My OTC scanner is telling me the computer is retarding the timing when ever i get on it.(3000RPM+) My base timing is set at 6° BTDC. What else should I look into?

 

The Knock Sensor is detecting knock and pullinig timing out. Very common on TPI cars, especially those with the stock GM heads. I have done a lot of playing with the timing and minimizing of the KS retard (in WOT) and I have found that as you approach 28*-30* the stock GM heads just won't tolerate any additional spark advance and start to cause audible detonation.

This is with the KS disabled, so this is the actual spark advance. If my KS is enabled, I could have the ECM pull out 6* to give a total spark advance (after subtracting the retard) of only 22*.

 

If you are not already,you could try a 160 degree thermostat
and fan switch - the lower engine temp will help detonation alot.
maybe your knock sensor is getting old - try taking that one out and wrapping a good amout of thread tape around the threads
and dont over tighten it (this will de-sensitize it).
a knock sensor senses vibrations.
if you have a bad exhaust leak near the engine, vibrating against the engine a knock sensor can and will pick this up as detonation.

 

The problem is the head design - they don't like a more that 28-30* of spark advance. You can use a colder t-stat, throw in "Octane boost" and COMPLETELY disable the knock sensor; you will still get audible detonation from 28-30* of spark advance. Been there, done it.

The most effective way I have found, is to limit the amount of Knock Retard during WOT to only 1*. Controlling the spark curve can allow you to gain another degree or two. But when you start getting near 28-30* of spark advance, you'll hear the pinging. The advantage to this method (over completely disabling the knock sensor) is that your knock sensor will continue to work when you are in part throttle and placing a load on the engine (you never know when you might get a tank of bad gas). You get the best of both worlds then. KS for protection during part throttle driving and the KS is effectively disabled during WOT when it is pulling a lot of timing out.

Noticing a lot of knock retard with the stock heads is one of the first things people observe when they get a scan tool. The method I mention above is the best course of action I have been able to come up with - and it is not without it's dangers. Just be aware that you may drive to different elevations and find that the max timing you can run at one elevation is different at another elevation. So you may not have any problems where you live (with audible detonation) but then take a trip somewhere and find your timing is too far advance.

Generally, the higher the elevation, the more spark advance you can run due to the thinner air.

 

If this isn't a problem, but rather something that happens, how do I tell if my base timing is set to high? I was in the process of increasing the timing for a little performance but stopped when it was knocking at the stock timing.

 

Well, this is the reason that simply increasing your base timing often does not increase performance on a basically stock engine. You may advance the timing a couple of degrees, but the KS takes even more out.

The KS does work, but not without it's problems. The KS tends to be sensitive when "noise" is first detected. It's first reactions is to start pulling timing out. But if the noise continues and gets louder, then the KS tends to go deaf, and that's when audible detonation starts to occur.

The problem is, with LOTS of retard happening first - when the KS goes deaf, the ECM will then give you ALL of the spark advance you were originally requesting. Thus it makes the detonation even worst, and this is when you are most likely to do serious damage to your motor.

The only place you can control of these factors is inside the eprom. And this is something YOU have test and tune yourself. I have probably burnt over 300 different eproms in the last year. The majority was in trying to understand how the KS works with the ECM and why it behaves as it does. Other than changing your heads (not a bad idea), the method I mentioned above was the best setup I could come with.

I have my entire spark table (from 2,000 - 5,600 rpm) set to just .4# (smallest increment) below the points I know I will incur detonation (because I have heard it already). A very common time to hear detonation is during the "upshift". This is partially caused by the transmission shifting and "deafening" the KS (saturation) - the KS stops working (no more retard) and then you hear the detonation.

The only people that I have found that can run 32+* with NO detonation are with non-stock heads. I have tested a good dozen other vehicles and shared information with another dozen so. We get asked this question all the time on the DIY Prom Board. AND the method I suggested above is NOT RECOMMENDED for a "newbie". This is very risky and may result in damaging your motor. I have been very cautious in my testing of this and always back-off at the first sign of detonation. Once you've heard it, you'll always remember the sound.

I know some people are working on a different KS behind the scenes. They are working on "narrowing" the frequency monitored by the KS to make it more discerning. I.E. Ignore other noises in the engine and concentrate more on the frequency when detonation is occuring. There are many challenges and while it sounds simple enough, making it work in practice with the stock ECM has proven elusive.

 

I would try the basics first.
all of the ive mentioned above can and will cause detonation.
with a stock L89 iron headed T/A my 87 T/A ,i used to get away w/ 89 8 degrees initial and 29/30 degrees advance w/no knock retard. there is no doubt there is disigning flaws but you can make the best with what you have - ecpecially if your not a custom burner.