2012 Mercedes C250 coupe 1.8l turbo P2229 and rough idle
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2012 Mercedes C250 1.8L turbo
2012 Mercedes C250 coupe 1.8l turbo P2229 and rough idle
I recently replaced the thermostat on my wife's C250 1.8L turbo. I now have a rough idle (that sometimes evens out but then gets rough again) but other than that it runs great. Also I get a P2229 code which I never had before I changed the thermostat. When I replaced the thermostat I made sure the coolant system was bled correctly and the coolant level is fine. As far as I can tell there are no cracked hoses and all connections are tight. So all I can think of is that I forgot to connect a sensor (as far as I can see things are all tight) or I introduced an air leak somewhere. I did crack the cheap plastic line that has the red clip/tab that connects to the airbox to turbo air intake hose. But I used a rubber hose that fits tight onto each end of the plastic tubing. Hopefully that's ok.
So was thinking about doing a smoke test. I don't have a proper smoke machine so was just going to buy a cigar and use a small pump to pull the smoke into the air intake system. My question is where is the easiest place to hookup a hose where I can introduce smoke into the system. I think it makes most sense to disconnect one of the small hoses on the airbox->turbo inlet tube and hookup my smoke tube there. Then I think I have to plug it somewhere so the smoke doesn't easily escape.
Richard
So was thinking about doing a smoke test. I don't have a proper smoke machine so was just going to buy a cigar and use a small pump to pull the smoke into the air intake system. My question is where is the easiest place to hookup a hose where I can introduce smoke into the system. I think it makes most sense to disconnect one of the small hoses on the airbox->turbo inlet tube and hookup my smoke tube there. Then I think I have to plug it somewhere so the smoke doesn't easily escape.
Richard
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Joined: Apr 2019
Posts: 111
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2012 Mercedes C250 1.8L turbo
So I took off the air intake hose and the air box -> turbo inlet pipe. I then checked everything connection and put the pipe back on. I noticed that I really had to push on the air box -> turbo inlet pipe back on to get it to seat in the groove. I then made 100% sure that clamp was tight (which I think it wasn't before). So it seems to idle much more evenly now. But I'm now getting only a P0108 code. Also the torque light app says in Intake Manifold Absolute Pressure is pegged at 255. So I think this points to a wiring issue or the sensor (the one located at the throttle body intake) is bad. I'm going to try to back probe today and see what I get.
Richard
Richard
Last edited by Richard Koop; Apr 5, 2026 at 06:46 AM.
