02 4.6is p0491 and p0443
 

Hi Guys. Im new to the forum so sorry if the question has been asked before. My '02 x5 4.6is engine light is on and the codes read p0491 and p0443. I took it to the stealer and they told me that there's carbon build up in the heads and that one of the banks is holding 40 PSI of pressure. To fix it they said they would have to pull of the heads and clean them manually. The car runs and drives fine lots of power. No issues. ANy idea if they are trying to take me for a ride? should i try something else? Any suggestions would be great. Thanks

Code p0491 is related to your secondary air pump and p0443 is your evaporative emission system. Check your vacuum lines first to see if any cracks or leaks.

P0443 trouble code symptoms could be just an malfunction indicator lamp (MIL) illumination. There may be no drivability problems at all. But, it's also possible to have a lean condition or a rough running engine if the purge valve is stuck open. Usually though, these symptoms are accompanied by other EVAP codes. Another symptom may be excessive pressure in the gas tank in the form of a "whooshing" sound when the cap is removed, indicating a purge valve that isn't working at all or stuck closed.

I have seen this issue before, and if they came to that conclusion then they must have already tested the pump, lines and valve operation, then checked the flow of the actual passages in the heads. The passage ways in the heads can get clogged with carbon, and the only real fix is to remove the heads and run brushes with solvents etc through all the passages. If this happens to my X I'll be running the cleaning brushes in as deep as I can go through the front main passages and trying to flush out the secondary passages with some potent solvents, (soak, then blow through) but you'd still have to remove the exhaust headers to avoid blowing all that trash in the headers...

Thanks for the info guys. Is it safe to still drive the X5 if there's carbon build up. Will i do any damage? The 4.6 still drives and runs smooth and is still very strong power wise.

thanks again

It is still safe to drive, the passages are for the secondary air system which is just for emissions readiness on cold starts.

I have carbon buildup in my 4.6. It's nothing to worry about, and BMW is sick of fixing them under any sort of warranty. The only thing is the ever present CEL. Otherwise it wont hurt anything.

Do you guys think Seaform will help with the carbon build up? Please advise.

No. It wont even scratch the surface of the problem...both literally and figuratively.

The only attempt-able fix I can think of that wouldn't require removing the heads would still be a labor heave operation including removing the exhaust manifolds among other things...

I'm ttt'ing this, because I am having a recurring P0491 and P0492 code that keeps popping up, and I've replaced the secondary air pump and valve. Next up, I'm going to clean out the lines going to the head, since they have to come out in order to do my upper timing cover gaskets, which need to be done anyway. Anyone find any other solutions?

Edit: Dunno if this helps, but the light comes on right AFTER the pump turns off.