Symptoms of bad/faulty knock sensor

project_skyline · Oct 16, 2009, 08:02 PM

Alright Im just curious if there are any signs or a bad or faulty knock sensor.

The reason I ask is I was recently tuning an 8 MR that would knock like crazy no matter what timing looked like. AFR was in check and very conservative.

All tuning was done on 91.

Just to reference I've tuned an 05 MR with almost identical mods and it doesn't see any knock on a similar tune.

I'd also like to note that I looked for things that might have been causing the knock sensor to go off.

I appreciate any suggestions or advice. Im more then willing to post logs and maps.

Thanks

ChuckP · Oct 16, 2009, 08:34 PM

swap knock sensors

iturregui · Oct 16, 2009, 08:58 PM

Boost level? Downpipe/exhaust hitting engine somewhere?

project_skyline · Oct 17, 2009, 10:01 PM

Quote:

Originally Posted by iturregui

Boost level? Downpipe/exhaust hitting engine somewhere?

Max boost was 26.5 and tapers to about 19.

As far as I can see or tell the exhaust is very solid. All the mounts are connected.

ChuckP · Oct 17, 2009, 10:25 PM

26.5psi on 91oct? What kinda timing are you running?

0xDEAD · Oct 18, 2009, 05:40 AM

I've never really seen a bad one on an evo yet, but that doesn't mean that they don't go bad. On 1g's they would let the goo out, the 2g/evo I don't think have that design/problem. Was this motor recently built? Sometimes people either install the sensor too loose and it rattles causing fake knock or they install it too tight. Also check for metal to metal contact. This isn't as big of a deal on the evo's but it still alters the noise background to some degree. IE: downpipes rubbing, transmission rattle/noise (5th gear TSB), even some twin discs can cause a problem.

BarryC · Oct 18, 2009, 06:00 AM

I tuned an evo 6 a while ago same problem
it would show 36 to 40 counts of knock at different rpm's
pulled timing and changed the fuelling no different
had the det cans on it and there was nothing there
changed the sensor problem was still there
only thing that was changed before the tune up was it got a new clutch
must of been driveling noise causing the false knock
tuned the knock tables checked again with the cans
never had an issue since
its not ideal to mess with the knock tables but sometimes its the only option

0xDEAD · Oct 18, 2009, 06:12 AM

Was it a single hub clutch or a twin? If it is a single sprung then one needs to possibly pull the inspection cover and make sure none of the springs have tried to make an exit out of the hub. Most of the unsprung clutches to include twin discs are just noisey. They allow drive train parts to go harmonic while cruising or coasting down hills. I'm not sure how to properly fix it but keep in mind that some of the earlier evo 8's had a 5th gear rattle issue that would cause ecu problems when stock. I even heard of one car that was having false knock due to a rod bearing that wasn't quite audible above the exhaust yet. It finally spun of course. Also make sure if the HLA's were just out that they were bled before re installation.

So I guess the tip is, just make sure everything is tight. Unfortunatley the real problem arises down the road sometimes and it is usually a mechanical failure.

awddyno · Oct 18, 2009, 07:57 AM

This just gave me an idea. About people having false knock after the build or clutch job.
The front engine mount has a bigger hole than the bolt itself. By the time you put some power down, the engine will twist a bit and possibly start rattling on the bolt. Just an idea for now. I have a car to test on tuesday that has a false knock problem. I will report back then.

I've also seen another that had a really bad false knock that ended up to have spun main bearings.

0xDEAD · Oct 18, 2009, 08:43 AM

I know that some aftermarket front engine mounts cause false knock problems. I told one person to switch to the style that I run since I don't have the problem and this cured his problem. From what I recall he was having problems when cruising on the highway. I run a purple one, forget what brand but I think it was from the UK.

LeXcite · Oct 18, 2009, 11:02 AM

Same Problem Here ... My front Engine Mount is PowerFlex (Purple one from UK), and Carbonetic Twin ...

project_skyline · Oct 18, 2009, 12:50 PM

Quote:

Originally Posted by ChuckP

26.5psi on 91oct? What kinda timing are you running?

I've tried everything from 1-7 degrees at peak tq and going to 14-18 peak timing. AFR is was low 11's tapering to 10.8-10.9.

Quote:

Originally Posted by 0xDEAD

I've never really seen a bad one on an evo yet, but that doesn't mean that they don't go bad. On 1g's they would let the goo out, the 2g/evo I don't think have that design/problem. Was this motor recently built? Sometimes people either install the sensor too loose and it rattles causing fake knock or they install it too tight. Also check for metal to metal contact. This isn't as big of a deal on the evo's but it still alters the noise background to some degree. IE: downpipes rubbing, transmission rattle/noise (5th gear TSB), even some twin discs can cause a problem.

Motor is completely stock although he is the second owner so not sure of the car's history.

Quote:

Originally Posted by 0xDEAD

Was it a single hub clutch or a twin? If it is a single sprung then one needs to possibly pull the inspection cover and make sure none of the springs have tried to make an exit out of the hub. Most of the unsprung clutches to include twin discs are just noisey. They allow drive train parts to go harmonic while cruising or coasting down hills. I'm not sure how to properly fix it but keep in mind that some of the earlier evo 8's had a 5th gear rattle issue that would cause ecu problems when stock. I even heard of one car that was having false knock due to a rod bearing that wasn't quite audible above the exhaust yet. It finally spun of course. Also make sure if the HLA's were just out that they were bled before re installation.

So I guess the tip is, just make sure everything is tight. Unfortunatley the real problem arises down the road sometimes and it is usually a mechanical failure.

He is running an ACT HDSS, which seems to maybe going out. It shudders really bad in reverse and in first.

I have not gotten a chance to put DET cans on the motor.

I do however want to mention that it happens every time between 4800-4900 and knock just ramps up from there. And I've spend 4-5 hours trying to get rid of it but nothing has changed it.

iturregui · Oct 18, 2009, 01:01 PM

Quote:

Originally Posted by project_skyline

I do however want to mention that it happens every time between 4800-4900 and knock just ramps up from there. And I've spend 4-5 hours trying to get rid of it but nothing has changed it.

Do a pull from low RPM's up to 5K and try to keep it off boost or with very little boost. If it's related to something rattling/moving it'll show up as well

rolly1818 · Oct 18, 2009, 03:43 PM

Quote:

I've tried everything from 1-7 degrees at peak tq and going to 14-18 peak timing. AFR is was low 11's tapering to 10.8-10.9.

for 91 octane the timing is a bit high IMO. try -2 and peak TQ and 11/12 up top. what kinda knock number are u seeing.

OR

i said this is another post - throw in some Q16 and see if knock reduces.

if the problem persists i have another solution, but try the above first.

JohnBradley · Oct 18, 2009, 03:47 PM

When my stock clutch went south (springs were rattling against the hub) it was right at 4900-5100 and nowhere else.