Trouble shooting knock sensor.
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
Trouble shooting knock sensor.
89 zf6 383 SR
Tracking down knock issues for a while now. I have never changed the distributor and am wondering could that be a potential source for knock? Should I get an aftermarket distributor and if so, which one should I be looking at?
Tracking down knock issues for a while now. I have never changed the distributor and am wondering could that be a potential source for knock? Should I get an aftermarket distributor and if so, which one should I be looking at?
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
The engine runs at an ideal temperature with it's 180 deg. F thermostat (175 deg F = 80 deg. C) on the highway and in town (180-192 deg. F = 82-89 deg. C).
It knocks upon hard acceleration, not like 300 knock counts but still noticeable on DataMaster and it pulls a pre-programmed maximum of 7 degrees of timing.
I strictly use 91 octane gas and have even tried a 20/80 mixture of racing (114) and supreme (91) giving me an effective octane level of 95.6 octane or so. The problem still persists.
I have had my mechanic check for vacuum leaks before and came up with none present.
I have set up the tps to 0.61 V @ idle and 4.52 V @ WOT and the throttle body has been cleaned and even ran a can of Top Engine Cleaner (a GM parts can) through it.
It knocks upon hard acceleration, not like 300 knock counts but still noticeable on DataMaster and it pulls a pre-programmed maximum of 7 degrees of timing.
I strictly use 91 octane gas and have even tried a 20/80 mixture of racing (114) and supreme (91) giving me an effective octane level of 95.6 octane or so. The problem still persists.
I have had my mechanic check for vacuum leaks before and came up with none present.
I have set up the tps to 0.61 V @ idle and 4.52 V @ WOT and the throttle body has been cleaned and even ran a can of Top Engine Cleaner (a GM parts can) through it.
Race Director
Joined: Sep 2003
Posts: 16,836
Likes: 337
From: Database Error Indiana
I also use Datamaster. I was getting a lot of knock counts on my 87.
I chased the problem a long time and ran a lot of datalogs. I never found the actual cause. The thing I did find was that , I only got knock counts when the back tires were spinning.Been going on for 20000 miles. No real problem. I posted here and got nothing, so I just gave up. Something to look at. Good luck on this.
I chased the problem a long time and ran a lot of datalogs. I never found the actual cause. The thing I did find was that , I only got knock counts when the back tires were spinning.Been going on for 20000 miles. No real problem. I posted here and got nothing, so I just gave up. Something to look at. Good luck on this.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by black_89_vette
89 zf6 383 SR
Tracking down knock issues for a while now. I have never changed the distributor and am wondering could that be a potential source for knock? Should I get an aftermarket distributor and if so, which one should I be looking at?
Tracking down knock issues for a while now. I have never changed the distributor and am wondering could that be a potential source for knock? Should I get an aftermarket distributor and if so, which one should I be looking at?
RACE ON!!!
Safety Car
Joined: Apr 2004
Posts: 4,532
Likes: 7
From: Lahaina Hi
The TPS should be set at .54 idle,did you follow the proper method of setting up the Idle and tps?.
When you put the timing light on it and the dist diconnected to set the timing is the timing mark moving around?
When you put the timing light on it and the dist diconnected to set the timing is the timing mark moving around?
Last edited by REDC4CORVETTE; Dec 31, 2005 at 06:44 PM.
Le Mans Master
Joined: Jul 2001
Posts: 6,252
Likes: 2
From: Silicon Valley Kalifornia
Do you get audible knock??? Has 'base' timing been set? Has the knock sensor been re-installed ever? I know GM recommends not reusing the sensor; it seems the sensor case is designed for one install. I know that the 1985 factory manual states this.
Last edited by GRX; Dec 29, 2005 at 01:10 AM.
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Racer
Joined: Nov 2005
Posts: 456
Likes: 3
From: Sumner Texas
Well, you have gotten lots of responses, but for some reason no one has answered your original question.
To test the knock sensor connect a test light to the knock sensor connector and the other side to ground. Rap on the exhaust manifold near the sensor with a medium size hammer and the test light should blink. If it doesn't blink you have a wiring problem or a bad knock sensor.
Although you don't mention it anywhere except your moniker, is this a 383? If it is, are you still running stock fuel pressure, injectors and chip? If you are, you may very well be running a too lean condition when in open loop mode.
