Misfire.

[richyb66]

Time for a further update. The slight hesitation on petrol has persisted and as proposed in my previous post, I had the petrol injectors cleaned and flow tested.

The outcome was that 6 injectors were OK but 2 were down on flow rate and had poor spray patterns and so were replaced with new items. Typically, this made no difference to the running on petrol but was a quick, easy way of spending £200 and at least eliminating the injectors from the equation.

Cold starting on petrol is generally ok, maybe 1 start in 10 the idle is very slow, it struggles to tick over and I just wait until it settles down before I select drive. The most noticeable thing is how much smoother the engine feels when it switches from petrol to lpg so it still obviously isn't right.

Coming home from work tonight I switched to petrol at 60ish on the motorway and it drove ok, no obvious hesitation, roughness and it accelerated normally so I thought that maybe the poor running was confined to starts from cold. However I've just run the car again when I had cooled off for a couple of hours and the idle was lumpy until it switched over to gas.

I've read out the fault codes and got the following:

VCDS-Lite Version: Release 1.1
Tuesday, 15 May 2012, 20:27:39.
Control Module Part Number: 4D0 907 559 A
Component and/or Version: 4.2L V8/5V G 0003
Software Coding: 10752
Work Shop Code: WSC 00000
VCID: 2C2B87B3CF05
Additional Info: WAUZZZ4BZ1N044499 AUZ7Z0Y1472110
3 Faults Found:
17537 - Fuel Trim; Bank 2 (Mult): System too Rich
P1129 - 35-10 - - - Intermittent
17535 - Bank 1, mixture adaptation (mult.) System too fat
P1127 - 35-10 - Please Register/Activate - Intermittent
16804 - Bank 1, catalyst system effect too small
P0420 - 35-00 - Please Register/Activate

The check engine light is generally on all the time, I can clear it but it comes back after maybe 30 miles of driving. It's been like this since I bought the car (and even when it ran perfectly) so the appearance of the light isn't a great concern.

What I am wondering is whether the codes are pointing to possible faults with the lambda sensors. I was going to try and do some logging on them but my VCDS is shareware and doesn't have this facility. I have got VAGCOM as well but as it just started lashing down with rain, I haven't given that a try yet.

With the car running ok on lpg, the petrol issue at least doesn't cause me any day-to-day inconvenience but I'd like to get the issue bottomed out and sorted once and for all and have the car running 100% all the time regardless of what it's running on.

I've now done around 30k miles in it in about 14 months, the fuel bill has been frankly shocking (but not unexpected), general maintainence (tyres, discs, pads, cambelt and numerous parts) has cost me the wrong side of £3500 and to cap it all off, as I have the private fuel costs paid by my company (but none of the running costs), I'm getting royally rogered by HM R & C for the tax benefit in kind. Although it is a stonking car, I'm getting to the stage now that I'm thinking of swapping for something a bit lighter on the pocket and considering going back to another VW T4 van.