mk3 abf no longer feels a bit unresponsive - now odd MPG!

my throttle body wiring has got a couple of little clips on it, so i've secured it to the throttle cable (i'm guessing that's how it's supposed to be?)

thanks for the plug part numbers, I'll order a set.

Jon.

 

Are there any signs that those plugs actually need replacing? they seem to be quite expensive and now they're sandy lookin I don't really wanna swap them unless there's definitely going to be an improvement in mpg (and you know she'll moan either way)

Jon.

 

is it possible to make a mk3 drink a little water to clean the chambers out? I've done it on the mk2 before, but i'm unsure which hose to remove to perform on a mk3 - perhaps one of the airbox to TB ones?

Jon.

 

The item which does not show a fault code is the throttle idle switch which is used as a base line for the ecu.
You can test the switch using vcds in measuring blocks. If you are certain the wiring is ok then a simple test can be made on the switch with a multi meter on the ohms setting.

 

I was picking up some service parts in GSF yesterday (almost made back my 10 membership! ) and saw some stuff advertised to clean out cats and oxygen sensors, think it was a fel additive.

It just made me think - would a dead lambda or sooted up cat cause bad MPG? I would have thought a sooty lambda would send a signal off "mixture too rich" to the ECU which would then adjust fuelling (making it weaker) and then would read values from the knock sensors to determine whether it was running lean and hope fully find a happy medium.

Excuse my ignorance, this is the first car we've ever had new enough to have a cat and so the marvels of lambdas and closed loop systems is all new to me!
would it at least be worth pulling the lambda sensor out the exhaust and having a look / clean? wonder if I can reach under whilst it's parked as suspension is stock.

 

May I suggest this will help ?

http://www.clubgti.com/showthread.p...-useful-info&p=2224968&viewfull=1#post2224968

I had the same issue, narrowed it down to the Lambda. The tests I did will help you pin it down easier.

 

cheers NigeP , I'll have a look now.

Edit: brilliant write up NigeP ! i'd love to be able to DIY half the stuff you have done there - I hate doing exhausts so if my issue is lambda I will definitely be farming that out. I'll try to grab a multi-meter and get to work!

Edit #2: NigeP , does the exhaust have to be removed to take the lambda out or can you just unscrew it? I'm dreading it's location - perhaps its hidden up in the transmission tunnel or somethin

 

Hope it works, reading your problem was the prompt for me to start the thread !

 

Might I suggest a path that was suggested before?

Get the vehicle scanned, with VDS or similar for faults or sensor mesurements.

In measuring blocks group 1 (for digifant 3.2 systems) you will be able to see lambda switching voltage, and coolant temp as well as general fault status.
I will also add for lambda sensor (HEGO) diagnosis, you should attempt to observe with the engine coolant over 80 deg C or fully warmed and in idle.
NB the ECU regulates & monitors sensor heater voltage after water from combustion can evaporate in the hot exhaust. Before heating to ~350 deg C the HEGO voltage will sit at 0.45v.
I would expect the HEGO voltage, in an idle condition, w exhaust gas/sensor tip over 350 deg C to oscillate between 0.1 to 0.7v on VDS. If this does not not occur and you are sure there are not other faults that would influence engine fuel mixture, then replace the HEGO.

Regarding HEGO replacements, I would replace with an original Bosch unit and not a universal part. You may ask why?
The sensor response voltage characteristic can be altered on so called "universal" brands meaning the ECU responds in a manner that makes the mixture biased lean or rich.

If is difficult to judge what are your expectations for a MK3 Golf 16v. Perhaps bring it to the dyno day!

If you think 32mpg is bad, try a MK3 VR6 driven 'average'. 28mpg is normal.

Hope this helps.

 

You can do it in situ.

Why the symbols instead of my name

 

I actually have no idea. I think i may have a dyslexic swear filter or something?!

Cheers Eddy, I guess I could make another trip down to London!

 

You welcome to come to London.

Typical screen shot of group 1 measurement data from an 03790624AE calibration and ECU.





Use VDS and save yourself significant amounts of time with troubleshooting

 

I was actually in Wansdsworth yesterday Eddy, near Tooting underground!

Just to update this for other people searching, I swapped the air filter and dizzy cap and arm and the MPG has jumped up 2 to 34mpg average now.