172 Engine cut out at Track (plus some hesitation)

[dweezle]

G'day from Down Under

My 172 had an issue on the last run at a Club event a week ago.
It was a very hot day, Plus 35 Degrees PLUS, and on the last run they allowed us to do 2 x runs at once.

The car had been faultless all day but on the last run, just after starting my first Hot Lap the engine just lost all power, as if the ignition or fuel had been cut.



After coasting back into the pits, i turned everything off, had a good look under the bonnet and then proceeded to start it back up and she fired right up.
I drove the 300ks back to Sydney.

The car has had lately a slight hesitaion/Jerkiness at low throttle.
Almost like a misfire or fuel issue.
Passengers do not usually feel it but i can so it is not that huge.

Could this be a failing Coil Pack or would it be a Lambda Sensor or something else entirely?

At the track day the fuel gauge read on the last line before empty.


Any help Much Appreciated!!!!!

 

[Dan@SJM]

More than likely a crank sensor fault.

 

[dweezle]

Thanks for the reply.
Is there a way I can check this?

I have to do the 2 times ignition to start the car every morning.
Would this be related?

 

[Toastfrenzy]

Get another crank sensor to test and away you go.. or remove and clean might have a bit of something on - they are magnetic so attract swarf.

 

[dweezle]

Thanks Mate.
I have ordered a new TDC sensor, the Blue One, so hopefully that will help the issue.

Next will be a new Coil Pack/Leads & Plugs.

 

[INZ 18]

What fault lights did you get?

Maybe the notorious pedal/loom/throttle body issue...
Ideally get codes read on clip instead of chucking money at it!

 

[dweezle]

Yeah really don't want to just throw money at it.

I do not get any fault lights.
Can I ask what Clip is?
If I can find a RStuner locally would that pull any faults stored?

It feels like it is getting worse.
Basically if I cruise say at 80km/hr in 4th and with just a slight amount of throttle to maintain speed the car bucks/hesitates.
If I use more throttle it seems to go away.
Even shifting to 5th seems to make it go away or just less noticeable.

The car is a bit lurchy when cold but has been like that since I got it so assumed its kind of normal.

 

[dweezle]

Well.a mate here in Sydney helped me out today with another Coil Pack to test with.
It did not seem to help much at all.

I decided to try new plugs but could only get hold of 3x PFR6E-10 Plugs so my mate kindly gave me a good used Plug to use just in case.

I got home and removed the Manifold Plenum for the first time and took out the plugs.
The first Plug i took out i noticed straight away that it was not the correct Type.
For some Stupid reason the car had NKG PFR6B-11.

On all 4 plugs the electrodes were burnt down and messed up!!
Cylinder 1, Nearest Gearbox was the worst but they where all bad.
C1 was clearly not firing correctly as it was corroded and missing almost the entire Electrode.

I just hope no permanent damage was caused from Detonation on the Piston ringlands.


Here is a the used correct plug vs what was in there.

So with that all fixed up i went for a short drive and Touch wood, all seems good now!!

Will find out tomorrow on the way to Bathurst for a Hill Climb event on Mt Panorama!!

Thanks to all you guys for the help with this issue.
Just wish i had of checked those damn plugs ages ago.

Track days on Hot days with those plugs would not be a good combo

 

[-J-]

Good news, hopefully it solved the running issues.

 

[dweezle]

Well the car ran faultlessly over the weekend and that included a hill climb event at Mt Panorama which is approx 250ks away.

So I think safe to say the issue was wrong plugs in the car.

Again thanks for all who helped

 

[dweezle]

Bugger!!
The problem resurfaced yesterday on the way home from work.

I got stuck in traffic for about 15 mins and then once cleared and at about 80kmhr in 4th the hesitation/stutter/stumble returned.

So I think I can rule out plugs/leads and coil pack.

I am thinking maybe o2 sensor or injector?
Would anyone agree with that?

I did notice that the map and ait sensor are loose in the manifold.
ie- they wobble back and forth easily.
Could there be a air leak and this causes some issues?

The car was perfect for the few days so maybe while changing plugs I bumped something good again and it has gone bad.

 

[dweezle]

I have noticed that i appear to have a small crack at the front of the Cat.
Could i be right in thinking this could be messing with the O2 Sensors readings and causing the stutter at low rpm?

 

[dweezle]

I finally think I have fixed the low throttle hesitation.

The gearbox speedo sensor.
A new one from EBay cost me $25aud delivered to Aus from the UK.

2 min job to swap out and all cured.
Well for the past 500ks anyway.

Early PH2 must use that sensor to feed info to the ECU.
I believe later ones used the ABS rings.


Also the cutting out happened again at a track day yesterday.

I believe it is fuel starvation.

Do clios not like low tanks?
Say less than 10 liters??