jwmaxse

iTrader: (1)

Okay, first a few questions about the infamous knock sensor. I replaced mine but it is still giving me problems with hesitating and throwing a code. The car runs PERFECT with the 470k ohm resistor in there. I tested the sensor for continuity and there WAS continuity. Then I tested the OHM's at a fellow org member's place and the resistance of the KS and at the harness was like three times that of the resistor. I will double check that tonight but it was the same two times in a row when checked earlier today. What would cause this and how would this affect my motor? When I replaced the sensor and harness they gave me the wrong harness and the plug didn't line up with the notch on the sensor and the harness was a little shorter than the original. A supposed technician from a nissan dealership told me to shave off the notch and put it on anyway and it should be fine. Could this be why the resistance was so whacked out? I just need to know if this is my problem before I go and tear the motor apart again. If anyone knows anything about this please reply.
Second, I put some seafoam through my car by sucking it through the brake booster vacuum hose. Is this the best way to do it, and will this get to all the cylinders evenly, the front and rear?

eric93SE

iTrader: (1)

We'll if your reading 1.5 Meg Ohms, then thats pretty high. You should have insisted on the correct harness, that tech at nissan is a F-ing idiot. Are you sure after removing the plastic tab that the connector is on with the correct polarity?

I didnt replace my KS, but I tested it and saw that it was just the harness terminal badly corroding ( KS plus harness read 5 Meg Ohms), So I thoroughly cleaned it and applied a little dielectric grease to prevent future corosion. Anyway, I saw that the sensor plug and the harness read 0.6 Meg ohm (or around there), so it was still higher what the KS is by itself ( ~0.5 Meg Ohm). I saw another org member had these exact same values after installing a new KS and the new subharness, so I'm not worried about mine. So it looks like the harness is adding a good amount of resistance, I don't know why though.

With the Seafoam, just make sure the engine sucks it in SLOWLY.

eric93SE

iTrader: (1)

Well just to point out, the connector has two wires, but only one wire is used, the other ONLY serves as sheilding. The connection is made through the surface at which the KS is mounted. When I re-mounted my KS I used a wire brush to remove any rust/oxidation on the mounting surface (but I doubt thats what your problem is).

«§»Craig B«§»

iTrader: (5)

there is a vacuum hose on the upper part of the throttle body that I used and will ensure that all cylinders will get the Seafoam

jwmaxse

iTrader: (1)

So how do I check the knock sensor? The chilton's manual says that I should just check for continuity or to see if it was a closed circuit, and it was. Do I just use the two prongs on the harness to test for OHM's or should I ground the black wire and put the other one on the live prong? I just want to make sure that I don't tear apart my motor again for no reason. Yes, I think that the guy who told me it would be fine was an idiot, but I too was kind of new to this stuff a few months back and I should have had a multimeter to test it while the motor was apart. BTW, the resistance should be about 500k ohms right? I get a little confused with the electrical talk and conversions and stuff. I just bought the multimeter a few days ago and I want to make sure I'm using it correctly.

jwmaxse

iTrader: (1)

Okay, I just went out and tested my knock sensor throught the harness again and it came out to be .538 megaohms when tested either with the ground lead on the battery or on the other prong on the harness. I know my resistor tested to be like .463 megaohms and it works really well. The only thing that I can think is that it maybe is way off with the motor running or something when more current is put through it. Maybe the sensor is actually working, I don't know, but any help is appreciated. I am considering tearing apart the motor and changing that harness to the right one but I don't know if that is the problem yet. HELP!

eric93SE

iTrader: (1)

Dude, it seems that you've tested it properly, and that reading is fine. You should use the black to the cars ground, and the red to one of the connectors running to the KS (you have to try both because the other is just used for sheilding and should not give a reading).

Something to try is to reset the ECU, just unplug the negative cable on the batt. and let it sit over night.

But, since your car runs fine (or at least doesnt throw a code) while using the resistor, it would lead me to believe that either the KS or the cable is bad. Are you sure that the cable is connected with the proper polarity, I'm asking since you had to modify the cable to make it work if it was possible that the connector be installed with incorrect polarity.

jwmaxse

iTrader: (1)

Polarity, you mean did I put it on upside down? I hope I wasn't that stupid, but you never know, that job took a really long time and I was up for a long time and may have been a little high on gas fumes That may very well be. Would it matter if I plugged it in upside-down on the knock sensor? Also, do you think there could be much of a difference between the harnesses? Lastly, if the computer throws a KS code, is it just telling me that the motor is actually knocking, or is it telling me that the knock sensor is malfunctioning? If it is telling me that it is malfunctioning for sure, I will tear into this next week and be done with it. But how do I know for sure if it is the harness, or a bad knock sensor? Lots of questions, I appreciate the help.

eric93SE

iTrader: (1)

Your probably right, the connector would not have been easily put on up side down. With the ecu giving you a code, it's because the sensor is not working, not because the engine is knocking. Its possible that the wrong cable, has the wires backwards internally, so, even though you put the connector on properly the wires are still backwards.

I've done this job as well, and I agree its not fun, But it looks like your in for round two I would replace the sensor and get the proper sub-harness.

jwmaxse

iTrader: (1)

Thanks, I'll take your word for it and tear it apart next week. I can check the KS itself to make sure it works though right? Just ohm it out and make sure it is around .550 M?

swowlinc

iTrader: (10)

Which vacuum hose? I want to try this also.

jwmaxse

iTrader: (1)

Which hose for the seafoam? I used the brake booster hose and it worked fine. It goes straight into the manifold in about the middle. To use a hose in the thottle body, just pull one off and feel to see if it is sucking. I think you just have to pull the right end off. Then put the hose in a cup or shallow container with the stuff in it and let the vacuum suck it up VERY slowly. I stopped every once and a while and revved it up a bit. Then shut the motor off for 5 minutes like the instructions say and turn it back on and enjoy the smoke show. BTW if you let it suck the seafoam up too fast, you may hydrolock your motor and bend rods and stuff I think, not good. So don't hold me responsible if you screw up your motor. Just follow the instructions on the back of the bottle if your not sure.