Corsa petrol - no go in higher gears

[DIYspanner]

Just had a phone call from the family.

The young lad's precious first car is loosing power in higher gears.

Run alright in 1st and second.

I said I'd call around tomorrow and look under the hood.

My 1st thoughts are a fault on the ECU, not metering the petrol properly!

Any known bugs with Cora cars regarding the engine dying?

 

[Burnerman]

Have you serviced this one - new air filter and so on?
Check the car isn't overheating when he's going for it - they aren't noted for loads of power at the end of the day.
Any fault codes recorded?
John

 

[DIYspanner]

Haven't touched it at all, apart from a door handle lever repair a while back.

Its actually a friend of theirs who's got a budget of flat broke.

I'll look at it and post results.

thanks John

 

[DaveHerns]

Clutch slipping?

 

[DIYspanner]

It was the spark plugs!

I was gong to test drive but as soon I started it and gave it a bit of rev, the misfires were obvious.

Lifted the bonnet and surprised to see a 3 cylinder engine, the first I ever dealt with!

Took the combined spark plug head off, got the plugs out and the gaps were big to say the least and the centers were well back to the insulation.

Closed the gaps, plugs back in and no misfires. Took it on to the local dual carriage way and no bother getting up to 5th gear.

I put a new set of NKG in to make the job right.

I've had a message tonight telling me the owner is a delighted young fella.

Apparently, I may be commissioned to get the car mot'd in a couple of months.

 

[Burnerman]

Mr. Spanner, you are everyone's favourite uncle......
Three cylinder engines have the best crankshaft balance of them all, expect every manufacturer to produce one eventually.
Regards
John

 

[DIYspanner]

thanks John!

I presume one of these 3 cylinder engine is basically a straight 6 cut in half and a piston at every 120 degrees.

Why not do a 4 cylinder with pistons at every 90 degrees? ...... it'd be lovely and smooth!

 

[DIYspanner]

On the matter of plug gap, I presume too big a gap won't allow a spark of sufficient thermal energy for the air/petrol mix to get a good start when ignited?

Having said that, an uncle of mine once had a 2.0 Vauxhall Carlton on which I change the plugs when servicing it. I swear, the outer electrodes were melted away to stubs and he'd never noticed any misfires!

 

[Burnerman]

Too wide a plug gap actually gives the coil pack a hard time, and in high revs can cause a misfire so I guess you got there just in time! Wondering what state the rest of the car is in though.....
The combustion burn pattern is affected by the plug gap, but whether we mere mortals would notice it is debatable. In the good old days, ignition voltage was much lower but current higher, hence the need to replace the plugs more frequently. Nowadays, the voltage is much, much higher with minimal current so you get long plug life - with the trade off that folks forget they are there!
John

 

[DaveHerns]

DIY Spanner, do you do all your family's and their friends' cars for free? I hope you get some gratitude in return. I just got taken for granted and don't do it any more.

 

[DIYspanner]

........ and there's all the PCs I sort out, and the joinery.

Golden rule, I don't do cars on cold or rainy days.

To be honest, the Corsa I've sorted out was a 10 minute fix on a nice warm day.

 

[Burnerman]

Keeps the old brain cells tuned in, hey!
I'm the equivalent of yourself, Mr. Spanner......car work in the summer, odd jobs anytime if it suits me.
I should really have MUG tattooed on my forehead on occasions though but still get a buzz at showing 'young 'uns' what's what from time to time.
John

 

[DaveHerns]

Three cylinder engines have the best crankshaft balance of them all,

Why's that? You've got a firing pulse every 240 degrees of crank rotation and a 4 cyl has one every 180 degrees so why isn't the 4 cylinder smoother?
I did read that 333cc is the ideal piston displacement but I have no idea why.

 

[Burnerman]

The typical 3 cylinder engine has a firing rotation of 120 degrees, which gives nigh on perfect primary crankshaft balance.....but only on lower capacity engines up to say, 1200cc.
After that, a balance shaft driven by the crankshaft is needed to smooth things out and that will be driven in the opposite direction to crankshaft rotation.....an alternative is to put a heavy damping pulley on the end of the crankshaft. This is the technique employed by Triumph motorcycles, who specialise in the triple.
Other than that, I'll have to refer you to Google, I'm afraid!
John

 

[Mottie]

Whenever I drive a 3 cylinder engine, it always feels like driving a 4 cylinder engine with a burnt valve. Never seen one tick over smoothly either. May feel alright inside the car but under the bonnet the engine is jumping all over the place. Better/softer/different engine mountings I suppose or just may be that I only get the shagged out ones to work on! I used to feel the same with the Audi 5 cylinder engines too.