asian_xl

Hi all,


My S320 had engine warning light last month, the mechanic used Star and found out one of the cylinders is not firing, so he replaced the wire and coil. The engine rough rattling is gone, but I still can feel mild rattling at stop.


Should I replace all wires at once or the coils as well? how do I know whether the wires or coils have gone bad?

asian_xl

by the way, the engine was fine before the spark plug change in Jan.
I did not change the coils and wires.

959drew

Inspect the wires and boots for any cracks but I would think if the problem started after the plugs were changed its because something has not been set down properly. Torque the plugs and coils down to spec.

tusabes

Someone else recently change the plugs and one of the plug electrodes broke off , causing the misfire

ibeforreal

You never mentioned how many miles are on the car. I had a similar problem after changing my spark plugs and wires (since I was already in there figured might as well change the wires). Although my car never threw any error codes I could feel a slight hesitation/misfire when sitting at a traffic light. Upon further review I decided to reinspect the wires, retorqued the plugs and the problem went away. I used dielectric grease on the wires. Make sure to push the wires down until you hear a click. It is much easier with the special mercedes wrench to pop those wires off.

asian_xl

My car has 78000km (51000miles), it is a 2000 S320.


I live in an apartment, there is no garage for me to check the connection. If it is misfiring, I guess the engine warning light will come on? that's what happened to me earlier.


Anyway, should I just buy the wires for the mechanic to change first? I don't know how likely the coils are not working properly. Any idea?

wallyp

You don't need a garage to push down on every spark plug connector to make certain that they are all properly seated.

ibeforreal

Agree with Wallyp, no garage needed. However, if you aren't familiar with the wires and plugs on this car you might want a mechanic to do the work. If you get one of those wires crossed up it will cause you a lot of unnecessary headaches.

jnash

If you cannot solve this by pushing down (hard) on every plug wire to the spark plugs you should really inspect every wire connection at each coil and plug. I have seen newish wires fail because they were never properly seated. So, Look for green corrosion inside the connectors.
You can use a large flathead screwdriver or similar to push down hard on the plug caps onto the plugs (carefully). Pushing with your fingers is often not enough to know its seated correctly.

If you want to do a proper service, then replace all plugs and replace the wire sets.
You can get Bosch wire sets from ebay etc. New plugs should be iridium.

Kreuzfeuer

I'm having a few hiccups on my car as well in this same department... M112 Kompressor motor.

Didn't have a single problem until I switched to Magnecor wires. It was so bad, the Magnecor wires would literally slide off the coil packs (even after hearing them "click"). Going back to stock.

Best method I've found is to remove the coil pack, push the plug wires onto the plugs, connect them to the coil packs, and then secure the coil packs to the valve covers. MUCH easier than trying to "stretch" the wires to snap on both terminals.

ibeforreal

Agree with you Kreuzfeuer. Removing those coil packs certainly does make pushing the wires on the plugs a lot easier and must less frustrating. I used both Bosch plugs and wires. Bosch 09850 wires and Bosch iridium plugs.

asian_xl

I asked another mechanic friend to inspect the wires and coils, when we opened the hood, we already see the engine is rocking left and right slightly.


We were doing it without any tools, he only made sure no lose connection, still nothing found, but he is positive the wires are source of the problem. I wonder how likely the coils are bad on these cars? Should I change the wires first and see, or everything together (wires and coils)?

jnash

yes, ensure you have new plugs and wires first. Then use a OBDII tester to see if you have any misfires. If so, then determine which cylinder and switch coil packs with a working cylinder and determine if the problem follows the coil pack or not.