Pinging

[Wascally Wabbit1]

Curious if anyone else notices engine pinging at lower rpm with the automatic transmission. I am guessing it is because they have the shift points really low to keep rpms down to help gas mileage. I don't have pinging in sport mode but that bumps the rpms up quite a bit.

Could also be time to clean the air filter as it gets dirty pretty fast because it is very dry and dusty in the town I work in.

 

[MLue1]

Chris, try cleaning the injectors or have them flow tested and mattched.

 

[RustyTacoUK]

Mine has been doing it too, right at 4k RPM and only in 3rd and 4th gear that I can hear. I've tried 93 both with and without an additional octane booster, still happening.

 

[MLue1]

Pinging can be from low quality octane gas, or anything contributing to a lean fuel mixture such an intake leak, even carbon deposits in the combustion chambers. Try changing fuel suppliers, and checking for an intake leak, you will need someone with a borescope to have a look in the combustion chambers. If the O2 sensor or the spark plugs are old or the plug heat range spec is too hot, any of these could be the cause as well.

 

[RustyTacoUK]

@MLue1, thanks for the run-through. Not to hijack OP's thread, but if I walk you through what I've done so far vs. what I plan to do can you give me a sanity check?

Basics:
2014 Jetta Sportwagen 2.5 Automatic
29k miles
Second owner, full VW service records
Bone stock
Pinging occurs only briefly at 4k RPM in 3rd and 4th gears, sounds like it's coming from the far passenger side of the engine bay. Never happens otherwise.
Validated that it's detonation by logging in VCDS, shows a -3 knock retard when the audible pinging is occurring and then returns to normal as the motor continues revving.
No codes pending or set in VCDS

What I've done so far:
OE fuel filter
5 Genuine VW coils
5 Genuine VW plugs (old ones all looked normal, no white residue)
3 separate courses of Redline injector cleaner
Using only 93 octane fuel, switched from Irving to Shell and Mobil, pinging persists. All are top-tier fuel and busy stations.
Even tried adding 2 bottles of Lucas Octane Booster to one tank of 93 to really pump up the octane, still pinging.
Fuel trims all look within spec, +3 LTFT and 0 STFT
A/F commanded vs A/F actual is always very close, actual is almost always within .03
Performed throttle body alignment
Changed VVT solenoid

What I'm doing next:
Ordered a cheap borescope that connects to an android phone
- Will pull coils and plugs to check piston surface
Ordered a smoke tester
- Will connect to intake system and look for leaks

Video/Audio:
Mic in car, detonation at 4k RPM at ~7 second mark

http://imgur.com/a/tjeFsb7

Mic in passenger fender, passed through where it meets the front door, detonation clearer here again at 4k RPM

http://imgur.com/a/hMhE6OM

I'm hoping to find an obvious leak with the smoke tester, otherwise I don't know what else to do. I didn't plan to look at the O2 sensors given how low the mileage is, there are no codes, and the fuel trims all look good. But any further advice you have would be super helpful. Also, is there anything important happening at 4k RPM? Like a VVT profile switchover or a variable length manifold flap changing position?

 

[Wascally Wabbit1]

Mine only happens at low rpm and I have decided it is from engine shifting too soon likely to keep rpms low for gas mileage. If I drive in sport mode and the rpms don't drop down too low it doesn't ping. Could be an issue with the knock sensor. Out of curiosity what state are you in? I have suspected higher amounts of ethanol in the gas maybe being the culprit as it wasn't an issue until recently and California loves ethanol.

 

[RustyTacoUK]

Mine only happens at low rpm and I have decided it is from engine shifting too soon likely to keep rpms low for gas mileage. If I drive in sport mode and the rpms don't drop down too low it doesn't ping. Could be an issue with the knock sensor. Out of curiosity what state are you in? I have suspected higher amounts of ethanol in the gas maybe being the culprit as it wasn't an issue until recently and California loves ethanol.

Ah ok so yours is a bit different and sounds like more traditional spark knock too I think. I'm in Connecticut, I've also filled up in MA, NY and VT while traveling with the same result.

 

[GIACUser]

Mine only happens at low rpm and I have decided it is from engine shifting too soon likely to keep rpms low for gas mileage. If I drive in sport mode and the rpms don't drop down too low it doesn't ping. Could be an issue with the knock sensor. Out of curiosity what state are you in? I have suspected higher amounts of ethanol in the gas maybe being the culprit as it wasn't an issue until recently and California loves ethanol.

Quite often pinging is only heard at low rpm but may be happening at higher rpms too, but the increased engine noises at higher rpms can mask the sound. Best thing to do is of course log what is going on to find out when it is happening, what cylinders it is happening in, and the severity.

 

[Wascally Wabbit1]

Quite often pinging is only heard at low rpm but may be happening at higher rpms too, but the increased engine noises at higher rpms can mask the sound. Best thing to do is of course log what is going on to find out when it is happening, what cylinders it is happening in, and the severity.

True. In this case it had not been bad enough to really bother me. On an interesting side note, when I put the car back to stock for CA smog and then back to stage 1 the pinging stopped and my mpg went up 4 mpg. So far it has been good. Not sure what to think there. Maybe it was something with the tune.

 

[GIACUser]

True. In this case it had not been bad enough to really bother me. On an interesting side note, when I put the car back to stock for CA smog and then back to stage 1 the pinging stopped and my mpg went up 4 mpg. So far it has been good. Not sure what to think there. Maybe it was something with the tune.

My guess is that a tune for that motor would include advanced timing to get most of its gains. Ambient air temps could have a big influence on pre-ignition.

 

[Wascally Wabbit1]

I am noticing with this car that it doesn't downshift until very low speeds so you can be in 5th gear at 30mph before it decides to start going down through the gears and in traffic where you are bouncing between 20mph and 60mph constantly you really end up bogging this motor. I have taken to downshifting manually because of it and no pinging. The knock sensor can only do so much but when you get on the gas at 30mph in 5th gear it is not shocking you might get some pings.

 

[Wascally Wabbit1]

Well the pinging had gotten worse so I decided to scan for faults and got a low air flow at idle fault. I pulled the throttle body and it was filthy inside which I was not expecting. I cleaned it all out. Checked the evap purge valve which seemed fine. Cleaned the map sensor. Also, changed the spark plugs as well. Drove it 200 miles to San Diego and back and not a single ping.

 

[Wascally Wabbit1]

Well. A week later and still zero pinging. One final thought. The car drives amazing now. Much smoother at idle, great acceleration, smooth shifting. My guess is there was an issue well before the pinging started that I just didn't realize.

The humble mechanic says cleaning the throttle body should be considered regular maintenance on these cars and be done every 50K miles. I would agree with that.

 

[Wascally Wabbit1]

Interesting, never done. Doing that tomorrow.

Depending on your year (2010+ I believe) make sure to clean the map sensor while your at it. That gets covered with oil coming from the PCV.