technsandiego

My ML 500 has developed a miss while under acceleration. I have narrowed it down to the #8 cylinder with my trusty scanner.

Can this be a serious repair issue about to occur with the motor or ???. I'm a DIY mechanic but my iCarsoft Professional Diagnostic Scanner Tool either doesn't have that level of detail or I just don't know what to look for.

Maj. Dundee

There are six different things that can cause misfires:

1. faulty spark plug, 16.

2. faulty ignition wire, 16.

3. faulty ignition coil, 8.

4. faulty injector, 8.

5. too much fuel or too little fuel being delivered, fuel pump and or fuel filter.

6. eng. mechanical, valve or piston, etc.


Each cylinder has 2 spark plugs, two ign wires, and one coil.

Start by removing both spark plugs on cyl. #8 and inspect them. If they do not looked damaged, reinstall. Special tool needed to remove the ign. wire boot from spark plug. Do not pull them off by hand as they will be damaged.

The next is to remove one spark plug wire at cyl. #8 and swap it with one on cyl. #5. Clear the code and see if it is still on #8. If so, swap the wires back where they should be. Then repeat the process for the second wire on #8.

If the code is still on #8, remove the coil on #8 and swap it with coil #5. Those two coils can remain where they are.

Post back with results.

technsandiego

Maj,

Thank you so much for your help. As a new MB owner I truly appreciate your assistance with all my questions. I will be performing a lot of the work myself and staying clear of the dealer as much as possible.

All the Best!
Chuck
qkdnue0977@att.net

Maj. Dundee

You are welcome.

Forgot to include the firing order.

jacobsung

If you don't want to blindly replace plugs and wires, you can swap with another cylinder, and see if the misfire moves to another cylinder.