Bypassing the Knock Sensors on a J30

[heybilly]

Ok brought the '95 J30 to infiniti and was told id need to replace the 2 knock sensors... also found out this will take about 10 hours and a few infiniti dollars to get done... now my question is what resistance does the normal knock sensor put out so i can just place a resistor in the path to the ecu so the comp thinks its working fine? and anyone know how to find the sensors and trace the wires back to the ecu?

[VimyJ]

Ok brought the '95 J30 to infiniti and was told id need to replace the 2 knock sensors... also found out this will take about 10 hours and a few infiniti dollars to get done... now my question is what resistance does the normal knock sensor put out so i can just place a resistor in the path to the ecu so the comp thinks its working fine? and anyone know how to find the sensors and trace the wires back to the ecu?

What was your J doing that makes the service department feel you need these knock sensors replacement? Was your engine knocking badly?

[AZhitman]

heybilly - We need more info on your car, and where are you?

What about replacing the sensors yourself? Definitely NOT something you want to bypass if they are indeed bad. One bad tank of gas could be the deciding factor, it's not worth taking a chance.

[Q45tech]

The knock sensors when not operating throw a code which can be read on Consult [but don't light the check engine light].The general symptom is sluggish acceleration [and some bucking in 3rd and 4th gears] especially at mild throtle openings around 50-70 mph.

[heybilly]

I get sluggish acceleration till about 3500rpm so i brought the car to infiniti and the car returned the knock sensor code when the engine was up to temp.... what would happen if i used an lower then 93 octane on a disabled knock sensor system?

----------------------------------------------------------------------'95 J30 in Jersey w/ 95500

[AZhitman]

Again, bad idea. The knock sensors are there to protect your engine.

Just replace 'em if the Consult says they're bad. There's several J owners here on the board who can walk you through it.

[heybilly]

On that note i think ill um try the DIY... can anyone explain to me what is involved to remove and replace both knock sensors?

[Mayhem_J30]

On that note i think ill um try the DIY... can anyone explain to me what is involved to remove and replace both knock sensors?

does your J have the service manual in the trunk? might want to check it out or get a hold of one. the job doesn't look easy. unless i'm looking at it wrong you have to remove fuel lines from around the plenum, remove plenum/upper intake. from what i can tell it looks like two sensors site right in between the cylinders(in the V)

[Mayhem_J30]

ok. looks like you have to remove the upper and lower intake plenum to reach it. while that is all apart i'm sure there's many things that should be replaced...hopefully Q45tech could fill you in on that one. Maybe some coolant piping and stuff.

Check your connector harness first. I would think that these are more likely to be faulty then the sensor itself. it's gray and right in the middle of your engine. unhook it and clean the connections with some alcohol, inspect all the wiring around it to.

[Q45tech]

Yes, grasshopper the J30 only has one KS.

Substituting something for the single KS is dangerous since the ecu will go to full ultra octane advance if you guess right---- pistons are pretty expensive to replace.Remember the look on the guys face as it melted in the search for the Holy Grail/or raiders of the Ark......thats what can happen but they usually just shatter and crack.

[heybilly]

well thanx guyz for all your help... im probably just going to fork ova all my cash to infiniti just to get it done da right way... the thing is they told me there r 2 sensors in that engine but im still not sure.. anywayz ill post the outcome

[VimyJ]

"The two knock sensors are attached to the cylinder block and sense engine knocking conditions." - From the service manual

However, only one knock sensor is shown in an illustration and only one is indicated on the circuit diagram. The ECM flashes "code 23" but the check engine light will not come on when there is a problem.

[Mayhem_J30]

"The two knock sensors are attached to the cylinder block and sense engine knocking conditions." - From the service manual

However, only one knock sensor is shown in an illustration and only one is indicated on the circuit diagram. The ECM flashes "code 23" but the check engine light will not come on when there is a problem.

i read the same thing vimy. and just like you the illustration just showed one??

[Professor_Mike]

Unless your skills are fairly high, replacing the knock sensor on a J is very involved due to the pulley for the timing belt bolts to the lower plenum.

[VimyJ]

Unless your skills are fairly high, replacing the knock sensors on a J is very involved due to the pulley for the timing belt bolts to the lower plenum.

I take it from your use of the plural that there are in fact 2 knock sensors as opposed to the single KS shown in the service manual. Could the "single" unit shown in the illustration be a "double" unit?

[Professor_Mike]

It has been a long time since I have replaced a knock sensor on a J. Usually the client lives with the problem. The manual and parts info state there is 1 knock sensor.I'll correct my post.

[Q45tech]

The American Car Council states that 9 out of 10 cars on the road need some type of serious repair! Thats scarey with 12.5% of the cars new at any moment. But then again 100-125 minor defects on new cars is common.

"Usually the client lives with the problem. "

The OBD2 models will fail the MIL emission inspection and in Georgia you must spend over $688 [each year] before a waiver is granted ---- should be based on the value of the car but they give you a free ride for the first 2 years.