egr problems

[batch]

my egr vacuum solenoid clicks constantly while running. i took it to a shop and they said it was bad and i am not getting any vacuum. i went to a salvage yard to get one because they are disontinued the guy said it was fine. my truck failed smog so trying to figure out if i should try another just incase.

 

[dyeager535]

Sounds like something else is wrong, the EGR is pulsed by the ECM, not sure how it would continue to operate unless the ECM is telling it to, which it doesn't except when very certain conditions are met...mainly, cruise.

Are you getting a check engine light? How is idle?

With engine running, idling, there should be vacuum TO the EGR valve, but none to the valve itself through the solenoid.

If it clicks constantly, pull the solenoid connector, put a noid light between the wires (or analog voltmeter) and see if it pulses at idle.

 

[batch]

the check engine light comes on occasionally but only stays on for about 30 seconds. the idle seems inconsistont sometimes it will idle higher or lower than other times.

 

[dyeager535]

If the EGR solenoid cycling is constant, you'd likely have a horrid idle, ALL the time.

I guess I better find out first, what year are we dealing with? Not that it really matters, EGR solenoid was only used on TBI AFAIK.

 

[bigblock72]

What did it fail smog for: visual? cutpoints? If it was emssion cutpoints then which one(s) and how bad?

Also need to know what year your rig is so we can make some semi intelligent guesses as to what is going on.

 

[batch]

its an 86 . it failed the 15 mph CO by about twice then at 25 failed the NO about 3 times the limit

 

[bigblock72]

Carb'd huh. That makes things a little more tricky. High CO means rich mixture. Try turning the idle mixture screws in a turn or two and see if it changes anything. IF you can turn the mixture screws in all the way and the engine stays running then there's problems. Those carbs are notorious for leaking fuel out the metering well plugs and causing a rich mixture at low speeds.

As for the NOx failure the EGR is the most likely cause. Make sure the vacuum hoses are all intact from the carb to the solenoid and from the solenoid to the EGR valve. There should be vacuum to the solenoid when the engine is above idle and the solenoid should allow vacuum to go through to the EGR valve when the engine is fully warmed up.
Apply vacuum directly to the EGR valve to make sure it works. If the valve is working it should stall the engine at idle when vacuum is applied. If not check to see if the diaphragm holds vacuum if it does then the EGR ports in the heads and intake are plugged.

 

[batch]

i really know diddle about tuning the quadrajets , isnt the mixture screw on top of the carb

 

[bigblock72]

The mixture screws are in the baseplate of the carb. Google "E4ME Quadrajet" and you'll get some good pictures and more info than you'll know what to do with.

 

[apache]

The idle mix screws are at the very bottom about 2" apart or so on the throttle plate casting. Their recessed into the casting a bit, you may need a special oval shaped tool to adjust them.
On another note, Ive never bothered to check what made the clicking but even with the key on on my 84/350 I hear a constant clicking from that area also. Cant say if it does it while its running as I never paid attention,I have the same issue with a sometimes high then occasionally lower idle speed. It was smogged when I picked it up about 5 months ago but im starting to wonder about its actual ability to pass even when I bought it. Poor things a cluster fook of hoses and wires for the smog parts. Also as mentioned if the ports are plugged in the manifold you probably will have to remove the intake and chisle the carbon out which is what I had to do on a 74 I had.

 

[bigblock72]

The clicking noise is the idle mixture solenoid in the carburator and is perfectly normal.

 

[apache]

Well thats good news the clicking is normal,Ive had about 10 mid 80ies chevy trucks but never a 1/2 ton with this electric Rochester.