nycloving

ML320 2001 190k. I replaced the EGR valve, cleaned the tube thoroughly, replaced all and the truck ran fine for two months or so with no codes. A noticeable shaking at idle appeared and I rechecked the vacuum hose connections associated with the EGR replacement and found one lose connection at the air distribution hose connector above the main intake area. The idle improved and the shaking stopped, however, after a 5 mile drive, a very large thick, gray smoke plume came bursting out of the exhaust. It stopped a few minutes later, but continues to come out in a steady, smaller amount for a minutes after a cold start or after the truck has sat off for a few hours. There is no noticeable lose of engine oil, coolant or over heating, yet, as it has only been 24 hours. I suspect a clog somewhere in the vacuum system, maybe in the valve covers, but may be wishful thinking. The check engine light comes on and the only code is PO301. I ordered new spark plugs yesterday. Any ideas?

art_arev

P0301 is cylinder 1 misfire. Check the spark plug wire. Replace it with a similar one from another cylinder & see if the code will shift. If you get the same code, change the coil & see if the code shifts.
Plugs you ordered already.......Have you got the spark plug wire remover? You wont be able to change the plugs without it......

nycloving

Thank you Art for the advice on the wire and coil, that makes sense and I will try it this weekend. I do not have the spark plug wire remover and will look for that to order. I am a little concerned that I did not have any smoking issue until I removed the air filter and air intake pipe to the actuator when looking for the vacuum leak. The leak turned out to be from the air distribution hose connector at the top of the accelerator actuator, so I made sure that it was fitting snugly. put everything back, it idled smoothly, but then the burst of gray smoke from time to time, mostly at start up. Thanks again and I will definitely try this then update over this coming weekend.

art_arev

While you are at it you can also check that the Air Intake pipe is properly sited & clipped in correct position. Remember that ,even air leak in the intake pipe will create problems. You will have unmetered air entering the system which will confuse the Fuel mixture ratio......... So make sure all components of the Air Intake Pipe are properly secured & positioned.

nycloving

yes Art, I suspect that I should take off the pipes and hoses again and make sure that I seat all correctly.

nycloving

I replaced the plugs today; cylinders 1 and 4 plugs were caked with black carbon. The 17 mm offset wrench made the plugs replacement a breeze, thanks Art! The check engine light is staying off, but I am still getting a periodic plume of dark gray smoke out of the exhaust. Again, this smoke did not show up until I removed the air intake and other hoses to replace the EGR valve. After the replacement, ran fine for several months, developed what I thought was a vacuum leak and PO301 codes. Checked vacuum hoses by removing intake and hoses + connector, replaced and then developed the gray smoke problem, which I have confirmed is oil. Any ideas

art_arev

Clear the codes & rescan the car.

Maj. Dundee

Did you remove the #164 valves from their respective hoses?

Are either of the two clips broken on the air intake tube?

With the engine cold, disconnect the three hose ends from the valve covers, start the engine and see if smoke comes out of the valve cover nipples. Continue to run the eng. and observe nipples.

nycloving

Maj. Dundee, thanks for the schematic and response. I just removed the #164 valves and replaced the distribution #158 and checked the intake pipe connection last night. There was no smoke this morning, drove about 20 miles with no problem and then got the smoke again. I believe the connector at the bottom of the intake pipe is not making a "clip" and I am not sure if it goes "into" an opening or just clips over a lip. It is very difficult to see under the pipe working by myself. Do you know how that clip works? I may have broken it, although it does not appear to be broken. Thanks for the help.

Maj. Dundee

It clips onto the lip of the throttle actuator.

Did you remove the three hoses and run the eng. as I suggested?

You have to respond to all suggestions or this will be a waste of time.