I have an odd issue on my 2007 Fit manual-transmission which I have owned since new. I am hearing what sounds a lot like pre-ignition (pinging, pinking, knocking, whatever you call it). It occurs at very low rpm, which is to be expected if it is pre-ignition. However the odd part is that it happens even right after a cold start (even at sub-freezing temperatures) and on very light throttle, both of which I would not expect if it is pre-ignition. The car is otherwise running great, has relatively low mileage for its age (180,000 kilometres) and has been well maintained.
Any thoughts would be appreciated.

 

You're getting early detonation for whatever reason.

Advanced carbon buildup could lead to preignition, but not on a cold engine. Engine would have to warm up enough before carbon gets hot enough to detonate on its own.

Spark plug timing that's too far advanced can cause detonation at the wrong part of the compression cycle and can mimic preignition. But your engine wouldn't be running fine otherwise if timing were that screwed up.

So I'm at a failed engine control module /. ECM. They are not cheap, so you might want to get a second opinion.

 

A bore scope down the spark plug holes could be useful in diagnosing carbon buildup.

Excessive valve lash sounds like a regular metallic tapping, and is loudest immediately after cold start, fading as the engine warms up. Valve lash is what's being worked on during a valve adjustment.

Alternatively, it could be a failing bearing on an accessory component such as the alternator, A/C compressor or a belt pulley. They can make irregular taps and chirps in addition to the kind of squeaking you would expect. Look for red dust.

 

Warm that thing up and give it an Italian Tune Up! Sounds like some carbon has built up.

 

Thanks for the responses so far. I’ll try the Italian tuneup after I get some Premium gas in it! As for a faulty ECM, wouldn’t that trigger a CEL and/or throw codes?

 

The ECM cannot diagnose itself. When the ECM goes, ability to diagnose and generate DTCs goes as well.

 

good point. Electronics isn’t my strong suit! Thanks.

 

The ECM can't diagnose failures if it can't function, so we're talking about power and grounding failures, some internal hardware failures. Though modern ECM wiring generally includes redundant power and ground connections, circuitry to detect faults, and error codes to report those faults. Even the first generation of Honda ECUs (acronym of the time for ECM) had a checksum function that diagnosed program data corruption (which was stored on ROM and therefor very difficult to corrupt).

You'll notice that the replace-the-ECM step always comes at the end of the troubleshooting flow chart. It's the diagnostic manual writers giving up. "Exchange the ECM with a known-good unit. If the problem is resolved, replace the original ECM." They don't tell you what to do if replacing the ECM doesn't fix the problem because they've run out of ideas. Their understanding of system function and testing procedures has failed.

 

Are there any sensors that could fail and cause this issue? Also, do these engines have a knock sensor?
Thanks for the input so far.