Spark Knock/pinking

[Daniel Ley]

Has anyone had any experience of 'spark knock' or 'pinking' or whatever terminology is used? Just a copy of the definition below...

"Knocking (also called knock, detonation, spark knock, pinging or pinking) in spark-ignition internal combustion engines occurs when combustion of the air/fuel mixture in the cylinder does not start off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front.

The fuel-air charge is meant to be ignited by the spark plug only, and at a precise point in the piston's stroke. Knock occurs when the peak of the combustion process no longer occurs at the optimum moment for the four-stroke cycle. The shock wave creates the characteristic metallic "pinging" sound, and cylinder pressure increases dramatically."

Haven't had the issue officially diagnosed yet, simply because overtime I take my car into the garage, they can't seem to find a problem. The issue would be that during heavy acceleration, a rattling type sound would come from the engine... have read up a lot about what the issue could be and I'm 99% confident that the issue is spark knock. Have upgraded my fuel to BP Ultimate as suggested by many people as the higher octane fuel can reduce the effects of spark knock and the noise practically vanishes, and as soon as I return to using normal fuel the noise comes back. Struggling to get a garage to diagnose the problem, not sure what I can do?! Any suggestions would be grateful.

[turbohater]

Used to be a problem with older cars that had distributor ignition and points with vacuum advance and !Removed! but with ECU's etc i thought it was a thing of the past

[potter18]

Yeah back in the day you used to advance/!Removed! the timing by turning the distributor one way or the other but now its all computerised,

I suppose it could be the type of fuel used ( supermarket) but I'm sure someone will know on here

[David73]

If it is knocking and not something else, perhaps the knock sensor is faulty. Recent fours have one and it seems very unlikely that the turbo threes would not.

But it's difficult to know what the ECU does when the sensor stops giving a signal. If it can detect the failure, presumably it gives a dashboard warning and goes to full retardation, making the engine unresponsive. If it can't detect the failure, it might stay at full advance, causing the pinking.

[Daniel Ley]

All I know is that the issue seems to disappear when I use a higher quality fuel... there have been occasions where the engine loses power too, assuming this is done intentionally by the engine to protect itself? But yes maybe it's a faulty knock sensor, just at odds with how to sort it out as I don't want to have to use premium petrol just to stop the noise and knowing that there is still an issue.

[turbohater]

If it is knocking and not something else, perhaps the knock sensor is faulty. d it seems very unlikely that tRecent fours have one anhe turbo threes would not.

But it's difficult to know what the ECU does when the sensor stops giving a signal. If it can detect the failure, presumably it gives a dashboard warning and goes to full retardation, making the engine unresponsive. If it can't detect the failure, it might stay at full advance, causing the pinking.

If its a 2010 car it will be a four cylinder

[Daniel Ley]

Ooh okay... well there's never been any light come on the dashboard and it's had a diagnostic test run and no errors came up at all, so perhaps the failure isn't being detected. May visit a garage again and see if they can check the sensor or just fit a new one as they're only £30 and see if that helps.

[GingerFlame]

Have you tried iridium plugs? They may help the problem

[Daniel Ley]

Nope! May have to try fitting those and a new knock sensor perhaps then, doesn't seem too expensive.

[David73]

I hadn't previously noticed your model in your profile. Same engine as mine.

As aside, I am experimenting with higher octane petrol. Since the compression is 11:1 and the engine has a knock sensor, so long as the engine management uses it to the full potential, there should be benefit in using 97/99. Your experience suggests that 95 is not a natural diet and the management is holding it back.

It's early days so can't say definitively but early indication suggests it could be price neutral. If so, then does it give better response? Well, I have also just traded from a TD with double the torque so I am probably still adapting to that difference. We'll find out when going back to ordinary.

[pinkerman]

I was absolutely convinced that I had a pinking problem with my 2008 Fiesta 1.25 at low revs, particularly evident when it was cold outside but, daft as it may seem, after trying to solve the problem over a period of years, by replacing several "likely" parts and getting nowhere, I found that the pinking sound was actually caused by micro-slippage of the auxiliary belt with torque pulsations transmitted through the crank pulley.  Replacing the stretch belt cured the problem completely !!   It still sounds daft, but that's what it was.  I hope that it works for you.