V6 Bongo Misfires When Hot

[Ian]

This received from member Steve. I hope you can help.

"When my engine is up to normal temperature it misfires and I lose at least one third of power and it vibrates.

I cleaned and set the plugs and nothing changed. I put in new plugs and still no change. I went to a garage rather than buy loads of new parts and explained the problem and also had a MOT. It passed the MOT OK. The garage cleaned the distributor cap and the rotor arm but said I should try new ones.

I bought a new distributor cap and fitted it. I could not fit the rotor arm because someone else has ruined the head on one of the retaining screws (do they screw the same way as normal - who ever did had used a lot of force and the garage said nothing to me - perhaps the garage cleaned it without removing it; quite possible) Any way I started the engine up with just the new distributor cap and it does sound a lot better when cold. The Bongo accelerates like a wotsit out of hell until it gets to the normal temperature then it is pretty useless. I can not fathom out what effect the reaching of the normal temperature might have on anything that would cause the engine to misfire.
The old plugs were pretty good and a little black which was probably from the misfiring but otherwise OK.
When the problem started a few weeks ago the engine once suddenly burst into power with a pile of smoke coming out of the exhaust. It has not doe that since and the exhaust gas looks fine as the MOT testifies.
The air filter is clean but I have a spare one for the next service.

The garage has no response to the fact that it misfires only when hot.

Do you have any ideas? I live in North Wales and there may not be too many Bongo experts here.

Thanks in anticipation."

[haydn callow]

First the rota arm screws undo as normal....
My misfire was cured by a new rota arm......no amount of cleaning the old one had any effect....also I removed each HT lead one at a time and gave them a really good clean using a rag and white spirit.

[francophile1947]

Could be HT leads breaking down when hot - worth getting a new set.

[haydn callow]

If you get new leads...get Mazda ones....the ones I got for £80 were rubbish