Need help on 17536 and 16804. Fuel pump and injector flow specs?

[vwztips]

I have a 2002 1.8t A4 Avant Quattro and automatic.

Consistently get these 2 codes:

17536 - Fuel Trim; Bank 1 (Mult)
P1128 - 001 - System too Lean - Intermittent - MIL ON
16804 - Catalyst System; Bank 1
P0420 - 002 - Efficiency Below Threshold

Have updated the software to latest version (0005) for Catalyst issues.
New MAF (Bosch).
New coil packs (recall)
New fuel filter
New air flter
New PCV

VCDS shows front and rear O2's check OK
Aux vacuum pump checks OK in VCDS test
Have been over all the vacuum lines several times (it was not routed properly when I bought it)
032 block has idle staying in range. The additive keeps going to plus 14.

Fuel pump is flowing 138 liters/hr
Fuel pressure showing 55 PSI at the rail

What is the spec for the stock fuel pump flow?
What is the spec for the stock injectors?

Any other thoughts, or areas to look would be appreciated

[old guy]

Fuel pressure at the rail should be 4 bar. You are a few psi light. Was it an OEM fuel filter? The fuel filter has a built in regulator that controls the rail pressure.

[quattro16]

MVB 32 in engine. Whats it read??

[vwztips]

MVB 32 in engine. Whats it read??

032 block has idle staying in range. The additive keeps going to plus 14

[vwztips]

Fuel pressure at the rail should be 4 bar. You are a few psi light. Was it an OEM fuel filter? The fuel filter has a built in regulator that controls the rail pressure.

Thanks for the reply. That reading was before I replaced the fuel filter with an Audi filter. The flow test was performed afterwards.

[diagnosticator]

Stock AMB injectors flow ~276 cc/min.

[vwztips]

So with 4 injectors that is 1 liter/min and 60 litres/hr. My pump is putting out 138 litres/hr (actual measurement) and I am seeing 55 PSI at the fuel rail.

That rules out the fuel pump? Also just replaced the B1S1 O2 sensor and still have the 17536 code. The multi column in block 032 runs up to +14 to +25 within 2-3 minutes of driving after being cleared.

[old guy]

As previously stated 55 psi is a little low but not enough to cause a 25% fuel add. Have you pressure tested the system? You may have a significant leak somewhere between the MAF sensor and the turbo. This could cause a substantial amount of false (un-metered) air entering the intake track and thus a significant fuel add.

[vwztips]

Yes that is my next step. Also recheck all my vacuum line routings and check valves. PO had them all messed up.

However wouldn't the additive be a going off the chart too if I have a major leak?

[old guy]

Yes that is my next step. Also recheck all my vacuum line routings and check valves. PO had them all messed up.

However wouldn't the additive be a going off the chart too if I have a major leak?

Not necessarily. The additive or idle adaptation may not have enough pull through the TIP to suck in air from the problem area. However the multiplicative or partial adaptation would occur when more air is being pulled through the TIP and thus more likely to suck in false air.

[vwztips]

So last night I went over all my vacuum lines and check valves. Found a weak check valve and added two where PO had left them out. Still same result. After clearing codes and resetting 032 to 0's I go for test drive. after about 2 miles of driving and showing 0's the additive takes off and reaches +21.

I also ran some logs. At 6000 RPM most I see on the MAF flow is 110g. Should be seeing 136g (170 * 0.8).

Just for kicks, I installed a MAF that I have had on the shelf for years. The Bosch part #'s are not an exact match (current one is F 00C 2G2 049, the off the shelf one is F 00C 2G2 034). Also the old one I installed has an external diode whereas the new does not. I did not reset the 032 fields to 0, but within a mile the additive field started dropping from +21 all the way to 0 within 2-3 miles of driving. It eventually settled at -3.

Another observation of old vs new MAF. The lambda specified and actual values for the new one at idle stayed exactly on 1.00 for both. The old one at idle, lambda was specified at 1.00 but actual was 1.991. While driving it actual appeared to try to match specified.

Last bit of info. When changing the front 02 sensor, the old one had a lot of white residue appearing to actually being lean. Thinking about running the old MAF a little while and checking the O2 color again.

Old Guy, back to your thoughts on fuel pump, which field can I look at in real time that will show (or I can interpret) if it is getting enough fuel or not?

Thanks for your help!

[old guy]

The - 049 MAF sensor is the correct one for your engine. The “old” one is for a N/A engine. The diode is actually the IAT sensor that is incorporated into the MAF sensor for non-turbo applications.

There is no way to monitor the fuel pressure through VCDS. You can measure the fuel pressure at the rail (as you have done) and you can look for symptoms of low pressure such as fuel adds or extremely high injector duty cycles.

I don’t think low pump output is your problem. If that was the case you would not have been able to get your LTFT down to single digits with the “old” MAF sensor.
You mentioned that you checked your vacuum hoses. Have you tested your TIP yet? A split or tear in the TIP would be a source of false air getting into the intake but would not present itself as a boost leak.

Edit: Here's something else to try. Unplug your MAF sensor, reset the ECM and see what happens with your fuel trims. Once you unplug the MAF sensor the ECM controls the A/F ratio from all the other inputs such as throttle position, IAT, block temperature, engine load, etc. At this point a leak anywhere in front of the throttle body really won't matter since the flow through the MAF isn't being considered.

If the fuel trims remain in the normal range that would be a pretty good indication that either the MAF sensor isn't reading correctly or there is a significant amount of false air entering between the MAF sensor and TB. If the fuel trims remain really high that would be an indication that something else is out of whack such as air entering after the throttle body, low fuel pressure, clogged injectors, etc. This will help narrow down the scope of the problem.

[vwztips]

Well Old Guy I think you nailed it. Feeling kinda stupid right this minute as I had checked this before, but evidently not good enough. I went back and checked the TIP more thoroughly and found the nipple that goes into the TIP and goes to the jet suction pump had been jerry-rigged. Actually the TIP is the wrong one for the car so I picked up a good used one. Will install it tonight.

Thanks for pointing me in the right direction.