PontiacBonnevilleClub.com

I've got:

P0300 - Engine random misfire
P0446 - EVAP performance
P1441 - EVAP flow during non-purge

I think the EVAP codes are the relay being grounded constantly...I'm not sure though.

Are these related in any way? I've long suspected my MAF is going on the car, but no hard evidence yet.
It flashed the CEL when I took off hard from a light today. It was a 5 lane road and I had to dump the throttle on this ricer Honda next to me... It stumbled, flashed, and then was alright. I still managed to leapfrog the Honda for 100ft before letting off, because street racing is really dumb. It was around 4k (IIRC) when it flashed the CEL.

They could be related. A vacuum leak for the EVAP codes would cause a lean condition that could cause random misfires.

Pull all 6 plugs, keep them in order, and post pics of them, and describe what you see.
Inspect your evap system between the manifold, valve, and canister for leaks. Make sure the purge valve is connected electrically as well.

Where's the purge valve and the relay? or is there not a relay

I found the relay, but I still don't know where the purge valve is... I'm going to test the relay tomorrow.

It's bolted to the Lower intake manifold adjacent to the fuel rail. It'll have a vac line that runs to the canister.

Make sure the rubber fittings are not cracked or loose.

2000Silverbullet wrote:Make sure the rubber fittings are not cracked or loose.

X2!! It's 5/64" ID vacuum hose, IIRC.

Update bump...

I had 2 fittings that were loose\worn\cracked etc... Replaced...

I also noticed some odd things... Trials and tribulations, if you care to read, follow...
I appreciate your comments afterward.

The vent solenoid is always open unless powered, in which case it is shut. I think this is done so the canister can vent when the car is not running without using any battery power.

The purge solenoid is the opposite. It is shut unless powered, in which case it is open. I think this might be done for the same reason. If it operated the same as the vent solenoid, there would be air leaking from the canister vent into the throttle body.

I also noticed that, for both solenoids, voltage from each connector was low. With the car running and 14.8v at the battery, I had 9v-11v at the connectors. I also noticed that the solenoids were not moving in response to power.

So, to test them, I removed both from the car and wired them directly to a momentary switch and a spare car battery. They were both partially stuck open\close. After cycling them a few times, they both freed up and performed perfectly.

I reinstalled them in the car only to find once again, they did not operate when power was applied. I tried wiring a solenoid to the positive side of the connector and then grounding to the chassis. This worked. I measured voltage from connector to chassis. This read only 0.3v less than battery voltage on both connectors.

I assumed that whatever ground the solenoids shared was damaged in some way. Therefore, I came to the conclusion that I had to run new grounds for both solenoids. To keep it simple, I followed both solenoid grounds in the harness until they met, and then ran a new 12ga wire to my shock tower (the same location of chassis ground, much better than the stock fender).

Now, when power is applied to the solenoids, they operate correctly.

When the relay activates, it should remove power which ever one it operates, and should work correctly. I'm assuming the correct operation of the relay is "normally-closed."

Now with no vacuum leaks and no EVAP codes, the motor is stronger than ever. For a test run I took it out on a deserted road and it climbed up to 100 MPH effortlessly.

I am very pleased.

Measure the 12v pin of each connector to a chassis ground. Anything metal. With the car off and the car running. If you get full voltage, you'll KNOW it's a ground. To verify further, measure the ground pin to the same chassis ground for resistance.

That's one of the observations I have about the design of these Pontiac's. They all rely on grounds and some devices are low voltage so are very prone to grounding faults caused by corrosion. It doesn't take much corrosion and the wiring is very small low resistance which makes it worse.

Good work in finding your problem and correcting it.
We can all learn for your experience. Thanks.

I'm not sure on your year, but with most (and the general way that it is handled) switching is accomplished by switching the ground...not the source. The hot (power) remains constant, and the ground is applied and removed to provide switching.

Edit - Here's an example from a different year and car, but I'd bet that yours would be the same, or similar. The PCM switches them on and off via the ground.

Yeah so turns out Archon is right, and I had to run my new grounds back into the PCM harness. Fun. I had DTCs this morning for both solenoid circuits. Motor seemed like it was running a little rich, that was probably due to the canister vent being closed and the purge valve being open.

With it's new wiring and proper ground right at the PCM connector the voltage reads right. :D

Proper solenoid action now and after clearing the codes I have yet to see the 0446 return...

Good job.

Glad you got it, but the best solution would have been to locate the ground and clean it.

.....unless it was a broken wire.

Seems like the fix worked. Got to give him credit for doing it himself. .........with a little help from Pontiac Bonneville Club.

2000Silverbullet wrote:.....unless it was a broken wire.

Seems like the fix worked. Got to give him credit for doing it himself. .........with a little help from Pontiac Bonneville Club.

Hey ... you guys save me again :D even before i started posting

The grounding occurs within the computer through a switching transistor, according to the wiring diagram. A broken, or corroded wire or splice would seem to be a likely cause.

Tomorrow I'm going to look at the PCM ground and make sure its taken care of.

You will likely find corrosion or a loose ground somewhere, as a broken wire would more than likely leave you with an open circuit, not a high resistance/low voltage.

In any circumstance, it's best to repair what's there before adding more wires.

Don't forget Bill that these are multistrand wires. If a few are broken it could have higher resistance similar to corrosion or looseness, not an open circuit.
I have that problem on a couple of the 94's circuits...........whoops not my problem any more.