Read my spark plug...

[theholycow]

Originally Posted by Jay2TheRescue

back it off a hare.

Is that an Easter joke?

[Jay2TheRescue]

It could be...

[bowtieguy]

if he backs off the hare, can he then have feaster bunny to eat?

[theholycow]

Ok, I think this is my list of things to try:

Higher octane fuel - I have a bottle of dollar store octane booster, I'll try it when I'm down to 1/4 tank or something...then after that maybe I'll invest in some actual expensive fuel.

Port vacuum instead of manifold. Probably will be worse.

Retard timing (wouldn't this reduce FE?).

CAI - I'm thinking I can put in a CAI and run direct manifold vacuum to the intake air door so it gets cold air at low vacuum (which should help with the knock) and air heated by the exhaust manifold at high vacuum (when there is no knock). Jay, didn't you do something like that?

[theholycow]

Hey wait a minute...could EGR be involved? Failing EGR, for example, or maybe a modification I could do...

[GasSavers_Erik]

Check the EGR diaphragm to see if it will still hold vacuum. Try hooking the EGR up directly to ported vacuum.

If the EGR passages are clear, when you reach up under the EGR diaphragm with your fingers while it is idling and manually pull the valve open, the engine should stall.

Spark knock will reduce mpg, so back off the timing a bit (rotate the distributor) if you hear a lot of it. The timing must be more advanced now than it was before or you would not hear the spark knock. So- the timing was too retarded before and now it is too advanced- you just need to find the happy medium for good mpg and very little spark knock.

[theholycow]

Originally Posted by Erik

The timing must be more advanced now than it was before or you would not hear the spark knock.

Possibly. It only comes with heavy throttle/low RPM - lugging.

Before the manual transmission: Can't lug an automatic, it'll downshift.

Before the vacuum modulator valve removal/manifold vacuum connection: Can't lug because it gets busy bucking first.

Now: Can go wide open at any RPM (well, until I back off because of knock).

[theholycow]

I thought of another thing: If there's a lot of carbon buildup, my compression ratio could be artificially high.

So, my list, which I'll probably do in order of cheap and easy first...

- CAI
- carbon removal (Seafoam? Italian tune-up?)
- port vacuum (probably fail but it's way easy and free)
- EGR
- retard timing
- octane

[Jay2TheRescue]

Originally Posted by theholycow

CAI - I'm thinking I can put in a CAI and run direct manifold vacuum to the intake air door so it gets cold air at low vacuum (which should help with the knock) and air heated by the exhaust manifold at high vacuum (when there is no knock). Jay, didn't you do something like that?

That's very close to the stock setup, except there's a thermal vacuum switch to keep the intake air at a steady temperature.

[theholycow]

Exactly. By removing the thermal vacuum switch it changes its behavior entirely, running as a HAI except when vacuum disappears. Also, there's no CAI in the stock setup, it gets warm engine bay air when it's not getting heated air.

So, I'd go from temperature-regulated air (no colder than engine bay air) to HAI/CAI based on vacuum.