Case Study: Lean Condition Variables

This is one very interesting case study shown to us by Paul Danner. Interesting how one missing air filter can force the ECU to make the engine run lean (also poor on FC since the fuel trims are all the way to the roof)

Short Term Fuel Trim
Long Term Fuel Trim

Engine Noises - Knocking Sounds Types

So here's what I've gathered so far in regards of reading up about knocking sounds. 

PISTON SLAP: 

Makes a sharp metallic noise. Idle engine and short out each cylinder plug. The noise will disappear when plug with bad piston is shorted. Noise will also disappear at acceleration. This can be caused by worn or out of round cylinder, or broken piston ring. 

VALVE NOISE: 

Makes clicking or rattle noise. Caused by excessive wear on valve stem or lifter, out of adjustment, or stuck valve. Correct by adjusting valve clearance, replace worn valve or lifter, regrind cam, replace valve guide and /or valve. A stuck valve can sometimes be loosened by passing oil through the carburettor while engine is running. 

ROD BEARING KNOCK: 

Makes sharp metallic noise similar to a piston slap. Detection is opposite of piston slap. Rod knock is not heard at idle. Knock becomes louder as engine speed is increased. Caused by excessive rod bearing clearance. 

REAR MAIN BEARING KNOCK: 

Makes dull knocking or thud noise. Knock will normally decrease or disappear while pulling or decelerating. Noise will be detected the loudest at normal driving speed, when not pulling or decelerating. If knock is excessive, crank should be checked for out of roundness. 

WRIST PIN SLAP:

This can not be detected by shorting out the cylinder plugs. Rapidly accelerate and decelerate the engine speed. The engine will pass through a certain speed range when the wrist pin will rattle at about the same pitch as a valve tappet noise. 

Post top overhaul & engine noise/rattle

I have been testing the car for a few days and through extensive testing, its sad to say the knockings are still there.

What was fixed

- long crank during start or can't start 

- water/coolant loss from radiator/spare tank

The long crank & coolant lost definitely confirms the issue with the head gasket.

Now into the main issue the knocks. After the top overhaul, the knocks are now much more harder to replicate and observed.

Recreating the Knock

It is now harder to recreate the knock. Its less audible and happens less regularly.

• going uphill, RPM ranging 1500-1750 -> rattles if you can maintain at 1750
• cruising and accelerating after that -> can only get a occasional metal slap/tick with overdrive with RPM about 1500-1750 & speeds of 60-70kmh
• braking from cruising (observed occasionally but unable to recreate)

Current conclusion for the knock to occur (below conditions must fulfill)

• under engine load
• 1500-1750 RPM -> rattling
• Undefined RPM range -> tick/slap
• tick/slap happend at high gears & low gears - updated 29 July 2013

Next steps

• Feedback to the service center of course. Didn't pay them  RM1.7k to not fix the problem.
• Need data and lots of it. Nobody so far has been able to give me a proper diagnosis and support it with data. Guess work most of the time.
• Sell the damn car =P
• Ignore the problem by turn the volume up on the radio =P
• Floor the pedal more often to drive > 2000RPM =P

Update: 19 Aug 2013

• Cleaned the MAF sensor with contact cleaner yesterday. Better response but still knock. :(
• Revert to paper type air filter. Bought from spare part shop. Interesting that the Japan oily one continues to be out of stock
• Poured a can of Bardahl 1 in the engine

Update 16 May 2014 - All my research and troubleshooting points into the direction of the tensioner kit. If it was the rod bearing, it the car would have been getting worse. So far fuel economy is still within range and I've survived a few long round Malaysia trips covering over 2000++ kms. This Youtube vid had the same sound and symptoms as well and theirs was the tensioner.

To confirm and fix this I would need to send the car into the shop and spend close to RM1000++ but I guess I'll just hold back since its not really giving me any grief currently.