What exactly causes KR? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

Reply
 
 
 
Thread Tools Search this Thread
Old 03-03-2007, 10:17 AM   #1
Senior Member
True Car Nut
Thread Starter
 
Join Date: Aug 2004
Location: In your garage, swipin' da lug nutz
Posts: 3,067
Thanks: 0
Thanked 0 Times in 0 Posts
sandrock is on a distinguished road
Default What exactly causes KR?

First off, I know what KR is, and how the PCM responds to it, and how it is sensed. My question is more in regards to what the major causes of it are. I know some causes of it, and I am sure Jinx is still plauged by them:

1) Weak fuel pump and/or regulator. I also discovered something a bit disturbing on my car that could be related. For us 92-93 owners that have that mod done for the fuel gauge...you know, that diode that has to be soldered in? I crawled under my car one day and found several exposed wires going into the tank, one of which had a diode installed and all of the exposed wires had corrosion. When I get Jinx up on jackstands I will look into this further and repair as needed.

2) Bad or low-octane gas.

3) Faulty knock sensor. Is it improbable it will go bad? Yes. But not impossible. But irrelevant for me as I have a brand new one installed, and a backup still on the block (though not electrically connected).

4) Rattle cat. Not sure how much it affects KR, but I assume it would make the knock sensor pick up alot of false knock.

5) Bad tranny. I've seen it using the scantool and driving. It will start with about 3 or 4 (which is normal from my readings on here) expecting a shift to happen....but when it doesn't happen KR keeps going up until it DOES happen. I've been as high as 20 Though I am not sure if the tranny is the only culprit.

6) Hot air. Now that the engine is running near perfect (it still has a stumble when you burp the throttle when cold), once the trans is done I am going to work on an isolated air box and, uh, ditch the Ricerzone filter.

That'* all I can think of. If anybody knows other ways KR can creep in, please let me know.
sandrock is offline   Reply With Quote
Old 03-03-2007, 11:03 AM   #2
Junior Member
Posts like a Ricer Type-R
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

Running lean will do it too. Especially right before or at a shift.
willwren is offline   Reply With Quote
Old 03-03-2007, 11:31 AM   #3
Senior Member
True Car Nut
Thread Starter
 
Join Date: Aug 2004
Location: In your garage, swipin' da lug nutz
Posts: 3,067
Thanks: 0
Thanked 0 Times in 0 Posts
sandrock is on a distinguished road
Default

That would tie into the fuel pump/regulator issues. BUT....would dirty injectors cause ti as well? I'm thinking with all the stuff that'* already done, and what I would like to do in the future, I should either get new injectors or send mine in to FIE (doing the trans job/front brakes/suspension would be the best time to send the injectors in as they won't be needed at that time).

I also thought about coolant temp. Even with the 180* installed, the dash gage tells me it hovers around 220 w/o ac going....it drops to 190ish when it is. So I either need to install a bypass switch or when I get GM Tuners to do my chip have a lower fan-on temp burned in.
sandrock is offline   Reply With Quote
Old 03-03-2007, 11:32 AM   #4
Senior Member
True Car Nut
 
95naSTA's Avatar
 
Join Date: Feb 2003
Location: Philly
Posts: 4,508
Thanks: 0
Thanked 0 Times in 0 Posts
95naSTA is on a distinguished road
Default

Oil getting into the combustion chamber by way of worn rings or valve seals will do it too.
Sharp edges in the combustion chamber or spark plug tips can become superheated and cause knock too. For the most part our combustion chambers are smooth and the plug will only overheat if you get the wrong heat range.
95naSTA is offline   Reply With Quote
Old 03-03-2007, 12:10 PM   #5
Junior Member
 
Join Date: Apr 2006
Location: Purgatory
Posts: 0
Thanks: 0
Thanked 0 Times in 0 Posts
Bonneville92V688 is on a distinguished road
Default

Also KR can be caused by "false knock" Typically when the trans is shifting, the knock sensor will pick it up and consider it knock. Installation of Dynamat on the trans really helps this.
Bonneville92V688 is offline   Reply With Quote
Old 03-03-2007, 12:17 PM   #6
Senior Member
True Car Nut
Thread Starter
 
Join Date: Aug 2004
Location: In your garage, swipin' da lug nutz
Posts: 3,067
Thanks: 0
Thanked 0 Times in 0 Posts
sandrock is on a distinguished road
Default

