Engine Management Light after Service

AquariusTony

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Hi guys,

The other day I changed the oil, oil filter and air filter on my new Z3. It REALLY needed it! I then took it for a spin. After about 45 mins into the drive, my engine management light appeared on the dash.

I was wondering if you guys have had the same issue before, on one similar to mine?

My steps were:
  • Removed the air filter casing and then changed the air filter with the new Bosch one - set it aside.
  • Removed the top of the oil filter casing and removed the old oil filter - set it aside.
  • Removed the oil drain plug and let the oil drain out into a bowl. The old oil was awful. - set the plug and washer aside.
  • Put the new plug on with the new Bosch washer.
  • Put the new Bosch oil filter in, also replacing the 3 O-Rings, and tightened the top back up.
  • Filled the engine back up with Castrol oil.
  • Put the air filter casing back together and back in the car.
  • Let it sit level for a while, ran it, checked the dipstick (it was at the correct level),
  • Reset the Oil Service Inspection Dial on the dash.
  • Took it for a short trip, which was fine (no engine light).
  • Later in the day I took it for another spin and that's when the engine management light appeared.
I plugged in an oldish OBD tool I had into the footwell port and it came up with:
  • P0136 - 02 Sensor Circuit (Bank 1 Sensor 2)
  • P0170 - Fuel Trim (Bank 1)
I have tried to search for these and I'm not too sure on what they mean, I'm a bit of a novice! I'm not sure if it's a coincidence or not really...? :wideyed:

I think I've included everything.

Thanks in advance everyone!
Tony.

IMG_0638.jpg IMG_0643.jpg IMG_0644.jpg IMG_0660.jpg
 

Sean d

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Fuel trim could be an air leak on one of the rubber induction pipes, they are prone to splitting
 

t-tony

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What Sean said is really the only connection between what you did and the EM light coming on. Changing oil and filter would not trigger a fault.

Tony.
 

AquariusTony

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What Sean said is really the only connection between what you did and the EM light coming on. Changing oil and filter would not trigger a fault.

Tony.
Yes, it could
I've just had a quick look for any splits etc on the hoses but can't seem to see any. I might take off the air filter casing again and put it back together again.

Would an air leak such as this effect the performance when accelerating after a gear change?

Tony.
 

Mario

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If the air filter was that clogged and you had a small air leak maybe the ECU could compensate for the leak with a bit more fuel, now that the engine is breathing a bit better with the new filter it's sucking more air coupled with the air leak the ECU can't compensate and it's coming with the check engine light. my money is with the guys on the air leak on the intake boots first, check because it's not apparent, the intake boot is in two parts the top one can be checked easily but the bottom one is not so easy if the splits are in the bottom or in the small pipe for the idle valve, it's normally in between the ribs and not apparent at first sight. for the price of the boots and the problematic they are I change them as a matter of course in every zed I've had.
 

colb

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Agree with the likelyhood of an air leak being the cause of the EML. Check all the rubber hoses and intake bellows after the MAF, your car probably thinks it is running lean due to unmetered air getting in beyond the Maf that measures the air going in, the exhaust sensors are picking up more air than the Maf is reporting so it thinks it is lean, the fuel trims if viewed in live data will be high as it is adding fuel to richen the mixture up. Bad leaks will cause it to add up to 20% more fuel, this will reduce your mpg, another sign of things not being right. When it exceeds the limits the EML will light up. If you cannot find the air leak then a smoke test will certainly find it.
 

AquariusTony

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If the air filter was that clogged and you had a small air leak maybe the ECU could compensate for the leak with a bit more fuel, now that the engine is breathing a bit better with the new filter it's sucking more air coupled with the air leak the ECU can't compensate and it's coming with the check engine light. my money is with the guys on the air leak on the intake boots first, check because it's not apparent, the intake boot is in two parts the top one can be checked easily but the bottom one is not so easy if the splits are in the bottom or in the small pipe for the idle valve, it's normally in between the ribs and not apparent at first sight. for the price of the boots and the problematic they are I change them as a matter of course in every zed I've had.

