300E 1989 Mercedes Idle control valve and oxygen sensor 

Your are my favorite W124 instructor. Thank you for sharing to our Merc's lovers.

To check for vacuum leaks, remove your air filter and check all the small vacuum lines for cracking and damage where they connect, usually they are brittle and cracked from engine heat. There could be an air leak on the idle air control valve. There are two short rubber hoses that attach to it and it sits right under the air filter housing. The hoses may be cracked and leaking. During warm-up and at operating temperature, current to differential pressure regulator is determined by coolant temperature sensor, O2 sensor and the ECU. You could try changing your temp switch not the one for the fan but the one by the 6th cylinder. If that doesn’t work try changing your 02 sensor. Regards, Paul.

Many thanks for useful info. I have a 300CE also 1989. Purely for your info I have had a lot of clunking from the rear end and after replacing all the sub assembly and differential bushes finally traced it to the shock/strut bushes. Took the units to a Cape Town specialist who re-machined the fittings and inserted new bushes and now the car rides as new.

I just love you guys :) own a 89 300TE 4matic and all of you saved me a lot of money. My car was going nowhere even tried to die on full throttle. I've replaced the o2 (labmda) sensor and cleaned injection nozzles. Now it runs like a cat. Still need to do some adjustments (runs too rich), but just by checking everything you did saved me a lot of time and money. Regards from Slovenia

I believe I can follow all the steps you did with my 1992 190E 2.3, the only difference I see is on how your 300 sits. Thank You sir. godbless, you helped alot of people.

Looks like some great advice here. I just bought a 1989 300E for $325. Rough idle - gotta keep my foot on the gas at stop lights and when parked. Drove it about two hours to get it home. Highway speed wasn't bad - kinda pulsated when I tried to use the cruise control. Seemed like it wasn't catching 4th gear either. RPMs were steady at 2200 to maintain 55mph. I put a can of Seafoam Trans Tune in for the ride back and a can of Seafoam motor treatment in the gas, and some oil and engine restore in the crankcase. Seemed to run a little better by the time I got it home - actually idled by itself for a little while. I'm gonna get after that ICV and O2 sensor and check for cracks in the vacuum hoses. Thanks!

Thank you for a useful video solving my problem and a easy fix all the best from 🇬🇧

Hi, John Unfortunatly there are a few things that can cause this problem. Do you have a petrol smell under the bonnet, it could be your EHA valve. You could inspect all the soft fuel lines, especially the ones near the fuel pump. could be air sucking in through a crack that will allow enough fuel to run but when it tries to pull more through the air creates a 'block' and the car stalls.You could have a vacuum leak, most likely at the idle control valve. If you have harsh tranny shifts you definitely have a vacume leak. Check the idle switch on the linkage -- if it is failed, you would be in idle condition all the time, this will muck up the running mixture. And my all time favourite the Over Voltage Protection relay, if faulty this will make your idle irratic. I don't know what the knock at the back of the car could be, unless it's an air hammer from your fuel pump. Let me know if any of this has been useful. Regards, Paul

This ladies and gentlemen is what the internet was supposed to be all about. Helping others in a given community with shared expertise....Sound corny? It's not really! Check-out another guy here on You-Tube that goes by the moniker, FUPABOX who has scads of Benz knowledge and shares it quite liberally as well...Doesn't seem to be an era, model restirction or limit to what he shares either based on my '87 300E. Ok, Sunday sermon over but make sure you cherish these folks because my sense of it is that they are very few and far between.... Good on your day...

riffajazz, I hope that other's, who have viewed your you tube postings, have found them as useful and informative as myself.They are comprehensive, and coherent, as well, take an effort for you to produce. I have a 1991 300e 3 litre with a 4 MATIC transmission system, which still functions and is, is ideal in our snowy Canadian Climate I am happy Grandpa paid the extra $ 3500.00 -$4000,00 CAD for it when originally purchased.Best Regards, to you and of course you "assistant!"

Great videos. Thank you from California.

Very fast answer! I am impressed.When I get the car back from the dealer I will set right to this little job. The car has been at the dealer for six months. I have begun to suspect they are not trying hard to find out this problem.I will let you know the upshot.Thanks very much.Paul

Indeed,so much interesting this tutorial video,my master.

Sorry I did not mention it is a 1990 190E. But when I got my car from the dealer they told me my "air slide" was not functioning and I was getting no readings from my O2 sensors. I have no engine light on.

