GTi 16v slight starting issue and missfire

[Deee]

Hi Chaps

First post Ive used the forums a lot but never felt the need to register and post until now.

I have a 16v GTi.  Just changed the thermostat on the damn thing, decided to stick open on me, great during this cold weather.

Anyway Ive searched a lot but cannot seem to find any answers to my problems.

Firstly the car never starts straight away, weather hot or cold.  Its seems to take a good 3-4 turns until it fires.  While this isnt a problem I dont like it as its obviously not right.

Secondly the car has a slight missfire at idle.  Its very slight and not constant, then during driving you can often feel a little hesitation as your plodding along.  Its had a mass of new parts recently and looks like its been lovingly owned all its life as its the nicest one I have seen myself.

Any help appreciated. Cheers

[dom]

http://www.golfgtiforum.co.uk/index.php?topic=101400.0 

[Leon27]

Welcome to the forum

Mine does this and my friends does it too, feels like 4 spins till its starts. Hasn't bothered me much until i tried this, whilst it was cranking but hadn't started I had let go of the key, went to restart it about 2 seconds later and it struggled to start. I'd love to know if this normal or is it a fault, done a lot of research and it seems common though.

Your misfire at idle could be due to various parts, if you know what has been replaced list it up and if you search you'll see lots of 16v idle faults. Off the top of my head this would include to:

Scan the car for fault codes
Check if your vacuum hoses are in good nick, one from Inlet to ECU can collapse - one from Inlet to Fuel pressure Reg - one from Inlet to PCV (black square box)
Check the wiring loom to the throttle body - its placed over the exhaust manifold and normally gets toasty hot till it melts. The idle control switch/Throttle position sensor will be affected.
Crank sensor wiring could be breaking up
Relays 30 and 167 could be playing around

Assuming all the normal stuff has been done though, plugs/leads/dizzy cap and arm/coil

EDIT: He ^^^ beat me to respond!

[jonnypolish]

Leon, i swear i saw your car in Mc Donalds (Enfield) the other week?
Had to pass through on the way back from the cinema 
Wasn't driving the dub though

[Leon27]

That would most probably be me mate because we had an urge for Krispy Kremes

[Deee]

Dom thanks for the link but I have already seen that.

Generally Its had new leads, dizzy, rotor etc all your usual major service parts for a higher milage car.

Im aware that the coolant temp sensors on these cars also supply the instruments with temp.  The instrument temp is showing bang on after changing the thermo a few days ago.  Can i therefore assume the CTS is functioning correctly and supplying the correct signal to the ecu?

Im going to check them vacum hoses today as well as check for any leak after the air flow meter.

The starting thing like you say its not a problem, my car never fails to start, however I know its not right and it irritates me!

[rubjonny]

on the 16v the dash sensor is separate from the ecu sensor, even on the 8v internally the sensor has separate sensor elements for the dash and ecu. so just because dash is ok doesn't mean ecu sensor isn't playing up

[Deee]

Thats what I wanted to know.  Might be worth changing then for the sake of a ten sheet.  Top man.

[Len]

Mine has always been 3 to 4 turns before start. I dont see that as a problem at all.
Oh Ive had my car for nearly 8 years now!

[rubjonny]

actually yeah mine does this too! tho the missfire obviously isn't right. ideally get vag-com on it, can check for faults and look at the ecu measuring blocks. that way you can see exactly what temp ecu thinks engine is, inlet temp and also throttle position