Various names for the issue, pre-ignition, spark ping, spark knock, regardless of the terminology my 2002 MCS has been pinging when I put a torque load on the engine. The plugs are exact replacements with about 40k. New MINI plug wires, Chevron or Mobil premium fuel.
Could it be the cam timing sensor, 02 sensors or a knock sensor???
How do you sort it out? The car has 156k on it with original O2 sensors

Thanks for any suggestions

 

Ever do a compression test or a leakdown test?
The things you listare generally NOT the cause of pings....

 

Zippy I always appreciate your input.

The odd thing is that its the same noise you get with running low octane. Kind of a light tinny rattle in the top end. Definitely not a valve chatter or timing chain. That's why I was thinking ore destination or timing.

It's a hard noise to describe and most drivers wouldn't even notice it. I'm always tuned in to my MINIs feedback. I guess you get that way when you have done all the work on the car yourself. And with a MINI it's a lot!

 

An engine can ping for many different reasons. Here are some common causes for pinging starting with the most popular ones.

• Fuel octane rating too low.
• Compression too high. (usually caused by carbon build up inside the combustion chambers)
• Over heating of the engine or just an individual cylinder. (Hot spots)
• Knock detector faulty.
• Ignition timing
• Blocked exhaust, giving a high backpressure. (A significant loss of performance will be noticed)

You mention also 40k on plugs. Might be time to replace them.

 

You might have identified the problem with the carbon build up. Often at a red light the car has a hard idle. Not like a misfire but more along the lines if you had a bigger cam in the engine. The unevenness could be carbon due to lots of slow rush hour traffic.
The power is good so I don't suspect an exhaust issue. The octane should be ok, I only run various too brand premium. I changed the original plugs at 110k and they still looked new. 40k shouldn't be a problem, although that would be another inexpensive test. I'll try to find some good carbon remover fluid to see what happens

I can get live readings from my o2 sensors through my Networkfleet GPS tracking system that reports diagnostics and engine operating conditions, however I need to get the specs on the sensors to see what the range should be. My Bentley manual should be arriving by Friday. Hopefully it will have the millivolt readings.

 

It could be that your serpentine belt is slipping because of belt stretch and/or belt tensioner wear, either of which can result in belt slippage. When the belt slips, lower-than-expected S/C boost will not match what the computer expects to see for the sensed RPM, resulting in overly advanced spark timing and pinging. That's what my very capable mechanic told me two weeks ago when I brought my '03 MCS in with the same pinging symptoms and a slight rattle, thinking my timing chain tensioner was kaput. A new belt tensioner and belt made the engine run like new and eliminated the ping and the rattle. Good luck!