Different vag readings

[Hudster]

I've had the following readings from my car, still can't diagnose the fault so any advice appreciated!

2 weeks ago I scanned and got:

2 Faults Found:
17536 - Fuel Trim: Bank 1 (Mult): System too Lean
P1128 - 35-00 - -
17705 - Pressure drop between turbo and throttle valve (check DV)
P1297 - 35-10 - Intermittent


So I removed and cleaned the MAF with Isoclene Isopropanol. The car still feels the same (very uneven acceleration and little/no turbo at times) but now I have a different code coming up:

1 Fault Found:
17584 - Bank1: O2S (Lambda) Correction Behind Catalyst: Control Limit Reached
P1176 - 35-00 - -

Car is a 2001 1.8T Golf Mark IV with 62k on the clock

Help [img]/ubbthreads/images/graemlins/EEK2.GIF[/img]

[shark_90]

I can't understand why you'd clean the MAF based on those fault codes, or you mean you did it anyway, not as a reaction to the codes?

I don't know exactly what I'm talking about but as the O2 sensor measures emissions and alters the fuel mixture as part of the emission control system, perhaps a fault somewhere is causing the car to run lean?

[slol]

Dan,you have had this fault for ages.
The p1128 code is definitely a faulty maf and this will cause other problems,change this first,
clear the other codes then take it from there. [img]/ubbthreads/images/graemlins/169144-ok.gif[/img]
p1297 is usually a split hose,but you cant always detect the split unless the engine is under load

[Hudster]

Hi Steve, it's been a while [img]/ubbthreads/images/graemlins/beerchug.gif[/img]

These aren't the same as the faults you scanned. I had a replacement pressure valve fitted and it cured the problem back in Feb.

The faults in this thread appeared a few weeks ago. Happy to replace the MAF but don't want to do it unnecessarily - it's showing the correct readings in block 02.

The general feeling is that it's a split hose, but I can't locate it [img]/ubbthreads/images/graemlins/frown.gif[/img]

[slol]

The (DV)diverter valve is also a possibility,usually referred to as the dump valve, but it works differently on vag cars.
If you are logging block 2 are you doing this with the engine under load,ie flat out in 2nd gear?

[Hudster]

Yea, it settles around 3 when idle, and reaches about 80 when accelerating flat out in 2nd, which seems to be right for that engine. There is a very subtle whistling noise if you have the windows down, which I assume is a hose or the DV releasing pressure / vacuum filling - but as yet I've not found a way of getting my head under the bonnet to locate it whilst having the engine under heavy load - revving in neutral doesnt cut it

[slol]

[img]/ubbthreads/images/graemlins/blush.gif[/img]Under full load the g/s reading should be about 120 for a 1.8t 150hp

[slol]

Pasted from ross tech site,
Here's a good sanity check for the status of your MAF. Do a full-throttle run all the way to redline in a single gear (second works fine). Group 002 usually shows air mass in g/s. Your peak airflow should be roughly 0.80 times your horsepower. So, if you have a stock 150 hp 1.8T, expect around 120 g/s. If you see significantly less than that, you MAF may be on the way out.

[Hudster]

right, new MAF is on the shopping list, thanks for finding that Steve [img]/ubbthreads/images/graemlins/169144-ok.gif[/img]

doesn't explain the hissing sound but as you said before, might be wise to get the MAF fixed and then diagnose any remaining faults

[Hudster]

...unless there's a VAC leak, in which case air would be sucked in and not be measured by the MAF, causing low readings