Rough Idle Update on 300TE....I'm totally out of ideas - PeachParts Mercedes-Benz Forum

Ivanerrol · #1 04-08-2009, 03:02 AM

You must have a leak somewhere.

At idle with a warm engine and in neutral the vacuum gauge on my 260e sits at zero - the opposite of the red. With drive engaged it sits slightly off into the main section. Stationary in drive with the AC on, the needle sits about 3/4 to the top - nowhere near the red section.

Get a stand alone vacuum gauge. Go under the bonnet. Disconnect every vacuum line (including the large one for the brake assist) and block the exits off. Connect the external vacuum gauge to one of the outlets. Start eliminating leaks by connecting each vacuum outlet in turn.

Other suspects. The vacuum levels the lights - you may have a leak in one of them or the control switch near the light switch. The heater controls are by vacuum sometimes a controller is suspect and leaks vacuum. Make sure the AFM rubber is leak proof. Make sure the one way valves to the Brake are good. etc etc etc.

A warped valve cover can also cause a problem - even with a new gasket. Does it leak oil? How about the oil filler cap? Tight and the gasket in it good?

The Air fuel mixture must be spot on. The air damper in the AFM set at the correct level.

As mentioned above. The oil level stick has a gasket top and bottom.

With the engine on and car in idle. Can you hear a hissing sound in the interior of the car anywhere? Quite garage and no audio system on for this test.

pawoSD · #2 04-08-2009, 08:23 AM

Quote:

Originally Posted by Ivanerrol

You must have a leak somewhere.

At idle with a warm engine and in neutral the vacuum gauge on my 260e sits at zero - the opposite of the red. With drive engaged it sits slightly off into the main section. Stationary in drive with the AC on, the needle sits about 3/4 to the top - nowhere near the red section.

Get a stand alone vacuum gauge. Go under the bonnet. Disconnect every vacuum line (including the large one for the brake assist) and block the exits off. Connect the external vacuum gauge to one of the outlets. Start eliminating leaks by connecting each vacuum outlet in turn.

Other suspects. The vacuum levels the lights - you may have a leak in one of them or the control switch near the light switch. The heater controls are by vacuum sometimes a controller is suspect and leaks vacuum. Make sure the AFM rubber is leak proof. Make sure the one way valves to the Brake are good. etc etc etc.

A warped valve cover can also cause a problem - even with a new gasket. Does it leak oil? How about the oil filler cap? Tight and the gasket in it good?

The Air fuel mixture must be spot on. The air damper in the AFM set at the correct level.

As mentioned above. The oil level stick has a gasket top and bottom.

With the engine on and car in idle. Can you hear a hissing sound in the interior of the car anywhere? Quite garage and no audio system on for this test.

The US spec cars do not have the vacuum adjustable headlamps.

Ivanerrol · #3 04-08-2009, 09:08 PM

Quote:

Originally Posted by pawoSD

The US spec cars do not have the vacuum adjustable headlamps.

I see that Wagon has Euro headlights. Are these not converted to level control?

pawoSD · #4 04-08-2009, 09:15 PM

Quote:

Originally Posted by Ivanerrol

I see that Wagon has Euro headlights. Are these not converted to level control?

Not usually....my dad's car has euros without the level control as well....

I take it back, he does not have them "without" level control, the level control hookups are present, but it is not used. Someone just put little stubs of plugged vacuum line on them to keep dirt out. They are true Bosch Euros...

ps2cho · #5 04-08-2009, 09:21 PM

Quote:

Originally Posted by pawoSD

Interesting in the video. It really does look like either the idle control valve is fluctuating/hunting........possibly due to the Air Flow Potentiometer not being in spec......or there's a bad vacuum leak somewhere.

12.1 Mpg would point to massive overfueling.....does the exhaust smell like it? Is it clean? I wonder if the timing might be slightly off somehow?

It is clean, yes...but as for the smell...I have a brand new cat in there so that's hard to tell...
I checked the AFP with a DMM and it showed .7v which is on spec. I have replaced every idle air hose in the engine...I just don't get it

I have sprayed carb cleaner all over the engine at every hose and it makes no change.

Is there a way to check for crankcase pressure? Is there a spec for it or something?

Quote:

Originally Posted by Ivanerrol

No guarantee taking it to a dealer will be any good. The local M.B. factory operated stealerships near me have "technicians" instead of mechanics. Many of these technicians are not much older than my M103 engine. They are all geared up to operate on the computer controls of the newer models. - The diagnose and replace system.
When I need advice from them (extremely rarely) they need to call their "old guy" or do a search from their on line manuals. Sometimes they even point me in the direction of an indie specialist - often an old dealership mechanic out on his own.

You would need to find an Indie specialist.

For injection problems I take my cars to a franchise Bosch injection specialist. Even the dealerships send their cars to these guys.

