Oil Sludge Removal Recommendations?

[Manolito]

I have been fighting a rough idle on startup for years on my two '97 328s.

I just read in a 5-series review that a common problem in high mileage BMW 6 cyl engines is that just a trace of sludge in the VANOS will cause them to hang up, causing a rough idle.

This is consistent with the fact that one daughter complained yesterday that her cold idle problem got much worse immediately after we changed from synthetic oil back to 20W-50 GTX, the oil that I have used in all my cars for the past 30 years. (I got a slew of oil leaks when I tried Mobile1 in my BMWs and Volvo).

I know I don't have much sludge in this engine. When I recently changed the valve cover gasket, I found the valve train to be colored golden brown as you would expect on an engine with 240,000 miles on it, but no visible buildup anywhere.

When I was a kid, conventional wisdom was to add 1 quart of ATF to the oil and drive the car a few miles before an oil change. I don't know whether that actually worked or not, or whether it hurt the engine. My first vehicle was a '49 Chevy pickup with a road draft tube, so sludge was a bigger problem back then.

After some time on the web, I am seeing that the two approaches seem to be
1) Add a strong solvent like SeaFoam or Berrymans and drive the car just a few miles (some say just let it idle for 30 minutes) before the oil change, or
2) Add a milder additive that is compatible with all seals and metals, like Marvel Mystery Oil or Motor Rx, and run it several thousand miles.

I am leaning toward the Marvel Mystery oil approach due to the cost and my lack of familiarity with Motor Rx.

Any other recommendations or cautions?

[coolbear1]

Manolito,
Vanos, are you sure? I have seen alot of threads with idle trouble over the years, but I don't recall vanos being the cause. Have you checked the other more common causes for poor idle? What engine does your car have, I assume M50,52? If not, Does it have the same intake/idle air setup? I ask because I have a high mileage car and have had several idle problems over the years. Have you cleaned you idle control valve? How about the throttle body? Intake air leaks?
The last time I went through it it turned out to be the 02 sensor, and it never set a code. I pulled my last few hairs out over it.
Hope you find it.
Good luck.

[wswilburn]

I had a similar problem with my 1998 M3. My exact symptom was rough idle for the first minute after start in cold weather. Trying to open the throttle in this time would cause a stall. Sending the injectors to Witchhunter Performance for cleaning fixed it. My feeling is injectors need to be professionally cleaned every 100k miles in any case.

[Manolito]

It is an M52, and I am not at all sure that the problem is in the VANOS. That is just my most recent theory.

If I park these cars for several days, when I start them, they run on 4 or 5 cylinders. This usually clears up by the end of the block, but has been known to persist for up to 5 miles. They don't stall. This does not happen every time I park them for an extended period, and some times it is more noticeable than others. The lower mileage car sat in the garage for six months last year. I wondered what would happen when I started it - it purred like a kitten that time. The one with 240k miles on it is worse than the one with 150k miles on it.

I doubt that the problem is a leaking or dirty injector. I pulled the injectors from one car and sent them to Witchhunter for ultrasonic cleaning. The report said that they were fine, with no leaks and good flow and pattern before and after cleaning. The car behaved exactly the same afterward.

I doubt that the problem is the fuel rail draining down. When I replace fuel filters and the rail is empty, it fills completely and fires on all cylinders within about 3 seconds of when the first cylinder fires. As noted, this intermittent problem sometimes takes miles to clear up.

I thought that it might be a hydraulic lifter leaking down. That would explain why it does not happen every time (depends on the position the engine is in when it stops). However, I was advised that hydraulic lifters in these engines virtually never fail, so the chances of me having two cars with that problem are very slim, unless the GTX oil I use is hard on these lifters.

The higher mileage car has been doing this for 100k miles and several years, during which time it has had several sets of plugs and air filters, the throttle body and idle air control valve cleaned a couple of times, all four O2 sensors replaced once, crankcase ventilation system cleaned, etc. It recently got a new PVC (I broke the old one while working on the power steering) and a new rubber boot on the throttle body because I found cracks forming in the old one.

