Missfire

CubMG · Post by **CubMG** » Thu Apr 29, 2021 8:08 pm

HI I have a missfire on my 01 MGF mk2 1.8 mpi. 64k miles

If I lift off and then put the power back in it clears but after a while the MIL light comes on ,steady not flashing.
I have changed the cam position sensor for a new one , and I can reset the MIL light with a code reader , which comes up with a p130 fault .
Is p130 the precat sensor ? and what else could I change to sort this out ?

talkingcars · Post by **talkingcars** » Thu Apr 29, 2021 10:18 pm

OBD fault codes are a letter and 4 digits, please recheck the code and report back.

James

CubMG · Post by **CubMG** » Fri Apr 30, 2021 10:56 am

Ok it is P0130 ,and I have a ticking noise from around the multiplug midway down the inlet manifold.

markvrs · Post by **markvrs** » Fri Apr 30, 2021 3:11 pm

Hi,

That code is an O2 sensor circuit malfunction ( Bank 1 Sensor 1)

Unplug it and it should run in open loop mode without MIL light if it is faulty ( Runs a bit rich. O2 sensors are mainly emissions related)

Cheers Mark

CubMG · Post by **CubMG** » Fri Apr 30, 2021 3:30 pm

The question is though which one of the 2 sensors ? And is this the cause of the missfire? as that happens before the MIL light comes on . Drives ok and then when you put some power on it hesitates ,if I back off and put the power back on it clears .

ArntyR · Post by **ArntyR** » Fri Apr 30, 2021 4:22 pm

...a quick google said:- 'The 1st sensor is always located the closest to the engine, and the second is always located at the rear end of the exhaust system. Generally, in the case of O2 sensors: Sensor 1 = located before the Catalytic Converter Front (Upstream O2 sensor)'

Follow markvrs' excellent advice but it's probably going to need replacing, anyway, since sensors in these conditions don't last forever...

Let us know how it goes

CubMG · Post by **CubMG** » Fri Apr 30, 2021 7:24 pm

Ok where is the plug for the sensor on the pipes that go to the cat.

talkingcars · Post by **talkingcars** » Fri Apr 30, 2021 9:47 pm

CubMG wrote: ↑
Fri Apr 30, 2021 7:24 pm
Ok where is the plug for the sensor on the pipes that go to the cat.

Above the gearbox.

CubMG · Post by **CubMG** » Fri Apr 30, 2021 10:14 pm

talkingcars wrote: ↑
Fri Apr 30, 2021 9:47 pm

CubMG wrote: ↑
Fri Apr 30, 2021 7:24 pm
Ok where is the plug for the sensor on the pipes that go to the cat.
Above the gearbox.

Cheers for that ,I will whip the engine cover off in the morning and disconnect the plug and put a meter on the sensor .I have a TF airbox and 52 mm TB coming plus a front splitter so lots to do .

CubMG · Post by **CubMG** » Sat May 01, 2021 4:32 pm

Ok the missfire is gone with the sensor unpluged , but the idle is at 1200 rpm. MIL light came on again P0135 ,heater bank 1 . Time to change the Lambda sensor ,a 5 minute job . . . . I wonder how much a garage would charge to do it .

paul_mgb · Post by **paul_mgb** » Mon May 03, 2021 3:32 pm

Are you sure its not ignition. I had a misfire because the end of one of my HT leads was corroded. (as it went in to the plug top coil)

CubMG · Post by **CubMG** » Mon May 03, 2021 8:02 pm

paul_mgb wrote: ↑
Mon May 03, 2021 3:32 pm
Are you sure its not ignition. I had a misfire because the end of one of my HT leads was corroded. (as it went in to the plug top coil)

Did it throw up a P0130 fault code

Post by **Rob Bell** » Mon May 10, 2021 3:29 pm

Misfires on these twin coil pack engines is almost invariably a coil pack failing (*corroded HT lead connectors notwithstanding). Simple fix. You may find a misfire code on an OBD2 reader. Pscan can also report the burden of misfire and on which cylinder(s), which if high enough will cause an emissions error as you'll be throwing unburnt or incompletely burnt fuel down the exhaust manifold and the Lambda will be reading "rich".

If you can work out the pair of cylinders most likely to be misfiring, you'll be able to identify which of the two coil packs are misbehaving. Or replace both as they will likely be the originals and if one is breaking down, the other won't be too far away.

paul_mgb · Post by **paul_mgb** » Tue Oct 12, 2021 11:32 am

It did throw up the appropriate code for misfire on number 4 which was consistent with the corroded lead. I fitted a second hand coil and leads. 3 months later I got misfire on No1 which couldn't have been a lead. I've fitted new leads and plugs now and another secondhand plug top coil. Lights staying off for the moment. I suspect a duff plug because I didn't keep them in order the first time. They were Bosch long life plugs that had only done 30,000. I've fitted bogo NGK 'R' type now. The second hand bits came off a Rover25 I owned. It developed an engine management problem which was eventually traced to a bad connection on the MAF sensor but not before I'd changed loads of stuff.

CubMG · Post by **CubMG** » Sat Oct 16, 2021 2:33 pm

Just to close my bit down ,I changed the lambda sensor before the cat and the problem has gone and the car feels a lot better too. I popped into an exhaust fitting place with the sensor and they managed to get the old one out and fitted the new one with the car up in the air ,it would be very hard to do without a lift .

Post by **Rob Bell** » Mon Oct 18, 2021 10:08 am

Great updates, thanks chaps!

Swapping coil packs is something I've had to do on both a MEMS3 Freelander and ZR that I've had to look after. They clearly have a service life - which perhaps is unsurprising given the environment in which they live.

As for Lambda sensors - they're always a bit of a nightmare, particularly if they've been in the manifold for over 20 years...

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