wobbling idle

[dstan]

Hi errybody.

My 83 T4wd has a wobbly idle. I have suspected that this is normal. But I am writing to see if it is true of all old cars, or all tercels, or what have you. I've never given a car so much attention, and certainly never hooked a car up to a timing light, before owning the tercel. So I don't have a basis for comparison.

To explain better what i mean by wobble, I will do some explaining.

The idle is very regular. It idles well, strong, you might say. Never dies. But included in the regularity is minor fluctuation that seems to repeat. It's like all 4 will go for maybe two cycles or something, and then one or more will go more loudly or more quietly and then it will all repeat. Or something like that.

The phenomenon can be observed visually, too. When I hook up the timing light, you see the timing mark dance around zero (or whatever) in a very regular pattern. Maybe twice right on, once to the left, and once more slightly to the right, and then back to zero and repeat.

And again, when you look at the tach, which for me is on the timing light, the idle speed dances around. It dances faster than the refresh rate of the tach (which for me is pretty slow), and so the tach just bounces between, say, 790, 810, 800 (or whatever), and repeat, but perhaps a little more erraticly than that.

Cheers!!!

[ARCHINSTL]

This may be more info than you want, but...
http://www.tercel4wd.com/forums/viewtopic.php?t=1372
There are at least five pages above. My cycling was higher than yours and virtually unique among members. Mine was from 1900 to 2300 up and down continuously when 2300 was achieved. I had a blacksmith fix, detailed therein. I finally came to the conclusion, after exhaustive work over a number of years, that the "ECU" (such as it is) was ill. I installed the Weber and disconnected other stuff and that problem disappeared. Again, my situation was different, but others weighed in on this.

Some members here - and owners of other Toys of the era, notably those with the 22R motor - experienced idle probs more similar to your lower RPM cycling. But - read through the above link.
Tom M.

[Petros]

The jumping timing is usually due to the distributor gear slop, presuming your distributor bearings are good. this is one of many reasons all newer cars went to either direct drive distributors (off the end of the cam) or crank triggered timing. It is more precision, uses less parts, and improves both emissions and performance.

Take the cap off your distributor and wiggle the rotor shaft, there should be no noticeable side movement. You might also see if your mechanical advance is working, and not sloppy. IF those are good, that is about the best you can get with this engine.

Also, carburetors control fuel distribution much less accurately than EFI, and why they went away. So there is just a certain amount of precision you will not get with this obsolete engine. Swap to a 4AFE or 4AGE if you want precision.

[dstan]

Cool. Thanks for the info, gents.