misfire

Post Fri Jan 24, 2014 5:08 pm

My cab which is a m20b28 has started to misfire slightly and backfires a bit, but the car had not lost any power. The car was fine until yesterday.

Things that iv checked/done
Compression test all 6 are good
Changed leads
Checked for spark which is strong
Checked temp sensor which is good
Maf is good
Checked the injectors by putting a screwdriver on each one and heard the tick

I am going to change the rotor arm plus the distributor cap with new ones, but don't think that is the issue.

My question is can it be fuel Related? Has anyone got any other idea?

Post Fri Jan 24, 2014 5:38 pm

What's the colour of the spark plug tips - all a nice tan colour, or is one whiter than the others?

And, are you getting any loss of coolant, or steam out of the exhaust?

Post Fri Jan 24, 2014 5:41 pm

Speedtouch wrote:What's the colour of the spark plug tips - all a nice tan colour, or is one whiter than the others?

Plugs came out dark, I'll put up pictures up of them tomorrow

Post Fri Jan 24, 2014 6:00 pm

It's a possibility it could be fuel related, if you got a dodgy batch with some water in, say...

Post Fri Jan 24, 2014 9:09 pm

Speedtouch wrote:It's a possibility it could be fuel related, if you got a dodgy batch with some water in, say...

I only use v power on all my cars, but will check the plugs and put up a picture tomorrow.

I was thinking fuel pump, or the fuel filter

Post Fri Jan 24, 2014 10:18 pm

Could also be one of those at fault. Misfires can be quite hard to diagnose. My Minor once had an intermittent one that steadily got worse until one day, it wouldn't start; I checked for a spark and there was one, so I was about to remove the cylinder head for a look, when I decided to check the sparks again. This time round, no spark - turned out the ignition coil had failed. A new coil later, and all was well again.

Post Sat Jan 25, 2014 8:56 am

Speedtouch wrote:Could also be one of those at fault. Misfires can be quite hard to diagnose. My Minor once had an intermittent one that steadily got worse until one day, it wouldn't start; I checked for a spark and there was one, so I was about to remove the cylinder head for a look, when I decided to check the sparks again. This time round, no spark - turned out the ignition coil had failed. A new coil later, and all was well again.

Iv changed the coil with a known working one but no joy.

Post Sun Jan 26, 2014 8:08 pm

Pictures of the soak plugs, the first in the left is number 1 and the last on the right is 6

This is what all 6 used to look like in September

Post Sun Jan 26, 2014 8:11 pm

Got the misfire sorted after giving plug 2 a good clean.

I have not changed or done any modifications to the car in the past 6 months, so why would the plugs end up like that?

Post Sun Jan 26, 2014 10:19 pm

They don't look at all bad to me. Are they the correct spark plugs for the engine, and correctly gapped?

Post Mon Jan 27, 2014 9:40 am

Speedtouch wrote:They don't look at all bad to me. Are they the correct spark plugs for the engine, and correctly gapped?

The plugs are ngk-r can't remember the number. But plug 2 was not sparking, gave it a clean and it was fine. No misfire

Post Mon Jan 27, 2014 12:04 pm

Very odd; they normally have to be very fouled up indeed not to spark at all!

Indication of a failing coil pack, perhaps...

Post Wed Jan 29, 2014 10:20 am

Speedtouch wrote:Very odd; they normally have to be very fouled up indeed not to spark at all!

Indication of a failing coil pack, perhaps...

Plug number 2 was fooked, I needed to use a knife to get the crap off