2003 C230 surge at idle

[DavidBunin]

Hello, I'm new here and I have a few questions.

My wife has a 2003 C230 coupe with the 4 cylinder Kompressor engine. It surges at idle and the Check Engine light comes on. Right now I am trying to determine if the problem is a vacuum leak.

Is this car a "W203" model? I don't know the codes.

Where can I find a drawing or schematic of the vacuum lines?

David

[stevebfl]

Yes it is a 203 chassis but more important would be the motor as it changes to the 251 motor about that time. Need a chassis number to tell. The 251 motor has a common vacuum leak from the hose coming from the crankcase vent lower front to middle of teh motor drivers side. Not so easy to access.

[ejsharp]

When Steve speaks... the forum listens!

[DavidBunin]

Here is the VIN. Is that the chassis number you need?
WDBRN40J23A491533

There are three small rubber vacuum lines on top of the motor (they are also shown on the under-hood emissions sticker). They go to a control valve and to a thing that is either an EGR valve or an exhaust air injection valve. I can't tell.

Then on the driver's side there are some large plastic vacuum (I think) lines that go to the brake booster and the rear of the engine (PCV of some kind?) and seem to route forward under the kompressor. None of that is particularly easy to get to.

David

[Oracle12345]

Did you see what codes and what its telling you?

but i would start with the common stuff such as vacuum leaks.

[DavidBunin]

I've been getting email help from MBDoc. Here is a summary. His comments are preceded by >>:

My wife has a 2003 C230 Sport Coupe (hatchback) mit kompressor. The car has had a disappointingly expensive repair history, and we only just bought it in late-2006. The current problem is a misfire driving the Check Engine Light. The code is on cylinders 1, 3 and 4. The car "chugs" at idle. It does it more with the engine warm than when it's cold.

I saw on the Mercedes Shop forum that you said there were several service bulletins about this problem.

This 2003 car has just under 50,000 miles. I'm a handy guy with access to tools and tired of being taken by these repair shops (on the last repair I think $300 of the $500 bill was unnecessary work).

Are there any easy things I can check without a diagnostic computer?

>> I would start with a compression test. Several of the bulletins on that engine are about BURNT valves. Have the compression tested first.

I will. Thank you. This car has me really scared. I bought a subscription to AllData but the information available there is useless. For "troubleshooting" all it gives me is a list of codes. I already know what the codes are!

0301
0303
0304
and now also
0172

>>That list provides a start to a better diagnosis. The 1 (P0 172) is a fuel trim code & most likely causing the engine to run lean, causing the misfires. There is a bulletin on a vacuum hose that breaks & causes that type of problem. Possibly that is the problem.

Thank you. That IS very helpful (and easier to fix). Is there one particular vacuum hose that gives the trouble mostly?

Thank you for your great help. Here's what I've found...

The compression on the rear cylinder was 160 PSI. The three forward of it were each 155. That sounds pretty good to me. Do you agree?

When we took the plugs out, the front two were sitting in clean engine oil. There was oil on the stems of the ignition coils too. When I extracted the plugs, the threads were full of oil but the tips were dry. I think that somebody must have spilled some oil while they were adding a quart. I cleaned it all up.

There is a vacuum valve of some kind on top of the engine. I disconnected the line that feeds it and I hooked that to my suction indicator. First I can tell you that the check valve before it is good. When my wife blipped the throttle, the indicator went down into the low 20's and stayed there. I had a heck of a time getting the hose off the gauge. I moved across to the engine-side of the check valve and the suction was about 15 in Hg and wavering at cold idle. When my wife blipped the throttle, it went over to the boost side of the dial and then down to the low 20's and stabilized again at about 15.

The Check Engine light extinguished.

Then the trouble started.

I previously took this car to the shop for a code P0128 and P0172. The shop replaced the temp sensor and the thermostat and flushed the coolant. Well first-off, I should not have approved that whole action. If I had taken a moment to think, I would have known that the thermostat had to be fine because I'd been watching the temperature from the dashboard and it was fine. But I didn't think and it's my wife's car so I said, "Go. Do it."

Well, that repair was $500 and $300 of that total was the thermostat and the labor to replace it. The trouble? For one thing, we found the old temperature sensor rolling around in the windshield wipers. It had lodged in the rain drain at the base of the windshield. For another thing, my wife thought that the main coolant hose at the front of the engine "didn't look right" and when I touched it, it popped out and coolant sprayed everywhere. The shop didn't get it all the way into the clip. I'm sure it would have come out in the next few drives.

Needless to say I am NOT happy with the shop.

So I fixed the hose and the clip and she started the car again. While we stood there I guess the engine warmed up because it started surging again going chug-chug-chug-chug and shaking. It's only at dead idle. If she presses the gas (even only a little) then everything's fine.

What's my next move?

Now more details: Now wife says it’s worse when idling with the air conditioning on (under a load). We’re going to see if pressing or releasing the brake pedal makes a difference and laso see what the new fault codes are.

[DavidBunin]

What should the manifold pressure (suction) level be if there are no leaks? I can measure it easily from the hose that feeds the EGR (or whatever) valve.

[chrischelle]

I don't know much, but I susspect the MAF sensor. It causes your car acting weird and engine light on. Code show " fuel trim". It happened to my wife 98 C280.
Check following links. Hope this will help.

http://www.benzworld.org/forums/w202-c-class/1362432-my-c220-stalling-me.html?highlight=mass+air+flow


http://pages.prodigy.net/jforgione/MB_MAF.html

[DavidBunin]

Okay, so where is the MAF and what does it look like? Also, can any of you tell me what engine I have? I know it's 1.8 liter Kompressor but what did Steve mean by 251 engine? Is that what I have?

I don't think I'm done checking vacuum lines yet. The big ones appear to have a disconnect mechanism. How does it work? Do I squeeze it or stretch it or twist it or what?

[qwkstang50]

you really need to check the partial load vent hose that everyone is talking about. If it has never been replaced I would bet it is at least starting to tear. You have a 271 engine there is no 251 engine.

[DavidBunin]

you really need to check the partial load vent hose that everyone is talking about.

I'd LOVE to. Where EXACTLY is it and what the HECK does it look like? Keep in mind that I have NO manuals or diagrams for working on this car and none appear to be available. I need you guys to talk me through it like a blind man.

Okay, so at least now I know that I have a W203 chassis with a 271 engine.

Steve said:

The 251 motor has a common vacuum leak from the hose coming from the crankcase vent lower front to middle of teh motor drivers side. Not so easy to access.

So knowing that there is no 251 engine (or at least that I have a different engine) is that advice still valid?

If the problem hose comes FROM the lower front-middle of the engine then where does it go TO? How do I unhook the hoses without damaging them?

[DavidBunin]

After being unable to find the source of the problem myself, I resigned to take it to the dealer. They said that it WAS a vacuum leak, although they were not clear on exactly where the leak was (perhaps underneith the air filter assembly).

The good news is that in the time that I've been living with this problem, MB had a recall for this very issue, so the repair was done at no charge.