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Old 13-08-2010, 17:52   #1
mgljf
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Unhappy engine misfire when warm flashing engine management light

Hi i have a 52 reg 1.8 mg zs. Yesterday on my way to work after about 15 mins the engine started to misfire then the engine management light started to flash. I pulled over, called RAC and waited about half hour. When they arrived he turned engine over & could not find any problem. So he escorted me to work, about 10 mins, and it didnt happen again. On way home i went another route off motor way & went steady, It appeared fine.
Partner did a service on it last night, changed oil filter, fuel filter etc.
On way to work this morning after 15 mins exact same thing happened. So i waited a while and started up again, only got half mile before it did it again. Waited a while and only got 200 yards this time. Every time i restart the light is no longer on.
Called RAC he did diagnostics, gave error general misfire.
I'd been waiting over an hour this time so he escorted me back to garage. Yet again the problem never happened. Rac guy advised garage to check coils.
They've just told me that after 2 hrs looking at it they still have not found problem. They took it for a test drive themselves and it did the same to them.
What could it be?
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Old 13-08-2010, 18:20   #2
marty1a
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Could be a bad cam sensor? Inlet manifold leaking?

Do you no what the error code was? p0300? Or p0301,2,3,4 if its 1-4 at least it will tell you what cylinder is causing it where as p0300 is a random misfire across the cylinders.

I no its not doing it all the time but start with the basics, are they the right spark plugs? are the leads good?

compression test each cylinder
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Old 13-08-2010, 23:53   #3
2bellys
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do not i repeat do not use your car with the engine managment light flashing it is telling you that you are damaging your catalytic converter.

if the light is constantly on it is telling you a fault exists which will affect emmisions and needs diagnosing/rectifing

if the lamp flashes it usally means a significant ignition related misfire exists and is dumping raw petrol onto the cat monolith causing it to overheat and melt and then block the exhaust.

low compression wont cause a random misfire and make it intermittant likewise an inlet manifold leak

the fault is ignition related pure and simple.

you need to find out what cylinders are misfiring if its the inner 2 or outer 2 look at the coil that supplys these cyinders but before you replace the coil check the live and pulsed neg to it to make sure its not wiring or and ecu not suppling the pulsed neg (unlikely)

a fueling fault wont make the managment lamp flash

if its just one cylinder swap the spark plug with another cylinder and see if the misfire moves to the cylinder it was swapped with. if yes then replace all your spark plugs

if it is a cylinder that is supplied with a lead (coil not on top of plug) then try a new lead (im assuming it a EU3 engine)
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Old 14-08-2010, 07:57   #4
graphic
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I would also check all wiring, looking for loose connections and places where the wiring might have rubbed through causing an intermittant short. Check main ECU plug is clean and tight.

Have a close look at wiring beneath battery tray and L/H side of inlet manifold.
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Old 14-08-2010, 08:33   #5
marty1a
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[quote=2bellys;3983286]

low compression wont cause a random misfire and make it intermittant likewise an inlet manifold leak

Its does on a freelander 1.8k series engine, trust me on this one I chased my tail for a day until I compression tested it and found cylinder 1 down on compression!

As I said before start with the basics, as the RAC & the local garage have had it on diag equipment and cant find the fault

Have a look at http://www.random-misfire.com/ could be a vacuum leak

Last edited by marty1a; 14-08-2010 at 11:14.
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Old 14-08-2010, 14:49   #6
mgljf
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Done all of the above, and now it seems to have moved on to a different fault! its now running till it loses power completely to a stop and the engine management unit is no longer flashing and then it wont restart for ages.
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Old 14-08-2010, 22:04   #7
LORDPSK
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Sounds like it is either the temp sender unit or lambo sensor which is over fueling the car and choking it
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Old 17-08-2010, 01:03   #8
eddiemax28
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Quote:
Originally Posted by LORDPSK View Post
Sounds like it is either the temp sender unit or lambo sensor which is over fueling the car and choking it

id say the temp and lamba sensors too,, i had this on my 1.4 16v k, wouldnt start on cold mornings and when it did start it would misfire and blow out some smoke but once warm it was find untill the lamba sensor went down on it and lost power ect
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