Interesting knocking-type noise...

[samo]

Sunshine, my '93 EA82 has developed a new noise over this winter. It sounds sort of like a very loud case of pinging or knocking at partial throttle. It seems to occur most often when the car is working hard, like sitting in traffic or climbing up Snoqualmie Pass. If I let off the throttle, the noise goes away, and if I floor it, it usually goes away, or at least lessens. My first inclination was that it was something like piston slap, but that's generally a cold-start condition.

 

Any ideas on what said noise might be? And no, it's not TOD, it's something different .

 

Thanks!

[XWIND]

I have an 89 GL sedan 3 spd AT with 294,000 mi. on the engine that was doing the same thing (getting a mild pinging) at partial throttle. I connected the green connectors under the hood and checked my ignition timing. The ignition timing was right at 20 deg. BTC which was right on spec. I tried a tank of premium gas and the pinging did go away so I'm of the opinion that carbon buildup in the combustion chambers has raised the effective compression. I suppose the injector is running rich enough to cool the incoming mixture at full throttle to avoid the ping but not at partial throttle. My fix was to retard the ignition timing by 2 deg. to 18 deg. BTC and I'm now able to use regular gas again with out noticable pinging at partial throttle. My mileage is still in the 30 mi./gal range. And by the way, if the engine is running a bit hotter than normal, that could also contribute to engine ping. The EA82 may not be a high performance engine, but it's the most durable small engine I have ever experienced.

[NorthWet]

Any oil inducted into the engine will lower the knock-resistance of the mixture. Clean oil, clean PCV system, maybe even try a condensation can on the PCV system, and see if these help.

 

Another possibility is the EGR system being plugged or inoperative. Since the EGR system operates primarily at partial throttle, and its purpose is to lower peak combustion temperatures, it not working could allow part-throttle detonation to occur.

[RONAN]

Had a similar incident. I ended up having the engine exchanged. Turned out to be the timing belt tensioner pulley bearing had failed. Sure sounded like a rod knocking. Expensive learning curve.

[samo]

Pretty sure it's not a timing belt tensioner, as I just replaced those 2000 miles ago. Luckily, on the EA82s, if a belt goes, it's no big deal.

 

Oil's clean, PCV is working and clean, catch can is in place.

 

The EGR system seems to be a likely target, as I'm pretty sure mine is not working properly. I'll go through it and fix what I can on it.

 

Thanks guys!