Lots of pinging and lots of power - timing woes

[waynehoc]

I have recently had just the opposite problem with lots of pinging (actually, lots of detonation). This was my first time exposed to pinging/detonation in any more than just a mild version, so at first I didn't know what was going on, as it slowly snuck up on me over a few months. I passed air care easily in September, and the wagon was running well then with factory (5btc/13btc) timing, so the change happened slowly since then.

The problem coincided with changing the trans over to a full synthetic gear oil, and with major telescoping of sound from the engine to the transaxle, it was only natural to associate the noise with the recent change to synth gear oil, thinking I had done the wrong thing going to the synthetic. One thing, looking back, that was a dead give away, was that I recently had to turn the idle speed down by a full 1/4-turn of the idle speed screw over a two week period, as the idle speed was going up.

Anyway, I now know what serious detonation sounds like! One reason it escaped me for so long is that I am basically pretty easy on the Tercel - only discovered the worst of it by accident when having to accelerate quickly from a (too) low rpm without downshifting. Pretty ugly sounding - lucky I haven't done any damage as far as I know.

When I finally checked the timing, I had close to 25 degrees advance with the vac line to the distr disconnected, and more than that with it connected! In my case, it turns out the vac advance weights were not seized, but the 'signal rotor shaft' was seized to the 'governor shaft' at about 2/3 of full mechanical advance!

In the end, I installed my spare distributor (from an '86 Tercel 4-dr). Swapped over my newish vac advance, rotor, cap and wires to the spare distr first, and all is well again.

I think I'll check the timing once in a while.

One thing I did notice was that the wagon seemed to have more power, and my gas mileage actually improved (gas mileage was definitely noticed as improved in the two tanks after I had turned the idle speed screw down by 1/4 turn, but I mistakenly attributed that to mainly highway driving for those two tanks) . So there are certainly advantages to timing that is modestly advanced beyond the factory specs.