still having problems with knock sensor Options

[turboman23]

for quite some time i've been having trouble with my knock sensor. it keeps throwing a code even after i have replaced the sensor,rebuilt the motor, and redid my wiring( thanks tweak). we just rechecked the timing and its set at 10degreesTDC. i cant possibly think of anything else that could be causing a problem. could a bad ecu cause this to happen? if it was bad wouldn't the car not run at all? i've tried searching but all people ever say is to replace the sensor.... i'm really needing some more ideas on what else i need to check. Thank you.

[Smaay]

have you tried using the upgraded GM sensor?

[turboman23]

No. after reading over the wonderful discussion regarding Fastbird's swap (LINK) and a few others besides that one, i was wanting to stay with a sensor made for the 3s.
i was also wondering, once a KS detects knock, is it no longer capable of being used? or in other words once i get a code, do i need to buy another KS?

[Dr_Tweak]

If the wiring and the sensor is good, then I would first look at your ignition timing to be sure it's correct, and then I would try another ECU. I did one time see an ECU that kept throwing a code despite the fact that everything checked out. We tried another ECU, and the code never came back.

-Doc

[lagos]

How much boost are you running?
Why was your motor rebuilt?

This post has been edited by lagos: Feb 18, 2009 - 5:22 PM

[turboman23]

If the wiring and the sensor is good, then I would first look at your ignition timing to be sure it's correct, and then I would try another ECU. I did one time see an ECU that kept throwing a code despite the fact that everything checked out. We tried another ECU, and the code never came back.

-Doc

just checked timing a few days ago and it was correct.

How much boost are you running?
Why was your motor rebuilt?

i havent took it past 8psi since the rebuild. i rebuilt it bcz it spun a bearing and started knocking. everything was machined to spec. and/ or replaced except for now being bored .020 over.

it will throw a code even if i'm not boosting. as soon as i hit 1800rpm the cel comes on.

[lagos]

Let me rephrase that. How much boost were you running before?

Knock sensors are basically microphones. They blow out when they hear too much knock, in the same way that you can blow out a set of speakers when you play them too loud. You were probably running too much boost or have some kind of other problem (maybe afm?) that blew both your bottom end, and your knock sensor.

[turboman23]

before it was 12psi.

okay thanks for that explanation. didnt know they actually "blew". that kind of sounds like a strange way to design an overpriced sensor but whatever lol. are you talking about my air flow meter or air-fuel mixture or both? i never thought about either of those. would a cheapo gauge from autometer work fine for what i'm needing?

[Smaay]

thats why people upgrade to the GM sensor, it doesnt blow like the toyota one does

[lagos]

thats why people upgrade to the GM sensor, it doesnt blow like the toyota one does

It blows because its more sensitive.
This is exactly like having an issue with a fuse that keeps blowing out, and instead of identifying the problem, you go out and buy a bigger fuse because it wont blow as easily. Totally the wrong way to go about doing things.
Not to mention that in order to install that gm fuse, you need to cut/splice into your factory wiring and install a new plug. Many people have had the code pop up on them as a result of doing this, because its very difficult to do a wiring job while laying on your back, under the car.

turboman23, a cheap a/f gauge wont tell you anything. Take your car to a dyno and do a few low boost pulls, and slowly turn the boost back up while watching the a/f ratio and for signs of knock. A good dyno operator should be able to help you identify the problem.

[turboman23]

if a gauge wont tell me anything then how else could i watch the a/f ratio without taking it to a dyno? i understand that i need to spend big money to fix problems like these. But dynos get fairly costly (especially in Topeka, Kansas where there is virtually no real performance shops) and my car fund is running low.

[lagos]

You can buy a wideband. They cost around 250bucks, but it wont do you much good if you don't know how to interpret its readings.
You should be able to get your car dynoed for about 60 bucks. Start out with low boost, and work your way up.
This would tell you why you keep blowing knock sensors, but keep in mind that you will have to fix/replace your current sensor ( or whatever the issue is right now) before you do any of those things.

Its expensive, I know. Part of the reason why a turbo car is not the greatest thing to own when your young and broke.

[turboman23]

ok thank you very much for your help. its gonna have to wait a month or two then before i can dyno it. for now while i gather up the money, its going up for sale/ possible part out. hopefully i can get another stock GT

[lagos]

This might sound like a dumb question, but you did go under the car and check to make sure the knock sensor is plugged in, right?

[turboman23]

it doesnt sound dumb. it wouldnt surprise me if this has happened to somebody. but yes it is plugged in.