P38A Engine Rebuilt now have miss fire???

Hi All, Engine rebuilt and all looked well nice tick over could rev to 2500 to circulate oil and water, tappets went nice a quiet after 5 mins. No pressure build up in top hose nice and cool not like before. So i'll give it a little test drive. Well she now miss fires just over 1500 revs? I think it may be the leads breaking down as they are old and a miss match of types or spark plugs? What do you think????

Check n test

Lift the bonnet in darkness and look for blue sparks at the leads.

Check the plugs are all fine (you wouldn't believe the amount of times I have seen one or two plugs with a tiny bit of dirt between the anode & cathode!

Another possibility is a faulty crank sensor... But this usually makes it's presence felt after warm up and normally the engine dies, but not always!!

New Plugs and leads fitted, starts sweet, tic over sweet, on the road all is well unit it gets warm then miss fire at over 1500 rev's? No Power at all? Any ideas???

Have you reconnected the Maf ?

big mac?

Diagnostics are your friend. You can bugger about for ever guessing.

Someone should have said "Get an oil burner" by now.

Grrrrrr said:

Someone should have said "Get an oil burner" by now.

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GET AN OIL BURNER,BY NOW. How's that? I would have said it earlier but I'm tired and emotional.

tomcat59alan said:

GET AN OIL BURNER,BY NOW. How's that? I would have said it earlier but I'm tired and emotional.

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Is PMS contagious?

Grrrrrr said:

Is PMS contagious?

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As in catching or in taking a long time?

tomcat59alan said:

As in catching or in taking a long time?

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Long day. You've lost me on the long time part?

Grrrrrr said:

Long day. You've lost me on the long time part?

Click to expand...

Contagious as in "It's taking the c*nt ages"

Success ? She raw's again. Had chance to check all the plugs that i disturbed and i think it was either the crank sensor or oxygen sensor.
Didn't notice that even when cold she would misfire at 3000 revs then when warm 1500 revs???
So she now runs as she should but i still have a issue with the oil pressure switch flicking on when warm, I've replaced the pump strip and cleaned pump assembly and all in spec, so do i have a week pressure switch or cooling rad is u/s running on 10w60 oil????

Ledsam said:

Success ? She raw's again. Had chance to check all the plugs that i disturbed and i think it was either the crank sensor or oxygen sensor.
Didn't notice that even when cold she would misfire at 3000 revs then when warm 1500 revs???
So she now runs as she should but i still have a issue with the oil pressure switch flicking on when warm, I've replaced the pump strip and cleaned pump assembly and all in spec, so do i have a week pressure switch or cooling rad is u/s running on 10w60 oil????

Click to expand...

Check the o-ring on the oil pickup. If that is damaged it won't seal properly and the oil pressure will drop.

Ledsam said:

Success ? She raw's again. Had chance to check all the plugs that i disturbed and i think it was either the crank sensor or oxygen sensor.
Didn't notice that even when cold she would misfire at 3000 revs then when warm 1500 revs???
So she now runs as she should but i still have a issue with the oil pressure switch flicking on when warm, I've replaced the pump strip and cleaned pump assembly and all in spec, so do i have a week pressure switch or cooling rad is u/s running on 10w60 oil????

Click to expand...

10 w 60, do you drive in Saudi Arabia a lot?

It was recommended by another to be the best you can get???

Wouldnt be surprised if your oil pump is struggling to suck that from the sump

Never tried it but if it is 10w cold it should be OK.

Crank sensor will almost always die when warm.

O2 sensors will run hot or cold, but dump huge amounts of fuel down the pipes, but wont cut out on these massive engines.

Mine (read MoT failure thread) was running on five cylinders, yet still went. Mice had chewed through two spark plug wires and a third was simply broken, yet she "still" did 70mph (or more if asked) so if a motor dies or lacks power when warm it's almost always a crank sensor.

It tells the ECU where in the 360 degree cycle #1 piston is in relation to the timing. So if the ECU doesn't know when to fire a spark, it will die.