2006 Mazda 6 Engine Noise at start/idle

mazda
mazda6

#1

My brother’s car makes a horrible noise when starting and idling, which goes away as the car is driven. The error codes involved were P2187 (Fuel system too lean at idle), P0441 (EVAP Emission System Incorrect Purge Flow), and P2177 (Fuel System to lean at off idle.

It was suggested to me that the canister purge valve would be the most likely culprit. After watching some videos like this one (https://www.youtube.com/watch?v=F85dqJ9lxWY), I took it out and tested it. I could not blow through the hose when the valve was unpowered. When powered, air passed through, and the ‘click’ seemed decently loud, more like the noise produced by working valves than the broken ones. So it seems to work?

What are the next things I should attempt to pin down and fix the problem? I haven’t really done much car stuff previously (trying to learn to save money), so I was really hoping the problem would be the most straightforward thing.

I suppose it could be a hose thing. I know there are separate error codes for leaks, but considering the age of our vehicle, I’m not sure its error codes will be as detailed as more modern cars. If there was a hose leak, I think it would likely be on the hose section nearest to the engine, since I was blowing into the other side, correct? Would duct tape help?


#2

A faulty purge valve wouldn’t normally cause any weird engine noises. I expect you’ve got an exhaust leak which is confusing the O2 sensor. Possibly the leak is at the exhaust manifold/engine interface, or a crack exhaust manifold. Either would allow outside air to hit the O2 sensor, and make the computer think the mixture is too lean.

The two lean codes are probably unrelated to the p0441. p0441 means the computer isn’t seeing the pressure in the evap system drop as quickly as it should when it opens the purge valve. It could be caused by a blockage in the purge valve, but more likely the problem is that the system hasn’t built up the pressure to the normal level, so it can’t detect the normal change when the purge valve opens. Likely an evap system leak. Try replacing the gas cap, that might fix it. There’s a tank vent valve that could be involved too, but make sure the shop does a good visual check, as it might be just an evap line has cracked or fallen off.


#3

Thank you for the information. I was going by the printout Autozone gave me after reading the codes, and the descriptions online of the purge thing causing ‘rough running’ sounded like it could be what we had.

I ran the car today to avoid having problems with the battery. The engine light didn’t come on, and the car sounded a bit better on ignition, and then seemed downright okay-ish by the time I got back home. There were periods at idling at stop lights when there was a strong vibration through the pedal and wheel, but it didn’t seem to repeat.

So the problem went away somehow??? I’m not complaining, but I am rather confused. And also concerned that a problem disappearing for no immediately obvious reason may return unexpectedly as well.

I did check the gas cap gasket for cracks and make sure it was on tight before starting the car this time. There was a crack, but it was above the gasket on the outer edge, so it looked like it would not affect the seal (although there may have been non-obvious stuff). I will definitely consider the gas cap thing if that error code pops up again.


#4

Oil level and gas and oil and air filter change per manual up to date?


#5

Okay, despite sounding better during/after driving, the car still sounds pretty bad on start up now, without any warning lights. Let’s see, can’t attach things as a new user, how about: engine sound.

Oil was just changed (by a shop) and is currently between the two marks. Gas is at roughly 50% full. I don’t actually recall when I changed the engine air filter (but I do remember doing it…), but it still looked basically clean and white-ish, as opposed to being dirt stained with a bunch of junk in the filter, unlike the last time I changed it. That filter did sit in its box for a long time before use though - if they go bad from that I should replace it.