Hello and thank you for your videos, they were helpfull for my idle issues...I have A 300 sl with same M103 engine David

very good clip

Great Job 👍🏽 Nicely Done

I have a 1989 300sel, I bought it 8 months ago and it has been sitting since. I do start it once a week and let it run. the car will start up fine and stay started. no gas needed. the car will idle for approx 10-15 mins before it starts to bog down and eventually die. if I give it gas it will rev out and stay idle for a few more moments followed by the same thing. once the car stalls, it will not start back up. if you try, it will sometimes backfires. it smells rich, so I'm assuming it's running rich. I have replaced the fuel pump and the fuel filter, drained the gas and put new premium 93 in. I have taken apart the carbs and replaced the air/fuel adjustment thingy (adjusts a screw with an Allen wrench. before I put the fuel lines back on I checked to see if the gas fill up the holes evenly on the carb/injector, and it did. I've taken off the potentmeter and made sure that was good. But still the same thing happens. it will start, stay running for a little bit and then stall out. There also seems to bog down when you apply the gas. trying to fix it myself, and just throwing parts at it isn't seeming to work. hoping someone could point me in the right direction. I would appreciate it!

First thing is to check for any vacuum leaks, then change your spark plugs. I doubt if it's the fuel filter. Regards, Paul.

I have 88 Mercedes 300E body and interior and good condition but seem the have a bogging or loss of power when the car get to operating temp. I press on the gas going 30mph and rpms dont go up nor does my speed. When its doing that I feather the gas petal and on the 3rd feather I hear a knock in the mid to back of the car.And then there is power. After I do that and start to slow and stop the rpms surge up maybe 500 rpms then 2or3times and I can feel the car surge in time with the rpms then stop

thanks a lot for your great advice

I have a 1989 300te with a problem unlike all the others described here. Maybe you can suggest a fix.When the car went over a sharp bump such as a pavement crack that crosses the road, as the front axle hit the bump the engine would drop to a smooth idle and not respond to the throttle. When it did rev up after a few moments, the transmission was not engaged and did not engage again until the engine speed was allowed to go back to an idle. After several shops and many false diagnoses, including by the Mercedes dealer, I left it with them to give me the diagnosis, since this should be under their work warranty.They agree there is a problem but can't identify it by logic nor by experience.It has a new fuel pump, fuel relay, voltage regulator, over-voltage protection switch, catalytic converter, oxygen sensor, injectors, and others I forget at this time.It would seem sensible that whatever is susceptible to a bump is not likely on the engine, since it vibrates continuously. So it's outside the engine. If the fuel pressure is dropping, why? Since changing the catalytic converter the failure has happened independent of any discrete bump in the road.Please help! I have $14,000 in this car which is fit now only to sell for parts.Paul PhillipsSpokane, Washington

Hi! I have a 1988 300CE. It runs pretty well, but the idling is a bit uneven, also it doesn't start up very "distinctive" if you know what I mean. Do you think that these cleanups might help?

Hi, The benzene won't affect the valve, did you reconnect the wiring to the actuator. It's job is to allow air to bypass the throttle rising or lowering the idle speed, and is controlled by the ECU. It sounds to me that it maybe stuck in a closed position.

I didn't quite understand what you used to clean your ICV and the O2 sensor. Was it disel fuel or? Best reguards

Thanks again for the advice. The car just did an 800-mile drive with no problems, so maybe the problem healed.I put air shocks on the back axle and I am not happy with them. Seems to bottom out unless I can pump them up to 150 psi, and even then the ride is not great.Any experience with changing SLS system to plain hydraulic shocks? I see there is a Bilstein shocks part number for this car. Maybe shocks without springs won't work.

Awesome! Wondering if you could help me with a drivability problem. Warning this is a long post lol. Customers car. 1988 300es. When cold runs great, when at operating temp it has no power and will backfire through intake. Almost feels like in safe mode but if you lightly drive it's fine but when at w.o.t. it's got nothing...it doesn't bog just slow revving and feels like it's stuck in gear, let up on the accelerator and it bumps into gear. Unfortunately i have no way to test the fuel injection pressure with the tooling i have but the pump sounds a bit funny (sounds like it's possibly sucking air?) id like to do a volume test on it at least. Know where i can find a spec? Haven't found it on identifix (i hate identifix by the way lol) This thing is in bad shape, everything i check falls apart lol. During this diagnosis I'm checking every variable i can to get to the problem. Tomorrow I'm throwing it on the smoke machine (when engine is cold) to address any vac leaks. Engine runs at 17-18 inches of vac at idle and about 24 inches at 2000-3000rpm Ovp and fuel relays are good, adjusted the mix to 50% duty cycle. I checked the cap and rotor and cleaned up any corrosion, #1 plug wire broke when removed...replaced them. putting the lab scope on it tomorrow to check valve timing ( only checking this because of mileage and to eliminate a variable as well as let the customer know the condition) as well as checking to see if the o2 can recognise forced lean and rich conditions. ect (2 pin at rear of head) has been replaced last year. One connector was snapped off and it had a resistor wired in line (terribly soldered)...the resistor was also broken. I removed it since i couldn't find a resistor in the wiring schematics. Ran great after that. Around the same time last year the cap and rotor were also replaced along with a bad crank sensor.

