Collection of problems all linked??

[MadPhillyGTi]

Hey all,

My Golf is really starting to get on my tits, it has a few little problems which I think are all linked.

1.  Revs itself when at a stand still
2.  Revs dont drop straight away when changing gear
3.  Engine cuts out for a split second like it's kangaroo'ing while driving
4.  I can smell fuel and the economy is forkin atrocious!

When the engine cuts I can hear a clicking in where the fuses are - possible fuel relay problem??

I've handed it in to a mate of mine in a garage today to have a quick peek but as there is a wealth of knowledge in here (notice my subtle creeping) I thought I'd ask.  Reading similar problems the Lambda sensor has been thrown in countless times as has the temp sensor and airflow meter.

From my description can anyone make a diagnosis?

Yours in anticipation

Me 

[boneybradley]

fuel pump or ecu relay and temp sensor would be my first swappsies

[Paul86S2]

Sounds like your temp sensor.
If the sensor reads the engine is cold it will tell the ecu to supply more fuel, hence the occasional revving itself and your crap fuel economy.

Paul

[MadPhillyGTi]

Ok cheers lads, I think I'll swap out the temp sensor first.  I'm guessing the ECU relay would be the culprit for the rev cutouts?

Your explanation of the temp sensor problem has been the only one to make sense so far Paul lol 

Thanks again

Andy

[admc6]

Is that the air intake temp sensor?

[Rmachines]

The ECU temp sender is made to run the car richer when its cold,  meaning every ones golf would run like his when cold...?!? I cant see it making that much diffrence, i would exepect the engine to idle higher and loose economy but not to the point where it runs that badly and actualy smells of fuel.

The Air temp sender is built into the air flow metre, it could be either of them, the Air flow metre is measuring out the fuel/air ratio depending on how much air is taken into the engine, if its reading wrong.. your fuel mix will be wrong, hence having bad economy and running issues, ultimatly you would be overfueling to the point where it tryes to stall. the air temp sender is also adjusting the fuel mix. they are both built into the AFM so would be replaced together.

Which then leads on to the lambda sensor,  which is effectivly the other end of the air flow metre, the AFM measures how much has gone in and the lambda meansures how much is going out. So if the lambda is saying the o2 content is very low, the ECU will adjust the fueling to alow more power to the engine, and yes it does increase emissions but its ok as long as its within the lambda range. So if yours is reading wrong it will alow to much fuel into the engine and the lambda is not correctly telling the ECU to lean out the fuel mix.

So... Could be either of those two.

... other things as said before is the fuel pump relay..Its normal for these to click if the engine is about to stall or has stalled etc.. When the engine drops rpm it shuts off the fuel, if the engines happens to fire again it will click on to bring the engine back to life.  Also would not explain your fuel smell and bad economy.

Here is a list of other potentual causes of your problem
Air Filter
Air Intake system/vaccume system - leaks/blockage
ECT (engine coolent temp sensor)
Fuel pressure/delivery rate/pressure regualtor
Closed throttle position (CTP) Switch
Injectors
Mass Air flow sensor (MAF) aka AFM
Intake air temp snesor (IAT)
heated oxygen snesor (HO2S)
Exhaust system/catalytic convertor
ECM (Engine control module)

Idealy you need to get your car on diagnostics, rather can fork out for new ECUs and AFMs when all you needed was a relay or something 

[boneybradley]

my old driver had a faulty temp sensor....it was telling the engine it was cold all the time and giving the extra fuel! that caused the smell, bad idle and poor power but only when warm..ran perfect cold!!

[Pete Taylor]

When it revs itself do the revs bounce up and down quickly? If so it sounds like a vac leak, check all the hoses going into the throttle body

[MadPhillyGTi]

No the revving is gradual, just like if you were about to start a race only it goes to 1500rpm rather than 5500 lol!

Thanks for the extended explanation Rmachines, very informative.  I realise this could be a number of things and was thinking myself that the diags would be the best option now.  Funny thing is, the garage that looked at it the other day have given me a temporary replacement part, that isn't mentioned in any of these posts.  He told me that MK3's are notorious for failing coils!  So he's lent me one to try out for a few days, I must say this morning it didn't cut out but it's still not running right.  I can feel it coughing and spluttering as I'm driving.

I'll get it to my other m8 with the diag kit and hopefully will get a more comprehensive answer.

Thanks to you all

Andy

[Rmachines]

The coils do fail but usualy they will cause bad performance and misfiring, somtimes cut out,  Cant realy see it effecting the revs,  Unless its two seperate problems.