Lumpy Idle

After driving Gus everyday to and from work clocks up 32 Miles everyday.

No so bad but can take a toll on especially sitting in rush hour traffic.

BUT he does himself and me proud every day and still smiles per miles....

He has been causing a few worrying moments where he has a very lumpy idle. Very low RPM and also plenty of engine shake.

Initially I though an engine running on 3/4 cylinders but upon revving the engine it sorts itself out and he is still happy at 70mph with no loss of power.

So last weekend I did my typical see whats wrong.

1. Compression Test - Same a last time. Cylinder 2 lower at 105, rest OK at 120 but no worse.
2. Tappets reset - 2 slightly tight at 0.18 reset to 0.15
3. Plugs, HT leads,  Rotor & Cap checks - All okay swapped each and no issues

Plug on No 2 was black around top insulator- Could have been loose and blowing but cleaned and reset and swapped to a different cylinder.

Most plugs look a little rich BUT tips look normal and not completely soot covered black.

Also better rich and cool than lean and burned!


So after all that it idles better and more stable BUT I still get a random misfire noise - Not exactly a misfire at idle just a pinging noise randomly a few time a minute.

Occaisionly I also get a lumpy idle as well.

I have checked and swapped everything in the ignition except the coil.

so it could be:

1. Random air leak - Air leaks are worse at idle but don't typically cause misfire
2. HT coil arcing - Could explain misfire

Will pick up a replacement coil and see and check with the WD40 spray test