Check Engine Light w/ECM4801

[jthien]

At about 105,000 miles my Check Engine Light (CEL) came on. At same time I had major oil leak. Car ran fine. No noticable engine problems (other than high oil use).
Brought car to shop with 15 years experience.

CEL code was ECM4801. Confirmed oil diagnosis was leaking Cam Seal and lots of sludge in oil breather (can't think of the real name of it). Actually, lots of sludge everywhere in the oil system.
Fixed cam seals and breather and breather valve (PCV?).
Replaced 2 sensors on front of engine (O2 sensors?).
Also had timing belt and water pump replaced. They reset CEL.

After 30 miles CEL came back on and stayed on for about 600 miles. It then went off for about 100-200 miles. Now it's back on for the last 200 miles.
Still no noticable engine problems. Runs great.
I've read forum threads and most indicate that ECM4801 is Cat Converter problem but mechanic says that's seldom the real problem.
I'd be curious if anyone was able to fix without replacing Converter.

Oh, and I've checked the gas cap. It's o.k.

[ Unrelated? My gas gauge reads 1/2 full when tank is full, and empty 200-250 miles after I fill the tank. Been doing that for over a year.]

[Astro14]

OK - the gas guage is a red herring, interesting but unrelated and most likely the sender in the tank.

Your converter was likely over loaded with extra oil in the exhaust...clear the code and see if it comes back...

Your flame trap was plugged with sludge - not uncommon in cars that aren't maintained well. A plugged flame trap means no PCV and the build up in pressure inside the engine forces oil past any seals, like the cam seals.

Simply put, sludge is caused by the oil breaking down from contaminants. It breaks down faster under high heat, low oil level, frequent short trips (that allow moisture to build up in the crankcase). Cheap oil breaks down quicker than good oil (has to do with the additive package in the oil that manages the contaminants...)

You still have an engine full of sludge, sure the flame trap is clear, but the rest of the motor has it...your mechanic said so...

To fix sludge, fix it slowly. You can try an oil detergent called AutoRx, but absolutely no motor flush or any strong solvents, they attack your new seals and thin out the oil, potentially damaging the engine...The new oil has detergents, and the slow cleaning is best. Any quick cleaning runs the risk of getting all that sludge circulating, where it can plug the oil pump pickup or oil galleries and it's bye-bye engine...

So, change the oil and filter with good-quality oil, synthetic is best. Change after about 500-1000 miles, change them again at about 2,500 and then again at about 5,000. You can go back to regular intervals IF you use good quality oil and don't subject the car to severe service, including short trips, towing, extensive idling.

Any of those operating conditions are reason to change the oil more often than 7,500.

Or, you can do yourself a favor and go to synthetic...

And for Pete's sake, stay away from discount store brand oil and make sure that the oil you do buy meets the specs in the owner's manual...

[jthien]

Astro,
Thanks so much for your reply. Am currently on the course you've recommended oil-wise. I'll be seeing my mechanic tomorrow. I'll have him clear the code. Hopefully CEL will stay off this time. I thought I was in the clear when it went off the first time. Will post results.

[Astro14]

Have a bit of a variety of cars in the stable. Obviously, I am a bit of an oil geek...but if you want to see some real oil geeks, check out www.bobistheoilguy.com - I've learned a ton surfing their site and forums.

The real danger in cleaning up sludge is doing it too quickly.

I've owned several cars that went over 200K. My truck is just the latest example.. Good maintenance (including oil changes) has made it possible...

Cheers,