another EGR question.

[manimal]

On my '89 Suburban(R2500,454 TBI,TH400...2wd) I keep getting the code 32. I have vacuum at the TB,the vacuum will read on/off on the EGR side of the solenoid. When I compress the EGR diaphram manually(by hand) there is NO CHANGE in RPM...the engine does not stumble. This morning I removed the EGR valve to see if the passages were blocked. nope they are clear..even started it for a second to hear the exhaust coming through.
I cleaned the VERY LITTLE bit of carbon off the EGR valve,new gasket and back on it went. Started the engine and did the manual check again,still no change. So, my questions are;
1)Could the EGR valve spring/diaphram be weak and it is ALWAYS open(as in the pressure from the exhaust holding it open),therefore no change?
2)Could the passage TO the intake be plugged?
BTW, the engine was cold when I tried this,does it matter? And the vacuum source was NOT hooked up to the EGR valve. So it should not have been working in the first place...RIGHT?

[manimal]

back to the top.????

[wraprail]

Did the spring feel weak when you compressed it?
I have never seen one go bad.
I think you are on the right track with the clogged intake passage.
Pull the TB and EGR and blow air through the passage.
Also spray some carb cleaner into passage.
If it is clogged try a coat hanger

[rfmaster]

Originally Posted by manimal

back to the top.????

Manimal

I am no expert in BBC's. It is possible that PO installed incorrect intake gasket which blocked or restricted exhaust flow through the crossover passage. For example FelPro Q1210 has cross-over passage block off.
http://www.summitracing.com/parts/fe...make/chevrolet

while
FelPro Q1212 has the cross-over passage wide open
http://www.summitracing.com/parts/fe...make/chevrolet

Both have
Port Height (in): 2.050 in.
Port Width (in): 1.820 in.

//RF

[manimal]

I removed the egr valve and started the engine....exhaust came out of the port. Engine does not appear to have ever been tampered with.

[rfmaster]

@Manimal
OK then scratch wrong gasket idea!

However, idle should drop when EGR valve is enabled allowing exhaust gases to enter intake manifold plenum. There should be a passage from just under TB mounting flange to EGR cavity. That portion of EGR passage maybe blocked or obstructed (it is after the valve). IRC the 89 used Q-jet intake with adapter plate.

//RF

[wraprail]

Originally Posted by rfmaster

@Manimal
OK then scratch wrong gasket idea!

However, idle should drop when EGR valve is enabled allowing exhaust gases to enter intake manifold plenum. There should be a passage from just under TB mounting flange to EGR cavity. That portion of EGR passage maybe blocked or obstructed (it is after the valve). IRC the 89 used Q-jet intake with adapter plate.

//RF

You may be on to something. Great idea!