dirty36 0 Report post Posted September 2, 2015 (edited) Hey Guys So I've been having problems with my E46 318i for a few months now.. basically when I put my foot flat the revs will not go past 2-3000 rpm and it will backfire a few times whilst I have my foot flat, But it's weird because after about 5 minutes of being stuck at 2-3000rpm it lets me rev all the way up (Varies from time to time 5-10 minutes). It will seem like a normal car until I leave sitting for a few hours. Another detail is that when I have my foot on the gas the revs will rise and drop by about 200-500rpm at a time making it a really rough jumpy acceleration?? So far I have replaced the spark plugs, Cam positioning sensor, Pre cat O2 sensor, cleaned the MAF sensor twice with maf cleaner and I have also checked the rubber boot and looked around for vac leaks which I have failed to find yet.. I'm currently getting the error code P0170 Bank 1 fuel trim. Well that's everything I can think of, any help will be much appreciated! Edited September 2, 2015 by dirty36 Quote Share this post Link to post Share on other sites
B.M.W Ltd 950 Report post Posted September 2, 2015 What motor ? M43 or N42 ?? Quote Share this post Link to post Share on other sites
dirty36 0 Report post Posted September 2, 2015 What motor ? M43 or N42 ?? M43 and I also replaced the fuel filter. Forgot to add that in the description. Quote Share this post Link to post Share on other sites
B.M.W Ltd 950 Report post Posted September 2, 2015 (edited) I suggest you get it scanned by a professional...it's likely to be the MAF sensor It's an unmetered air fault code. Suggest you also check the PCV valve and the rocker cover breather hose Edited September 2, 2015 by B.M.W Ltd Quote Share this post Link to post Share on other sites
dirty36 0 Report post Posted September 2, 2015 I suggest you get it scanned by a professional...it's likely to be the MAF sensor It's an unmetered air fault code. Suggest you also check the PCV valve and the rocker cover breather hose The rocker cover breather hose had no clamp on it at all, I put a new hose clamp on it but didn't do anything. I will check the PVC Quote Share this post Link to post Share on other sites
B.M.W Ltd 950 Report post Posted September 2, 2015 The rocker cover breather hose had no clamp on it at all, I put a new hose clamp on it but didn't do anything. I will check the PVC They don't have clamps. Check suction on the oil filler cap with the engine idling. You should have positive vacuum under the cap, but it should not have too much suction that makes a noise when you release it Quote Share this post Link to post Share on other sites
dirty36 0 Report post Posted September 2, 2015 They don't have clamps. Check suction on the oil filler cap with the engine idling. You should have positive vacuum under the cap, but it should not have too much suction that makes a noise when you release it What's the best way to check the vacuum without oil spitting everywhere? Quote Share this post Link to post Share on other sites
dirty36 0 Report post Posted September 2, 2015 Okay I slowly removed the cap when it was idling and there wasn't much vacuum. It made a low pitch noise when I removed the cap (kind of like a Subaru) from the filler hole haha. Quote Share this post Link to post Share on other sites
B.M.W Ltd 950 Report post Posted September 2, 2015 What's the best way to check the vacuum without oil spitting everywhere? Keep your hand on the cap and gently lift it off slowly. If it's hard to pull off there is too much vacuum = PCV valve fault. If the breather hose has collapsed internally or split, this won't work Quote Share this post Link to post Share on other sites
dirty36 0 Report post Posted September 2, 2015 Keep your hand on the cap and gently lift it off slowly. If it's hard to pull off there is too much vacuum = PCV valve fault. If the breather hose has collapsed internally or split, this won't work The breather hose looks in good condition and the cap was really easy to pull off. Quote Share this post Link to post Share on other sites
allan 295 Report post Posted September 2, 2015 http://bmwfans.info/parts-catalog/E46-Sedan/Europe/318i-M43/feb2000/browse/engine/crankcase_ventilation/ Quote Share this post Link to post Share on other sites
dirty36 0 Report post Posted September 3, 2015 So I unplugged the maf and it idled like complete sh*t but once I started accelerating it was like all the problems above had disappeared. Could this be the answer? I have cleaned the sensor twice which made no difference at all. Quote Share this post Link to post Share on other sites
Ahmedsinc 414 Report post Posted September 3, 2015 As Glenn said - f**ked MAF. Cleaning it won't cure the issue - a new MAF will 1 Quote Share this post Link to post Share on other sites
dirty36 0 Report post Posted September 9, 2015 Chucked in a new MAF works 200% better now. Cheers. Quote Share this post Link to post Share on other sites