None of these maintenace actions had any affect on this problem. I think that the higher mileage car may have been a bit better while it was running Mobile1, but I could not keep that oil in the engine.

[wswilburn]

You have certainly tried a lot of things. Do you get any ODB codes?

[wswilburn]

You have certainly tried a lot of things. Do you get any ODB codes?

[Manolito]

No codes. I think the only codes I have ever pulled on either of these cars have been "catalyst efficiency low" which means that it is time for new O2 sensors, and "secondary air pump low flow" which I already know by that time because those pumps sound terrible as they fail.

Of the repairs listed above, I think that only the fuel injector cleaning was specifically done in hopes of correcting this particular problem. The rest were just routine maintenance. About all I have done about this cold start problem is read and scratch my head and post theories here for several years.

[wswilburn]

I'm certainly no expert on these cars. I only know about what has happened with mine. The only other time I had poor running was a bad ignition coil. It caused a miss that would come and go, at all speeds, not just idle. It did give me a code that told which coil was bad, so this doesn't sound like your problem.

Since both your cars have the same problem, you would think it is a common one that others would report. You haven't done anything unusual to them have you? Any mods?

[coolbear1]

Manolito,

Since both cars are doing the same thing, I wonder if there is somthing common to the two, such as a similar component that could have something to do with it. I know I have horror stories about aftermarket parts that drove me to drink, or drink more anyway. If you are using Bosch plugs, my experience is, THEY SUCK.

[Manolito]

I have been a little shy of Bosch parts since the Chinese bought the company and more and more of their parts come from China and India.

I use Denso plugs in all my cars, or NGKs if Densos are not available.

I would automatically suspect the 20W-50 oil, which very few people use, but back in the '90s, I noticed that both the BMW dealer and the Volvo dealer here in town were buying 20W50 Castrol oil in drums and using it as their standard engine lubricant. At one time, there were therefore a lot of e36s in Sacramento running 20W50.

I think what I will do is - when summer is over and she is coming back to California from her summer internship, I will tell her to top off the oil with Marvel Mystery oil before she leaves (should take less than a quart to top it off by that time) and drive the car home (12 hr drive) and I will change the oil the night she gets here while it is still hot. Then I will switch it to 10W30 Castrol.

On a totally unrelated note - I have been bragging for years that my wife's '04 330 was totally bulletproof - trouble free. Last night the fuel pump failed and left her stranded in front of the grocery store. So much for a perfect record, but at least it chose a nice place to fail.

[wswilburn]

20W-50 is a little heavy for your engine, but not a lot. The Bentley manual says 15W-40 should be good for warmer climates.

[coolbear1]

Sounds like a good place to start, the vanos and lifters are both oil driven and would most likely respond unfavorably to the heavy oil when it is cold. Also,I had to stop using the synthetics due to oil leaks, they don't bother to tell you that it attacks some types of O rings, and older high mileage cars are most vulnerable.
Let us know if it helps.
Good luck.

[PeterLech]

I would avoid use of a strong engine flush. I had bearing problems on a non-BMW vehicle after trying that. Typically Synthetic oil has a strong detergent effect, but you cannot use it due to leaks.

I have used a quart of ATF on my Porsche 993 to fix a sticky lifter that occurred after a long period of not driving the car that had racing oil in it. It worked quickly and then I changed the oil. I have not have a sticky lifter or any other problems since.

[Manolito]

I have a new theory. It may not be sludge. The check engine light came on and set a code for the cam position sensor. She cleared it and the code came back. I ordered a new sensor and new crush washers for the VANOS oil line and had them shipped to where she is. This looks like a job she can do herself with minimal tools.

On a positive note, she got her ASC light to turn off! Some idiot (who shall remain nameless on the grounds that I may tend to incriminate myself) put the screw on the hose clamp right at 12 o-clock on the new throttle body boot when it was installed. The ASC throttle lever was colliding with the screw on the hose clamp. I found a note on some forum where someone else had done this, so I asked her to check it. She rotated the hose clamp a couple of inches and Voila! no ASC light!