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I have this Golf GTI (CCZB engine), which is throwing a P0300, P0303, P0302. Very poor fuel economy and there is black smoke coming from the exhaust. The vehicle is a GDI (direct injection), four-cylinder single bank.
I went to live data via OBD and observed the following at idle:
short term fuel trim: -25
long term fuel trim: 0
MAF: 3.8 g/s
Equivalence ratio: 0.754
Rail pressure: 38 bar (551 psi)
The long term fuel trim do not move. The MAF is high at idle, it must be around 2.4g/s. I’ve invested a lot of time on this vehicle, with no success. I thought it may be a skewed MAF sensor and tested with a known good, without success. I’ve done compression test, back pressure test, ignition test, PCV test and EVAP test, no success. I just can’t figure this one out, please assist.
Thank you.
Last edit: 6 years 3 months ago by ShadeTree.
The following user(s) said Thank You: aboudi.naddaf
Does the rail pressure hold after the engine is shut off? 500-600 psi sounds a bit low for direct injection and thinking one or more injectors may be leaking, but I'm not as familiar with VW injection systems to know the pressure specs off hand.
The -25 trim would also support a leaky injector.
"Don't ever say 'easy' until the check clears."
The following user(s) said Thank You: aboudi.naddaf
I recommended to client that we change all four injectors and we did so. After changing the injectors, then I got a P0303 only in closed loop. I then did a smoke test and discovered a vacuum leak. I fixed the vacuum leak and have the following data:
I went to live data via VCDS and observed the following at idle:
Bank 1, sensor 1, partial load (Long term FT under load): -3
Bank 1, sensor 1, idle (Long term FT at idle): -4
Bank 1, control value (short term FT): 1
MAF: 2.4 g/s
Equivalence ratio: 0.999
Rail pressure: 551 psi
Thank you, the vehicle is running great.
Kindly advise whether there is a method of testing whether (GDI) injectors are leaking, which can be performed by a mechanic at his workshop.
The following user(s) said Thank You: Andy.MacFadyen, aboudi.naddaf
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