Rennlist Discussion Forums   classifieds | membership | rennlist | photo album    
sponsors | upload photo | chat    
 
Go Back   Rennlist Discussion Forums > 924/944/951/968 Model Specific Technical Forums > 944 Turbo and Turbo-S Forum
Sign in using an external account
Register Forgot Password?
Search


Reply
 
Thread Tools Search this Thread
Old 07-13-2005, 03:26 PM   #1
Oddjob
Addict
Rennlist Member
 
Oddjob's Avatar
 
Join Date: Aug 2003
Location: MN
Posts: 3,956
Default knock sensor failure? symptoms?

Unanswered x-post from the 944 board:

Anyone ever have a knock sensor go bad, and if so, what were the symptoms?

Thanks,
To remove this ad, register today or login if you already are registered!

__________________
Jim B

87 951 Cup Spec - PCA G Stock
87 951 Orig US Cup/Escort
93 964 RSA

Past: (2) 89 951s, 87 944S - PCA Club Racer
Oddjob is offline   Reply With Quote
Old 07-13-2005, 03:30 PM   #2
hosrom_951
UAE Rennlist Ambassador
Rennlist Member
 
hosrom_951's Avatar
 
Join Date: Jan 2004
Location: UAE & Germany
Posts: 9,142
Send a message via ICQ to hosrom_951 Send a message via MSN to hosrom_951
Default

VERY underpowered and max boost would be 1.2bar (stock gauge), i tested the knock sensor by unplugging it, night and day difference compared when the sensor was connected. The car feels slow, very slow, not responding properly, heavy etc.
__________________
Hussam Jamil <- Why is my name here?
RLM#:040430-3502
'86 944 Turbo-German Spec (In Dubai)
'96 BMW 328is-Japan Spec (Sold)
'06 BMW 325i-Gulf Spec (In Dubai)
'12 BMW 530i - German Spec (In Germany)
'13 BMW 530 - Gulf Spec (In Dubai)
hosrom_951 is offline   Reply With Quote
Old 07-13-2005, 03:53 PM   #3
Oddjob
Addict
Rennlist Member
 
Oddjob's Avatar
 
Join Date: Aug 2003
Location: MN
Posts: 3,956
Default

Im pretty sure that the KLR performs a periodic diagnostic check on the knock sensor, and if it does detect a problem, it will run in safe mode, which is the retarded timing and reduced boost - which is what you found when you unplugged it.

My interest, which was triggered off a discussion from another thread on power loss, can the knock sensor fail in a way that makes the KLR believe the engine is knocking, so the KLR/DME just retard the timing w/o cutting the boost? Or a follow on question, could there be a fault in the KLR or DME that triggers retarded timing, either internally or in the wiring harness (ground/short)?
__________________
Jim B

87 951 Cup Spec - PCA G Stock
87 951 Orig US Cup/Escort
93 964 RSA

Past: (2) 89 951s, 87 944S - PCA Club Racer
Oddjob is offline   Reply With Quote
Old 12-07-2006, 03:13 PM   #4
kasturbo
Addict
Rennlist Member

 
kasturbo's Avatar
 
Join Date: Aug 2002
Location: Grove City, OH
Posts: 3,524
Default

Sorry to bring up an old thread, but can anyone answer this for Jim. I believe I'm having similar problems.
kasturbo is offline   Reply With Quote
Old 12-07-2006, 04:08 PM   #5
Dal Heger
Addict
Rennlist Member

 
Dal Heger's Avatar
 
Join Date: Nov 2001
Location: NW Calgary, Canada
Posts: 1,303
Send a message via AIM to Dal Heger Send a message via Yahoo to Dal Heger
Default

No, the knock sensor can't fail such that it will "detect" knock and tell the DME that it's hearing knock. It'll be either good or "open" which will set a blink code in the KLR.

The knock sensor is just basically a microphone that picks up a very specific frequency. Very simple.

Dal.
Dal Heger is offline   Reply With Quote
Old 12-07-2006, 06:05 PM   #6
Oddjob
Addict
Rennlist Member
 
Oddjob's Avatar
 
Join Date: Aug 2003
Location: MN
Posts: 3,956
Default

Kevin,

Do a search on this forum for samluke's post on knock counting. He rigged up a little event counter to count the knock signals sent from the KLR to the DME (which would be telling the DME to retard timing). Thought it was interesting and possibly a good way to check for potential problems (either actual knock conditions, or for a false detection - bad KLR?).
__________________
Jim B

