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Timing Jumping around with spout but solid without?

9111 Views 9 Replies 3 Participants Last post by  89coupe
Hey guys,

I was trying to adjust my timing this weekend and I notice something funny. When I remove the spout I can adjust the timing perfect and it will stay on that mark with out bouncing around once I turn off the car and reconnect the spout my timing is jumping all over the place. I know if my timing jumps with the spout out then I might have a timing chain or gear issue but what if this only happens with my spout in?

89 Mustang GT - 306 / E-303 cam / BBK Upper & Lower intake / GT 40 aluminum racing heads / Forged Internals / BBK 70mm Throttle Body / MSD 6a ignition-Pro Bullet-Blaster Coil-8.5mm Plug wires / ProSport #30 MAF
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With the spout out, the computer is not controlling the spark. This allows you to set the "base" timing. Once the base timing is set, you insert the spout and the computer does its thing using where you set base at, as its "zero".

Since you have crazy timing when the computer is in control, I'd wager one of the other sensors is giving wacky readings and the computer is trying to compensate by adjusting the timing.

Have you pulled codes? Might be the time for that. :)
Perfectly normal for the timing to jump around. You must know that timing is part of the Idle Control Strategy also. And it generally reacts quicker to different timing advances, that it does the IAC valve.

In a nutshell, as long as the timing moves when the spout is in, that means the ECM is doing its job.

And yes, sometimes timing advance being to much or not enough, can be from faulty sensors. Part of the ECM strategy is set to pull or add timing depending and various ECT, ACT temps. Those two seem to have the biggest effect if I remember correctly.

And there will be times, when a sensor has failed, but not thrown a code. Simply because the codes are based on ranges. We don't have datastream capabilities like are SN95 buddies. So its harder for us, since we would have to break out the trusty voltmeter to actually check its functioning like it should.

I think you are just fine. Timing usually fluctuates from 18*-28* with the spout plug connected.
Wow, so it fluctuates 10 degrees to maintain idle? Does that include retarding the timing to? By that I mean, is it +- 5 degrees from base?
Very rare that you see it drop below 10*. But yes it can. I will look in the strategy tomorrow. But timing is generally pulled as a fail safe method when temps get high. But no, generally it does not subtract below base setting during idle. That's too much of a change, and you all should know what and engine idles like the closer to 0* timing you get.

I will post up the stock timing table for an A9L tomorrow as well. So you know what you guys are dealing with stock and through the rpm range.
Just to make it clear when I mean my timing is jumping around I mean when its in idle and the spout is in every time the timing light flashes the timing will be at a different degree. I don't mean for 5min it will be at 22 then change to 20 for another 5min. Just wanted to make sure we're on the same page.
If I am understanding 89Coupe, that is what you want to see, since it is indicative the computer is actively managing the idle.
Yes, drive the car man, quit worrying about it. :)
Just wanted to make sure that's all. It was weird to see that happen thought maybe I had something wrong with sensor or maybe my MAF. Thanks guys
Here is the stock A9L timing table. There are various subtractors,multipliers and adders that also come into play.
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