That's what I have read from a number of people.
I took the car to a specialist in Tarzana "Enrique"...and he replaced a hose that he said was leaking and said the car was perfect. It was far from it when I got it back...It was horribly slow and still had a rough idle. He must have adjusted the EHA because I had to turn it richer to get the lost power back. It was horrendously slow. I won't take it back to him again that's for sure.

Quote:

Originally Posted by Ivanerrol

I see that Wagon has Euro headlights. Are these not converted to level control?

They are just DEPO Euros. I have not done any conversions. The stock lights didn't have it either.

pawoSD · #6 04-08-2009, 09:51 PM

Quote:

Originally Posted by ps2cho

It is clean, yes...but as for the smell...I have a brand new cat in there so that's hard to tell...
I checked the AFP with a DMM and it showed .7v which is on spec. I have replaced every idle air hose in the engine...I just don't get it

I have sprayed carb cleaner all over the engine at every hose and it makes no change.

I wonder if a whole new air meter/distributor assembly off of another car would make it run any different. Then you'd be swapping the air meter, Potentiometer, EHA, and Fuel distributor/pressure regulator all at the same time.

ps2cho · #7 04-08-2009, 10:15 PM

Quote:

Originally Posted by pawoSD

I wonder if a whole new air meter/distributor assembly off of another car would make it run any different. Then you'd be swapping the air meter, Potentiometer, EHA, and Fuel distributor/pressure regulator all at the same time.

I have one...so I could. The potentiometer wire is cut off though. Got it one day at the junkyard and went the checkout window with the female who looked new....Charged me like $25 for the whole thing

...but I'd really like to figure out WHY there is an uneven flow of air in the intake manifold. It shouldn't be fluctuating like that...it should be rock steady, right?

But for reference, I have swapped the EHA, fuel pressure regulator, and fuel distributor before....

ps2cho · #8 04-08-2009, 01:57 PM

Quote:

Originally Posted by Ivanerrol

You must have a leak somewhere.

At idle with a warm engine and in neutral the vacuum gauge on my 260e sits at zero - the opposite of the red. With drive engaged it sits slightly off into the main section. Stationary in drive with the AC on, the needle sits about 3/4 to the top - nowhere near the red section.

Get a stand alone vacuum gauge. Go under the bonnet. Disconnect every vacuum line (including the large one for the brake assist) and block the exits off. Connect the external vacuum gauge to one of the outlets. Start eliminating leaks by connecting each vacuum outlet in turn.

Other suspects. The vacuum levels the lights - you may have a leak in one of them or the control switch near the light switch. The heater controls are by vacuum sometimes a controller is suspect and leaks vacuum. Make sure the AFM rubber is leak proof. Make sure the one way valves to the Brake are good. etc etc etc.

A warped valve cover can also cause a problem - even with a new gasket. Does it leak oil? How about the oil filler cap? Tight and the gasket in it good?

The Air fuel mixture must be spot on. The air damper in the AFM set at the correct level.

As mentioned above. The oil level stick has a gasket top and bottom.

With the engine on and car in idle. Can you hear a hissing sound in the interior of the car anywhere? Quite garage and no audio system on for this test.

No hissing sounds. No oil leaks. I have followed the DIY on vacuum detection using the O2 sensor voltage as the meter in the past and didn't find any changes when reconnecting all the vacuum elements.

At idle in drive, it sits just slightly left of the start of red. With A/C on, it sits dead on the very start of red.

The oil filler cap is leaking slightly though...but realistically is that going to really kill my MPG and power...this much? Is there a gasket that goes around the filler hole?

I found a very nice looking valve cover at the junkyard...even better than my one which still looks great. Maybe I'll swap it over to solve the leak?

Quote:

Originally Posted by EricSilver

See my remarks earlier today about cleaning the O2 sensor connector:
water in the floor cure for w124's

Hardly ever rains in CA, and my foot wells are fine.

EricSilver · #9 04-08-2009, 03:22 PM

Quote:

Originally Posted by ps2cho

Hardly ever rains in CA, and my foot wells are fine.

I was referring specifically to the O2 sensor connectors -- to be sure they are secure and not corroded.

pawoSD · #10 04-08-2009, 04:12 PM

Quote:

Originally Posted by ps2cho

No hissing sounds. No oil leaks. I have followed the DIY on vacuum detection using the O2 sensor voltage as the meter in the past and didn't find any changes when reconnecting all the vacuum elements.

At idle in drive, it sits just slightly left of the start of red. With A/C on, it sits dead on the very start of red.

The oil filler cap is leaking slightly though...but realistically is that going to really kill my MPG and power...this much? Is there a gasket that goes around the filler hole?

I found a very nice looking valve cover at the junkyard...even better than my one which still looks great. Maybe I'll swap it over to solve the leak?

Hardly ever rains in CA, and my foot wells are fine.

That doesn't sound right for the economy gauge, in drive mine sits in the black just off being all the way to the left, in Park its all the way to the left, in drive with A/C on it only moves slightly, but still way into the black....nowhere near the red zone.