Let me get this out of the way - I know very little about cars (but I'm learning). So:

I have a Magna 98 TF 3.0L stock. Yesterday I gave it a good punch to make a gap in traffic and when I pulled up at the next lights I immediately noticed a strong vibration / lurching rumble going through the car. Pulled up into an empty lot. Strong smell of petrol when I stopped. No liquids leaking anywhere under the bonnet. Oil seemed fine. Smelt bad - but mostly I'd say of petrol. Reconnected the spark plug leads I could reach (the long bits going into the head). Started it up again and this took much longer than normal - maybe six seconds - normally starts in one. Strong vibration, bad smell and sounded fairly rough at idle. Drove it the two kilometers home - huge loss of power - when I pulled on to the main road (accelerated a little) a lot of grey smoke came out the back. When stopped at some lights I could see some more smoke trail past my window.

Seems to me that one or more cylinders may not be firing - however I wouldn't have thought just one cylinder would have caused such a huge difference, to me this feels like it's running on only half of them. But like I said I wouldn't really know.

Another possibility is that the cars getting quite old and I know the head gaskets were going. Could they have completely failed when I punched it and caused this?

Any ideas and comments would be very welcome.

Thanks.

When it has cooled down check the water level in the radiator and overflow tank. If it is down, you have a coolant leak. Internal, if no signs on the outside.
As for smoke - white is coolant, blue is oil.
If a head gasket is going to blow suddenly, it will be at the point of highest stress. You may have breached the gasket between 2 cylinders and a water passage. Fire goes out in both, water enters the cylinders and comes out the exhaust pipe as white (gray ?) smoke. You may also see water spitting out the tail pipe when the engine is running in addition to the steam.


Pulling all plugs will tell you more. Some will not look like the others. If the internal leak is really bad, spinning the engine with the plugs out will see water spraying out of the affected cylinders.

(Had a Sigma with softened head, an exhaust valve guide shifted allowing coolant straight into the hot exhaust system. Instant steam generator. lol)

Once you have convinced yourself it's a head gasket, the head(s) need to come off to repair the corrosion.


PS Nothing to do with age, rather poor coolant is to blame.

Thanks for your quick and knowledgeable reply! Coolant level is still full at dead cold (as always with this car).

Started it up and it sounded very rough and uneven like previously initially. Checked the exhaust straight away and a small amount of smoke was coming out - very hard to tell the colour but it seemed fairly white to me - but unsure due to it being very light. Started looking for engine leaks - couldn't see any. However it was hard to see and there's a fair amount of dried oil (I think) that has build up around the head* (I expect from failing gaskets). I then realised the engine was sounding fine. Sat in the car and no vibrations. Revved it up to about 2k rpm (in park) with no issues. Checked the exhaust pipe and now no smoke is coming out.

*note when I say "head" I don't know what I'm talking about. Whatever the spark plug leads hook into and the thing I pour HPR10 into.

Seems odd that it would start running alright, would it be (relatively) safe to take for a test drive?

Not sure where you get the idea that your head gaskets are "going" Not sure where they are going but a head gasket does not wear out as such so if some clown has told you this, find someone else to work on your car

The loss of power, hard to start and then smoke all sound like 1 or more injectors are leaking. This can happen on an older car especially and when you punched it they would have been on a longer duration of opening to allow more fuel to get into the motor thus if a small particle from the system has found its way into the injector you may have found the issue

Best to get a fuel system check, pressure and how long it takes for the pressure to drop. If still running rough some diagnostic tools can actually disable each cyl and you can then at least pinpoint the exact cyl/s which are giving trouble thus then you will also limit your search

Not sure where you get the idea that your head gaskets are "going"

Had the car serviced a couple of years back and that is what I was told by the mechanic, I think due to dried leaks he'd observed. Will have a look at the paper - think I still have it.

Definitely sounds like an injector. Does it get hot? If it overheats then it would be a head that has warped or cracked. Doubt it though.

Does it get hot? No, it has always sat on the gauge's halfway mark once warmed up and it was no different yesterday.

Edit: Have just taken the car for a short test drive and everything seems back to normal for now. Think I'm still interested in cleaning or replacing the injectors - I'm worried.

Drove the car to work last night and once again no issues.

However I did notice that I had lost a large amount of fuel given the few kilometers I had travelled. This would seem to speak also in favour of Madmagma's diagnosis that one or more injectors were leaking?

You may also see water spitting out the tail pipe when the engine is running in addition to the steam.

Have to be carefull with that ones as a brand new car will have all the above coming out of the exhaust.
Just a result of the hot exhaust gas cooling as it comes down the pipe and the moisture condenses and runs out the end.
You would have to know the difference between a normal amount and excessive. Large mufflers can hold quite alot of water in them if there is not enough pressure to blow it out.

I had lost a large amount of fuel given the few kilometers
Quite normal when you have a couple of cylinders not firing as you have your foot down further to get the other cylinders to work harder to make up for the shortfall in performance.Vee