Mercedes-Benz Forum banner

1 - 12 of 12 Posts

·
Registered
1966 230S, 1991 560SEL
Joined
·
31 Posts
Discussion Starter #1
I replaced my passengers side fuel injectors, and all the seals, etc. Since I broke one vacuum connector, I just did the passenger side. (I temporarily fixed the vacuum leak, until the correct parts come in). But now it feels like its misfiring on idle, and the idle is too low. I test drove it, and it died multiple times when coming to a stop, but restarting is no problem, just too low idle. I put in the original injectors again, but it still feels like a misfire on idle, and that the idle is too low. It is my daily driver, so I have to drive it top work like this, and recommendations? When the vacuum connectors come in, I will obviously also do the drivers side fuel injectors.
Thanks
 

·
Registered
1990 420 SEC
Joined
·
106 Posts
To find out what is going on you could try disconnecting electric connector from idle control valve. That should make idle too high. If not then someone has been plugging idle control to get car idle somewhat normally with faulty idle control. Now that vacuum leak is gone engine is not getting enough air (if idle control was plugged).

Unless this problem has something to do with EGR which I'm not familiar with at all.
 

·
Registered
1966 230S, 1991 560SEL
Joined
·
31 Posts
Discussion Starter #3
I disconnected the electronic idle control vale, no difference. How much higher should the rpm's have gone when I removed it. Maybe I damaged the ICV when cleaning the engine, or while changing the injectors? My current idle is around 450 in drive. Before it was around 600-650. But when I accelerate the engine acts completely normal, is this a symptom of a faulty ICV? Thank You
 

·
Registered
1966 230S, 1991 560SEL
Joined
·
31 Posts
Discussion Starter #4
I unplugged the idle air control valve, to take a closer look. When I shake it, I can hear the slide move, which means it's broken, correct? I guess I have to order a new one. Found them in germany for around $120 from LÖWE. Please correct me if anything is wrong.
 

·
Registered
1990 420 SEC
Joined
·
106 Posts
When cable disconnected it should idle around 1500 rpm on neutral. Faulty valve usually causes high idle. That is then corrected by placing some kind of restrictor to idle passage as original valves are expensve and hard to find. Try finding that restriction someone has hacked in and make a bit larger hole to it. Now that there are less air leaks there is not enough of air for the engine to idle. Something in the valve moves when valve is shaken. That is normal. Try blowing air trough the valve. It should flow quite freely when no voltage at the coil. There are threads of fixing high idle here, there is a service manual in the stickies covering idle system testing and lots of YouTube videos on the subject too.
 

·
Registered
W107 W113
Joined
·
1,292 Posts
What is your "economy gauge" (vacuum gauge) showing upon start up and idle?

Then you should check the duty cycle to see if it's running too lean or rich.

Sent from my MAR-LX1M using Tapatalk
 

·
Registered
1966 230S, 1991 560SEL
Joined
·
31 Posts
Discussion Starter #7
My economy gauge is around 7-8mm from pegged to the left, but as soon as I apply throttle is goes pegged to the left? Which is wrong, so I created a vacuum leak, I think. But the ICV is still broken, because there is no difference when it's disconnected.
 

·
Registered
1990 420 SEC
Joined
·
106 Posts
If there is voltage at the cable and disconnecting it does not affect idle speed then the valve is no good. If idle is too low there might be no voltage at the cable from idle controller and disconnecting the cable does nothing. Pull the cable partially out so that valve pins are visible and measure the voltage while car is idling.

Did you take the rubber hoses and elbows next to the idle valve apart to see if there any objects that do not seem to belong there placed to restrict the air flow? That is the usual hack to get around from fixing idle control properly.

Applying throttle should do the same thing as disconnecting the cable from the valve except it disables idle signal from throttle body. Where does the needle go if you run the engine at desired idle speed by applying throttle? Too low idle could well cause low vacuum (needle not all the way to left).
 

·
Registered
1966 230S, 1991 560SEL
Joined
·
31 Posts
Discussion Starter #10
I checked both elbow fittings, but there is nothing out of the ordinary. I also tried to measure the voltage, but I don't how how, could you further elaborate on how the measure it? Thank You
 

·
Registered
1990 420 SEC
Joined
·
106 Posts
Connect/ disconnect the connector partially so that you can see some of the connector pins. From the pins you should be able to measure control voltage to valve. The lack of voltage there should allow high idle so this is not a primary problem.

Anyhow could you still blow trough the valve and the hoses it connects to? Air should flow quite freely trough them. If it is so then there is something else going on.
 

·
Registered
1985 500sel and 500sec 2012 E63 1989 Porsche 911
Joined
·
5,063 Posts
could it also be a fuel dist. issue, i had this in my 500sel, which i will post about in near future

also for my SEC which was idling too high when i got it, my mechanic rigged this up to manage the idle

2607611
2607613
 
1 - 12 of 12 Posts
Top