Misfire after work

[Bushwhacker]

Disconnected battery for a few minutes before trying again. Is that enough to reset ecu

Yes that should be enough.
When the ECU is reset, it will take a number starts/runs for it to learn everything again, so take it for a short drive to get the engine up to temp and check for codes again.
Is the AFM in good condition?

 

[dooleysl]

Thought AFM might be an issue so changed it for a spare, seems worse so will revert back to the original tomorrow give it a run and see what happens.

Thanks again for all the help

 

[Bushwhacker]

Thought AFM might be an issue so changed it for a spare, seems worse so will revert back to the original tomorrow give it a run and see what happens.

Thanks again for all the help

If your spare AFM didn't improve the issue, then maybe the problem is with the wiring in that area?

 

[dooleysl]

A further update, checked with a loan ecu, runs the same.

Have checked the HT leads, 5 of them reading 15,000+ ohms, 1 reading 10,000, 2 of them reading below 5,000! Think a new set of leads is called for

Will get some next week and give it another try, update to follow

 

[dooleysl]

Another few weeks of not much progress.

Changed plugs for a new genuine set, fitted spare set of leads and had wiring re checked, nothing discovered.Drained out fuel, cleaned filters and then put fresh fuel in. Car ran better with less of a misfire ran it up to temperature and shut down.

Checked for any codes the next morning, none other than the missing O2 sensors and fuel ecu. Started car and misfire is back. Going to take the plugs out again and see which ones are sooted up......

The search continues.

 

[dooleysl]

Can't believe its been 2 years! Been busy at work and moving house as well as repainting and re trimming the car. The Merc is now back at the house so the time has come to resolve the misfire and rough running.

Pulled the engine and box back out and removed the loom to inspect for damage, none found. Checked the loom pin by pin all checks out ok. Rechecked wiring in the car, all ok as well. Put everything back in and still runs bad.

Checked the crankshaft sensor and didn't appear to be in spec, ordered a new one and the car wouldn't run at all. Picked one up from main dealer and the car runs again but still rough and down on power.

Have changed ignitors, coil packs, leads, dizzy caps and rotor arms, plugs etc etc so not sure what's next? Might run a compression test for piece of mind.

I am sure it will turn out to be something stupid............

 

[dooleysl]

Update...

Timing belt back off and everything double checked. Put back together checked rotors and caps, new plug etc. runs a lot better but still not as it should.

Compression check show front left cylinder has NO compression! Not investigate further yet but guess it might be time to swap the motor out.

Cam/Valves/Piston....???

 

[George_R]

Would be nice if you consider collecting a short summary of what's been done already

 

[Zuffen]

No compression indicates a fairly large (no a big) flow of air from the cylinder.

If it doesn't have a hole in the piston (which would give quite an airflow out of the breather)it has to be valves.

The engine is a non-interference engine so a stuck valve or two won't hit the piston.

I'd take off the camcover and have a look at the valve operation as that's the only thing I could think of that would give nil compression.

 

[dooleysl]

Engine pulled apart and head off, both exhaust valves stuck open. No other apparent damage. Head gasket set on order and will start dismantling the head in the next day or two.

Will upload photos

 

[dooleysl]

Does anyone know who can supply new exhaust valves? Struggling to find a supplier other than shipping from the States.
Cheers