Today I've made an adapter to fit over throttle body and keep it pressurized and sprayed the engine with soapy water while keeping manifold pressurized at ~20psi. I noticed that it's quickly loosing pressure and there were bubbles coming from inside the ERG valve, presumably from an air leak around the valve shaft. So I swapped the old EGR valve with another EGR valve from a spare VX engine I have laying around. I tested for leaks with the other EGR valve and it's doing the same thing. Can they be both defective?
New EGR from Autozone is $230 ...insane. I'd try all options before getting a new one.
So my question is - how common is it for this EGR valves to go bad? Can they be fixed/rebuilt? And is it normal for them to leak some air around the valve shaft when pressurized?
What you saw is normal behavior for any EGR valve when you pressurize the intake manifold with 20 psi.
The EGR valve is made to regulate the amount of EGR that is pulled INTO the intake manifold. It is spring loaded and when the pressure in the intake manifold exceeds the spring setting, the EGR valve will be pushed open.
I did not see anybody mentioning air escaping through EGR valve, so unless this is something specific to VX, I would think it should hold pressure for a few minutes, right now it's leaking it all out in a few seconds
I now tested my second VX and it's got the same behavior ... may be I'll try pressurizing EGR valve diaphragm, to keep it shut and try this again
So I tried this test again, this time EGR valve diaphragm was pressurized from the same source as the manifold - and confirmed that EGR valve stayed closed but was leaking. So now I have 3 EGR valves that all leak air.
I'm stumped, they can't all be bad, or this would be a much more common problem, yet they are definitely letting the air out and both cars have an issue with idle, presumably from a vacuum leak. Any thoughts?
Hmm- well it would be hard for any rubber seal to last long with exhaust going by. Perhaps very little if any atmospheric air gets sucked in since the exhaust should be at least partially pressurizing that seal- kind of like positive pressure in a clean room or operating room keeping any dirt/germs or in your case oxygen out.
How about spraying the EGR valve with carb cleaner or starting fluid while it's idling funny and seeing if it straightens up? Another idea would be to wrap the valve most of the way in plastic and use propane from a small torch (like you would sweat copper pipes) to allow the propane to get into the leak.
Another idea- start it up and pull a manifold vacuum hose loose and see if the problem gets that much worse.
It seems like the oxygen sensor could partly compensate for a vacuum leak. Do you have a vacuum gauge? If so what is the reading at idle?
>> Another idea- start it up and pull a manifold vacuum hose loose and see if the problem gets that much worse.
I tried pulling EGR solenoid control valve on on cold engine idling - rpm went way up, probably around 2K. Doing the same on hot engine - it started revving between 1000 and 1500 RPMs (was idling at ~1100 rpm before).
>> It seems like the oxygen sensor could partly compensate for a vacuum leak. Do you have a vacuum gauge? If so what is the reading at idle?
Checked - it's steady at 22 inches of vacuum, engine hot and idling at ~1100rpm.
>> How about spraying the EGR valve with carb cleaner or starting fluid while it's idling funny and seeing if it straightens up? Another idea would be to wrap the valve most of the way in plastic and use propane from a small torch (like you would sweat copper pipes) to allow the propane to get into the leak.
Starting fluid did not do anything, unless I sprayed it directly in to the throttle body. Same with propane.
I've had similar results when I was troubleshooting my 92 VX last week, so I'm still puzzled.
Erik, yesterday I tried to set base idle on 94 Civic - connected tach and pulled off IACV connector - the idle was rough and a bit high (~800 vs 450 spec). I think it's vacuum leak causing it to run rough and idle high. If it was just base idle set too high, it would idle steady.
Today I'll do some more testing on both cars - plug PCV line, plug Charcoal canister lines. Make a steel plate to block off egr valve, and block off IACV valve with a rubber gasket. If it doesn't run well at that point, I'll be looking in to replacement engine
Eliminating all of the possible sources of vacuum leaks sounds like a good strategy.
Does the VX have a vacuum operated fuel pressure regulator diaphragm on the fuel rail? If so, remove the vacuum hose and make sure it isn't ruptured (sucking gas in through that vacuum hose). If you have a vacuum pump, you could pull vacuum or vent the regulator vacuum hose while its idling and see if the car runs better/worse.