I've seen my car pulling 7 degrees of timing due to knock retard.
I've been trying to figure out why.
The car pulls no timing at idle or normal driving conditions, but @ WOT it'll pull timing whether it's in gear (load) or neutral (no load).

Is this normal for the car to pull timing in neutral with no load? Could it be a bad knock sensor? I've had it replaced last year and I'll try tapping the block tomorrow with a wrench to see if it still works that way.

 

Good question. Mine only knocks when not under load. In nuetral or tires spinning. Got rid of most of it, but not all by installing a colder spark plug. You may want to give it a try.

 

I run NGK TR6 (1 heat range colder) due to nitrous use.

 

Also, the knock sensors are very sensitive to their torque tolerances. I think the manual says tighten to 15 lbs. If you OVER or UNDER-tighten, this can cause the sensor to behave in the mannner you're describing. Check the connection for dirt, oil, grime, etc...

If you remove the sensor, the orange coating that comes on there is ALL you need. Do not add threading tape or compound because that can ALSO affect the sensor's operation.

 

But also the Electronic Spark Control modules in these cars were overly sensitive and will send false knock signals to the ECM resulting in timing retard.

Headers, for example can create noise the ECM will receive and interpret as knock

Gorden Killebrew has long recomended changing the ESC module to another GM module, I think it is a mid 80's Malibu

I believe the NAPA part # is ESC 313 or 33

Tha solved my problems

seeya

 

Don't waste your time tapping on the block. The knock sensor is working. It is sending signals to the ESC. If it sends signals in neutral, it is hearing noises other than "knock". The source of the noise(s) could be internal or external to the engine. I don't know if you can "get away" with this on an '89, but I simply disconnected the sensor wire from the ESC module. I use my EARS to detect knock, the old fashioned way.

RACE ON!!!

 

Your ears can hear any knock that occures? I doubt it. I know someone who swore he could hear it too. Looking at the plugs, I could see that detonation has occured. However, running the car with me inside and a stethoscope, I couldn't hear it all.

 

I guess it's truly amazing that cars lasted more than 6 months, before knock sensors became available.

RACE ON!!!

 

This might sound like a stupid question, but what kind of gas are you running?

I would burn off the rest of the tank and then fill it up with some good 91, 92 or even 94 octane (they sell the 94 at Sunoco) and then give the car a good drive, WOT ofcourse and see if the knock is still present. Sound like the car only has knock when the engine is reving under load.

By the way, I have no diagnostic tool ... what are you using to count the knocks? I should seriously buy one

 

Cars did last for more than 6 months as long as there was lead in the fuel and a much richer mixture than what we're sniffing today, but they had a myriad of other probems too, so why even go there? As a test, the '89 advances timing until it pings, once in closed loop, the first time it approaches WOT, so make sure you're not seeing the "test" on your scanner. Then, look at total timing and post that number.

 

??????????

 

As far as I know, the ESC/ECM circuit relies on the TPS (over 4 volts) & CTS signals (194 degrees) for the initial test, retarding timing 4 degrees or so once it pings. In fact, the detonation test calls out 1500 rpms, in neutral, well below that threshold. At that speed, if it pings, you need to investigate for some other source of the noise. The key is total timing. If it's below say, 28 degrees, then there might be some other problem, but there's going to be some guesswork to determine just how much timing it can handle without the ESC circuit.

 

I only run 91 octane gas, which is the highest available to me here.
No, it pulls timing on different occassions on the same run, not just the first WOT run. I didn't redline it too bad, but the R's were high enough. I usually shift it at 5500-5800 RPM.

