V6 cutting out

[Tony C]

My V6 has started cutting out about 1 minute after starting from cold, this has happened for the last two mornings, it starts perfectly on first turn of the key but starts misfiring and then cuts out after traveling a few hundred yards, it is difficult to restart needing up to 10 attempts, once restarted the misfire continues for a short time before clearing & then running all day normally, there is now a warning light showing on the right of the speedo which says "heat" I have never seen this on before when running. Any ideas what the fault is please?

[mikeWalsall]

Not all V6 have the cat light (mine never as) ..



Unless the internals have collapsed .. it It seems very unlikely that it is overheating after such a short time ..

When mine started to cut out when first going onto LPG I changed the Dizzy cap /rotor/ plug leads and spark plugs and that cured the problem ..

Spray some WD40 (water dispersal) fluid around the plugs / lead / dizzy to dry out any dampness ..

Maybe try some new spark plugs .. They are child's play to change ..and quite cheap on eBay ..

http://www.ebay.co.uk/itm/NGK-SPARK-PLU ... Sw8w1X-0B1

[Tony C]

Thanks for that Mike, I will give the WD a try first.

[rita]

The first thing you need to check is that from start up ,the engine is in fact firing on ALL 6 cylinders, if its running minus a cylinder/s it will be dumping unburnt fuel into the Catalytic converter and turning it into a furnace.

Good Luck

PS if you remove the spark plugs Cover the plug Holes to avoid any objects from entering the cylinders.

[Tony C]

it is running on all six for the first minuet then starts misfiring, as you say the cat light is on because of unburnt fuel. thanks Rita.

[mikeWalsall]

maybe your ignition system is due for an overall ..??

Some recommend genuine Mada plug leads .. I used far cheaper English made guaranteed for life ones .. been on for around five years now with no problems ..



Bit of a fiddle removing the dizzy cap and rotor but still a DIY job ..

[Bongolia]

The fault appears to be in open loop, when the engine is cold and running on basic settings, so not sure why the heat light. When the engine goes closed loop your problem seems to be gone.
It may be on the change over so could be O2 related or ECT signal, but that is pure guess work. Best to have a methodical approach.

Check the basics first plugs leads dissy cap and rotor etc as Mike says bit of WD or Dampstart over the plugs and leads and dissy cap may help.
You need to go through all the basics,they are well covered on here.
If you cannot find a fault then it would be worth getting it scanned and see what fault codes are logged. Get them cleared and run it again then rescan in case you have induced any, look for the common ones across both scan readings.
Or any Bongo type garages near you?

[Tony C]

Thanks for that Bongolia, have just run it from stone cold following wd treatment, ran perfectly but heat light still on, have contacted Allans of Plymouth to carry out a diagnostics.

[Bongolia]

Ahh. leads probably damp or sommit. Let us know the outcome. I would be interested.

[Bongolia]

Just having a think on that and expanding on Rita`s theory.
Your vehicle may be equipped with a later ECU.
These unit employs two Oxygen sensors. One pre cat and one after.
The pre cat O2 sensor reacts to the amount of oxygen in the exhaust stream and adjust your fueling to maintain the correct air to fuel ratio.
Earlier versions with a single pre cat O2 sensor correct the fueling to a point then the cat would burn of the unwanted pollutants but if the cat itself were to fail you may be unaware until your next emissions test flagged it up.

To avoid killing unnecessary penguins in later systems a second O2 sensor was fitted after the cat. This sensor has much tighter parameters and has no effect on the fueling that is still done by the pre cat one.
What it does do is send a message to the ECU that a fault has developed and that the cat despite whatever is happening to your fueling is not converting.

It may be that your system has gone into closed loop early or you have a very fast warm up O2 sensor, this normally works in conjunction with the Engine Coolant Temperature sensor to arrive at at time to switch to closed loop.
The aft cat sensor is normally ignored by the ECU until this state is reached.

So the misfiring would be sending excess quantities of fuel to a fairly cold cat that would not be able to handle thus flagging up your heat light ,the cat may simply be overwhelmed.
Now some systems will hold that fault code for several start stop cycles before it decides that every thing has sorted itself and then it may put your light out and simply store the code in long term memory.
If all checks out it may be worth an overhaul of the ignition system anyways now the cold and damp is on its way.
Just a thought. The scan will tell.

[Tony C]

Ran perfectly today although the Heat light is still on, will give it a day or two to see how it things go but will take it to Allans ASAP for check up. will post results.

[Bongolia]

Not all V6 have the cat light (mine never as) ..



Unless the internals have collapsed .. it It seems very unlikely that it is overheating after such a short time ..

When mine started to cut out when first going onto LPG I changed the Dizzy cap /rotor/ plug leads and spark plugs and that cured the problem ..

Spray some WD40 (water dispersal) fluid around the plugs / lead / dizzy to dry out any dampness ..

Maybe try some new spark plugs .. They are child's play to change ..and quite cheap on eBay ..

http://www.ebay.co.uk/itm/NGK-SPARK-PLU ... Sw8w1X-0B1

Maxda dealer??

[windywatson]

I have 2 V6 bongos, one has the exhaust overheat light(97reg) the other doesn't(2001 reg). On inspection the one with has an additional sensor on the exaust adjascent to the CAT with a single wire connected. I suppose that there is every possability that the sensor has failed itself. Intrestingly if you replace the exhaust system the new ones don't come equiped with it, so you would just disable it. I would suggest disconecting the wire & see if the lamp goes out. I was informed that the lamp is just to warn when the cat is running very hot so that you don't risk causing a fire under the vehicle by parking over flamable meterial like verges with long grass etc.

[Bongolia]

That is interesting, so the earlier type has an after cat sensor and the later one doesn't is that right?
If yes I wonder why they stopped fitting them, curious.

[windywatson]

Yes thats correct, my older pre face lift 97 has it & my 2001 face lift doesn't. If you buy a new exhaust there is only one option & that is without the sensor so you have to disable it if you have the earlier model.

Cheers