Topic

Hi there, I know I have posted this on org/f reg too but thought I would spread the net as widely as possible in my search to sort this out!

For those with a good memory you may recall that I had problems with misfire and low fuel codes. Anyway the car drives fine and the misfire disappears at higher revs (say 2k or more).

When I had it remapped Mark checked all of the sensors to try and help me diagnose and he didn't think it was an electrical problem. Now I have had it compression tested, the IACV is a replacement (which initially improved it). Mark did say that the valve seems to be open much more than it should be at idle and he thought that it may be compensating for a leak somewhere. How would I go above searching for an air leak into the system?

Whilst mark has turned the constant EML off for me I have had the occasional flashing on cold start ups until I rev it so would like to sort it as it is sounding a little rough.

During my previous investigations I changed the plugs, leads and a coil pack. I also swapped them around and the code kept referring to the same cylinder. Mark also mentioned that it could be an injector and I have run some cleaner through to no avail. I haven't changed the post cat O2 sensor, but have changed the pre-cat one. I know this was going to be the next thing for me to try buy my local garage didn't want to do it as the code didnt refer to the sensor and didnt want to do what they felt was unnecessary work!

Any help would be appreciated, as I have put up with this for a while and would love to sort it is there anyone local who could help me out or do I need to get back up to Techspeed?


my earlier posts:

http://forums.mg-rover.org/showthread.php?t=432804

Jackson wrote: wrote:

...When I had it remapped Mark checked all of the sensors to try and help me diagnose and he didn't think it was an electrical problem. Now I have had it compression tested, the IACV is a replacement (which initially improved it). Mark did say that the valve seems to be open much more than it should be at idle and he thought that it may be compensating for a leak somewhere. How would I go above searching for an air leak into the system?

My understanding is that if you had an air leak in the inlet section the revs will be above normal ...but the IACV would be closed trying to lower the revs.

With regards to finding leaks on air systems, I have in the past applied a thick grease to joints in vacuum tubing one at a time to see where the leak is.

I wouldn't have thought this would be the source of a misfire. If elctrical faults have been ruled out, I would be inclined to check the fuel filter/pump and fuel lines.

I'm a bit far from you but if there is anyone near Bromsgrove who could help out, it sounds like Jackson could really do with a hand.

What was the result of the compression test?

I had a similar intermittent misfire and I found that there was corrosion on the bottom of the coilpack. There is a spring under there that transmits the spark between the plug and the coilpack. It's hidden under the rubber boot. The corrosion was between the metal of the coilpack and the spring causing a poor connection. Cleaned both coilpacks and the misfire disappeared.

David Aiketgate wrote: wrote:

What was the result of the compression test?

I had a similar intermittent misfire and I found that there was corrosion on the bottom of the coilpack. There is a spring under there that transmits the spark between the plug and the coilpack. It's hidden under the rubber boot. The corrosion was between the metal of the coilpack and the spring causing a poor connection. Cleaned both coilpacks and the misfire disappeared.

Ditto! I had an intermittent misfire and set about changing the leads and plugs and giving the coil packs a visual with a view to changing them. On all of the plug connections there was what can best be described as a black carbon-like dust together with oxidation. I too found that the the coil pack to plug connectors needed a good clean: the lower rubber boot that goes over the plug insulator puls off fairly easily.

After a thourough (careful!) clean and reassembly with new leads and plugs (NGK) the misfire has gone.

Have a look at this

Geographically, I'm just up the road. Technically, I'm not on your planet. Sorry and good luck in fixing this problem. Hopefully some of the answers above will help.

Thanks for the replies guys it is very much appreciated. I could check the coils although the mgf centre did change one without effect. Also changed the plugs (which looked ok to me?). Just one of those things that has gone on for so long I'm losing the resolve to sort it! Any other suggestions so I can have a few areas of attack when I get my hands dirty?

Noticed a few whiffs of petrol under spirited driving today and some crud has come out of the exhaust again