turbocobra10

Hi Guys,

So I have a p0140 code which is mass air flow I intermittent. I replaced the mass air with a Remanufactured Bosch and still had the same code so took it back and they ordered me another Remanufactured Bosch thinking the first one was defective. However, same problem persist.

Symptoms: while vehicle is idling in park it is a little rough. It idles at 550-650 rpm but once it's put into gear the rpm drops to 400-450 rpm and the vehicle idle is extremely rough. The weird thing is once I get going it drives perfect with good acceleration and no signs of any kind of miss.

Does anyone have any suggestions? I'm thinking maybe the mass air plug has a bad wire? What are your thought?

Thanks in advance for any help I an get! I'm trying to avoid being bent over at the stealership! Lol

Glyn M Ruck

Is your airbox clipped down tightly over the MAF? Clean the MAF plug with switch cleaner. If you unplug the MAF which forces the ECU onto a default map does the problem go away? Check all vacuum lines for leaks.

turbocobra10

Glyn,
The air box is snug all the way around the mass air. After you suggested the vacuum lines I went out on traced every vacuum line I could find. The only one that looked half bad was the vacuum line that comes out of the bottom/front of the intake and feeds into the sensor on the left/front side of the engine so I decided to go ahead and replace the vacuum line. Unfortunately, I broke the line off near where the line comes out of the intake and my hand were too large to pull it out so I had to remove the intake. After removing the intake I noticed that where the line comes out of the intake that there is no nipple to slip my new vacuum line upto. I'm guessing somehow the line goes into the intak so what I did was plug the hole and splice off another vacuum line to feed the sensor. Is there a specific reason that the vacuum line is coming out of the bottom of the intake? Should I remove intake again a buy whatever vacuum line that goes into the intake?

I unplugged the mass air and the idle became slightly rougher than before but after I plugged it back in it still has the rough idle.

After driving the car I'm getting new code P0112 (intake air temperature sensor 1 circuit low input). I'm guessing I unplugged this sensor when I lifter the intake up! Where is this sensor located?

Any other suggestion with maf code? I obviously know its not a bad sensor since I have put 2 new sensors in whitin the last week.

Also, I don't know if this makes a difference but my CLK500 is a 2004 and has 38k miles.

Glyn M Ruck

The most common cause of rough idle & spurious MAF codes is airbox to MAF leak causing the MAF to hunt or leaking vacuum pipes on M112/113 engines. Presume the air cleaner elements are good & clean & correctly installed?

If I understand you correctly you have now blocked off the IAT sniffer pipe. Please take the car back to standard & replace that pipe.

You can't have O2 sensors cycling too slowly at such low mileage. Does the car do a lot of short trips with such low mileage with the plugs operating outside the self cleaning range? When last did this car have a new set of plugs?

The next thing I would check is the throttle body. Make sure it is clean & that the throttle plate actuator is behaving. Hard to check other than doing a clean up including electrical sliders. Sometimes throttle plate actuators develop an oscillation & then idle is affected. If this occurs then replacement is the only answer. Easy for a dealer. They can try a new one. Expensive for you to "try out" parts.

Is the vehicle storing any other codes? They might not have reached CEL threshold.

Please run a tank of fuel with Chevron Techron Concentrate in it to get the possibility of a dirty injector behind us.

Good luck!

turbocobra10

Glyn,

I installed new IAT line and that code is gone. All vacuum lines are good.

Yes, the car makes a lot of short trips and plugs have never been changed. Could plugs be the issue even though it drives perfect besides the idle?

I put a can of Techron in the tank.

As far as CEL the only codes are the 2 mass air codes and both are the same P0104.

turbocobra10

I replaced all 16 spark plugs but it did not help with rough idle.

I'm still getting P0104 confirmed and pending. What's does it mean if I have both codes?

Recap:
I have replaced 2 mass air sensors, no vacuum leaks, replaced all 16 spark plugs, ran a bottle Chevron Techron in tank, pulled maf connector, disconnected battery overnight to reset ECM and I still get these codes! Any suggestions anyone? I have never been so frustrated!

Rudeney

Here are more details on the error:

http://benzbits.com/m112/dtc1345.pdf

My guess is you may have a wiring harness problem on the MAF sensor.

turbocobra10

Rudeney,

I think I have exhausted my mechanical abilities. Going to make apt for dealership and will report back so maybe it will help someone else down the road.

Glyn M Ruck

I think the time has come to get this car onto a Star at the dealer. We have pretty much exhausted the options.

I agree with Rudeney that we may have a harness/plug problem. It might of course be the rebuilt MAF.

With a Star they can measure all values properly.

Rudeney

Yep, SDS is an amazing tool. It actually give the technician the ability to double-click on the error codes and then it provides step-by-step diagnostic procedures. They can watch the live MAF sensor values and it gives them the expected ranges. Of course it's not all "easy button" repairs - the technician still needs the expertise to be able to understand what is happening, check for broken wiring, excessively worn parts, etc. But as a diagnostic tool, it is most excellent! The best $500 I've ever spent.

waveterrorist

I thought I had a brown shirted gremlin.

For no particular reasons there were just some days it gurgled and stumbled.


And of course followed the same basic roadmap.
New vacuum lines, gaskets, filters, Bosch MAF (got a second under warranty),
Ran a few tanks with techron but every now and then it would mis-behave and even stalled a couple of times.

I had been buying no-name premium gas.
Switched back to Shell and my issues went away.

Just my very frustrating experience with a simple resolution...

graemep

I came across P0112 error code after I removed the air filter box, disconnected the MAF and then revved the engine. It did run a bit rough

Rudeney

P0112 is a short in the intake air temp sensor circuit (which is part of the MAF sensor)

Wodeshed

I was getting the same codes as you guys after taking out the MAF housing to do the CPS. Turns out the problem was that I didn't get the breather hose on the housing deeply enough. Fixed it by connecting the hose before sliding the housing onto the motor.

I'm no expert, but that's what worked for me. Erased the codes and reset the check engine light and now it purrs like a kitten with no hesitation from a dead stop.

alexprokopchik

Hello turbocobra10,

Did you ever figure out the solution to this issue?
Seems that Im having the same exact symptoms.
Thanks
-Alex