General misfire on startup

[levemircento]

last couple of days when I have started the car from cold [cinq sporting] it has misfired, and only ran on 3 cylinders for about 5 seconds, by which time the 4th fires ok

it then runs faultlessly from then on, if its left to go cold again that same day the problem doesnt reappear

water usage hasnt changed, I cant smell or feel anything like oil or petrol in the water, one thing I did notice, was if I filled the water to MAX, next time I check it its back between MIN and MAX, but never any lower

I would guess the compression is ok, as the engine idles very smoothly, engines with low comp on one cylinder tend to idle roughly.

I wondered if it might be a coil on its way out, but then would it make two cylinders misfire?

as I said, once running its fine, takes a while to get to temp, always has, mpg and power is great still, it never overheats - temp never goes over 90, the fan keeps a hat on it ok.


any ideas?

 

[GoBe]

last couple of days when I have started the car from cold [cinq sporting] it has misfired, and only ran on 3 cylinders for about 5 seconds, by which time the 4th fires ok

it then runs faultlessly from then on, if its left to go cold again that same day the problem doesnt reappear

water usage hasnt changed, I cant smell or feel anything like oil or petrol in the water, one thing I did notice, was if I filled the water to MAX, next time I check it its back between MIN and MAX, but never any lower

I would guess the compression is ok, as the engine idles very smoothly, engines with low comp on one cylinder tend to idle roughly.


I wondered if it might be a coil on its way out, but then would it make two cylinders misfire?

as I said, once running its fine, takes a while to get to temp, always has, mpg and power is great still, it never overheats - temp never goes over 90, the fan keeps a hat on it ok.

Go do a compression test as beside still having top end power you've exactly described the symptoms of my Mk1 Sei's HG failed. Mine isn't a fully blown HG fail it's a slight one but it's confirmed with exhaust gasses in the coolant & one cylinder is slightly down on compression.

Check to see if the pressure cap is blowing off a lot of water, that's where my water loss seems to be from. It'll vent about 1/3 of the 'extra' coolant in the header tank then stablise there with minimal coolant loss from then on.

 

[allanhelen]

I know we are all sat here waiting for our Head Gaskets to fail and we know it will at sometime but start with the basics first

When was it last serviced? what state are the spark plugs in are there gaps ok? are the HT leads OK?

if OK check all the connections, do a compression test, Check the coil pack resistance........

 

[GoBe]

My point was don't rule HG falure out, not it will be. As I said get a compression test done.

 

[levemircento]

well I been out and started it, and it was ok - last night also in the freezing cold.

I know somebody with a compression tester, so I will borrow it at weekend

 

[levemircento]

Go do a compression test as beside still having top end power you've exactly described the symptoms of my Mk1 Sei's HG failed. Mine isn't a fully blown HG fail it's a slight one but it's confirmed with exhaust gasses in the coolant & one cylinder is slightly down on compression.

Check to see if the pressure cap is blowing off a lot of water, that's where my water loss seems to be from. It'll vent about 1/3 of the 'extra' coolant in the header tank then stablise there with minimal coolant loss from then on.

Well, a few days later now and I think we are looking at a possible h/g fail.

Some days it has started fine, no misfire and smooth idle, but most days it doesnt - and has a misfire until the engine has run for up to 30 seconds then it runs ok.

Water usage has crept up, although I can never find where the water has gone .... it must be pressured back into the cylinder at rest or when running, as even after a motorway run [10 miles] there was steam coming from tailpipe when I had it running and had a look when parked up, if started from cold yeah, it gonna steam but not after a decent run at temp.

The engine this evening, is idling roughly all the time now, sounding like its on just 3 cylinders, but when revved up much higher it smooths out but you can hear a note from the exhaust that just isnt sounding right.

I await some more replies, but I think its time to whip the head off. I cant understand why it would go - its never gone over 90 on the temp gauge, never run short of water, rest of cooling system is A1, car is at 57,000 miles. There also is no sign of water in oil, or oil in water.

talk to me

 

[fingers99]

Like the man said, do a compression test.

Some HGs seem to fail spontaneously around the 50-60k mark.

 

[levemircento]

Do I just screw the compression tester into a spark plug hole, and crank it over to get the result, or do I need to make sure both valves are closed? ie, remove camshaft?


If the h/g has gone, I know that it will be down on compression on one cylinder, and that when i remove the head the old gasket will have a 'track' through it, do I have to get my head skimmed? if so, do I have to present it to the engine machinists minus all the valve components? or can it be done with the valve components in place?

 

[rallycinq]

Yes screw the tester into the spark plug hole.

Take all the other leads off

Watch the gauge as someone else turns the car over. You should see a gradual rise in pressure. If it flutters on two cylinders more than the other two, and those cylinders are adjacent, then you could have a failure between cylinders.

Yes get your head skimmed (well the car's head anyway)

Cheers

D

 

[fingers99]

Don't forget, you're supposed to test withy the throttle wide open.

Machine shops vary: some like it stripped, some will do it built.

Really makes sense to replace the valve oil seals (they'll come with the full gasket set) and get the valve seats re-cut if you plan to keep the car.