What's causing my knock? (help!)

  • Thread starter Thread starter dave84gn
  • Start date Start date


Got a turbolink the other day (great tool!), hooked it up to my car and the computer is detecting quite a bit of knocking whenever I open up the throttle. It retards the timing about 10 degrees, even as much as 18!

Here's a sample bit of data.

4 699 32 133 95 1625 0
5 851 60 133 69 2350 0
6 878 138 133 69 3150 10.4
7 843 158 133 69 4000 10.4
8 824 161 133 69 4825 7.3
9 816 149 133 69 3325 5.4
10 820 157 133 69 3650 4.2
11 808 159 133 69 3925 3.1
12 804 159 133 69 4225 1.6
13 812 128 133 100 3200 0.5
14 820 75 133 100 2625 0

Looks like I went through two gears... and it *seemed* to have only knocked at one point (3150rpm) and went down from there.

Also, in ALDL mode each time I open up the throttle, ESC counts jump by about 4 knocks.

I hold about 10 psi of boost at WOT (cracked headers are hindering my boost). I don't think I hear any knocking/pinging sounds while I'm driving (but I ain't an expert). My car runs around 16.5@86 on the GTech. Owned this car for 2months so far. 104miles on the car. I run premium fuel at 92 octane on the stock chip.

Fairly stock car:

-removed cat
-dual dynomax super turbos
-k&n cone filter (removed air box)
-160 stat
-adj. FPR (set at 41psi static)
-new valve springs

My car generally runs fine. At idle, it sounds healthy, no noises to speak of, except a *little* bit of chatter. The car drives fine, it's even fairly responsive. Just seems to give me little power at WOT because of this knock retard.

I hope I'm sort of on my way to getting the power of my car into something acceptable. So what the heck could be causing so much knock? Is it possible my knock sensor is shot? Detecting false knock? Other mechanical problem? Timing related?

Thx for reading this!


Note: I'm fairly new to this car, so any suggestions/ideas that anyone has would be greatly appreciated.
Thx slow_85.

Nope, not in ALDL mode... if I was I wouldn't get the spark retard reading, just the ESC counts.

As for MAF, I'm only getting 10psi of boost (due to cracked headers I believe), so I shouldn't get as high MAF as usual, right?

Looked down the checklist on the website, most of that stuff is either OK or I have no idea about. One thing on the list is EGR. My EGR is troublesome, it's been throwing codes about once a week. Think that may be related to the knocking? I wouldn't think so, but I really don't know.

Anyone else have any ideas or ever experienced this?


First of all I see that you don't have a upgraded fuel pump and hot-wire kit. These are a very important part of a TR. Although they may not be causing probelms yet, they will down the road.


Everything looks good - Maf is on the low side, but 10psi you not flowing any considerable amount of air. Is it a GM or aftermarket MAF?

Fix the problems you know exist! Cracked headers are bad news, they mess up the 02 readings - very important to fix them.

I don't see an TPS voltages there either. Verify .42-.48 @ idle/4.5+ @ wot.

As far as the EGR I dunno if a malfunctioning one would cause knock - maybe. It would be a good Idea to fix that too.

Good luck
Originally posted by Nocooler
I don't see an TPS voltages there either. Verify .42-.48 @ idle/4.5+ @ wot.
hehe Nocooler forgot about the old TPS, 85 ecm limited data.
You can check it with a volt meter while the car is off.
As far as the EGR I dunno if a malfunctioning one would cause knock - maybe. It would be a good Idea to fix that too. It's possible it could contribute to causing the knock. (Recirculating hot gas)especially if your getting a code.I would try your other chip. It should shut-off the EGR under WOT. Prolly a combination of things. Shouldn't see any knock at 10#'s boost.

Also, have you checked your coil?
should OHM out tower to tower(front to Back) 11k-13k
I would check your plug wires too, especially Passenger side.
Thanks for the responses guys!

Nocooler: I just put in a walbro 307 and wiring kit two days ago. Just poped in my new 92 JL chip today. I'm now seeing 13# of boost as opposed to 10# with the stock chip (woohoo!). The turbolink data I posted was from before my fuelpump/chip mods.

Unfortunately I haven't been able to get much reliable data from the turbolink (maybe the extra drain on the alternator is causing problems). Like, sometimes the tlink will show my rpms going from 2k to 4k then back down to 2k, when they never changed at all. Or suddenly I'll get 50 degrees of knock retard then 0 :) Hard to diagnose stuff with that going on. Anyway, the car does feel stronger.

MAF is stock GM I believe. Although it seems fairly clean when I looked at it.

Will fix the headers once I determine how much of a pain in the a$$ that'll be!

In ALDL mode I get TPS, which is reading low... 0.38 at idle and 4.08 at WOT. I'll fix that soon, I guess :)

EGR code may have been caused by me having a 160 stat in there on the stock chip.. i hear that upsets them sometimes. We'll see if it comes back.

Hmm, no idea how to check the coil, got a webpage I can refer to? Or do I just hook a volt/ohm meter up to it? Also, how do I check plug wires? Volt/ohm meter? what sort of readings should I look for?

New chip is in Bob, I'll try to get my turbolink reading properly so I can get some accurate readings. From what I saw, I was getting less retard (3 to 6 degrees at WOT), but still some. But I really don't think my engine is actually knocking, because if it was actually knocking so bad to retard the timing 18 degrees I think I'd hear it... or maybe I'm too much of a newbie to notice :)

OH Yea... also I wanted to add... I'm getting knock at idle when I rev the engine up to around 3.5k or 4k. Basically I press the throttle a bit to get it to 4k then let it go, and my tlink was showing 2 to 4 knocks from the ESC and I can't remember how much retard (5 degrees maybe?) This most likely isn't real knock is it?

Ok how about this. Suppose, at idle, I held the throttle at 4k rpm for 30 seconds. If my engine was really knocking I would get a LOT of knocks coming through on the ESC, right? Like I'd be constantly knocking that whole 30 seconds. However, what if (now I think this is the case) I only get knock when I rev the engine, and then no knocking as it holds steady at 4k? Wouldn't that indicate false knock -- maybe something loose around the engine clangs when the engine twists on its way to 4k rpms.

What do you guys think about that?

check your cat hanger bracket. If it's broke or loose it can cause
knock from banging around. Motor mounts, hell put a wrench on
anything you can get to. :D
On the plug wires hard to tell even if you check resistance(ohms)
Usually the passenger sides go bad due to heat from up/down pipes.
I finally went to wrapping mine in protective heat sleeving on that side.

4 2 6
1 3 5 (coil pack facing towards rad)

use voltmeter set on 20 OHMS.
Measure 1 to 4, 3 to 2, 5 to 6
pull plug wires off coil, do one bank at a time.
should read 11k to 13k.

More food for thought:
If t-link started acting funny with the chip-change
might reseat prom and reset your computer.