Bad knock at wot

[Tom87GNX]

I'm pretty new to the turbo buick scene, and even newer with the hot air cars. I recently purchased my first hot air car. I love the car but can't enjoy it cause of WOT knock. I know I should have a boost gauge, fuel pressure, and knock gauges but I haven't gotten there yet. I do have a Scanmaster, hot wire on fuel pump, LT1 MAF and translator, 86-87 ECM with TT chip and 42# injectors. The car runs really good during normal driving and pulls hard under about half throttle, if I nail it from a stop it knocks after the turbo spools, if I ease into it I get the same results. I have mixed fuel in the tank right now (about 5 gal of 93, and 5 gal of VP 100 octane). Still knocks like crazy, fuel pressure is set at 45 with line off, I've even tried setting WOT fuel in chip and received no positive results. I'm getting knock anywhere from the 3-4 range (I back off immediately) and as high as 9.1 early this afternoon. Don't have SM numbers at the moment but could get some in the morning. Any ideas?


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[Tom87GNX]

Don't think it has any effect on anything, but it is a "109" long block with hot air injection and turbo etc. I bought it this way.


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[notacarlo]

One idea. Keep out of WOT.

Check for vacuum leaks.

What plugs and what gap?

Test the coils (ohms across the towers) good write up on gnttype.org.

What is the scanmaster showing for 02's at WOT at the top of third gear?

There are so many variables to contribute its crazy. Start with the basics and make sure everything us operating normal. TPS, 02 sensor, etc.....

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[Tom87GNX]

I know to stay out of wot with knock, I've been trying to make adjustments and since that's the only way it knocks, I'm off the pedal completely when I see anything, but as everyone knows, knock happens very quickly. I have been thinking about just replacing every hose on the car, checking for vac leaks etc.

What should my fp be at wot, roughly?



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[notacarlo]

1 psi per psi of boost

So if its at 42 at idle and you run 10 psi you should see 52 psi fuel.

Pound for pound increase

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[Tom87GNX]

Ok, that's what I thought. I think I may have a pump problem. I have 42 at idle w/vacuum connected. Pressure seems to struggle passed 45 ish. Looks like I'm dropping the tank and putting in my 340 pump. Previous owner said he installed one with the hot wire.


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[we4Mateo]

Drop some timing in the TT chip and see if that helps. How do you know how much boost you are runnng?

 

[notacarlo]

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[notacarlo]

Stop driving. If your FP isn't rising your regulator could be shot if not the pump. Pull the line off the regulator and see if there's gas in either or a strong fuel smell. If so, get a new regulator or rebuild kit if its an adjustable.

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[Tom87GNX]

It got it fixed. I found a few questionable vac hoses and a small crack in the air intake pipe right after the MAF. I have installed a boost gauge, and she cranks out about 12psi right now with zero knock. The only issue I have now is I'm not getting a mph reading on digital dash or Scanmaster. This stopped after trying to adjust wot fuel on the chip. I have unhooked the battery, ECM, and even removed and reinstalled the chip. The cable is noisy so I'm hoping that it broke, what's the likely hood of that happening at the exact time I change chip settings? Weird.


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[billy 420]

sounds like a bad contact at pcm connector or the connector behind the glove box (15 wire connector is shot ).your vss runs through both

 

[Tom87GNX]

I got it working, the vss buffer was bad. I replaced the buffer and it worked perfectly. Car now runs 14psi on 93 octane with 0 knock


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[we4Mateo]

I got it working, the vss buffer was bad. I replaced the buffer and it worked perfectly. Car now runs 14psi on 93 octane with 0 knock


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Interesting. So the timing being off was causing your knock? I haven't seen a buffer go bad yet.

 

[Tom87GNX]

Interesting. So the timing being off was causing your knock? I haven't seen a buffer go bad yet.

I actually fixed the knock problem by replacing vac hoses, just so happened that the buffer went bad at the same time. I replaced it and everything is good.


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[billy 420]

nice!! glad to hear youre running well