Steve Ashforth
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- Joined
- Jul 16, 2018
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- Your Mercedes
- 2006 1.8 C180K Coupe (CL203)
I have a 2006 c180k Coupe (CL203), which was running like a Mercedes should. But recently it’s developed some sort of problem, causing bad mpg. It was 43mpg (ish) & now down to 35mpg (ish) which I’m finding hard to cure. It seems to start well & idle well. Although, the (auto) gear change is erratic as in it holds on to a gear longer than it did.
I’ve done loads of Googling, but all I find is conflicting advice. So I thought I’d post on here, just in case anyone else has had the same issue, or has some good advice.
Anyway, here’s the scenario. The car was running ok, but the exhaust was sounding a bit ‘fruity’. “Ahh, there’s a hole” I said to myself. This was confirmed by the MOT man when I got an ‘advisory’ for the back box blowing.
After much searching on the web, (Coupe exhausts are hard to come by!), I found a replacement back box. This was fitted in due course & everything was ‘normal’. However, after a couple of days the CEL came on & using my iCarsoft OBD II fault diagnosing tool, I got the fault code ‘P0171’ “System too lean bank 1”.
I know if anything is changed or replaced it can take a couple of journeys for the ECU to ‘re-learn’ & settle down, so I put it down to the fact the back box had been replaced & therefore didn’t have an air leak anymore. I cleared the fault. This fault has been re appearing near enough after every 30 miles or so & I’m flummoxed as to what it can be.
This is what I’ve done up to now:
I’ve cleaned the MAF sensor, (with the correct MAF cleaner). I’ve seen on some posts that the MAF on the 271 engine never goes wrong. Is this correct? Or might the cleaning I’ve done not worked? It didn’t look too bad anyway, to my amateur eye.
Whilst the air box was off, I had a check of the pipes/hoses I could see & didn’t see any obvious splits etc.
I’ve replaced both of the O2 sensors. Although the ‘downstream’ one was replaced before the exhaust leak. I’ve not taken it out & checked it, but the OBD II isn’t showing any O2 faults.
Is there anything else I should/could be looking at?
Shortly after I did the exhaust, I did let the fuel tank run down below a quarter. Not something I usually allow to happen & no ‘fuel light’ came on. I mention this as could some crud have blocked an injector & is causing the problem maybe? I’ve got the car booked in for a ‘Terraclean’ next week, so if there is anything in the system, I’m hoping that’ll clean it out.
So, after going around the houses, I’ve read that MAF sensors 1). never go wrong on the 271 engine. 2). MAF cleaner is good stuff. 3). MAF cleaner is a waste of time.
O2 sensors when changed, cure all ills.
Terraclean (other systems are available) is brilliant/only works for some cars/not worth it.
A late ‘update’. I went out to clear the P0171 code last evening. I decided to do an ‘analyse’ using the ‘Benz’ bit of the OBD II as well. It threw up a couple more codes that I didn’t know about. Namely: P201c-000 (part-load ventilation hose?) & P2029-000 (Fuel Fired Heater Disabled?). Could they be part of the overall problem? I’ve cleared them & will check again after a journey or two.
As I said above, any advice will be most welcome. Thanks in advance for your time.
I’ve done loads of Googling, but all I find is conflicting advice. So I thought I’d post on here, just in case anyone else has had the same issue, or has some good advice.
Anyway, here’s the scenario. The car was running ok, but the exhaust was sounding a bit ‘fruity’. “Ahh, there’s a hole” I said to myself. This was confirmed by the MOT man when I got an ‘advisory’ for the back box blowing.
After much searching on the web, (Coupe exhausts are hard to come by!), I found a replacement back box. This was fitted in due course & everything was ‘normal’. However, after a couple of days the CEL came on & using my iCarsoft OBD II fault diagnosing tool, I got the fault code ‘P0171’ “System too lean bank 1”.
I know if anything is changed or replaced it can take a couple of journeys for the ECU to ‘re-learn’ & settle down, so I put it down to the fact the back box had been replaced & therefore didn’t have an air leak anymore. I cleared the fault. This fault has been re appearing near enough after every 30 miles or so & I’m flummoxed as to what it can be.
This is what I’ve done up to now:
I’ve cleaned the MAF sensor, (with the correct MAF cleaner). I’ve seen on some posts that the MAF on the 271 engine never goes wrong. Is this correct? Or might the cleaning I’ve done not worked? It didn’t look too bad anyway, to my amateur eye.
Whilst the air box was off, I had a check of the pipes/hoses I could see & didn’t see any obvious splits etc.
I’ve replaced both of the O2 sensors. Although the ‘downstream’ one was replaced before the exhaust leak. I’ve not taken it out & checked it, but the OBD II isn’t showing any O2 faults.
Is there anything else I should/could be looking at?
Shortly after I did the exhaust, I did let the fuel tank run down below a quarter. Not something I usually allow to happen & no ‘fuel light’ came on. I mention this as could some crud have blocked an injector & is causing the problem maybe? I’ve got the car booked in for a ‘Terraclean’ next week, so if there is anything in the system, I’m hoping that’ll clean it out.
So, after going around the houses, I’ve read that MAF sensors 1). never go wrong on the 271 engine. 2). MAF cleaner is good stuff. 3). MAF cleaner is a waste of time.
O2 sensors when changed, cure all ills.
Terraclean (other systems are available) is brilliant/only works for some cars/not worth it.
A late ‘update’. I went out to clear the P0171 code last evening. I decided to do an ‘analyse’ using the ‘Benz’ bit of the OBD II as well. It threw up a couple more codes that I didn’t know about. Namely: P201c-000 (part-load ventilation hose?) & P2029-000 (Fuel Fired Heater Disabled?). Could they be part of the overall problem? I’ve cleared them & will check again after a journey or two.
As I said above, any advice will be most welcome. Thanks in advance for your time.