[pegasus]

Hi all
My gems 4.6 has developed a small problem and i am hoping someone can help.
When left standing overnight so it is really cold at the moment the car starts but missfires for about 30 seconds and there is a strong smell of petrol from the exhaust. The rest of the day its fine. I changed the plugs yesterday and they were a perfect colour, and it has had magnacore leads fitted along with new coil packs, the temperature sensor was changed about 12 months ago and the MAF is reading correct and the iac was changed a while back too. So is there anything else i should be looking at?
Thanks for your help
Mark

 

[viperover]

As you say its really cold, proberly icing up on throttle body until warm then ok for rest of the day.....
Seems like its not a problem to worry about, cold is cold and it throws alot of sensors out

Petrol when cold doesnt ignite very well untill combustion chamber warms up and that includes intake system

 

[pegasus]

I hope youre right with so much work to do on it another problem at the moment would mean it gets traded in,and to top it off today my faultmate decided it wasnt going to connect to car or laptop.
Thanks for your reply
Mark

 

[viperover]

another problem at the moment would mean it gets traded in
Mark

No no, Range Rovers are like Volvos, as the advert goes "its for life" cos you'll never sell the darn thing

 

[pegasus]

i`ve had 3 volvos great cars until i had the v6 renault/peugeot engined one, that dropped a cylinder liner
Now where have i come accross that problem before? :think:
The thing with this problem is that it didnt have the missfire when the temperature was -7 it ran great but now its still cold but warmer than it was, its playing up.
Range rovers whod have em
Mark

 

[diff]

You have obviously done a lot of work on your rangie. Did you solve a problem with all the parts you have changed. Ouch. Here in Canada, with -15 to -20 C when she starts it seems to run fine but there is a stronger smell of fuel not being burned perfectly which gradually dissipates. I have to say that my gmc van has a similar smell on a cold start up so I don't worry too much but both motors seem to run smoothly. I can only imagine what a drag it must be after all that you have done to have her run rough so I hope you find the cheap solution culprit soon.

 

[Keijo]

Pegasus,

I cured a rough idle cold running problem a short time ago, after going through the checks you have carried out, failing to find anything wrong and nearly comimg to a frustrating end.

HOW?

An often overlooked source of problems is the purge valve. Overlooked as it does not fall under the heading of "engine or fuel management" and it can not be found in RAVE in that section. You have to read through the Emission Control section to get any info' on the device.

However when you look it up in RAVE you will find a lot of stuff on it, including this interesting paragraph:
"To maintain driveability and effective emission control, EVAP canister purging must be closely controlled by the engine management ECM, as a 1% concentration of fuel vapour from the EVAP canister in the air intake may shift the air:fuel ratio by as much as 20%"

My problem was caused by a faulty purge valve being either stuck fully or partially open, allowing the accumulated concentrated fuel vapors which had accumulated in the system when stopped, to affect the idle mixture on start up.

I proved the fault via a temporary fix of removing the purge valve connection and blanking off it's inlet manifold connection.
The intersting thing is that a faulty purge valve can also affect the fuelling adaption and consequently have detrimental effects on your MPG.

After the fix, starting immediately became faster and easier, the idle speed was smoother and correct, and after a couple of hundred K's my fuel economy improved by around 5%.

May not be your problem, but worth a check eh?
Reading some other posts similar to yours, I bet a few others here have had some issues with this valve.

Good luck and cheers,
Keijo

 

[pegasus]

Intresting reading keijo certainly something for me to look into, as you say it can have an effect on the mpg. up untill a few months ago i was averaging 14mpg and now its 12mpg so i will certainly check that out. ray:
Thank you
Mark

 

[Bestold1]

Nice info. I've also been running rough at start up and have had terrible fuel mileage - 18L/100km; normally 15L/100km.
I was looking for O2 sensor reading values when I stumbled on this read, thanx a ton!

 

[rayodunne]

Lol mine is 25L/100km with 100% in town stop and go traffic.