87' 300E power loss
 

Since you people helped me out with my defroster problem I though I would throw another one out there. Once my car is warmed up and I stop at a stop sign or just slow down in traffic and try to accelerate again my engine seems to bog down or not respond to gas pedel. It usually picks up power again slowly. runs great at high speeds and idle fine. The rpm's seem to stay up and the car doesn't stall. Is there any vacuum problems associated with the transmission perhaps Any Ideas out there.
Thanks
Vinnie Laraia:confused:

Vin:

You have a vacuum leak, most likely at the idle control valve. Those big rubber hoses get hard, shrink, and fit loose with age. All the rubber vac hoses on the engine are likely to be bad by now, I'd replace them all. The plastic lines are probably OK. If you have harsh tranny shifts and the defrost comes on when you accelerate, you definitely have a vac leak.

The vac leak means that when you open the throttle, no air goes down the fuel metering flap for a second, so there is no throttle response. If it then suddenly roars off, this is even more likely.

It's also possible that the throttle posistion sensor "pot" on the side of the throttle body is bad, too, so that you dont' get good enrichement on throttle opening. It can be replaced.

Peter

87' 300E power loss
 

Thanks Peter I will check it out as soon as I get a chance. I figured it must be a vacuum problem but didn't really know where to start. where is the idle control valve located.
Thanks Vinnie

Hesitation Problem
 

I had a hesitation problem with my '88 260e that turned out to be the EHA. My car would run fine when first started and after it was warmed up but during warm-up would hesitate badly. I suggest checking simple things, such as vacuum leaks and adjusting the fuel mixture to specs with the engine warmed up first before replacing the EHA.

Vin:

Idle control valve is under the air filter housing, held down with a strap. Single two-wire connector and two large hoses. Check the hoses -- mine were actually loose on the barbs. They are a pain to replace, but it cured the stagger at takeoff!

Peter

Similar 87' 300 power loss
 

Hi,

I have a 1987 300E, completed tuned up and replaced two fuel pumps last months because the car has been neglected excepting adding water and oil. The car starts fine however when the speed is gradually increased 20-25 mph the car would hesitate then pick up the speed, the engine rpm would increase from 2000 rpm to 3000 rpm then drop down to 2000 rpm, after that it seems fine without any problems. When returning home, I have to drive up a slightly steep hill, the car would, sometimes, behaviors the same and hiccup 3-4 times when I press the accelerator along the climb. Do I have the similar problems, as posted this thread #16215 and I should check vacuum leaks and adjusting the fuel mixture and EHA?

Approximately how much would it be costing me if I let a mechanic, specializing in Mercedes but not from dealers, to do the work? Certainly I hope my problems have nothing to do with the transmission.

DL

Getting closer
 

I think I am getting closer to my problem. I hope.
I finally got to check out vacuum hoses and idle air control and they seem fine. For some reason when the temp. gets up to 80-90 C the mass air flow I guess you call it a butterfly does not open all the way when the throttle is opened it only opens a little and you can hear the engine bog down but the engines rpm's still stay up to 7-10k but the mass air sensor doesn't open enough to let more air in. If I open it by hand the engine revs up.What controls when it opens and closes. Is there a cold start valve that controls this. My car idles fine. Only seems to lose power once engine gets up to operating temp.
Thanks Vinnie

It's not supposed to open all the way. If you rev the engine with no load it will only open a small amount.

What controls it is the air passing through it into the engine. In fact, its function is to measure how much air is passing through and report to the KE Computer.

87' 300E power loss
 

But when the engine is running OK the butterfly seems to open about double the amount as when it isn't runnig well. Is there an air flow sensor that tells it when to open or close.
Thanks
Vinnie

Probably a sticky control plunger or bad seals. Also can be dirt in the ventrui causing the plate to bind. With the engine off, press it down and take a paper towel wetted down with carb cleaner and wipe it all clean. May fix it.

Otherwise, you will have to remove the fuel distributor and remove the plunger, inspect it, and clean it. If it is scored or has ridges, it will cause the symptoms you have, but replacement of the plunger may also not fix it. May need a new fuel distributor ($$$).

Peter

Re: 87' 300E power loss
 

The butterfly IS the airflow sensor. It's entirely mechanical and is moved by the air going into the engine. As it moves down it enriches the mixture mechanically and sends an electrcal signal to the computer. Does it move smoothly when you push it down with your finger (engine off)?

i'm trying
 

The air flow sensor doesn't seem to hang up when i push it down slowly with my finger with the engine off and the rim is clean. It will open about an inch when the engine reaches operating temp. and I give it some throttle the plate stays where it is and it seems like engine is getting to much gas (poor gas milage too) and not enough air flow. Peter how hard is it for me to replace seals or clean the plunger. If I let up on throttle air flow closes and car idles fine. The Temp. it only seems to happen as the car reaches operating temp. 80-90C this has me a little frustrated.
Thanks

Vin:

you need to get a digital VOM that does duty cycle and test the fuel control system. Described many times on this forum, but the basics are that with the red lead connected to pin #3 of the round diagnostics connector and the black lead in #2 (or another ground), the duty cycle reading shoudl be around 50% and fluctuating on a warm engine. Should to low (I believe, check the DIY engine controls post) as the throttle is opened and drop back to 50% or so quickly. Should go way high on coast (fuel shutoff), returning to 50% when idle is achieved.

Check the idle switch on the linkage -- if it is failed, you would be in idle condition all the time, this will goof up the running mixture. So will a bad engine temp sensor.

Peter

Re: i'm trying
 

That plate should be barely cracked open at idle. It's open an inch??

I see you have 2 300Es. Have you looked at the other one to see how far it opens?

We ARE talking about the round metal plate right under the air filter, right?

87' 300E power loss
 

Right.... Yes it only opens a crack at idle. When I give it throttle it opens further. If I really rev it up the plate drops down about another 3 inches. However during the transition from cold to warm there is a point when it is almost to full operating temp. that plate will only open about an inch or two even when I rev the engine. And when I do its almost like its choking for air. if I push the plate down by hand as I give it gas it seems to run ok. I have never had this happen twice while driving. It happens once just as the engine warms up to operating temp. I have a multimeter without a duty control (below) and I hooked it up and set it on 20 DC as shown. I put in in #3 and grounded it with just key on. Got 6.6 reading. I started it and as engine warmed up it dropped. When fully warm it stayed steady at 1.07. Does this help or do I need one with duty cycle.
Any help to you guys. I also tested the engine temp sensor when fully warm and it reads .52 ohm 's.
Thanks Again for trying to help a benz newbie out
Vinnie