Timing retards when revving

[Mark]

I noticed today when checking my timing on my '84 wagon that the timing retards about 5 or 10 degrees when revving the engine. I thought the centrifugal weights are supposed to advance the timing. On my '81 Tercel, revving advances the timing. I checked the rotor in the distributor to see if it rotates slightly by hand and then springs back and it seems to slightly, but not as much as I remember when doing it before. I sprayed lots of lubricant deep inside where the weight mechanism is and wiggled the rotor, but it didn't seem to make a difference. Before I take the distributor apart to see what's going on with the weights, has anyone else seen this happen?

[irowiki]

Try it with the vacuum advance disconnected and report back.

Some vacuum advances were backwards and retarded instead of advanced.

[Mark]

I was pretty sure that I tried it yesterday with hoses connected and disconnected and it didn't make a difference either way. Today, I couldn't remember for sure so I did it again this afternoon and it retarded about 3-5 degrees when I revved it with the hoses either connected or disconnected. I was now pretty sure that the centrifugal advance wasn't operating. The rotor in the distributor seemed to rotate slightly and spring back, but it seemed like less that I remember when doing it before on other cars. I took the distributor cap off my '81 Tercel and checked the rotor and it rotated obviously more. I sprayed a bunch of lube deep down in the mechanism of the distributor on the wagon and tried to wiggle the rotor to loosen it up, but it didn't move. The small amount of play I felt in the rotor was just backlash in the drive gear I think. I removed the whole distributor so I could tilt it up and really see where I was spraying the lube. I also loosened off the screw down the middle of the rotor shaft and sprayed a bunch of lube down there too. Eventually, the mechanism worked free and the rotor advanced slightly and sprung back as it should. I re-installed the distributor and set the timing again. Now the timing advances as it should when I rev the engine. The problem was just a seized centrifugal advance mechanism. The slight retard when revving the engine must be a normal feature of increased rpms when there is no centrifugal advance to counteract it.

[dlb]

wow, good catch, mark. i've never noticed this with stuck mechanical advances. very good to know, and i'm glad it was a relatively easy fix.

[irowiki]

I only brought it up because half of the 1st gen vacuum advance was actually designed to retard timing because of emissions.