Finally fixed my misfire at long last!!!
 

Hi guys you may or may not know I have been having problems with my car since oct/nov and it's only today that I have actually fixed the problem.


Apologies for the essay but maybe this will help someone else in the future.

It started back in October when my car started behaving badly with the cold weather etc; Steamy exhausts and check engine lights, lumpy running, stuttering, coughing, jerking, surging, etc.
It then got progressively worse and started to misfire alot especially under hard acceleration....

1st off I replaced the spark plugs from NGK platinums to NGK V-Grooves as this was all I could afford at the time and there was a noticeable difference in smoothness. But the car was still not right....

I then replaced the coilpacks which made no difference....

So I though OK I'll replace the HT Leads- again no improvement either.

I was pretty sure it wasn't the turbo vacuum pipes as I had previously replaced them with petrol pipe... But anyway just to be sure they hadnt started leaking I bought some new silicone tubing and replaced all 3.... But as suspected no improvement again!

So in the few months I spent wondering WTF is wrong with this Bl***y thing I bought a VVC inlet manifold to swap over as I thought maybe there is a crack that is opening up under load... It had a few sensors on it so I took the throttle position sensor off to try a swap with mine and again this did nothing, except maybe idle slightly lumpier. I havent got round to swapping the manifolds over yet....

So as time went on the exhaust has developed a rather deep noise as I think the baffle has gone or is going maybe related to all the misfiring, so my next thought was some bits of metal floating about and causing a blockage in the exhaust at high revs.... So I started contemplating a new back box which I cant really afford an OEM one and dont want a cheap noisy stainless one.

I also thought maybe the fuel pump had began to pack up or I was experiencing FFS. So I checked the fuel filter and it was fully tight so that was a relief...

All this time I had been researching the causes of misfires under acceleration and there are loads of reasons why it could happen!

Next thought was lambda sensors, Inlet manifold gasket, cam sensor, leaky throttle body, catalytic covertor,etc. - The expensive stuff


Anyway turns out the spark plugs I fitted were gapped to 1.0mm +/- 0.05mm as recommended. After my extensive research I thought I'll just try reducing the gap as it cant hurt to give it a go and it costs nothing!

So I regapped the spark plugs to around 0.5mm earlier today and guess what the misfire has gone completely!!!

So glad I didn't spend anymore money on things that didnt need replacing!!!

I love my car again and might even give it a clean 2moro http://forums.mg-rover.org/images/smilies/wink.gif

That .5mm equates to 20thousands of an inch in old money which sounds about right. Most cars use about 25 thou. The 1.0mm was too big.

JCW

Very pleased you've solved it, must store this information away for future reference.
It's surprising that a lot of potentially expensive problems turn out to be the simplest of solutions.

starting to read your post when you mentioned a steamy exhaust and a miss fire i thought inlet manifold gasket..anyway the MIL light is very sensitive to a miss fire and the cheapest option is the spark plugs.

glad to hear your sorted.

Sounds interesting, I have had a misfire on my 1.8 T now for around 2 months, changed coil packs, MAP sensor and plugs but to no avail, I will try the plug gap, it is in the garage at present as they are scratching their heads as what to do next, see my thread ' Engine misfire '

Which is what MR Z T and I both told you to do in February???? :shrug: :confused:

We have both seen your thread and put the same answer on it back then.

Gaz

I missed this post as mine has also had this problem, had new plugs, then coils packs, then had the exhaust done, and lambda sensors. now going out today to check my gaps to see if the garage did the right gap, please please, please let this be my problem :bowdown:

Well spark plugs now done (they were all well over 1mm and now all down to .5 mm, and this was a garage doing the plugs) and heres the moment of truth, will let you know in about half hour or so. (Touch Wood) :bowdown:

OMG, I now love my car again.

After everything I have done to get rid of this mis fire feeling and it looks like it was just the spark plug gap. (Never going to get a garage to do it again)

Yaaaaaaaahhayyyyyyyyyyyyyyyy

:):):):):):):):):):):):):):):):):)



:bowdown::bowdown::bowdown::bowdown:Praise be to this site :bowdown::bowdown::bowdown::bowdown:

How can i check on my car that? I also changed plugs,leads,coils,cam sensor and still it doesnt pull like it shoud? How can i regap my plug's to 0.5mm?