cnn

Hi, I just bought an SL500 1998 80k miles and drove it for 200 miles, no problems. Then I took it for a oil change (Mobil One 5w30) and 5 minutes later the check engine light came on. I took it back to the place and they pulled the code which said 'Cylinder 2 Misfire', they cleared it and said that it had nothing to do with their oil change.
Is it possible that it has to do with their oil change (Check Engine Light) something or is it just a coincidence ? It seems to run fine now, should I check spark plugs and coil packs ?
I am a little panicking sicne I bought the car 4 days ago,

ohlord

5w30 is the wrong oil.
mobil 1 0w40 synthetic is the correct oil.
Check that the wires are properly pushed onto the plugs.
Clear the code with an obd2 scanner(59 bucks at harborfreight) or others and see if it returns.
Last check oil level,if the shop that put in the wrong spec oil overfilled it that could lead to a misfire condition.
Last last if you bought it and had not had a pre purchase inspection performed,The person or place that sold it to you could have erased codes((which could have been discovered with a good inspector looking for hidden stored codes) and now that you have driven it the codes have reappeared.

cnn

ok, update, I went to a shop and they diagnosed a bad coil on cylinder 2. They said it has nothing to do with the oil change. They replaced the coil and charged me 240 USD. I took the car (no CEL) and 4 miles later: same problem: check engine light and running only on 7 cylinders. I go back to the shop and they told me that they would not have reset the computer COMPLETELY. So they they reset the computer again and I took the car. Now I drove about 15 miles without problems, but I really don't feel good. Is it possible to clear the codes not completely ?

cnn

ok I drove about 40 miles in 2 days with no problems. To summarize: the shop has changed my coil and reset the codes twice (!). I will closely watch what is happening next (my oil pressure is ok with 5W30 and I have no CEL anymore). My 90 day drive train warrenty didn't cover the cost. I am shopping for a OBD2 reader as well. Keep you posted.

hineywineries

There are several points. First of all I agree with the repair facility that the oil change probably had nothing to do with the CEL or misfire.Assuming they diagnosed the problem in depth, it is possible for a second coil to fail and not have anything to do with anything else. Also a check engine light has nothing to do with the running of the car. You can drive across country with a check engine light and have no problems. The check engine light is merely an indicator that an event occurred, and a code for that event is stored in the main computer.

You can buy a scanner if you want, but a scanner alone won't tell you very much. It will only tell you that there is a problem, but not necessarily what is causing the problem. As an example: the number two cylinder misfire doesn't necessarily mean there is anything wrong with that cylinder. You need a scanner that not only reads codes, but can read voltage, currents, and things like fuel trim. If fuel trim is way out of specs it can produce random misfires, and cylinder number two was unlucky enough to get caught.

cnn

Thx for all your answers, I finally got it figured out:
Most likely the dealer pressured washed (detailed) the engine and water got stuck around my spark plugs, which finally led to different misfires. I replaced the plugs and all seems fine now.
I am still trying to find out what I should do concerning my oil. It seems as if they put 5w40 ( Mobil 1 ) in my car (SL500 98), should I get it changed ( I mean it's a hundred bucks and I have new oil right now) ? What can happen when I drive this oil until the next oil change is due ?

hineywineries

It kinda depends on where you live. If you live on the Siberian border, you may want to change it. Oil viscosity is measured in Saybolt seconds.They use a structured test to determine how many Saybolt seconds it takes for a given weight of oil to pass through a specific orrifice. The only reason you need to run synthetic in a 98 is bevcause the flexible service system is caliberated for it.

Post Script: I got thinkin about it, and someone is going to try to nail me for my answer. The SAybolt second is not used much anymore by SAE, but was the original method for measuring viscosity. I had to learn all this in tribology school.

cnn

I live in Texas, where it's about 5 C in Winter and 40 in the Summer (friggin hot). Actually I did notice a ticking sound when the engine is warm (sounds like a lifter). My oil pressure is 3 when idling and falls to 2 when driving.

Rocco Vespe

Probably a faulty ignition module- try replacing

hineywineries

CNN,
A pressure of 2 bar while driving is totally unacceptable. You possibly have a defective oil sender or dash gauge which I doubt. I suspect a defect oil filter. Hopefully you are not getting your oil changes at goofy lube.You are driving a very sophisticated and well engineered machine, so don't screw it up with cheap oil changes. If you do not have the mechanical skills to do the work yourself, I suggest you find a good independent that you can trust and work with to keep you on the road.

cnn

Hi Hiney,
What should be my oil pressure ?

Ausmbtech

I'd definately be getting the oil pressure confirmed with a mechanical gauge, oil pressure dropping when driving isn't good. 2-3bar cold idle, above 1bar hot idle is fine as long as it rises immediately when revs increase and reaches 3 bar above 1500rpm hot.

If it doesn't reach this pressure then I'd be putting in a genuine oil filter and taking the rocker covers off to the check oil bridges for the lifters. they either break or the seals leak which can easily reduce oil pressure and cause noisy lifters.

As for your misifre problem, I would definately consider checking the cam timing as these engine do have a little habit for jumping a tooth on the cam and it's a bit of a ***** of a misfire to chase. If it's happened immediately after an oil change then it's definately something I'd be checking very soon!!!!
It's an easy thing to check with the cam covers off.

hineywineries

AUSMBTECH answered the pressure question in his first paragraph.

cnn

Ok, ticking gone..I replaced all 16 connectors with blue aluminum ones (430 USD just in parts )...the valve cover gasket gave me a hard time..other than that ....it seems to work fine. One was bad. My pressure site now most of the time (idle, reving, driving) at 3, sometimes after a long drive it goes down to 2. Is that considered ok ?
I got the misfire solved too...wet spark plugs.

Let me know if you want pictures.

RickP330

Sure! The more the better! Manual states that the gauge may fluctuate, but as long as it rises under revving it is ok.
RP

cnn

pictures:

hineywineries

cnn,
Congrats and thanks for posting solution. Many on this site ask for help, and when they get it they don't bother to make a final post with fix. They name streets after people like that. They're called ONE WAY.

casper_c230

Did I read that right? $240 to change one coil? I'm sure you got a free inspection and car wash too. I'm not trying to make you feel bad b/c it's a learning lesson but coils are $40/each at least for my car. I can't imagine they're that much more for yours and the installation should be pretty straight forward. Remove the engine cover, remove two bolts securing the coil pack and just swap. It's easier than changing spark plugs. Again, don't feel bad. I paid $55 at Jiffy Lube for a $12 cabin air filter b/c the guy told me it was the same price everywhere. Liar! It's the same price alright, $12 but $43 installation? Ugh.

cnn

yep, they ripped me off

hineywineries

Nope, they're called monitors, and the car has to be driven several miles to reset them. Standard procedure.

abiby

That sounds pretty cheap. Where do you buy parts?