Thanks for sharing the video. It was really helpfull. I have a couple of questions. What it is the liquid where you put the Control Valve and the Oxygen Sensor? And how long did you let this pieces in the liquid?... without have any kind of damages. I hope to get the answer. Thanks again!

Hello thank you for making these videos... I have a 89 260 e and it ran smooth when I bought it, it has 180,000 miles and the odometer stopped working which the guy that sold it said was common and the engine looks very clean, when I first drove it, it would run so smooth and then it all of a sudden had a rough idle an would be smooth sometimes and then get rough, originally it would be smooth when i first started it and drove and then would get rough after driving, but then got worse and would always be rough at idle and seemed to kinda smooth out with acceleration... do you by chance know what that might be? I was thinking as you have been working on this same car you would know better than most mechanics. I was thinking voltage regulator on the back of the alternator but was not sure if you had run into any similar problems. Then i had it garaged for 2 years and the battery is just dead and wont get any power at all but those were the symptoms before I let it sit and now I am going to try to get it running again and really could use some of your expert Mercedes mechanical advice if possible. Thank you

my car starts cold just fine, but when it warms up it stalls out and will not start again until it cools off. is that the oxygen sensor or idle control valve. Have changed the MAS and Overload - OVT. Any suggestions.....how do you check for vacuum leaks?....saw that you mentioned that in a post.

A bit late to the party but my w124 300E's exhaust does NOT have an o2 sensor and no hole for it either. It's also RHD. Did ALL 300Es come with an o2 sensor on the exhaust pipe?

Thanks for the good video. I drive a 124.023/ M102/ 1987 230E and recently my economy guage shoots to the redline mark after slight acceleration or pushing the gas pedal at operating temperature while driving. Fuel consumption has worsened too. Any suggestions why it does this or which part(s) I need to diagnose?

I was going to use heat shrink tube until i get a hose. only about quarter inch crumbled. but enough to allow air.

I went out for a drive on our first cold day (20F) and the car acted up badly. This was the first time in several hundred miles. Would not respond to the throttle and transmission went to 'neutral' when the motor speed eventually increased.I hear nothing from the control valve when the key is turned to 'ignition'. But the hose to the manifold was split and loose. I got a new hose, but it must go in from under the car, so I have to wait while for weather before I can get under it to try installing it that way.PaulSpokane, Washington

You might want to consider having a separate channel for Jazz. If this channel was solely focused on automotive matters; your channel would probably grow faster and you would receive more views for your videos - its "all" about marketing. What does Jazz have to do with Mercedes Benz? Anyway, its just something to consider.....thank you for the video.

Please explain the pcv valve

A J Hammond Need help bad,have a 1990 300 SL R129 it will only start when the throttle body damper is blocked open slightly and idle well until the the object that has it blocked open is removed.Then it cuts off and will not start until blocked open again. I changed out the cold start valve. Is my problem the Idle control valve or something else? Dummy need help

Hey Paul, I have a 1992 4-matic. Are you familiar with the trans-axle problem they had for a couple years? Mine has gone bad and I am trying to find a way to rebuild it or find the appropriate used part. Any resource you might have for rebuild kits or used parts would be appreciated. Thanks

I have this problems where the engine will start perfectly but once it's warmed up it will start to idle like shit and will suddenly stop after that it will not start again until the engine is cold again any ideas? i was told it could be the CPS ¿is this right?

hi riff.. I just got my car back from the dealer. I was having issues with my car idling high then low and my car dying. Also my car would die at stops and when i turned. The dealer told me im getting codes with my IAC and my O2 sensors not reading anything. So i did what you did in this video. Once i cleaned my IAC my car would not start. I tried it about 4 times then pressed on the gas pedal. When using the gas pedal it would start but i would have to keep my foot on it. Now i disconnected the IAC to see if it would start. And it did. So does this mean the IAC is no good? Its a $300 dollar part and this guessing game with this car is draining me. Im just wondering if i should scrap the car now :(. Any thoughts would be appreciated. also there is a hole in the hose right above the mass air flow sensor. Right before the air goes into the air filter. Does this play a huge roll??

Greetings from across the pond. My 89 300SE died while idling after 15 minutes. I was able to start it right up but now the "check engine" light is on. It runs, idles and drives fine but the light remains on. Any suggestions and cheers. Rick

my 1991 300e idle shutters a bit, doesn't always start the first time, and hesitates when you try and accelerate, could this be the problem? Or is it possible I need to change my fuel filter?

