How to adjust idle speed (2.6)?

[LittleB]

There is a screw or knob adjustment for the idle speed, like in most cars, right?

While in P or N it idles at about 750 rpm, and while in D at about 550 rpm. It really rumbles at stoplights. How can I adjust it, and what speed should it be at?

[weneakhborz]

i belive it is not that easy..
wait untell the experts answer you

[PhilipM3]

I have the SAME problem. Only now I think I have an intake gasket leak so it idles great lol.

I havent heard of actually adjusting the "idle" You can change the air/fuel mixture. That is in the center of the air box, there is a hole on top. Stick a hex key in it and turn it 1/4 a turn at a time till you have the right adjustment. Some of them, like mine, are actually caped off and I cant adjust it without grinding down the cap. You can remove your air box completely to get a better view and see if yours has been capped also.

With all that being said, I dont recommend adjusting this. Take it to (MB/your mechanic) have them set it at the right mix.

Good luck.

[Holson]

Originally Posted by LittleB

There is a screw or knob adjustment for the idle speed, like in most cars, right?

While in P or N it idles at about 750 rpm, and while in D at about 550 rpm. It really rumbles at stoplights. How can I adjust it, and what speed should it be at?

I have a 190E 2.6 and it idles at the same speeds as yours. My 95 E420 did and so did my 2001 CLK55.

I think it's OK, what's the issue? Is it stalling?

[PhilipM3]

Originally Posted by Holson

I have a 190E 2.6 and it idles at the same speeds as yours. My 95 E420 did and so did my 2001 CLK55.

I think it's OK, what's the issue? Is it stalling?

He says it rumbles, which I believe means it shakes, as does mine. Your other 2 cars tho were electronic fuel injected as to the 190's we have which are mechanical. Sometimes the air fuel mixture, due to time i suppose moves a little. So even tho he may not raise his idle, he wants to smooth it out so it doesnt shake.

[spinlps]

I had the same problem with my 92 190e 2.6 and found this in the E-Class Owner's Bible regarding the M103 engine:

"Some M103 engines develop a slight hesistation off the line when the engine is cold. They may also cold start instantly and then die, but restart easily and then continue to run. By adjusting the fuel distributor lower chamber pressure to 0.45 bar (6.5 psi) instead of 0.4 bar (5.8 psi), both of these symptoms tend to disappear. The car also seems much livelier off the line and idles better when cold.

You are not really richening the mixture when making this adjustment. Instead the adjustment is compensating for basic wear and tear and any unmeasured air leaks that have developed over the years. You will need a CIS fuel pressure gauge to measure and adjust the fuel pressure. If you reset the EHA, the idle mixture should also be checked and adjusted. Refer to the factory repair info on making this adjustment."

I showed this to my new indy tech the first time I took the 190 in and he said, of course, we do this all the time. He turned the knob 1/8th of a turn and it measured spot on at 0.45 bar.

The car runs MUCH better now and idles at just over 750, about 800 after warm up.

[PhilipM3]

Originally Posted by spinlps

I had the same problem with my 92 190e 2.6 and found this in the E-Class Owner's Bible regarding the M103 engine:

"Some M103 engines develop a slight hesistation off the line when the engine is cold. They may also cold start instantly and then die, but restart easily and then continue to run. By adjusting the fuel distributor lower chamber pressure to 0.45 bar (6.5 psi) instead of 0.4 bar (5.8 psi), both of these symptoms tend to disappear. The car also seems much livelier off the line and idles better when cold.

You are not really richening the mixture when making this adjustment. Instead the adjustment is compensating for basic wear and tear and any unmeasured air leaks that have developed over the years. You will need a CIS fuel pressure gauge to measure and adjust the fuel pressure. If you reset the EHA, the idle mixture should also be checked and adjusted. Refer to the factory repair info on making this adjustment."

I showed this to my new indy tech the first time I took the 190 in and he said, of course, we do this all the time. He turned the knob 1/8th of a turn and it measured spot on at 0.45 bar.

The car runs MUCH better now and idles at just over 750, about 800 after warm up.

Very helpful! Ill give this info to my tech.

[Holson]

Originally Posted by spinlps

I had the same problem with my 92 190e 2.6 and found this in the E-Class Owner's Bible regarding the M103 engine:

"Some M103 engines develop a slight hesistation off the line when the engine is cold. They may also cold start instantly and then die, but restart easily and then continue to run. By adjusting the fuel distributor lower chamber pressure to 0.45 bar (6.5 psi) instead of 0.4 bar (5.8 psi), both of these symptoms tend to disappear. The car also seems much livelier off the line and idles better when cold.

You are not really richening the mixture when making this adjustment. Instead the adjustment is compensating for basic wear and tear and any unmeasured air leaks that have developed over the years. You will need a CIS fuel pressure gauge to measure and adjust the fuel pressure. If you reset the EHA, the idle mixture should also be checked and adjusted. Refer to the factory repair info on making this adjustment."

I showed this to my new indy tech the first time I took the 190 in and he said, of course, we do this all the time. He turned the knob 1/8th of a turn and it measured spot on at 0.45 bar.

The car runs MUCH better now and idles at just over 750, about 800 after warm up.

Hmmm I have a hard cold start just like that - it seems like it's starved for fuel. I'm gonna bring this up to my mechanic, thanks!

I do have that w124 owner's bible, it's a pretty good read

Thx,

[sun111]

I wouldn't mess with mixture, carbonized plug, idle microswitch not actuated by throttle assembly, vaccum leak at idle control valve or sticky, insufficient voltage to distributor, coil wire faulting to ground, look for blue sparks in total darkness, while engine is running, fuel pump relay weakening, IDLE POSITION SENSOR wiring or gunked up throttle body.

[LittleB]

Originally Posted by sun111

I wouldn't mess with mixture, carbonized plug, idle microswitch not actuated by throttle assembly, vaccum leak at idle control valve or sticky, insufficient voltage to distributor, coil wire faulting to ground, look for blue sparks in total darkness, while engine is running, fuel pump relay weakening, IDLE POSITION SENSOR wiring or gunked up throttle body.

I noticed one day that there are blue sparks in the spark plug wires in total darkness, is that what you meant? Like I can see the sparks through the rubber insulation. They don't look like OEM wires (from what I've seen at the junkyard).


P.S. Thanks everyone for your replies.

[sun111]

the wires are attempting to ground, see what they are touching in light i.e. other wires, grounds. Mild sparking is expected, factor of resistence, I know that regular copper plugs are recommended for 190e's, platinum has a higher resistence and I know this will meet with some resistence (ha ha) in this forum, a MB tech to me this. It might be time to change distributor cap and rotor, mainly focus on coil wire routing, It should only touch rubber.

[sun111]

It may be time to replace your alternator, low voltage causes a lot of resistence, I switched to a 90amp form a 70amp. Mb shows both as replacements. I had the same symptoms your describing. Try loading your electrical system defrost and all lights on, see if idle increase to 725 when you switch them off. fuel pressure is crucial with this type of injection, fuel filter.

[sun111]

93 octane

[sun111]

egr sticks open a little, i lubed the piston from top and sucked and blew on it a couple times to free it from carbon.