so, after having read about how advancing the timing a couple of degrees on this car can make a difference, I decided to advance mine. took only a couple minutes and my timing was set at 15 degrees BTDC. my idle now sits at about 900-950 as opposed to about 750 like it's supposed to be. but when I started driving I felt the difference right away! it's not uber dramatic but it's noticable. especially in the low rpms, from like 1-4K, and it feels like the normal power drop at 5500 isn't as sharp, I mean, it's still there it just doesn't feel like it drops as sharply. I'm running 91 octane gas with and I didn't feel/hear any detonation, even when I tried to put the car under load by riding it 4th at 1400 RPMs I didn't notice any. I'm thinking of either going back out and setting it to 16-17 or just using 89 octane. anybody else done this?

hmm, the idle speed shouldnt have been affected at all. did you reset the PCM when you did this or bump into anything else along the way?

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here's a quote from mr2oc.com: "This is one reason a lot of people tune there timing by ear, you listen for the highest rpms while adjusting the timing more advanced." I think the idle rpms are supposed to increase with advanced timing. I didn't reset anything or touch anything else when I did advancement. I just pulled the jumper wire out while the engine was still running and immidietly went for a test drive. I'm wondering if resetting the ECU will also return my timing back to stock?

should I go back and re-adjust my idle speed to 750? do you think it makes a difference?

It will help your gas mileage a bit if you adjust back to stock idle.
But isn't that controlled by your ECU?

And yes, advancing/retarding ignition timing WILL effect your idle.

it will affect the idle quality, but shouldn't affect the idle speed that much.

you advanced using a timing light or you just guessed as you turned it? 5 degrees is like 1/16th of an inch of movement of the distributor and didnt affect my idle speed one bit, however i do have a slightly different motor.

I heard that if you advance your timing it shortens your engines life is that true ??

It won't necessarily shorten life.
It does increase the chance of detonation and will somewhat increase initial cylinder pressure, so it could.
But so will pretty much any performance mods....
As long as you watch out for detonation I wouldn't worry too much about it.


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It will directly effect the idle speed. Advancing it raises idle, retarding lowers it.
Up to a point. And every engine is somewhat different.

yes, but what i meant, and sorry i wasnt more specific, is that 5 degrees shouldnt raise his idle by 200 rpm. the idle is set by the PCM via the IAC motor and several sensor inputs. at 20 degrees base timing my idle was the same as it was at 10 degrees base, and at 15 degrees base its still the same. the PCM will adjust. its not like the idle speed is set by a screw holding the throttle plate cracked, or some other mechanical device on these engines.

How many RPMs per * timing I have no clue.

Here's the thing though.
The ECU [ECM] does control idle speed via ISC valve and ignition timing.
However, with the valve fully closed and the timing as retarded as it can get it, the ECU can do no more.
Once you change the base timing, the ECU can only adjust so much for this.
Every engine will be a little different, but the ECU only has so much leeway it can work with.

I used a timing light. and actually, according to my hayne's manual idle speed can be adjusted by a screw on the throttle body. and I'm not so sure it actually is 950 rpm. my idle always fluctuates anyway, it might've been just cause the car hadn't warmed up yet or something. but when I turned the dizzy I could hear the idle increasing the further it turned.