Hi Riff, where does that small vacuum line lead to. Mine is not connected to anything at the other end. I might of pulled it out when removing air filter box. 0:53 in your video

I have a 1993 Merc 300E and the CEL hasn't come on yet, but last night it started idling terribly and when driving, the car was "bucking" and revving on it's own. (For example, I was coasting with my foot off of the gas and it would speed up on it's own) Do you think it's an O2 sensor problem? I smelled some Sulfur for a quick second so I know that too much fuel is making it to the Cat. Just wanting a second opinion before I spend $120 on a new one. TIA!

HI PAUL I HAVE 1987 300 E MB.I WAS CHARGING THE BATTERY .AS I LEANED ON THE CAR IT ROLLED BACK BECAUSE IT WAS LEFT IN NEUTRAL AND I COULD NOT CONTROLLED IT .IT WENT ALL THE WAY DOWN TO NEXT HOUSE'S WINDOW .IT STARTED UP I BROUGHT IT UP BACK ON MY HILLY DRIVE WAY .BUT NOW IT IS NOT STARTING AT ALL .SOMEONE SAYS WHEN IT ROLLS BACK AND GET KNOCKED IT IS LOCKED DOWN .I DO NOT KNOW ABOUT IT .BUT IT DID STARTED ONE TIME .I HAVE REPLACED THE ALTERNATOR REGULATOR ALREADY IT WAS BAD .WOULD YOU PLEASE LET ME KNOW IF IT IS LOCKED UP OR SOMETHING ELSE .I THANK YOU SIR .

wondering if you are still giving advice out. I have a 300 E that will run around 40 most of the time, sometimes it gets up to 55 but most of the time between 30-40. I have replaced the fuel filter but am not sure what else to really do. Mercedes is a bit foreign to me LOL

I'm thinking I'm having an o2 sensor issue with my 300TE. When the car warms up it idles very rough but smooths out when driving, and rolls black smoke out the tailpipe (raw gas) as well. I know the o2 sensor can cause this problem, do you think that would be a good chance?

I have a 1991 420sel that idles fine when the engine is cool, but once the car is warmed up to operating temperature it idles high IF you put it on P ark. Idle will immediately go back to normal if the car is put on D rive. Could it be the idle control valve?

yeah won't start. poor old gal has 300k. runs great. no oil issues. just hesitation in morning. until warm. those 2 tubes are cheap. but how the heck I pull em out? do I have to remove carb?

hi there my farther has a 300e when you take for drive and once it warms up it konks out and once it cools right down, then it will restart and all over again the mechanic said there is something on the inlet manifold and you cant buy that part he said here in aus so im on here to try to fix it as car is in shed for the past 5 years ..if you have any ideas would be much preciated cheers plus great vids

at 1:04 can you tell me where that clear plastic hose runs thats in the middle of the hose that goes from the valve cover to the top of the airbox?

I have my 1989 300te back from the dealer, who did nothing with it in six months. But it has not acted up yet. Fluttered once going uphill over a pass at 60 mph, but maybe the cruise control did that.I will check the intake control valve in any case. I see them on the eBay for USD $69Another problem with this car: A transmission leak, said to be at the pump. Have you had experience with switching this car to a manual transmission? I think a very few of these came with manual transmissions in this market, but maybe in your area there might be more of them. I am assuming you are in the antipodes somewhere.Thanks once again!Paul PhillipsSpokane, WashingtonDid not vote for Trump

My '88 300CE (m103) has a burnt (rich) gas smell from the exhaust, idles rough for just a second when first cranked and then runs fine. Also, it is under powered under acceleration and the economy gauge is over at the full RED mark even at half acceleration. But once you smooth out at 60 - 65mph interstate speeds it's perfect. As well as city driving is fine. I'm averaging 18.5 city/highway and about 23-24 highway. I went ahead and bought a new o2 sensor but could it be something with my idle air control valve?

I got a problem. I followed your instructions, but the hose crumbled on the end, right side of sensor. what do i do now

Hello. Can you tell me the ohms readings that the O2 sensor should have? Thank you

hmmm... RHD 300E and the fan behind O2 sensor suggests that you are OZ.. XD hello there

How come you guys don't have any videos or instructions for a 19 89 Mercedes Benz 300E series PCV valve I need to know where my PCV valve is on this vehicle can someone please help me immediately thank you

What u used to clean that idle?

Hi Paul! My 1992 260E with M103 engine has not O2 sensor. How can I adjust the idle speed???

After cleaning my idle control valve my car won't start ,I cleaned it with benzene ..:(

hi what is up man i very very need help here i have broke the plug when i try to open it, can u just tell me what color put in 1 and what color put in 2

you dont have to clean an O2, it will do more harm then good...if it is clogged up, something else is wrong