Annoying engine knock problem
 

About a week ago I ordered a PCM and the Aeroforce Interceptor gauge from Intense Racing. Everything installed flawlessly. I noticed when driving though that I would get a lot of knock (up to 7 or 8 degrees when flooring it). Under normal driving conditions it would sometimes spike up to 2-3 degrees. Thinking that the knock was due to the new PCM I put the old one back in and noticed that I still got knock (up to 5 or 6 degrees instead of 7-8). I had never checked if my engine had this before I purchased the gauge.

Any ideas on what could be causing it?

Things to note:
I've been using 93 octane.
Besides the new PCM, my car only has a 2.5" downpipe w/ magnaflow cat and a new intake.
When I first realized I had knock, I called the company and they suggested that I try putting in new, colder spark plugs. I did, and that didn't seem to help at all.
I have a 2001 NA Monte Carlo.

Thanks!

The first thing I like to try with knock is to go find some race gas (like 100 unleaded) locally. Run your tank almost completely empty- throw in a couple gallons of race gas and scan again. If after a couple runs, you still have the same amount of knock- its false (meaning something else is causing it other than actual knock).

However, if you changed PCM's and it dropped down, it sounds like it may be real- in which case you may have a maintenance issue (ie lots of carbon buildup on the pistons/valves, leaking valve seals, etc)- how much mileage do you have on the car?

Seafoaming the engine couldn't hurt, it would help with some of the carbon buildup.

I've put up to 95 octane in my tank with no difference in knock.....

Under normal driving it stays at zero... and normal acceleration it stays at zero too. It's only when I hold the gas down or accelerate up a hill that it starts to show, and it holds through until I let off the gas.

The car has approx. 90,000 miles on it.

And I'll try the seafoam, and if that fails I'll probably suck it up and bring it into a shop.

you said you have a new intake, what kind is it?

Also you may just need to actually mod the engine a little more with KR reducing mods, such as a powerlog, or rockers.

But will a powerlog or rockers help with 6 or 7 degrees of knock?

Depending on how your tune is set up to handle things.

Also what kind of intake are you running??

If you ran higher octane gas and still had the same amount of knock- its likely false knock then.

Thats the only time you'll get knock- under heavy load. No car should ever see knock under light load, or it would probably explode under heavy load.

A normal shop probably won't be able to do much of anything- many cars have KR bone stock.

No, not if it is real knock. It will help, but not 7 degrees worth.

That would be a relief.... what do you think the chances of that are?


My intake is mandrel-bent aluminum tubing with a K&N filter..... and is in the engine bay. The incoming air hovers around 80-100 degrees, with the outside ambient air temperature being in the 40's (I was asked the same question about the intake somewhere else).

Well If its sucking in hot air, that could be a problem.