Intermittent starting and idle issue

[mattsrallye]

Hi all

I've used the search but couldn't find anything covering this but apologies if it has been covered!

I'm having an intermittent problem with my 1.6 petrol whereby it will turn over fine but doesn't fire - won't even try. Then after anywhere from 5-30 seconds it will usually splutter into life, with a strong smell of fuel which makes me think it's a spark issue or it's over-fueling a lot. Then when it starts it will idle high, something like 2-3k.

This happens maybe 10-20% of the time, the rest of the time it starts and drives perfectly.

I have changed the MAP sensor, lambda sensor (you never know!), spark plugs and ignition pack. I can't see any signs of a vacuum leak.

Any had this problem or have any ideas what might be causing it? Any help much appreciated!

[bashbarnard]

Checked the idle control valve??

[mattsrallye]

Not yet, I'll check it and clean it later to rule that out. Just seems odd to me that it starts and drives perfectly most of the time and then occasionally won't start at all.

[rocker8742]

Could be the icv as said, does it e we cut out if you have it in neutral or put the clutch in while driving ?

[bashbarnard]

Well if the valve is coked up or closed the car won't start well either. Pull it out and give it a clean.

[mattsrallye]

It has cut out in the past but hasn't done that in a while - never say never though...

[mattsrallye]

Hello again

So yesterday I removed and cleaned the ICV as suggested. Looked fine tbh, but best to rule it out. Also replaced the MAP sensor again in case the replacement one had failed (it was just a cheapish one from the local motor factors). Started the car no problems following this, drove perfectly, I was happy...

Then this morning it was back to turning over for ages before eventually spluttering into life. Running out of ideas now!

How does the immobiliser work on a phase 3? If it doesn't recognize the key does it turn over at all? Just wandering if it cuts the spark to stop the car starting, or whether it would be fuel, or just not turn over at all...

[vincent1]

is there a sensor on these that tell the ecu what fuel to put in etc? (im sure ive read green sensor) also what about a intermitant crank shaft sensor?
i may be totally wrong but im sure ive read a thread whith symptoms like this.

[mattsrallye]

Thanks for the reply.
Crank position sensor is the only one I haven't replaced yet so that's the next step, I was expecting it to be back firing and all sorts if that went tho.

The amount of fuel to put in will be calculated by the ECU based on the amount of air passing through the inlet, which is calculated from the air pressure (MAP sensor) and the air temp.

[vincent1]

inst there a coolant sensor thats connected to the ecu to richen the fuel when engine cold etc?

and yes agree on the crankshaft sensor but being intermitant i guess you have to ruel everything out.

[RetroPug]

The ICV isn't ruled out by being clean.
The ICV is now only assuredly clean, not necessarily working.

[mattsrallye]

Just in case anyone ever has a similar issue and finds this thread, yesterday I replaced the crankshaft position sensor as it was about the only thing I hadn't touched. When I went to change it I found that the cable tie which I thought was, well, tidying cables, was actually holding the connector together! So I've swapped this for a Bosch replacement and all has been ok since.

Out of morbid curiosity I started the car with the new sensor - fine. Unplugged and tried again and it just turned over without trying to start as before. Plugged in again and it's fine so it must just have been an inconsistent connection at the plug, which the cable tie was not solving. Who'd have thought.

Hope this helps someone one day.