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Engine Sludge

I have a 2006 Kia Spectra with 74K miles. It was apparently neglected before I bought it (at 55K miles), and has a case of engine sludge. It’s clogging my oil control valve, and a couple engine flushes (by Kia dealer) over the last year have failed to correct the problem thus far. The car runs ok, but cannot pass an emissions test due to the check engine light and corresponding codes. Can I perform the flushes myself? What product should I use? Can I safely remove and clean the OCV myself? What product should I use? Thanks for any help!

“Oil Control Valve” sounds like a “Muffler Bearing” to me. Please post the actual OBD-2 fault codes so we can see what is going on…

P0011. The dealer is the one saying the valve is getting clogged.

I don’t know this car, but it probably has variable valve timing & the OCV is probably the control valve for that.

Cleaning sludge is almost impossible without actually disassembling & physically removing it. If you want to continue to try flushes, auto parts store shelves are not short of such products. I would probably try SeaFoam which is actually multi-purpose.

Since I don’t know the car I can’t tell you about changing the OCV but I’m sure you can find it with some internet searching & perhaps via Autozone’s online repair info. But it may be like putting a band-aid on an amputation.

Have you been given a quote for OCV replacement?

The OCV is supposedly still operating within specs, so they have only cleaned it, and not recommended replacing.

You can read up on the code here:

The OCV might operate within specs some of the time - and maybe not others.

Or you could have a whole different kind of problem. Perhaps its time to have someone else take a look.

P0011 code:

"Possible Causes:
Incorrect camshaft timing
VCT solenoid valve stuck open or continuous oil flow to piston chamber
Camshaft advance mechanism binding, or faulty VCT unit

If this code will not clear, and you can not pass an emissions test, the repair may or may not be sludge related…One sure way to determine sludging, remove a valve cover and LOOK ! There is no need to guess…

Yes, I’ve considered having a different garage look into it. For what it’s worth, looks like I’ll be able to get a waiver on my emissions test since I’ve spent more than $200 to address the problem.

Not being a “car guy” myself, I wouldn’t know how to remove the valve cover to check. I know you can’t always trust some of these shops, but I’ve had the same diagnosis, first back in September, and second time yesterday. Granted, it’s the same shop…

4 cylinder or a V6 ??

4 cylinder


At the moment I am inclined to believe the dealer about the sludge clogged valve since they have had it out and cleaned it several times. So, back to my original questions: Can I perform the flushes myself? What product should I use? Can I safely remove and clean the OCV myself? What product should I use?

There’s a difference between oil sludging and oil coking. Coking is basically hardened, cooked engine oil and many times nothing is going to clear this up except actual physical removal.

This may be present on the oil pump pickup screen and to clean that requires removal of the oil pan. Think of it this way too. If you succeed in breaking any oil sludge or coking loose where is it going to wind up? Right in the oil filter first thing.

Personally, I 'm not keen on using products to desludge or decoke an engine but to each his own.

On a 4 cylinder, the valve cover can be removed easily (by a mechanic) and the parts in question inspected. Any sludging or coking will be plain to see…If the engine is reasonably clean, then isolate and replace the defective parts that are causing the CEL and fault code…

Thanks for your help folks – I think I’m just going to do some frequent oil changes, and clean the OCV and its filter periodically. Hopefully I can get it cleared up without spending massive amounts of money on this problem!

I Searched Bulletins For 2006 Kia Spectras With DTCs (Diagnostic Trouble Codes) Set. Here’s A Link To A Kia Technical Service Bulletin (Written For Kia Technicians) That Discusses OCV Inspection .

Also, note the Tech Tip:
Make sure the oil filter is OE; aftermarket oil filter flow rates differ and may affect the CVVT system performance.


Thanks for this info , CSA! I was able to get a waiver from the state on my emissions test, so I am good for a year anyway…I decided to try Auto-Rx after reading lots of good things about it, so am in the early cleaning phase with it. We’ll see how it goes, and maybe take it to another shop if the problem doesn’t clear up after that.

I’ve used Gunk brand engine flush with relative success, but I would be concerned about using it in a car with variable timing, but no matter what type of engine flush you use, make sure you follow the directions to the letter to avoid engine damage.

The directions on most containers of engine flush recommend letting the engine idle while the flush is in the engine, and warn NOT to drive the car with the stuff in the engine. In fact, I might be tempted to make sure to flush all the engine flush out of the engine by doing an additional oil change a few days after doing the flush.

The trouble with using any engine cleaner/flush is that you never really know if you have to remove the oil pan afterwards to clean-out the oil pump pickup screen.

There is no question that flushes/cleaners do work. However if chunks of the loosened sludge plug your pickup screen, you now have a bigger problem.