I need help again


Active Member
Jul 7, 2003
O.K. guys I need your help again. I finally got time to take the TTA out. When I got into the boost I did a gradual climb. I had no knock at 6,7, or 8 pounds of boost. When I hit 9 I had a reading on the scanmaster of 4.2 degrees but my knock guage read 0. Then when I hit 10 I had a reading of 10.8:eek:. But again I had 0 on my knock guage. I couldn't hear any knock though. Would I be able to hear 10.8 degrees of knock? After that run I made two more runs only reaching 6 pounds of boost. Those runs made 0.0 degrees of knock on my scanmaster and my knock guage. I'm stumped and could use all your help. Thanks again. Dean
Your scanmaster should be telling the truth. Check what chip you have in the ECM and/or throw some zylene in the tank and that would give you a good start. Plus, check motor mount,tranny mount,downpipe,and anything that could knock against the frame.

If it's knockin at 9 psi, I would guess false kr....... The SM will detect any signs of kr weather it's false or not, so I would find out if that gauge really works . Start with the above and check back.


The SM will detect any signs of kr weather it's false or not

I think a knock detector is supposed to be "tuned" to look for the same vibration frequency (knock) as the stock computer. So a knock detector could be wrong and not be showing the same thing as the computer is seeing. The scanmaster actually shows how much timing the computer is retarding (knock retard) d/t picking up knock. So like Bo is saying reguardless of the knock gauge the computer is seeing it and the scanmaster is showing it to you.

Let me know what you find out. My nephew was fighting a false knock problem last fall. He parked the car for the winter before I had much of a chance to help him. He did say the other day that he started the car and it was acting funny, idling goofy and crap like that. He said he started to wiggle the wires to his computer and the car straightened out. He's starting to think his computer may be bad, because he said he tried all the things he found on this board to try to fix the problem.

Hey I was just thinking as I typed this.............heres a little research from www.gnttype.org

ESC is used to sense spark knock (pinging) and retard the timing to eliminate it. A knock sensor (located at the rear of the engine block) sends signals to an ESC module which then signals the ECM that knocking is being detected. The ECM will retard the timing by as much as 20 degrees in 1 degree increments. A loss of knock sensor signal or loss of ground at the ESC module will cause the signal at the ECM to remain high. The ECM will act as if no knock is present, and may possibly result in engine damage, if there is detonation

Loss of the ESC signal to the ECM will cause the ECM to constantly retard the timing to its maximum. This results in sluggish performance and a Code 43.

What you may be having is a intermitent loss of the esc signal to the computer. The computer will see this as knock and retard the timing like your seeing on the scan master.

Now depending on where exactly the knock gauge ties in could help you find the problem. The knock gauge is supposed to be tied into the black and yellow wire at location B7 on the stock computer. This wire is the one that goes from the ESC to the computer. The smaller of the two connectors that plug into the stock computer is the one with row B. So look at the wires on the smaller connector (its a 2 row 12 pin per row connector) the black and yellow wire 7 places from the end is the one your looking for. Now if the knock detector is good then the problem will be between where the knock detector ties in and the computer. So lets say they tapped into that wire 4" back from the computer, then the problem may be in:
the last 4" of wire going to comp
bad connection between the wire and its connector where it plugs into the comp
the computer itself
Now I'm an electronics tech at the post office and I work on the machines that sort the mail. We constantly are trouble shooting circuit cards and cables and such. What I have found there, is that alot of times you just get bad connections and d/t the low current and voltages of electronic stuff just a slightly dirty connection can give you goofy symptoms. I would take and unhook your battery, and then unplug and plug that connector a couple of times. By doing this the connector will mechanically scrape the contact points a few times and can fix a bad connection. Its sounds easy and it is and man does it fix alot of goofy ass problems at work.
When you have the connector unplugged take a good look at that B7 wire where it goes in. The plastic body is supposed to hold the metal connector part in there good. Ive seen them loosen up and not hold properly. Then when you push the connector on instead of it sliding into/over the connector for that pin it just pushes that wire and its connector half out so the tip is just there kind of touching and not getting the tight connection.

HTH: Jason
I would rely on the Scanmaster reading and after exhausting the usual list of suspects for knock, keep in mind that low boost knock can be caused by EGR
Thanks for the all the replys and help. I know it's not the downpipe hitting but I will have to check on the motor and tranny mounts next week when I get it on a lift. mark b, we no longer have the EGR hooked up. If you don't have it can you still get the knock caused by the EGR? Thanks Dean
By "not hooked up" do you mean the passages have been filled? If not, the chip is still commanding EGR and I guess you just have the vacuum lines plugged at the EGR solenoid? EGR is not a bad thing. For pure race applications, blocking it off is a good deal, but for a street driven car EGR can be your friend :)

BTW - if you ever get into IM240 and emissions tests that read NOX, EGR (and a cat) become real important.
mark b,
Yes it is blocked off. A previous owner blocked all of the passages in the intake. Dean
Ok Dean... should be able to rule that out...

Assume you have done the basic like new plugs gapped 035 (max), fuel filter, check F/P under boost, healthy coil pack, etc.?

Here's another "oddball" item to check: the ground at the back of the passenger side head.