CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

EGR valve

I have been getting an EGR code after driving at sustained speeds above forty mph. The code gets stored for say less than thirty starts then disappears until I hit the highway again. I took the EGR valve off, cleaned it with carb cleaner (really soaked it) until all the black crud stopped coming out, replaced the gasket and reinstalled it. Back on the highway and the CEL is on again (goes out after a few minutes/miles) and the code is back. I went to the auto parts store and got them to show me a replacement valve. When I shook it there was a slight rattle (which I assume is the diaphragm). On the other hand mine offered no rattle sound after cleaning so I’m wondering if the valve is pooched. Anyway my question: Before I spend money on a new valve can anyone tell me if a shop can isolate whether the problem is a) the valve, b) the solenoid or c) dirty EGR passage in the manifold? Depending upon the cost of the diagnostic (ie if it exceeds the valve) I’m probably going to just go ahead and replace it. I don’t need a smog test until next Spring but I know this sucker is not gonna pass if I can’t get the problem solved. Thanks all.

lets start with the basics yearr make and model and the code “p0???” please

Ithink the auto parts store showed you a PCV valve, not an EGR valve. An EGR valve does not rattle. Did what you clean have wires attached to it? If not, you are messing with the wrong component.

As Marc mentioned, there are several EGR related codes. Please post the exact OBD-2 code you are getting.

94 GMC 5.7 K1500 Suburban. The code is 32 which my manual says relates to EGR valve. And for criminy’s sake Keith, I may not be particularly mechanically inclined but I do know the difference between a PCV valve and an EGR valve. And what wires? The EGR on my truck is secured to the intake manifold with two bolts and has a detachable hollow connection to a solenoid. Not an electrical wire in sight.

Okay…1994 is OBD-1 and the codes are not as precise as to what the problem is…Different manufacturers used different codes. Yours simply says an EGR malfunction. Somewhere in the EGR system there is an electrical sensor that is generating that fault signal…Look for the wires…Many engines use a pressure switch to detect flow rate through the EGR system. The exhaust gas passages get plugged up and the sensor generates a fault signal…The EGR valve is vacuum controlled. But what controls that vacuum signal? The fault may be there…

Unless the CEL is causing an emissions test problem, you can ignore it without damaging anything. This is NOT an operational problem. This is an emissions problem and a fairly minor one at that…

Assuming a decent reputable shop is going to charge you a hundred bucks for your diag and you can buy a valve for far less, let’s say you’re going to fix it yourself. Possible causes are faulty EGR valve, faulty EGR solenoid, a vacuum leak, carbon plugging the intake manifold, faulty MAP sensor, faulty engine control computer.

Your car has no EGR sensor or monitor. The EGR valve is vacuum operated through a solenoid mounted nearby. The computer commands the solenoid to pass vacuum, thereby opening the valve. It then watches for a corresponding change in MAP sensor reading to verify operation. If you’re just going to replace parts, start with the valve. When you have it off, try starting the engine. It should run horribly–hot exhaust out of one of the ports and a big vacuum leak at the other. If it doesn’t, you have a plugged intake.

Thanks C-man and ase. You are right that there are no ‘operational’ issues arising out of this code. Truck runs great, with maybe the odd little idle stumble which may or may not be EGR related. Tail pipe is clean and fuel economy respectable for this truck (but terrible when compared to just about anything else). A few years ago I had a real problem passing smog because of dirty intake manifold passages. The mechanic just sprayed a bunch of carb cleaner in the passages and worked on them with some kind of wire or brush and the truck managed to just pass…I’m told the better (and no doubt more expensive) solution is to remove the intake manifold to properly clean the passages. I mentioned the ‘rattle’ noise in the new valve I looked at only because I assumed that the valve is open when the vehicle isn’t operating? That’s why I thought the valve I pulled off my truck might be defective because I couldn’t hear a darn thing when I shook it after cleaning. The only other question I have is should I go with OEM or aftermarket? I’ve read stuff on other boards that says I should stick with GM to avoid problems. The auto parts store I deal with has no qualms about selling me aftermarket which they claim is as good as the original (and quite a bit cheaper).

I’d go aftermarket. If you are using a spray carb cleaner, it would hurt to spray it down the passageways to the exhaust and to the intake manifolds, sticking teh little red tube in as far as you can get it.

Sorry about the insult, I did not know your level of car knowledge. When you started talking about the rattle, PVC came instantly to mind.

No EGR valve should rattle. Yours may have a weak return spring causing excessive EGR operation on throttle tip-in, giving a slight surge or hesitation. Anyway, EGR valve operation is easily tested with a hand-held vacuum pump. In my experience, the most common causes for your fault code are bad valve, broken vacuum lines, no vacuum to vacuum lines (caused by plugged passages in the throttle body), plugged intake manifold, faulty vacuum solenoid.

The EGR system is there for more than just tailpipe emissions. I suggest you fix it regardless of pending emissions testing.

I’m going to replace that valve before the snow flies - and give the EGR passage a carb cleaner colonic for good measure. Thanks everyone!