How To Identify Leaky Injectors?

[feb 47]

Recently the car has been spluttering when starting it up from cold.

 

When trying to start from cold it will start but on the 3rd try.

 

It will then splutter and be very rich (sounds exactly the same as when trying to start a car with manual choke and giving it unnecessary choke when it is warm).

 

I have to keep the gas pedal pressed for ~20s in order for it to be able to maintain an idle by its own and clear up.

 

Either something has to be adjusted in the startup (not very sure what) or I may have a leaky injector I think.

 

Cold starts have never been its forte since the Emerald was fitted and I thought I "fixed" the issue in the past by recalibrating the TPS sensor; it seemed to have helped for a couple of months but it is now much worse than before.

 

I'll take a look with the laptop tonight to see if it the TPS min value has changed or what but in the meantime is there a way to identify a leaky injector?

 

I know they have been ultra sonically cleaned with (I assume) new O rings but could the local petrol that (I guess) contains 5% bioethanol have caused them to leak hence causing this?

Edited July 16, 2012 by feb

[kyepan 291]

check the ecu temp sensor, that may throw out what it's doing for the cold start compensation.

[feb 47]

Is there a way to test it rather than change it for a new / known good one?

[Anthony 1,000]

Look at the Help - Diag Data screen on the Emerald software, and check the sensor is reading an accurate looking temperature and that it increases as you'd expect as the engine warms up.

 

My guess would be that the TPS has drifted slightly again, as that would result in the idle control not working properly. Is the hot idle speed far too high as well like last time? It should start on the button without throttle in this weather, only struggling a little in winter thanks to the lack of SAD/ICV.

 

Given that chances are you'd only have one injector leak, you would normally see it start and run on 3 cylinders for a second or two while it cleared the flooded cylinder. It wouldn't take over 20 seconds, and besides, it seems unlikely given that they haven't done many miles since being cleaned.

[feb 47]

OK, I just youtubed "running on 3 cylinders" as I had no idea what this sounds like and it does run on 3 cylinders indeed ("machine gun" sound) if I compare the sound of the below video with mine but when I keep the gas pressed at 1,500-2,000 rpm it clears up after a while

Not my video but sounds like it (only I haven't revved it to hell like this)

http://www.youtube.com/watch?v=phIJCLt3Qmk

 

So what should I do first?

 

If it was an ignition problem it would always happen no matter if cold or hot right? So the fact that it happens after being parked up and it is cold points to a leaky injector or anything else?

 

Hot idle is "perfect" (~900-950rpm or so on the laptop)

 

Cold idle AFR's are rich too ~13.

Edited July 16, 2012 by feb

[rallysteve 22]

Maybe try letting the fuel pressure out of the rail after switching off which should stop the injector leaking if that what the problem is.

 

Steve

[BlueBolt 156]

Did you ever get to the end of this?? I had a very similar sound from my GTI6 with jenvies tonight on the way home, felt like it was running out I fuel, but I know there was fuel....??

[dcc 855]

I had this once on my jenvey setup. It turned out to be damp leads. Pulled over, wiped them down and also fitted a spare coilpack i had in boot.

[BlueBolt 156]

Could be that, car was sat over Christmas and new year... I'll check it out in a bit