Engine problem

If it's not ignition (which it 95% is), then it could be something as simple as the wiring for the valve which controls the oil supply to the camshaft phase variator. So the intake cam advance intermittently drops back to 0 degrees. Had this on the Alfa, it was pretty undrivable above 3500RPM, but I did get an injection light on the dash.

The oil level is OK I take it?
 
TBH I havent checked the oil and I dont have any warning lights. I had a quick look at the dipstick and it seemed fine but I didnt wipe it and have a proper look. I will be doing that before I remove the MAF.
The car seems fine as long as I dont put my foot down. I will be having a good look at it soon.
 
that was a classic thread too. wasnt that on a veyron?

hey, vin diesel, you dont even know how to check your oil but youre looking to become a street racing extraudinare?

If you can’t find the right tool in this garage, Mr. Arizona, you don’t belong near a car
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Well I took my MAF Sensor out and it was really dirty, so Ive given that a clean and the car seems to be better now. Only thing is, is that it seems a little restricted but Im not to sure I only took it out for a 2 minute spin. I will give it a proper test on the long drive home.
 
rover416i said:
sparks don't lose strength as revs increase so it would be the same across the board, not just above 3k surely.
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With higher throttle openings (and hence higher cylinder pressures prior to the spark), you need more voltage to ionise the spark gap. This is why a failing ignition system will very often work ok with small throttle openings, but will keel over at WOT or under boost in the case of a super/turbocharged engine.

At higher RPM the coil has less time to charge between sparks. With conventional points systems this always led to a decrease in ignition output at high RPM. With modern "constant energy" systems this shouldn't happen, but any fault causing the peak coil current to be reduced (e.g. poor ground, high resistance connection, poorly ignition amplifier) will tend to cause problems at higher RPM.
 
Now then. After my drive home I have still have a problem. I cleaned the MAF I think. Its a blacky/brown colour with a hint of orange. I dont know if thats normal. Now the car goes nicely to 4.5k rpm then starts to cough and struggle to get past that. I do now believe the coil pack is in need of changing but Im hoping that its just the MAF that will need replacing if it had broken due to it been a strange colour.
 
What type of MAF and how did you clean it?

Can you pull a coil/HT lead out and look at it? It's usually pretty clear where the insulation has broken down.
 
I was going to say MAF, looks like I win :D

Chances are you've borked it by cleaning it - they're VERY sensitive and cleaning them properly is tricky. Run it with the MAF disconnected and see if it's better - if it is then it's new MAF for you
 
If I unplug it my car just goes dead because it cant work without it.
I cleaned it with some contact spray and then used air duster to dry it. I think tomorrow I will have a look at it again and have another look. I do hope it the MAF but Ive got a feeling its probably going to be the coil pack.
 
That's odd - most cars work without them.

You should have left it to dry, the air duster probably damaged it,there's a fair bit of pressure in them.

If the MAF improved it, why do you think its the coil pack?
 
My friend had the same problem with his car. It isnt a Yaris. I also let it dry over a 5 minute spell and I spray gentley with the air duster not to damage it. Im going to give it another clean tomorrow when I can see outside. Unless anyone else has any better ideas other than taking to a garage to have it looked at.
 
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