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EggYolkedZX3 04-22-2011 01:08 AM

knock sensor issues
First off, I have an '01 ZX3 with the Zetec/ATX and have an XCAL 3 w/ Tom's tune.

I'm wondering what others who datalog with the first "KNOCK SENSOR RETARD LIMIT" DMR in the SBAF6 processor code list see as far as values or on the graph while doing a normal cruise datalog. My issue currently is when I log the KS (on either the stock tune or on Tom's tune, doesn't matter), it shows that I'm always knocking and pulling -5 degrees of timing usually right around 2000 rpm or above. The problem is though, I'm not hearing or feeling any detonation at all. I believe my KS is bad or something else making noise is setting it off but not positive. My graph would show a straight line at 0 when idling and almost always goes straight down to -5 when it hits the 2000 rpm mark and eventual goes back to 0. But there is never an in between, always at 0 or a straight vertical to -5 with the occasional advancement.

So I was wondering what should I be seeing on the graph or in values as far as the KS? Should it mostly read at 0 with very little timing being pulled at any rpm range with advancement here and there or what? I'd appreciate any advice or suggestions on this issue from others who know what I'm talking about. Its causing me to not be able to get tuned and I'd like to change that asap. Its impossible to get a proper tune when the KS decides to max out pulling timing.

Thanks in advance,

EggYolkedZX3 04-23-2011 01:50 PM

Bump for some help!

I'd really like to know what I should be seeing on the graph when I log the knock sensor.

1turbofocus 04-23-2011 02:45 PM

You shouldnt see anything 0


JCH841 04-23-2011 06:04 PM

We used to see false knock in boat engine EFI from loose motor mounts, etc. I think even a couple of loose knock sensors. Make sure you don't have anything like that.

EggYolkedZX3 04-24-2011 12:33 AM

Well today I found a few new things but the problem is still there.

First thing I found was the wire that goes from the battery to the alternator was rubbing on the stud where the knock sensor mounts. I moved it but the car still shows knock during a datalog.

I decided to log the car while free reving not in gear and in drive while on the jack stands still and the KS read 0 all through out the rpm's, couldnt get it to show knock. Then I go to put the car on the ground and go for a cruise. Well the same thing as before happens anywhere above about 2000rpm while accelerating in a gear, the KS goes off.

I guess I'll play with it more tomorrow and see if I get anything to work correctly. Is it unheard of to have a KS go bad? Starting to think its the problem.

EDIT: I tried transbraking while on jackstands to create load and the KS shows knock. Graph looks the same as if driving it on the street. So now, I think I've got this narrowed to a load issue. Gonna try a new set of Motorcraft spark plugs tomorrow and see what happens, cant hurt anything. I believe now its either ignition related or the KS itself is way too sensitive. I'll update tomorrow. Oh and I've run 87oct, 91oct, and 96oct all with the same knock results on the stock tune.

BowerR64 04-24-2011 02:32 AM

If the knock sensor was bad or going bad wouldnt you feel a major power loss?

I read the life of the knock sensors are like 10 years. I read you can trick the sensor temporarily to trouble shoot problems. emergency solution not a long term solution.

1turbofocus 04-24-2011 09:10 AM

We talked about all the things that need to be checked and I dont see where you have tested any of them


EggYolkedZX3 04-24-2011 12:35 PM


Originally Posted by 1turbofocus (Post 3646420)
We talked about all the things that need to be checked and I dont see where you have tested any of them



The first thing you said was run 5 gallons of 91oct and 5 gallons of 100oct which averages out to 95.5 but since I had a little less 91oct in the tank already it came out to be about 96oct. Knock still showed in the datalog, just like the 87oct log, after wasting over $50 for a 3/4 tank of gas (remember jobless high school kid here)... That rules out bad gas though, right?

Next you said to get a piece of garden hose and listen around for metal noise while someone holds the rpms around 2000rpm. Well since I can only do that in place and already stated the KS doesnt pick up anything while revving in place, then what am I supposed to hear? I already said there's nothing out of the ordinary. Acording to datalogging, this only happens when driving around or transbraking on jackstands. Must be a load issue now, right?

And that's all you've said.

1turbofocus 04-24-2011 02:46 PM

You will only see knock after a set load and RPM , you have to have load to have/see knock

I was asking you to check thing to see if you had something loose and vibrating and that would cause the knock sensor to go off

I can adjust the sensitivity of the knock sensor but I would like to know for sure it isnt something else


redZX300 04-24-2011 05:37 PM

is this an NA focus?

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