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Mysterious Problems - Knock Sensor

SuAvE-1

By SuAvE-1,
in Engines & Forced Induction

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SuAvE-1 Collaborator

SuAvE-1

Posted
Posted

hey ppl,

I need a BIG hand with something

My check engine light comes on here and there - at IDLE and WOT and all inbetween randomly and sometimes flashes very quickly under hard acceleration. I hooked up NewKleer's Consult port reader to the car and the knock sensor is going off. Does anyone know what is going on? the system acts randomly only operating sometimes, but more and more recently its becoming more frequent. The car itself (r32t) runs perfectly fine, but it did hesitate today.

When looking at the readout from nissan data scan, nothing appears to be any different. Timing still looks normal 15deg at idle (not that I completely know what normal is). The error seems to have popped up after I recently took a look at the cold-start valve, although i'm not sure if its got anything to do with it. I do know that at full peak acceleration the duty cycle is at 96-97 and the AFM is at 4.7v or something. I had an aftermarket adjustable fuel pressure regulator but i took it off when trying to eliminate this problem.

Car is stock apart from a turbo-back exhaust, 14psi, walbro fuel pump and pod.

Is my engine really detonating or are the sensors picking up something they shouldn't be?

sorry for the slab of story. anyone got any comments or ideas??? any help greatly appreciated!

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SuAvE-1 Collaborator

SuAvE-1

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i've been thinking about trying to cancel out the signal from the det sensors, something which could immitate the sensors without making them 'go off'. Doesn't anyone know anything??

If not... where can i get new det sensors from?

TurboX Mentor

TurboX

Posted
Posted

Damn, similar to mine!

DONT change those sensors yet as I changed mine and still have a problem.

Mine just started after engine out and back in.

rob82 Mentor

rob82

Posted
Posted

There is a plug right next to the cold idle up valve that goes to the knock sensorsand picks up detonation. If this is going open circuit then thats your problem. Make sure its connected and also check continuity from the plug to the sensor itself.

SuAvE-1 Collaborator

SuAvE-1

Posted
  • Author
Posted (edited)

i've looked at the r32 engine manual, rob82, are you talking about 4 pin connector? Ive run a multimeter on this and get the voltage as specified in the manual.

Funny thing was though, when I had that connector completely disconnected (ie no det sensor hooked up) the car ran so very poorly however, the check engine light still flashed in the same random manner as when it did when it was connected...

EDIT: Note taken turbo X, when i was searching through the forums there were a few posts of people changing their sensors to no avail either!

Edited by SuAvE-1
rob82 Mentor

rob82

Posted
Posted

If it drops that wire it goes into diagnostic mode where it will only run 15degrees advance all the time thats why it will be a slug to drive as the timing will be lots retarded. Chances are if it keeps pulling that code then you have a wiring issue or the knock sensor is faulty, both are possible. You could always just measure the impedance across the knock sensor and put a resistor across it as the knock sensor doesn't do a whole lot any way.

predator Grand Master

predator

Posted
Posted

14psi is not recommended for a stock ecu'ed rb20 unless you really don't give a shit about the engine lasting.. get it on a dyno to be sure what it is really doing..

some can get away with it for a while, but it is often borderline.

SuAvE-1 Collaborator

SuAvE-1

Posted
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That might be the direction I'm looking for Rob82. Thanks for the consideration. I'm not exactlty sure on how I would go about choosing such a resistor or where to wire it in, but I'd happily be a guinea pig if there are no other solutions.

Predator, my check engine light comes up at idle, at cruising speed, deceleration, whatever. On hard acceleration the check engine light comes up very rapidly (this is the only time where the error does not seem to be random). What do you mean that the engine won't last - the engine operates almost perfectly (aside from this minor issue)? PM me.

slip Mentor

slip

Posted
Posted

i just had a misfire in the maxima (coil on plug) and took it to nissan for ecu diagnostic. knock sensor came up as only error - but i was 99% sure this was not the error. misfire was occuring low revs, load, and mainly when engine at full operating temp. was a dead/dying coil.

could be an avenue to look down.

Cubes Grand Master

Cubes

Posted
Posted
i just had a misfire in the maxima (coil on plug) and took it to nissan for ecu diagnostic. knock sensor came up as only error - but i was 99% sure this was not the error. misfire was occuring low revs, load, and mainly when engine at full operating temp. was a dead/dying coil.

could be an avenue to look down.

slip... I've often had the knock sensor read high from a missfire/stuffed coils. Its quite possible when it missfires it does indeed knock.

As for SuAvE-1,

Throw it on the dyno for a power run. Be sure its not the cats temp sensor going off. The ecu pinout also doesn't have provision for the cat temp sensor so chances are it won't show in diag mode, maybe there is a code for the cat temp sensor, I haven't looked at the stock ecu for some time and can't remember.

:)

SuAvE-1 Collaborator

SuAvE-1

Posted
  • Author
Posted

MAJOR RESPECT TO CUBES!!!

I was just about to update you all on my discovery, and he has said it! Something is up with my temp sensor in the cat - i had these problems come up when i put my exhaust on (and a bunch of other stuff, so i didn't know where to look straight away) and while i played with the temp sensor a while back, it didn't seem to make any difference. As a last resort, i completely unbolted it and tucked it up.

NO ERRORS HAVE COME UP IN THE SHORT TIME I HAVE BEEN DRIVING THE CAR! I still have to check error codes after a longer drive, but i know that the check engine light hasn't even blinked. Good call cubes.

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