Problems after service - misfire?

[mlarj]

Firstly, a hello from a fairly new 3R owner! (a couple of months) What an amazing car, even though I have already had to replace the starter motor and sort a water leak filling the driver’s side foot well.

Whilst I have a complete service history for the car I always like to complete a full service myself so I know everything is ok and have a good starting point. This weekend I completed a complete exhaust change (I will cover this is another post) and a full service. However, yesterday whilst driving to work the car was very hesitant at part throttle and had an extremely lumpy tick over. Returning home later in the day the symptoms were still very evident but once cleared the car drove fine.

Yesterday evening I reverted the spark plugs back to the motorcraft ones I removed (NGK fitted from WIKI during the service) and took it for a test drive. Initially the car was misfiring but then it cleared and drove fine for the rest of the test drive (15 minutes). Not convinced I had fixed the problem, this morning’s journey to work has confirmed my suspicions and again very lumpy/misfire at light/part throttle but when the car picks up speed the problem clears. The old spark plugs do appear to have helped the problem, and at the end of my during the car appeared to be running correctly again but the problem is certainly not fixed! I am now at a bit of a loss as where to look next.

I have visually checked that none of the hoses have come disconnected and I am pretty certainly I have them all connected correctly but I will double check tonight but I’m open to suggestions/ideas. I'm more than aware it is very difficult to describe the problem and I'm not sure if it is a misfire/over fueling or something completely different!

Thanks,

Mat

[F.C.]

Check the Plug gap is correct.

[mlarj]

Thanks for the fast response, I thought reverting to the old plugs would have ruled out the plug gap? I didn't have a misfire previously?

[TuxMan]

Check to make sure you have refitted the inlet manifold correctly , could be a air leak , also check all pipes ect to make sure nothing is loose . You could also disconnect the battery for 1/2 an hour to reset the adaptive maps ect .

Tux

[Hollowpockets]

Try checking the vacuum hose to the inlet manifold is in place too.

[Gadgeroonie]

Hollowpockets said:

Try checking the vacuum hose to the inlet manifold is in place too.

if the vacuum pipe to the map sensor is pushed on too far it will block the flow of air

[brappage]

Welcome from another new owner ( 2 weeks. ) I have also in my first couple of weeks found a water leak and a few rattles which I am going to have to sort, think the leak is from a split grommit at the bulkhead so possibly have a look there if you havent already managed to find it. Initially thought it was the floor until I stripped out the interior panels around it and there was still a drip from above. Will seal it this week and hope for the best.

[mgbond]

Prob not the issue but has the car been left outside in the rain, Sometimes this gets in the wrong places and causes an issue until dried out?

Bondy

[mlarj]

Thanks for all the suggestions, I will try to leave work early and double check all of the connections etc. Hopefully it will be something simple like a split pipe!

Not long after I bought the car I had a strange misfire on the way to work that cleared and never returned. If I had a coil pack breaking down would this cause the problems I am experiencing? Assuming I have the fault when I get home, could I unplug the LV side of each coil pack in turn to try to identify which cylinder/coil pack 'could' be the problem? Is there any risk to the ECU?

Edited by mlarj on Tuesday 17th July 12:59

[priestja]

I had very similar symptons after replacing a cracked front exhaust manifold. Tick over very "throbby", wouldn't pull between 1500-2300 revs and black exhaust tips.
Yellowshed kindly helped me out resetting the adaptives on the ECU and everything sorted.

[R0162]

It doesn't sound like plug gap with such low rpm and boost, but just want to add that the NGK are better for this car than the original motorcraft, the stock ones are not really suitable for our cars,but that aside lets eliminate the plugs...

lumpy running at low rpm can be a leak on the manifold or a lambda sensor.

Disconnecting the battery to reset the adaptive map is one worth trying, i do not think it is the vaccuum pipe under the throttle body being pushed on too far, but pull the 90deg bend back a little bit to make sure it is not restricted.

It could be an injector, as when the car warms up you are getting better combustion, and when pressure increases you are getting better combustion, may be dripping a little rather than atomising the fuel..

[mlarj]

Typically I couldn't spend too much time on this tonight but other than a few minor hiccups driving home it ran perfectly and tickover was fine. I decided to disconnect the battery whilst I inspected the hoses etc but unfortunately nothing appears to be split or folded . I did discover something not quite right...a small ammount of oil appears to have collected in the 'trough' where the rear coil packs are, and appears to have come from above. When I changed the plugs I did clean up a bit of oil but thought nothing of it. I think I am going to completely remove the plenum at the weekend when I refit the new ngk's, is it common for plenum to split/crack?

Thanks again for all your suggestions.

[Hollowpockets]

A turbo seal maybe gone and letting a lot of oil through to the inlet side?

[hoyin]

priestja said:

I had very similar symptons after replacing a cracked front exhaust manifold. Tick over very "throbby", wouldn't pull between 1500-2300 revs and black exhaust tips.
Yellowshed kindly helped me out resetting the adaptives on the ECU and everything sorted.

How does one do this?

I just got my manifolds changed and am experiencing similar.

[playalistic]

Via dealer software (if you're local or can travel to Reading I can do this for you) or just disconnect battery for half hour or so!

[hoyin]

playalistic said:

Via dealer software (if you're local or can travel to Reading I can do this for you) or just disconnect battery for half hour or so!

Oh I am about 45mins away!

I'll take you up on that.

Not around this weekend ... maybe next weekend if you are around?

Thanks

[playalistic]

Sure, drop me an email with a day or so notice and we can get it hooked up

[andygtt]

if your new exhaust is much better or replacing one with an issue then the ecu will struggle to put it right... resetting the adaptive maps as Tuxman mentions might resolve.

Id recomend you contact yellowshed, he is in essex and can resolve a slight ecu map issue in minutes that other garages can never find/solve... ive found this out myself when I had a silly missfire a few months after I bought the car

[mlarj]

How long does it take the ecu to relearn? Since removing the battery for 30 minutes on Wednesday evening ,things have been improving daily. I'm still not convinced I haven't a another small problem but it is a lot better. When I refit the NGKs I will double check everything.