Purge Valve Testing and Diagnosis??

[tblake]

Anyone know how to properly diagnose and test a purge valve off a 3100/3400 motor? This is actually for the alero, but the folks over there are less than helpfull, and the 3100 in 01+ GP SE's use the same valve, so I thought it might be ok to ask the question over here. Hopefully Bob, Rich, and Lynn don't demote me.

I keep getting this pesky p0440 code on the alero. Its sparadic, I could go a week or two without it, but then again, one day it could come and go 3 times. I'm at the point where I'm considering just deleting it with my powertuner and being done with it.

On these purge valves, its just a on off vacuum switch, right? So I could see if it flows vacuum with and without voltage. Is it 12V or 5V or is it pulse with modulated?

Reason I suspect a purge valve...

I have a goofy idle only when warm, it seems like its a random missfire, although no missfire codes are present or pending. When the car is cold started or accellerating, there is no missfire at all. It runs good.

So one day I got to work, car was warm and running goofy as it always does. I had a little time so I popped the hood. I could not hear or find any vacuum leaks. The purge valve, sitting near the throttle body has a 180 degree vacuum line coming off it that goes to the throttle body then to the PCV valve. I pinched off the vacuum line, and the motor idled down a little. Another thing I thought was odd was when I pinched the vacuum line with my fingers, I could feel what seemed like a pulsing senesation inside the vacuum line. The vacuum source pulsed rythmiclly about twice per second. It didn't match the random missfire from the motor which was odd. Thats why I was wondering if maybe the purge valve is pulse modulated. For some reason I don't think it is.

Another odd thing this car does, cold starting is fine, hot starting, it starts, RPM jumps up to 1000, and brifly dropps to 500, back to 1000, 500, 1000. Does this for a few seconds until it smooths out at 800 or so. It only does this on a warm restart, and whats funny is if I hit the gas pedal, and let off, it stops this cycline and idles normally. Sounds like a vacuum leak to me.

Any insight would be helpfull.

I suppose I could borrow the Purge valve off natalie's 02 SE and swap them out, but she would have a fit, she hates this little car.

Thanks guys!

[BNaylor]

Personally Tim I would swap it out instead of wasting time. Either off the SE or get a pull at the junkyard you plan on visiting.

A post on any make or model car over here at GP is fine with me. Especially since many AF Forums are dead.

Is it just the P0440 DTC and no other evaporative emissions codes?

[olopezm]

Hi Tim,

According to my manual the solenoid isn't operated with a PWM signal, so I'm guessing you might have a wiring problem somewhere. Check the PDF I uploaded, I hope it helps!

Oscar.

[tblake]

I swapped the sensor out and I'm still getting P0440. Sounds like its time to dust off the good ld power tuner and take care of that code once and for all. The car is not worth the headaches of trying to diagnose.

[tblake]

Just to update everyone, I downloaded the updated calibration ID for the alero, opened it in my powertuner, made P0440 a type 3 DTC (no reporting), means it wont turn the SES light on, and I flashed the PCM. So far so good! The new cal ID seemed to help a little with a goofy idle too, so that is a plus. I suppose new plugs and wires would make a world of difference, but I'm not spending the money until they are totally necesicarry. I'd rather spend it on the GTP. Its such a nicer car.

Next project is to swap out a caliper cause its stuck and change tranny fluid and filter but that shouldn't be a problem.

[richtazz]

P0440 is a gross leak, and could be anything from a pinhole in the filler neck to a cracked or broken vacuum line. Disabling the DTC with your powertuner is a whole lot easier than trying to track this sort of leak unless you have access to a smoke machine.