Besides improper tuning, what are some things that can cause knock?

[lyonsd]

After a couple of WOT blasts I filled up the tank with gas.

Since then, I haven't been able to drive it hard at all without a lot of KR on the Scanmaster. I'm talking 8-12 degrees at part throttle and before I even get to 5psi.

So either I screwed something up in those WOT blasts, or I got some bad gas.

When I can get rid of most of this gas I will add some 100 to it to see if that helps.

But what if it's not the gas? What else could cause knock like that? BTW, I don't hear any knock - just seeing it on the Scanmaster.

I don't see how a cracked header could cause it, but what about a blown head gasket? Could that cause it?

I've also heard about something to do with the torque converter activating the knock sensor. What are the details on that and how do I check it?

 

[Carolinaturbot6]

http://www.geocities.com/rad87gn/tech/knocklist.html

False knock can unfortunantly be caused by lots of different things. The link above, in case you haven't seen it, lists most of them. I'm sure you're looking for some of the more obvious scenarios, but I thought the above link may help some.

Hopefully, it's just a case of "bad" gas this time.

 

[John Larkin]

I saw that level twice. I was way too high on fuel pressure first time. Second time, the car overrevved due to a governor problem. Tune your car to spec (gnttype list) and see what's going on afterward.

 

[BLACK6PACK]

Dump a can of xylene in there and see if that helps.

 

[lyonsd]

Originally posted by Bmason
Dave:

Start with the exhaust leak first, to eliminate that from the equation. I had a knock problem that was resolved when the leak was fixed.

-Bobby

So then a cracked header could cause knock retard like this, right?

 

[lyonsd]

Well, I don't think there's an exhaust leak. If there was an exhaust leak, I should be able to smell it, right? Once I had the wrong PCV in and the fumes were detectible in the cockpit when I had the vent or AC on. So I figure I'd be able to smell an exhaust leak, too.

I increased the fuel pressure. When I was tuning at Reynolds it seemed to run best around 40psi. I turned it up to 45psi and now I've getting 7-8 degrees as I approach 10psi. So it's getting "better".

Man, I hope it's just bad gas. I wish there was a way I could tell for sure. Because that ticks me off if I paid a premium price for a full tank of 93 octane and only got 87 or something.

So where can I get a can of xylene? I guess it's worth a try.

 

[Slo86GN]

I get my Xylene at Ace Hardware. Check in the paint section of the local hardware store or stop by a paint store to see if they have it.

 

[BLACK6PACK]

Lowes, home depot, etc

I've found sherwin williams the cheapest. If you have a full tank of 87 you may want to add two gallons of xylene.

 

[lyonsd]

*sigh of relief*

Evidently it was just a tank of bad gas.

That ticks me off that I would go to Amoco and pay the premium price for 93 octane fuel and get something of a far inferior grade.

Anyway, I eventually ridded myself of that tank of gas and put in a few gallons of 93 from another station. Got on it a little and I was able to go WOT. I still got some knock retard (2.X to 4.X degrees) but nothing like before. I was getting as much as 8 degrees at part throttle as I approached a mere 10psi.

I'll attribute this good gas knock to the hot afternoon air.

Hopefully, the Power Plate will cure the hot weather knock I get on good gas.

 

[BLACK6PACK]

Don't you just hate bad gas! I know my coworkers hate it when I have a full tank of bad gas!

 

[REDS HOT AIR]

amoco isnt what it use to be...

hate to say it but i have best luck with exxon.

 

[scottyb]

Man, if I ever suspect that I am getting bad gas, I'd call whoever regulates that immediately. I think it would be too easy for a gas station to rip off people because most would never know the difference.

 

[PRSRIZD_V6]

Can a bad ECM really cause the knock sensor to go off?

I've got one that started not to long ago, right about the time I switched to my Direct Scan ECM..... hmmmm

 

[lyonsd]

Actually I'm a little disappointed that it wasn't something like a cracked header or blown head gasket. Because when my headers cracks, that will be my reason to get a new set from Houston or ATR. If the heads had to come off, then that'll be my reason to put on GN1s.