Help, Leon Cupra running lean?

[flyinlo]

Hi guys,

I'm new to the forum. I drive a LC '08. I'm currently experiencing a few problems with my car and hoping someone can help.

My car recently started leaning out to a point where it's pinking at low rpm's. I had a low pressure fuel error on vag that was due to the thrust sensor on the hpfp. The sensor is now changed and I don't get the error anymore but still hasn't made a difference to the fueling. I've logged the hpfp (230 on VAG) and the specified and actual values are the same. The knock levels are high through out the rev range on all the cylinders. Could this problem possibly arise from the LPFP?

To date I have done the following:
-Changed the cam lobe
-Inspected the cam
-Changed to Iridium plugs (It's burning white indicating a lean mixture)
-Changed the thrust sensor on the HPFP

The car has JE pistons+rods because I was planning on going the BT route. I dont think this issue is a result of compression because the car drove fine for about 4 months. My car is currently standard and the only mod that I have on is the Autotech HPFP. Your help will be appreciated.

 

[Blade]

You shouldn,t be getting any timing pull on standard coding. What numbers are we talking about?

 

[flyinlo]

timing pull of 8's and 9's. The spark plug is burning white, so I think it's definately something on the fueling side. Is there any way of testing the LPFP?

 

[-pseudonymous-]

How lean are we talking? What are your AFR's on block 031 in VCDS and how do your fuel trims look on block 032? You can check the LPFP duty cycle on block 106 to give an indication of how hard its having to work to meet the requested fuel pressure.

Are you currently running the stock air filter/maf housing?

 

[Blade]

timing pull of 8's and 9's. The spark plug is burning white, so I think it's definately something on the fueling side. Is there any way of testing the LPFP?

hmmmm, something wrong there then. Has it been previously mapped before you got it?. i wouldn,t want to run it hard with those c/f,s. I would be having another look at the hpfp before i do anything else.

 

[flyinlo]

How lean are we talking? What are your AFR's on block 031 in VCDS and how do your fuel trims look on block 032? You can check the LPFP duty cycle on block 106 to give an indication of how hard its having to work to meet the requested fuel pressure.

Are you currently running the stock air filter/maf housing?

I just logged the above parameters. The AFR on block 31 is ~0.9 under accelaration but the strange part is it's 1.99 under normal driving (knocks are 0 under normal driving).

Block 32 (lamda idle) is 0.8 throughout and (lamda partial) is -6.6. The LPFP duty (106) is ~85% till 5000rpm and goes up to 92% from 5000rpm-6000rpm. What should the normal duty cycle be?

I still have the stock air filter/maf housing on the car

 

[flyinlo]

hmmmm, something wrong there then. Has it been previously mapped before you got it?. i wouldn,t want to run it hard with those c/f,s. I would be having another look at the hpfp before i do anything else.

I have the car from brand new and it was remapped for about 1,5years. I reverted the car back to stock due to the current problem. If it is a problem with the hpfp wouldn't block 230 on vcds indicate this. The specified pressure and actual pressure match each other, in some cases the actual pressure is higher.

 

[Blade]

I have the car from brand new and it was remapped for about 1,5years. I reverted the car back to stock due to the current problem. If it is a problem with the hpfp wouldn't block 230 on vcds indicate this. The specified pressure and actual pressure match each other, in some cases the actual pressure is higher.

Yes i would agree with you if thats the case.

 

[-pseudonymous-]

Are there any lean fault codes stored? I would think not as your LTFT's on block 032 are within spec and are actually indicating that your running slightly rich.

If you multiply the lambda readings from block 031 by 14.7 (stoich) that will give you your actual AFR's, therefore 0.9 (13.2 afr) is on the lean side. On a mapped car you should ideally aim for AFR's of no higher than 12 (0.82) at redline for best performace and safety, but i'm pretty sure the standard map runs a fair bit richer than that.

I'm not sure what LPFP duty cycle you should see on the standard map but its normal to see it rise into the mid 90's on a mapped car towards redline. Block 231 will also show you the requested vs actual fuel pressures on the low pressure side.

Can you post your VCDS logs up? You will need to copy them from MS Excel and paste them here between [ CODE ] [ /CODE ] tags.