seagel1000

Hey everyone:

My car has this weird idling issue. On to the point, this issue has been on and off for about a year now (maybe 14-15K miles, i currently have 74,850 on the odometer). Basically in the morning or when the car has a chance to cool off for more than 3-4 hours, many times (maybe half the time) the car has a "purring cat" idle. It goes from 700-600/580ish on the RPMs. When it does dip down it seems like if an vac hose has been unplugged but not to the point where the car wants to turn off. It is pretty annoying because the people that ride with me at times ask me why it has such a rough-ish idle. It happens on and off. I would say every other time i start up my vehicle in the morning. No CEL or codes are detected by the ECU nor has the car shown me any major issues. I do hear a hissing sound when the RPMs dip from 700 right at the A/C compressor as if it making a loud "SHHHHH" sound. Not sure if that is related. I recorded the video on my iphone but need to figure out how to transfer it. Sometimes it'll do it if i turn on anything that has to do with the heating or AC (A/C, heater, defroster, etc..)

Any help is appreciated and suggestions taken...

Chris

seagel1000

Also, what is the normal idle range for my car (2005 C230 1.8L Kompressor Engine)

LILBENZ230

Has your car had the $12 hose recall performed? I'm not sure.. my RPMs dip suddenly sometimes at low speed. I think Glyn told me as O2 sensors get older they don't cycle like they should and this could cause it, but I can't be sure. Maybe he can chime in. My car idles (and always has) between 700 and 800 RPM when warm and at 1200 at first start of the day.

seagel1000

I never looked into the $12 hose replacement actually. I know around Sept of last year i took it in with one of the top MBZ tech who is a good friend of mines did all the recalls MBZ had for the C230K or the M271 engine 1.8L. But i can check. Shouldn't be hard.

Glyn M Ruck

Check the hose replacement. It could be an air leak. It could be an O2 sensor. It could also be a troublesome throttle body actuator. This would be aggravated by the aircon loading the engine.

Please do a throttle reset to make sure the pedal is talking to the throttle plate properly. See DIY stickies.

pogijeffrey

i've been having that same problem for 1 1/2 years now. i took it to the dealers to get it checked, and could never duplicate the problem or figure what it could be. now i'm over 100000 miles on the car. with that stupid idle problem coming back every now and then. mostly happens when i have the A.C. on...

AdidasC230

Did you check the IAC, and see about cleaning the throttle body? In the volvo world a rough idle could be caused by a dirty TB

Glyn M Ruck

In the Benz world a rough idle can be caused by a failing TB actuator.

seagel1000

Glyn

Where can i find the TB act.? Also, is there a way i can test it voltage wise with a multimeter tester?

Chris

Glyn M Ruck

It's under a black plastic cover on the side of the TB. These damn things chatter but read properly & don't throw a code unless they go open circuit. One of our moderators - nlpamg (Phil) had all kinds of hell with his until he replaced the TB & his idle has been perfect since then. The dealer also had a hard time with it.

Here's his pdf on accessing & cleaning the TB with splinter. Also read his rough idle thread

seagel1000

Ok. So i checked the hose. This is the # i found. A203-018-12-82. It had the turquoise mark at the manifold intake side of the hose. I also inspected the hose carefully. I installed it back on the car and blew on it, seems good.

Hmm. Don't know what else it can be.

Chris

Glyn M Ruck

Start by cleaning the TB. Do you have a good friend who could loan you a known good throttle body? I know they are expensive. That's where dealers have an advantage over us DIY'ers. They can try a new one from spares & return it if it does not fix the problem.

I presume you are happy that you don't have leaking cam sensors or CPS trouble? These generally throw codes so I'm doubtful

seagel1000

Correct. No leaky cam sensors. My tech friend did all ye recalls possible at the time (Sept 08) including even replacing the magnets and sleeves and sensors just for kicks as well as the $12 buck hose it seems. I've never seen a code on my vehicle since I've owned it Oct 07. Other than the time I had to get my thermostat replaced but the code dissapeared after replacing the stat. It was related to a code identified as too cold of a start up but like mentioned it was gone after the thermostat job. Car has been good since.