per this thread for reference
http://web.camaross.com/forums/showthread.php?t=331191

Basically, I have a the car stumbling and pulling alot of timing. First I sent the PCM to madwolf he desensitized it and I have a lt4 KM. Went from 15 degrees pulling to about 8 max.

However, it still pulls timing, and when the car stumbles, it's always pulling loads of timing. I've replaced so much things I just want to work one thing at a time, I want to have it so the computer pulls 0 degrees no matter what so I can trouble shoot this and eliminate timing being pulled as the cause, I have another thread for the stumbling issue as a whole.

http://web.camaross.com/forums/showthread.php?t=329594

replaced:
-opti
-plugs
-wires
-ICM
-Coil
-PCV valve
-vacuum check fine
-Fuel pressure OK
-no OBDII codes

car pulls timing like a **** still.


ANyway, here's is what i tried to disable the knock retard issue.

-disconnected knock sensor sensor alltogether, still pulls timing when at part throttle to WOT.
-replaced knock sensor with a 100k resistor, same as above.
-ordered a new knock sensor and hooked it up except left it dangling out of the block, same as above.

It seems like the PCM doesn't care whats hooked up to it, it acts the same way ALL THE TIME.

And yes i disconnected the battery for like an hour to reset the computer each time.

What am I missing, how do i disable this thing?! Is my PCM hosed up, is this maybe the cause of my car running like crap?? Any help, thanks. has anyone succesful disabled an OBDII knock sensor without programming??

 

I don't think the right resistance is 100K for the OBD2 knock sensor. I may be wrong though. Either way, I'd recommend disabling it through programming. You won't need to replace the computer or anything. Just make sure you run premium all the time.

There are a few of these cars in a bunch that will do something like that no matter what you try. My old '95 used to be like that and I ended up disabling the knock sensor through programming. Worked fine.

 

I've read through your posts & threads with interest, as I have a similar problem. I have an OBDI 383 w/ LTCC igniton & am getting code 43 (knock circuit) along with a stumble around 2K RPM. This has taken place since day 1.

Engine mods:
Eagle 4340 crank & h-beam rods
HOT cam
1.6 Roller rockers
52mm TB
Granatelli MAF
LTCC ignition
Mac mid length headers
New 3" high flow cat
Hooker 3" catback w/ Aerochamber muffler
LT4 knock module
Siemens 55# injectors
LT4 heads & intake

I have a PCM4Less tune and Bryan has tried to help but I don't think that is the issue since I replaced the PCM with another 1995 six speed PCM from a wrecked car, same result, same code, same stumble. I reset the code and it comes back almost immediately at idle. The knock count at idle on PCMCOMM is really high- can't hear anything out of the ordinary under the hood at idle.

As far as the knock system goes, I found I had a bad meter when I first checked the sensor. I bought a new meter & replaced the sensor. Same problem. I then checked the wire and found it had been burned by touching a header tube. I cut out the bad section & soldered in a new one. Checked voltage at wire (unplugged from sensor w/ key on) and got 4.87 volts. The weird thing now is I'm getting no resistance on the installed knock sensor or the old one I took off a while ago (it takes a while to throw things away ), testing w/ ohm meter center tip to bare end of threaded part. Can these things burn out if the sensor wire goes to ground? Both were connected to the bad wire at one time. From what I've read, this thing is in effect a microphone.

I'm also curious about the engine timing. While looking at the timing via PCMCOMM, it fluctuates greatly at lower RPM. At higher RPMs, it is showing like 41 degrees. The LTCC LEDs light up like they should, and I have dialed in retard across the range (0 to 3 degrees per 1K RPM) with no effect. It seems like there is some type of timing conflict here, as the PCM wants to pull timing due to the Code 43, but the LTCC which is supposed to be able to control timing is not pulling any timing.

I'm going to try the desensitizing mod for the KS and see if that helps and welcome any other help or advice.

 

An OBDI knock sensor should read around 3.9 kOhms. Their working principle is by varying this resistance with specific sounds and the knock module reads this variance, filters it and then send it to the PCM.

The knock sensor circuit consists of the knock sensor, the wire, the knock module and the PCM itself. If you replaced the knock sensor, the knock module and the PCM, it means you still have a problem with the wire.
Since it's just one wire, you can run a new jumper wire from the KS directly to the PCM connector if you want. Or you can take off the connector from the PCM and measure continuity (use your multimeter) between the pin on the PCM connector and the knock sensor connector. (it should not be connected to the KS) If you get good continuity, measure continuity between the wire and the engine ground to see if it is grounded somewhere. You should not get continuity in this case.

I'm sorry if you already know this, but to read the resistance of the knock sensor, you need to use the next-up setting on your multimeter. I set mine at 20K for readings 3.9K because the next lower setting is 2K which is too small.

Also make sure the test wires are in the right spots on the multimeter.

While in the car, you can connect one of the multimeter wires to the needle tip inside the plastic connector (on the KS) and the other, you can connect to the engine ground bolt neat the motor mount arm.

If it doesn't read anything, either you are not using the right settings on the multimeter or your ground isn't good enough.

Your timing problem may be related to the KS code. Every time there's a problem with the KS circuit, the PCM will try to retard timing, but then again, it is also normal for timing to fluctuate in the logs. It shouldn't fluctuate a wide range though. +/- 4 degrees or so is ok on a cammed car for idle.

If you can download the free version of datamaster from www.ttspowersystems.com and do a log, I'll be happy to take a look at it for you.

Let me know if you have any questions.

 

Thanks! I downloaded the file, need to burn it to CD & put it on my laptop. I'll get back to you ASAP.

 

Emailed the .csv file to you. Also rechecked the old sensor & it reads 3.8K resistance . I guess I was really tired last night when I was doing this. Still no reading on installed sensor, and I noted the knock count stayed the same on the Datamaster log, which indicates a bad sensor.

I also checked the KS wire, voltage is the same at the PCM (key on) as at the sensor, so I think the wire is OK now.

Thanks for the help.

EDIT
Got a webpage setup, and the .csv file is also available here.

 

Don't qoute me on this but I heard if the knock sensor wire is routed near your spark plug wires it can cause a false knock to be dected because the spark plug wires can cause RFI or EMI. Good luck.

 

well, update on my situation I've given up trying to mess with the knock sensor and tricking the PCM, NO luck with it.

http://web.camaross.com/forums/showthread.php?t=343271

I'm trying to get it programmed out but I'm even having problems with that, very very strange.

I am 90% sure that the stumble is DIRECTLY related to the timing retard, whatever is causing that is causing the car to stumble when the timing is suddenly yanked.

Brian

 

I pulled the existing (NAPA replacement) KS & put the old one back in since it was registering the correct resistance. Fired 'er up & no trouble code . Then I realized I still had the LT1 KM (I had left the LT4 KM in the other PCM I tried). While it was sitting this way, I ran another Datamaster scan.

I then replaced it with the LT4 KM & ran a third Datamaster. I'll link the results as soon as I can.

Still no code! The stumbling is still there right at 2K RPM, but I have not road tested under load.

LT1 KM

LT4 KM