It could be. You need to check it. It should be closed, and there
should be no vacuum from the source at idle. The pintle should also
make a good seal when it's closed. You can test the valve itself with
a known steady vacuum source.
IE: any port that has steady vacuum when the engine is running...Or a
vacuum pump tool. Disconnect the normal vacuuum hose from the EGR
valve, and hook up the known vacuum. The rpm should drop, and you
should hear a noticable difference. "Worse running" The main thing is
to listen for a difference. If it does change, most likely the valve
is good. Clean it, and reinstall. If applying vacuum makes no
difference at all at idle, the valve is most likely shot and has a
ruptered diaphram or a pintle that is not seating well. As far as the
normal vacuum source, modulator, whatever... there should be none at
idle, but increase as you give it gas. As long as it does that, it's
But it's possible you have other problems. Check fuel filter and flow,
make sure it's not starving for gas. "don't forget the strainer in the
Also make sure it's not drowning. Rochesters like to have the float
stick...A recent rebuilt "should " be ok, but all it takes is a spec
of dirt to cause this.
If gas runs all over from the base of the carb, the float/ needle/
seat is sticking. Also you will smell the excess gas. BTW... Make sure
no vacuum leaks. Check all rubber hoses, etc. MK
I had this problem on my 327 (I put a HEI in) Chevy has a common problem with
the ignition modular going bad once it heats up. If it runs fine when cold then
like you said after 5 minutes dies and won't restart until it cools down I
would changed the ignition modular. It's like 7 bucks and 10 minutes work. Try
that, pretty positive that will fix it. Ask a good proven Chevy guy who knows
older motors I am sure he'll give ya the same answer.
You should make sure that you are only running six volts to the module.
Twelve will cook the coil and it will act like your running out of fuel. The
ballast resistor knocks down the twelve volts to six.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.