erratic mgf misfire

Hi,
First post on the forum,I have a 2000 Mk 2 1.8 MGF that has developed a misfire that only occurs after about 10 miles driving,noticable around 3000 to 4000 revs.Had short service and cambelt change about 1000 miles ago,new exhaust flexi and backbox a while ago, the exhaust fitters managed to destroy the sensor in the front flexi pipe which I had renewed.I have read practically all forum posts regarding HGF and am aware of the possibility of inter cylinder leakage problems causing a misfire.
I will be fitting a new fuel filter shortly,checking the plugs, compression check etc.I was wondering how often the coil packs broke down under temperature.As the cost of these items is quite high,it will probably my last resort if everything checks out ok.
Any information,recomendations gladly received.It may be a while for any progress reports due to the wife insisting I have more urgent jobs to do!
Regards Neil

Hi Neil! Welcome to the forum! I've just moved your thread over to the technical section so that hopefully the right people see it and can give you some advice.

Good luck!

Kara

Thanks Kara,I had realised my mistake but did not know how to rectify.
Regards Neil

neilowen1;9090 wrote: Thanks Kara,I had realised my mistake but did not know how to rectify.
Regards Neil

You're welcome.

So how long have you had your F?

:welcome2:
I would look at the plugs, plug leads and the connectors underneath the coils first.

The coilpacks are pretty reliable but not bombproof, but the plugs, leads and connections are often overlooked because they're out of sight.

Kara,
Had the F since last March,went out in it today with the hood UP for the first time!
Regards Neil

Thanks David,Previously read your entry regarding your misfire,will check every item on the coil packs when time available.
Regards Neil

I would start off with the plugs, leads then if there is still a problem check the coil packs.

neilowen1;9100 wrote: Kara,
Had the F since last March,went out in it today with the hood UP for the first time!
Regards Neil

Wow serious respect! I think I've had the hardtop on since November!

I think the key thing is the 10 miles. What changes at ten miles?

It could very well be the heat from the engine causing a HT component to breakdown.

Also remember that the engine changes state at around this point due to the engine warming up. The coolant temp sensor sends a signal to the ECU which basically tells the system that the engine has warmed up. This changes the fuelling etc from cold start to warm engine. One of 2 things could be happening. The temp sensor is not reporting that the engine is to temp and the engine still thinks it is warming up. This would result in the engine overfueling and caould cause the engine to run roughly. You could also have a fuel problem where once it switches to warm engine running you are getting insufficient fuel, due to the injectors being dirty or th fuel filter etc.

To be honest, it could be a lot of things, but the clue is the 10 miles.

If it was due to HGF etc I would suspect it to run roughly all the time, even when the engine is cold.

Rough running could also be down to a damaged cat, if the bodgers damaged that too, but I would suspect lack of power etc.

CJJ;9115 wrote: I think the key thing is the 10 miles. What changes at ten miles?

It could very well be the heat from the engine causing a HT component to breakdown.

Also remember that the engine changes state at around this point due to the engine warming up. The coolant temp sensor sends a signal to the ECU which basically tells the system that the engine has warmed up. This changes the fuelling etc from cold start to warm engine. One of 2 things could be happening. The temp sensor is not reporting that the engine is to temp and the engine still thinks it is warming up. This would result in the engine overfueling and caould cause the engine to run roughly. You could also have a fuel problem where once it switches to warm engine running you are getting insufficient fuel, due to the injectors being dirty or th fuel filter etc.

To be honest, it could be a lot of things, but the clue is the 10 miles.

If it was due to HGF etc I would suspect it to run roughly all the time, even when the engine is cold.

Rough running could also be down to a damaged cat, if the bodgers damaged that too, but I would suspect lack of power etc.

could the pre flexi sensor have anything to do with it? if its not registering correctly the ecu will fuel incorrectly wont it?... apologies if im wrong just seemed like his problems started after this was damaged

But it would do that all the time. If it has a pre and post cat sensor it would probably light the MIL warning lamp anyway.

The best way to check is get a diagnostic done. Plug it into a Testbook computer.