syoo8

Hi everyone.

My 87 S4 makes a pinging sound in the low 2k rpm range, in 2nd or 3rd gear. Not in first.

I originally thought that my engine was pinging. The sound reminded me of pinging. However, letting the engine rev freely between idle and about 4k rpm, I don't hear anything remotely similar to the 'pinging' sound that I get in gear.

Is it possible this pinging noise is coming from the transmission?

BC

Any chance of catching a video with sound? Or just sound?

Dave928S

If it is pinging/detonation then it's more likely to occur under load and not when free revving or in a, more appropriate for the load, lower gear.

Your description that it doesn't occur when free revving, and when in first gear ... but does at 2K in 2nd and 3rd sounds like it might be detonation.

syoo8

BC and Dave,

I just recorded the sound of the 'pinging.' It occurs under load at 2000rpm.

Link to pinging sound mp3

Imo000

Have you tried higher octane to see if there is a change?

syoo8

I always fill the engine with 93 octane. However, I don't have a Chevron (or Texaco) station in my town. I just received a case of , which I will put into the gas tank to see if it helps.

dr bob

Scott--

Pinging/detonation has some spark plug symptoms that are easy to see. Pull the plugs and look at them carefully. Serious detonation will trash the ground electrode, sometimes bending it to close the gap. Otherwise the deposits on the plugs are a little splotchy white.

All it takes for this is one or more partially-obstructed injectors, a vacuum leak, or dodgy ignition timing. Bad fuel is a very common cause too. I'm not sure how much info you can grab from your '87 WRT knock counts and diagnoosis of failed sensors. Someone with more knowledge can chime in.

Also: many years ago I joined a 'group buy' on Autothority chipsets. I had some pinging under the same circumstances you describe, but pretty much only with AC running in hot weather. Autothority replaced the chips with a GT set, supposedly with a little less timing advance for the higher-compression engine. That helped some, but I decided to shelve the chips in favor of stock to make sure there was no possibility of damage. So you might want to look at the LH and EZK boxes to see if they've been opened. If so, look inside and verify that you don't have any unknown "performance" chipsets in there boosting the timing advance for you.

the flyin' scotsman

The '87 knock count is easily checked by upgrading the eproms to the '88 MY......I believe they can be sourced from JDS .

The knock counts are then read by a Spanner or Theos diag tester.

Id go with a high octane fuel after you check the points dr bobs advises.

syoo8

I pulled the spark plug from cylinder 5, and found this. The ground electrode is thankfully intact.

Does this look normal to all of you?

the flyin' scotsman

Can you turn the plug and take a pic so we can see further down.

Try turning the flash off so it doesn't distort the lightness of the image.

The pic posted does suggest a more lean mixture but hard to fully tell.

dr bob

You want to check all the plugs. If you have a lean condition on a few cylinders you'll see the differences in the plugs. When all are weak, the oxy sensor picks up the condition and adjusts mixture.

Dave928S

What Malcolm and Dr Bob said ... and I've listened to the audio a few times and, very difficult to hear well, but I think I'm hearing the characteristic 'tinkle' of detonation.

As the doc said ...get all the plugs out. Line them up in cylinder order and take a pic of the lot so they can be compared, and get the best possible macros you can looking down at an angle, so you can see the centre better.

Imo000

That plug looks prefectly normal.

FredR

It also looks Japanese...?

BC

I honestly can't hear anything through my computer speakers. I do know that knocking under load will happen more often in this RPM range according to certain research papers.