EGR and increase fuel unneccesarily. To find out you can scan the computer or test the emissions. if you scan the computer and it gives a running lean code, it is either that, or the o2 sensor. if you wanna clean out the egr spacer, a drill works good just to get through if its completely blocked, then soak it in a solvent and scrape the rest out in 2 days. goodluck