Help requested please.....P0105
It's been pretty cold here in Texas the past few days (20s during the day, teens at night). Not extreme, but cold for Texas. My car had been sitting for a few days without starting it, and I needed to go to the grocery store Friday night. I drove it about 1/2 mile to the store, went i, came out and started it again, and it was idling VERY rough. I couldn't even give it gas to go - it just shook and stuttered. I shut it off and restarted and was able to get home, but the rough idle was still there. I got a code reader last night and checked it out today. The rough idle is still there, but only at idle. When it's warming up over 10k RPM, it's smooth. As soon as it kicks down to idle, it starts shaking and stuttering again, then stalls. No problems starting it, just idling. The code I get is P0105 Manifold Absolute Pressure/BARO Circuit. I did a search and found a little information, but I want to ask everyone for advice. Is there a common problem with the C32 that could cause this one? One thing I found during a search was a possible vacuum hose leak, which I need to search for. I can see a hose freezing up and cracking after a few days. I also saw a possible MAF sensor. Anything else I should check? I have Magnecor wires, Johnson pump, SL55 full intake, K&N filters, and ASP pulleys. No problems before this happened.
Thanks for any suggestions anyone can give me!

How many miles do you have on your car and have you tried clearing this code? Is this the only code that you have?
I have seen P0105 come up at the track when the boost goes above 22 PSI. Also since it's an electronic component, it is possible that it just gave up after the resent temp. drop.
BTW, our cars don't have a MAF sensor.
How many miles do you have on your car and have you tried clearing this code? Is this the only code that you have?
I have seen P0105 come up at the track when the boost goes above 22 PSI. Also since it's an electronic component, it is possible that it just gave up after the resent temp. drop.
BTW, our cars don't have a MAF sensor.
I'll wait 4 weeks until the cast comes off, and drive my wife's A4 until then.
Any other suggestions or opinions are greatly appreciated.
How many miles do you have on your car and have you tried clearing this code? Is this the only code that you have?
I have seen P0105 come up at the track when the boost goes above 22 PSI. Also since it's an electronic component, it is possible that it just gave up after the resent temp. drop.
BTW, our cars don't have a MAF sensor.

I don't know if the above condition is normal but I can tell you that my RPMs changes when I shift from Drive to Park with the Park having higher RPMs. So, there is a different map in the ECU for Park vs. Drive.
See if you can wiggle the wiring harness? Play with the wires that connect to the TB and MAP. It's hard to recommend anything until you eliminate the MAP sensor by replacing it. It's a good idea to replace it anyway with your mileage. It's under $60 on parts.com. You can replace it without removing the SC. But you do need two hands. The good thing is that you don't have any other codes (like P0301-P0306).
I don't know if the above condition is normal but I can tell you that my RPMs changes when I shift from Drive to Park with the Park having higher RPMs. So, there is a different map in the ECU for Park vs. Drive.
See if you can wiggle the wiring harness? Play with the wires that connect to the TB and MAP. It's hard to recommend anything until you eliminate the MAP sensor by replacing it. It's a good idea to replace it anyway with your mileage. It's under $60 on parts.com. You can replace it without removing the SC. But you do need two hands. The good thing is that you don't have any other codes (like P0301-P0306).
Anyway, thanks for the info. It makes sense that there's a higher rev through the gears. Any idea what the part number is from parts.com?
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I don't know if the above condition is normal but I can tell you that my RPMs changes when I shift from Drive to Park with the Park having higher RPMs. So, there is a different map in the ECU for Park vs. Drive.
See if you can wiggle the wiring harness? Play with the wires that connect to the TB and MAP. It's hard to recommend anything until you eliminate the MAP sensor by replacing it. It's a good idea to replace it anyway with your mileage. It's under $60 on parts.com. You can replace it without removing the SC. But you do need two hands. The good thing is that you don't have any other codes (like P0301-P0306).
What could have gone wrong or died "just like that"? One minute the car is running fine, I get out and go into the store, then start it up again and it's junk. Does anyone have any other ideas?
If so I would guess a problem with a connector or wire.
If not I would suspect a vacuum leak, except I can't explain why the symptom of a rough idle is not consistent (only in Park and not in D,R or N).
I have seen the old trick of checking for a vacuum leak by spraying short squirts of ether around the hoses that hold vacuum; if you spray a short blast of ether close to a leaking hose, the engine will ingest the ether and the idle will increase momentarily.
Good luck, and post your results!
EDIT: I have read a couple 'rough idle' threads here that were caused by accidentally switching the two plug wires on one cylinder. Double-check to ensure all your plug wires are connected to the correct spark plugs.
Last edited by MountainStone; Jan 21, 2010 at 06:43 PM.
If so I would guess a problem with a connector or wire.
If not I would suspect a vacuum leak, except I can't explain why the symptom of a rough idle is not consistent (only in Park and not in D,R or N).
I have seen the old trick of checking for a vacuum leak by spraying short squirts of ether around the hoses that hold vacuum; if you spray a short blast of ether close to a leaking hose, the engine will ingest the ether and the idle will increase momentarily.
Good luck, and post your results!
EDIT: I have read a couple 'rough idle' threads here that were caused by accidentally switching the two plug wires on one cylinder. Double-check to ensure all your plug wires are connected to the correct spark plugs.
I guess I'll try putting the OEM wires back on and check the plugs too, since I have no idea what else to try. I'm thinking there's a vacuum leak somewhere.
Does anyone have a drawing of all the vacuum lines in the C32, so I can check them 1 by 1? I would greatly appreciate it.
With the car off and the key out, Unplug the cable going to the throttle body, it's right on top. Wait one minute.
Plug it back in, put in your key, turn to position two and wait one minute.
Start your car.
Hope it works!

As others have suggested check the wiring harness that goes to the TB. Make sure the contacts are clean. You may also need to clean the TB. There are instructions for it somewhere. Just be very careful. A vacuum leak can also be a problem but you said that you checked all the houses.
You have some kind of a initialization check failure. Then at higher RPMs, things go back to normal.
Last edited by 02C32guy; Jan 22, 2010 at 03:59 PM.
So it seems to be running again, for now (thanks Gramma_Benz!). I cleared the code, and it hasn't come back yet. I'll keep a close eye on this one for a while.
Any ideas what the high-pitched chirp sound could be? I happens just as the engine shuts off.