Quote:
Originally Posted by Bonneville94V688
Also KR can be caused by "false knock" Typically when the trans is shifting, the knock sensor will pick it up and consider it knock. Installation of Dynamat on the trans really helps this.
But...wouldn't the PCM be pulling KR during this time anyway? During gear shift I can see KR being there, and though the knock sensor may very well be picking this up as false knock, would it even matter that much? BTW...I have seen those false-knock elimination kits and wondered about the dynamat on the trans extension...guess that'* the answer why
sandrock is offline   Reply With Quote
Old 03-03-2007, 12:43 PM   #7
Junior Member
 
Join Date: May 2006
Location: BonnevilleHell
Posts: 0
Thanks: 0
Thanked 0 Times in 0 Posts
clm2112 is on a distinguished road
Default

Quote:
Originally Posted by sandrock
But...wouldn't the PCM be pulling KR during this time anyway? During gear shift I can see KR being there, and though the knock sensor may very well be picking this up as false knock, would it even matter that much?
Good topic...

What is a knock sensor? It'* a piezo buzzer. Just like the one that goes "bleep" when your PC comes on. It conducts with vibration. The ones in our cars listen to a specific frequency of sound being transmitted through the block. When it hears that sound, it changes it'* ability to conduct and the PCM sees that as an indication of detonation of the fuel/air charge under compression in the engine.

True knock is when the problem is really there (as enumerated in the posts above) False knock is anything that generates that frequency and isn't caused by actual detonation of the fuel/air charge. This could be anything from tapping on the motor with a mallet, something metallic rattling in the frame of the car, etc.

I don't think the ECM is sophisticated enough to know when to ignore the sensor...for example, I don't think it knows to ignore the knock signal when the transmission is shifting gears. Actually, the transmission shouldn't be generating the frequency that is tripping the sensor. My first remanf. A/C compressor rattled bad enough to trip the knock sensor. I could see it on the scan tool...KR comming in at the same time the clutch kicked in.

So, the first order of business is to figure out if the knock is really there and being caused by detonation. I would try deadening the knock sensor, or removing it from the block, but leaving it in the circuit. That will turn off all KR from the PCM. (If it can't hear it, it can't do it.) Then use your own ears to listen for actual engine knock while driving Jinx around. It'* always going to be a sound under heavy load...lugging the engine in the wrong gear should do it everytime.
clm2112 is offline   Reply With Quote
Old 03-03-2007, 01:15 PM   #8
Senior Member
True Car Nut
Thread Starter
 
Join Date: Aug 2004
Location: In your garage, swipin' da lug nutz
Posts: 3,067
Thanks: 0
Thanked 0 Times in 0 Posts
sandrock is on a distinguished road
Default

Is it possible to do that? I thought the knock sensor grounded through the block...which is the reason why there is only one lead going to it.

I DO know my cat is probably causing some of the retard. It rattles HARD, and I will more than likely bypass the cat altogether, at least until I have the money for a full exhaust, as I see no sense in welding in a new cat just to have it come out when I do the full exhaust anyways. My transmission (the one currently in the car that is) also has alot to do with it I think. The PCM sees slippage and retards the timing quite a bit to save what is left of the trans I think. My fuel pump, though it is showing good pressure at idle, might not be fairing so well on demand, and will be dealt with when Jinx gets put up on blocks for a month or so.

Hmm...would a faulty tensioner hopping around everywhere translate to false knock as well? I noticed mine is a bit on the loose side.
sandrock is offline   Reply With Quote
Old 03-03-2007, 02:57 PM   #9
Member
Posts like a V-Tak
 
Join Date: Mar 2007
Location: Alabama
Posts: 43
Thanks: 0
Thanked 0 Times in 0 Posts
swifty is on a distinguished road
Default hello

I am new here, what is KR?
swifty is offline   Reply With Quote
Old 03-03-2007, 02:59 PM   #10
Junior Member
Posts like a Ricer Type-R
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

KR is knock retard. When the knock sensor and PCM detect knock (pre-ignition and detonation are commonly and loosely related terms), it retards the ignition timing to prevent it. Knock and detonation are very dangerous animals.
willwren is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
where exactly are the evap core drain tubes at? zo6vette 1992-1999 1 02-15-2005 09:30 AM
Hey look - exactly 2500 members... theJMFC Lounge 0 05-17-2004 02:05 AM
What exactly does high resolution do? ssesc93 Lounge 12 02-13-2004 11:48 PM
where EXACTLY is whole in firewall grey3800 Audio (and aftermarket electronics) 12 09-12-2003 09:27 PM
Looked for exactly this...... showhat9 Introductions for new members 2 08-25-2003 11:14 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 05:12 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.