Good luck,
To test the knock sensor connect a test light to the knock sensor connector and the other side to ground. Rap on the exhaust manifold near the sensor with a medium size hammer and the test light should blink. If it doesn't blink you have a wiring problem or a bad knock sensor.
Although you don't mention it anywhere except your moniker, is this a 383? If it is, are you still running stock fuel pressure, injectors and chip? If you are, you may very well be running a too lean condition when in open loop mode.
Good luck,
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by MBDiagMan
Well, you have gotten lots of responses, but for some reason no one has answered your original question.
Originally Posted by black_89_vette 89
zf6 383 SR
Tracking down knock issues for a while now. I have never changed the distributor and am wondering could that be a potential source for knock? Should I get an aftermarket distributor and if so, which one should I be looking at?
Tracking down knock issues for a while now. I have never changed the distributor and am wondering could that be a potential source for knock? Should I get an aftermarket distributor and if so, which one should I be looking at?
Editorial, omitted.
RACE ON!!!
Last edited by CFI-EFI; Dec 29, 2005 at 11:53 AM.
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
CFI, thanks that was basically what I needed. Someone at some point (a mechanic) told me that I should check my entire ignition system including the distributor so the distributor was basically the last thing to check, not knowing whether or not to change it.
RED, I followed the correct procedure for setting TPS voltages.
GRX, my exhaust is too loud to actually hear it, but whenever I was standing beside it at the dyno I could actually hear somethng that I hadn't heard before and it sounded like detonation or knocking. I've had the knock sensor changed before and am not using the original one.
MBDiagMan , I mentioned in the very first line of my very first post that I had a 89 zf6 383 SR (1989 Corvette , zf6 transmission , 383 cubic inch stroker and a super ram intake). I am running 45 psi (stock fuel pressure) 30 # FMS injectors and a PCMFORLESS chip
RED, I followed the correct procedure for setting TPS voltages.
GRX, my exhaust is too loud to actually hear it, but whenever I was standing beside it at the dyno I could actually hear somethng that I hadn't heard before and it sounded like detonation or knocking. I've had the knock sensor changed before and am not using the original one.
MBDiagMan , I mentioned in the very first line of my very first post that I had a 89 zf6 383 SR (1989 Corvette , zf6 transmission , 383 cubic inch stroker and a super ram intake). I am running 45 psi (stock fuel pressure) 30 # FMS injectors and a PCMFORLESS chip
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
You need to look at total advance. All the ESC systems (assuming you kept it) allow the ECM to advance until it knocks the first time you approach WOT and retard from there with about 22 degrees of backpedaling built into it. If I remember correctly, there's about 45 degrees of total timing available and about the only time you should see anything close to that is open loop start up. Otherwise 28 to 32 is what most Chevy's like when you floor it. Post something meaningful including test conditions or quit worrying about it (or start worrying about the noise you're hearing and try to trackdown that).
Racer
Joined: Nov 2005
Posts: 456
Likes: 3
From: Sumner Texas
Originally Posted by CFI-EFI
Your response has good information, but it does NOT address the original question. Which was:I quoted this opening post in my response, post #5, and answered it directly. But YOU say, "no one has answered your original question".
Editorial, omitted.
RACE ON!!!
Editorial, omitted.
RACE ON!!!
Happy New Year,
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
That was the title to the topic. Not only isn't it "The first line of the post", it isn't even a question. YOU ignored the question. You accused others: but for some reason no one has answered your original question., and then ignored it yourself. Then you chose to answer a question not asked. Like I said, "Your response has good information, but it does NOT address the original question."
RACE ON!!!
RACE ON!!!
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Another topic of mystical proportions - the only reason to troubleshoot the knock sensor is with a Code 43. Assumming there's something wrong based on knock counts is as foolish as saying it's running too rich/lean based on pulse width. If you want to troubleshoot/improve performance, you need to look at the big picture and post it. Otherwise trying to out guess what the ECM has built into it to account for fuel quality, air temp/altitude, engine temp, and host of other varibles before it hits whatever magic number that keeps the holes out of the top of the pistons makes for lively discussions but little substance. Unfortunately, it also offers the opportunity for the naive to screw things up. To try and offer solutions without even knowing what total advance is/was, conditions of the test - oh well - no need to ramble -