The first quick WOT punch revealed

The timing jumped from
24.3 @ 1125 RPM - 3.5 * retard - O2 @ 901 (TPS 2.35)
26.7 @ 1650 RPM - 3.2 * retard - O2 @ 852 (TPS 3.49)
29.2 @ 2125 RPM - 2.5 * retard - O2 @ 888 (TPS 4.22)
32.3 @ 2550 RPM - 5.6 * retard - O2 @ 901 (TPS 4.45)
33.0 @ 3025 RPM - 4.9 * retard - O2 @ 884 (TPS 4.51)
33.0 @ 3575 RPM - 3.7 * retard - O2 @ 866 (TPS 4.53)
33.0 @ 4100 RPM - 7.0 * retard - O2 @ 848 (TPS 4.53)
33.0 @ 4575 RPM - 6.0 * retard - O2 @ 728 (TPS 4.53)
33.0 @ 5000 RPM - 7.0 * retard - O2 @ 821 (TPS 4.53)
33.0 @ 5225 RPM - 7.0 * retard - O2 @ 244 (TPS 4.45)
38.3 @ 5050 RPM - 5.1 * retard - O2 @ 604 (TPS 0.61)

A second quick punch revealed

Timing jumped from
36.9 @ 2575 RPM - 0.0 * retard - O2 @ 826 (TPS 1.02)
36.9 @ 2625 RPM - 0.0 * retard - O2 @ 924 (TPS 0.61)
32.7 @ 2625 RPM - 2.1 * retard - O2 @ 18 (TPS 4.53)
33.0 @ 3500 RPM - 7.0 * retard - O2 @ 852 (TPS 4.53)
33.0 @ 3800 RPM - 6.0 * retard - O2 @ 852 (TPS 4.53)
33.0 @ 4175 RPM - 5.1 * retard - O2 @ 848 (TPS 4.53)
33.0 @ 4500 RPM - 4.4 * retard - O2 @ 706 (TPS 4.53)
33.0 @ 4900 RPM - 4.7 * retard - O2 @ 790 (TPS 4.53)
33.0 @ 5275 RPM - 4.0 * retard - O2 @ 719 (TPS 4.53)
33.8 @ 5450 RPM - 6.9 * retard - O2 @ 337 (TPS 4.35)
38.3 @ 5050 RPM - 4.9 * retard - O2 @ 582 (TPS 0.61)

I probably put in too much info , but do you also need the Inj BPW and/or Inj DC?

Inj DC highest was 54 on first and 55 on second WOT runs.
Inj BPW readings ranged from 8.1 to 6.2 on first and 7.81 to 6.03 on second run.

 

Although I know it is too rich @ WOT, I have been adding fuel to it (AFPR) in order to try to level out the L Term-C Counts to around 128 at normal driving operation since that's where I have the car the most.

Presently I hover around 128 - 130 or so with 44 psi, but won't this also cause the car to go richer @ WOT?

Maybe I should find the correct psi to get O2 counts of 920 @ WOT for racing, that way I can just drop fuel pressure for racing. Make sense?

 

First 920 MV at WOT is PIG rich. You want it to be around 820mv.

My guess is that you have a rattle, header hitting the frame or something else that is tripping off the knock sensor.

IMHO if your racing your car and have serious mods, the knock sensor is the first thing that you should disable. Its can be worked around, but it causes more problems in my opinion than its worth. Again this is not for everyone, but if you have a clue about motors - its really not necessary.

 

Also check to see if any other wires are touching the knock sensor wire, it can actually pick up on them and create a false knock. If so, reroute the wire.

 

Ski, how would I disable the knock sensor?

I'm going in on Friday for some minor work (oil change, plugs, fix my shifter handle, etc.) and the knock sensor is one of the things I'm gonna have him look at as well as the connector to the coolant temp sensor in the driver's side head.

 

How can I say this. Its your call to disconnect the sensor. IMHO its one of those things that GM put on there to keep emissions people happy and since everything is computer controlled, ensure that if something did go haywire, it would be covered.

To remove it, the easiest way is to put a resistor at the end of the line, so the ECM can see the resistor. Not sure what the resistor value needs to be.

Or you can just zero out the values in the table via the chip is what I do. That way when tuning you can see if there are counts, but it doesn't effect the timing.

I am YET to see a motor failure from lack of a knock sensor. Not to say that is someone put their car to 45* advance on 86 octane fuel and ran it WOT for 2 hours it wouldn't fail. But with some common sense and knowledge, I really think its a worthless sensor.

 

Bypass,..... Disconnect and place a 4.3KOhm to Gnd. I'm sure 1/8watt will be fine.

The less sensitive 87->89 ESC module is GM P# 16038331 (As I recall, later years have the ESC in w/ the PCM.)