Agree with the likelyhood of an air leak being the cause of the EML. Check all the rubber hoses and intake bellows after the MAF, your car probably thinks it is running lean due to unmetered air getting in beyond the Maf that measures the air going in, the exhaust sensors are picking up more air than the Maf is reporting so it thinks it is lean, the fuel trims if viewed in live data will be high as it is adding fuel to richen the mixture up. Bad leaks will cause it to add up to 20% more fuel, this will reduce your mpg, another sign of things not being right. When it exceeds the limits the EML will light up. If you cannot find the air leak then a smoke test will certainly find it.
Had that issue this Monday. Swerved to miss a pot hole, EML came on. Had a look at the intake trunking post MAF sensor (4cyl M43 same as yours) and the angled plastic connector joining the breather pipe to the main intake trunking was not seated squarely. Realigned it to stop air leak and all was well, EML went out on it's own. Guess there was sufficient flexing when I swerved to miss that pot hole - took a telegraph pole out and demolished a bus shelter mind :whistle:
Thank you all for your detailed responses, I’ll take a proper look tomorrow on my dinner hour (the benefits of working from home ;)) and get back to you all with an update!! :D
 

mrscalex

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I would think very strong chance it's an air leak. The rubber rots and splits on the 2 rubber boots from the air filter casing back to the throttle body.

It's probably no coincidence the light came on after a service. I expect you already had a split and disturbed it, opening it up.

If you don't at first find it keep looking - it will almost certainly be there. There's enough certainty I would remove both boots and inspect off the car if you aren't seeing in situ.
 

AquariusTony

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I would think very strong chance it's an air leak. The rubber rots and splits on the 2 rubber boots from the air filter casing back to the throttle body.

It's probably no coincidence the light came on after a service. I expect you already had a split and disturbed it, opening it up.

If you don't at first find it keep looking - it will almost certainly be there. There's enough certainty I would remove both boots and inspect off the car if you aren't seeing in situ.
Thank you for that, hopefully I find it tomorrow on my dinner hour! I’ll let you guys know!
Cheers,
Tony
 

t-tony

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A quick way of locating air leaks is to spray around the boots with carburettor cleaner or bake/clutch cleaner with the engine idling and listen for increase in engine revs.

Tony.
 

AquariusTony

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A quick way of locating air leaks is to spray around the boots with carburettor cleaner or bake/clutch cleaner with the engine idling and listen for increase in engine revs.

Tony.
Thanks Tony! I’ll have a go with that if I can spot anything!

Tony.
 

Nodzed

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Any joy?
 

AquariusTony

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So I had a quick go on my dinner hour, but was also fixing the cigarette lighter on it.

I removed the air filter casing, had a check of everything that I could see (hoses etc), but couldn’t see anything wrong with them. I checked that all the hoses were on properly and everything was sat correctly.

I then turned the engine on and put my reader on it. Instead of two errors, it just came up with the Fuel Trim code.

I cleared the codes and I’m going to wait to see if EML comes back on again.

I also took some pictures of the live data (it might be useless but I’ve included anyway).

Thanks,
Tony.
74FFB7B4-AB35-4707-9D14-14D3161473B3.jpeg 8FEE4C84-8031-4E35-9F92-EFF5851695C3.jpeg 9C237F21-95EF-4949-93D2-E7EAB8BDA9F0.jpeg 5AFD896B-8D2F-4872-9DC8-6A88880C6F55.jpeg
 

mrscalex

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STFT = Short term fuel trim and looks fine suggesting no current air leak
LTFT - Long term fuel trim and I think 20% is the maximum adjustment possible, certainly it's way out, suggesting there's been a previous air leak.

Both are ideally 0% but +/- 3% is perfectly fine.

Conclusion is there is a leak and you've temporarily re-seated the rubber and closed it up. It will be back.
 

AquariusTony

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STFT = Short term fuel trim and looks fine suggesting no current air leak
LTFT - Long term fuel trim and I think 20% is the maximum adjustment possible, certainly it's way out, suggesting there's been a previous air leak.

Both are ideally 0% but +/- 3% is perfectly fine.

Conclusion is there is a leak and you've temporarily re-seated the rubber and closed it up. It will be back.
Thank you for explaining what they were haha! What would you suggest doing, based off the information we now know?
Tony.
 

colb

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Yes would agree that Long Term Fuel trim is the cause of your EML, bound to be an air leak thats in there somewhere. If its not the intake bellows up to the throttle body its in any number of places. A smoke test is my preferred method of finding these type of leaks if visual inspection fails to find them. Smoke pumped in from engine side of the Maf will work its way through the system and reveal where its leaking from. Have seen small blanking rubbers at the back edge of the intake manifold be the cause when they perish and fall off introducing an air leak. Also seen cracked plastic cam cover on a 2.2 be the cause of high fuel trims at 20%. Out of interest have a look at how the Maf is reporting in live data when you rev the engine up, see if it increases as you open the throttle.
 
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