87 951 Cup Spec - PCA G Stock
87 951 Orig US Cup/Escort
93 964 RSA

Past: (2) 89 951s, 87 944S - PCA Club Racer
Oddjob is offline   Reply With Quote
Old 12-07-2006, 06:13 PM   #7
kasturbo
Addict
Rennlist Member

 
kasturbo's Avatar
 
Join Date: Aug 2002
Location: Grove City, OH
Posts: 3,524
Default

Thanks Jim. I'll check that out. I need to do some testing. I've got about 50 rwhp that is hiding somewhere and we think it's a timing issue. I've replaced the klr, and knock harness. The klr isn't throwing any codes. I may try unplugging the knock sensor just to see if the car changes. I also still need to check the dme with my spare.
kasturbo is offline   Reply With Quote
Old 12-07-2006, 06:33 PM   #8
PorscheMD
User
 
Join Date: Feb 2006
Posts: 295
Default

Just fixed one with a bad knock sensor. The symptom was no power. The car was not building boost. The code it gave me was 2-2. I did not try to unplug it but, to check it: connect an ohm meter on term. 11 and 13 of disconnected klr control unit plug. You should get 270-330ohms. If 0 or inf. ohms check wires, if good replace sensor. torques to 11nm.
PorscheMD is offline   Reply With Quote
Old 12-07-2006, 08:03 PM   #9
kasturbo
Addict
Rennlist Member

 
kasturbo's Avatar
 
Join Date: Aug 2002
Location: Grove City, OH
Posts: 3,524
Default

Thanks MD. I'll try that. Ignition doesn't need to be on right to test?
kasturbo is offline   Reply With Quote
Old 12-07-2006, 08:38 PM   #10
skene
User
 
skene's Avatar
 
Join Date: Nov 2003
Location: Baltimore MD
Posts: 962
Send a message via AIM to skene
Default

On a somewhat relate note, if you've pulled the CV does the KLR just retard the timeing?
skene is offline   Reply With Quote
Old 12-07-2006, 09:41 PM   #11
Jfrahm
Addict
Rennlist Member

 
Jfrahm's Avatar
 
Join Date: Mar 2002
Location: Boulder, CO
Posts: 4,691
Default

I had one fail on an Audi such that it detected *lots* of knock and pulled out tons of timing. Very bad fuel economy but no error codes. The crystal must have cracked or something. It's more common that they fail open due to wiring issues.

-Joel.
__________________
Joel Frahm
1987 928S4
1987 928S4 - Murf supercharged
1992 968 Cabriolet
1994 968 Cabriolet - 928 Motorsports Supercharged
Jfrahm is offline   Reply With Quote
Old 12-07-2006, 10:21 PM   #12
kasturbo
Addict
Rennlist Member

 
kasturbo's Avatar
 
Join Date: Aug 2002
Location: Grove City, OH
Posts: 3,524
Default

I just probed pins 11 and 13 and I'm not getting any readings. The wiring is new, so it must be the sensor. Is there a way to pull the sensor and test it outside of the wiring?
kasturbo is offline   Reply With Quote
Old 12-07-2006, 10:27 PM   #13
Trucho-951
Addict
Rennlist Member
 
Trucho-951's Avatar
 
Join Date: Jun 2005
Location: Napa Valley, CA
Posts: 589
Default

On my 86, I was able to take out the old knock sensor without pulling the intake manifold. I used a "woble" extenstion and a long standard screwdriver to push the ISV bracket out of the way.
Trucho-951 is offline   Reply With Quote
Old 12-07-2006, 10:39 PM   #14
Porsche-O-Phile
Banned
 
Join Date: Feb 2004
Location: In self-imposed exile.
Posts: 14,072
Default

Blink code 2-2 on the diagnostic plug after 1.2-bar "limp home" mode.

Check the resistance across - should be 280-330 kOhm IIRC. If it's bad, a replacement is about 75 bucks but beware, I've been told they're going on backorder with Porsche N.A., which means it might take months to get a replacement.
Porsche-O-Phile is offline   Reply With Quote
Old 12-08-2006, 12:47 AM   #15
PorscheMD
User
 
Join Date: Feb 2006
Posts: 295
Default

Quote:
Originally Posted by por951turbo
Thanks MD. I'll try that. Ignition doesn't need to be on right to test?
No the ignition should not be on when you test it.
PorscheMD is offline   Reply With Quote
Old 12-08-2006, 12:47 AM
Rennlist



Paid Advertisement
Reply

Tags
1995, 66, az, bad, bmw, chevelle, dme, failure, false, faulty, knock, m3, malfunction, sensor, signs, symptoms, symtoms

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

Forum Jump


All times are GMT -3. The time now is 12:54 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
SEO by vBSEO 3.6.1
Copyright ę 1998 - 2007 Rennlist.com

Advertise on Rennlist - Privacy Statement - Terms of Service - Jobs