3/8/08...urgent, Someone Please Help Asap(1990 190e 2.6)

[lsmalley]

my idle is way too high (22-25rpm) on my 1990 190E 2.6 i need to know how to lower this. i just replaced my brakes and rotors in december, but because my idle is so high, they are already squeaking again and it is only march. ive been having to put the car in neutral as i am approaching a red light just to help out on the brakes. im not mechanically challenged, but please be specific in telling me exactly where i can find certain engine parts related to the problem (overload protection relay, airflow valve.....all familiar terms, but i have no idea where they are or what they look like). pictures or diagrams would also help. thanks.

[downeywu]

it could be as simple as a sticky microswitch...but if u want to be real lazy and have a temporary fix you can unplug your IAC..which is something i did until i was able to find out what was causing my high idle

[lsmalley]

where is the iac? what is that? where is the microswitch?

[have mercy]

Having problem with 300 to .OVP>behind battary U/red with cover over 1-2 fuses your should have 2 -10 amp fuse (plug in type) Air flow (looking at engine from left side remove air cleaner (watch little hose>goes to fuel pres. regulator)this can mess up idle to infront of where air goes in (fuel lines hook up to it) Air flow sensor under where air goes in .wire comes out plugs in close to fuel pres.reg. 4 prong?

[lsmalley]

will unplugging that switch mess anything up? do i just leave it unplugged or what? someone please advise?

[EricSilver]

Originally Posted by lsmalley

will unplugging that switch mess anything up? do i just leave it unplugged or what? someone please advise?

It's a switch under the air cleaner, connected to -- or rather, nudged up against -- the throtttle linkage. I had the same engine in my 260E and that caused the high idle. The part is called "Thrust Cutoff Switch."

It is a fast, easy, inexpensive repair.

[EricSilver]

In fact, it is available right here (click "Buy Parts" above) or this link.

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2BG122QHI2BG122XS1&year=1989&make=MB&model=260-E-001&category=All&part=Throttle+Microswitch

$27.00 and your troubles should be over.

[EricSilver]

Originally Posted by lsmalley

my idle is way too high (22-25rpm)

When I had that issue (on the 260E) the high idle was around 1500rpm. Yours seems unusually high. (At 2500 rpm I am doing about 55mph+).

[lsmalley]

cool. i just went under the hood and found the switch. i unplugged it and plugged it back in and i found the other one with 7 pins and loosened it up slightly as i have unplugged it and found my car idle so low to the piont it was gonna shut off. i am testing my car now (remote start is the best!) and so far so good....now if i can just pass smog and get my emissins level low....im at 128 (hc) and the max is 114....any suggestions? does that stuff you put in your gas tank help? its like the never ending battle

[EricSilver]

Originally Posted by lsmalley

does that stuff you put in your gas tank help? its like the never ending battle

If your throttle/thrust/micro switch has failed, unplugging and replugging will not help. You need a new one. Do you know, for sure, whether it is this switch, or the IAC, that was the probnlem?

For emissions, Techron helps; can't comment about other additives. Just make sure there is none of it left in the tank when you get the test, or it will send your HC numbers off the chart.

High HC can be caused by of incompletely burned fuel, or piston rings that are not sealing. AutoRX will help with ring issues, but not quickly.