question on knock sensors

[crimsone96Q45]

could someone tell me what they do , where they are located, how much they cost. also since buying this car and finding out how much it costs to maintain it, trying to fix it has scared the crap out of me, after going from a 525 BMW and being able to fix most things on it, this car didnt even have spark plug wires, every one i called to do a tune up wanted at least 350 to just change the spark plugs, after going on this site i've learned that changing them doesnt look to be that hard, so i went under the hood and took off the covers that cover the coils, the question is can it be that easy after they told me that it would take 6 hours and 750.00 for a complete tune up ? what am i missing. also how would i replace these gaskets that are under the spider looking thingy lol

[CrimsonQ]

Replacing the spark plugs isnt really hard per se, just extremely time consuming, hence the charge for labor.

I have 1 hand and a back that doesnt like bending, so mine took the better part of my saturday.

[maxnix]

First, get the FSM and TSB. Read them.

Then read all posts by Q45tech. All of them, and follow the links.

Questions like yours are answered thoroughly in Infiniti Online Mechanic. Try the SEARCH feature.

[texasoil]

Q45's are MUCH lower cost to maintain than BMW iron.

[Q45tech]

Q45's are MUCH lower cost to maintain than BMW iron.

ASSUMMING one speaks of apples to apples! V8 vs V8 and V6 vs I6 and in the same general year group 90-95 vs 96-2000.

We are quite lucky in ATL that we have lots of large BMW graveyards and many small Infiniti ones.............the East Coast's California in many ways just with the wives of the Cable Guy and Bubba at the front counters. No offense. I was born here.

Members can get Infiniti FSM, Consults, and parts cheaper than BMW and the good techs don't ignore you unless you speak German or bring them a Bratwurst.

Try finding a good low mile BMW V8 engine or transmission for $1500 delivered.

[Jeff Williams]

The knock sensors are like little microphones on the engine block, deep under the plenum. They sense when the engine is making a knock, and adjusts the timing to reduce it. The harness and connections get corroded and brittle. The sensors get hot and break. If a Q has ever overheated, then the knock sensors are more than likely toasted.

Once the knock sensors fail, they throw a code to the ECU. The ECU reduces the advance, jsut as if the sensors are sensing a knock all the time.

This reduces your HP.

You can reset the ECU, but if the knock sensors are bad, they will throw a code again. Sometimes, they throw a code, but resetting the ECU will release it for a while.

Layla had a knock sensor code. I reset it, and it never returned.

Lola threw the code, and I had T3 in Atlanta replace them, along with the harness. Byron did a great job with her.

I even got Dennis to do a couple WOT runs, to give me his impression of her.

[deepsouthq]

i have a 97 w/150K mi. , no CEL. my power seems to be lacking, good plugs(NGK), clean intake, etc. could my KS be bad and that be my power loss? ps wife put 87 gas in and it ran ok but did ping under hard acceleration with the AC on

[yodawill2000]

Do knock sensors get flaky before they completely fail ?My J30 seems like it looses power after warm up but its not constant?I can be cruising about 40 and all of the sudden it feels like its getting the timing retarded ,, then it comes back to normal.Im wondering if I dont have knocking going on after warm up, although I dont hear anything.Fresh oil and Chevron 93 is all she see's.Coolant is topped and the temp gauge stays where it always has. Weird.

[Q45tech]

YOU CANNOT TRUST the inside gauge it is designed to make you feel good in that no movement is shown between say 160F and 200F and any movement is very time damped [slow].

A Consult/OBD2 scanner on the road test or developing some method to actually read the coolant temp accurately.

Good OBD2 software on a laptop/palm etc.........

I would think any KS older than 7 years 100k are always suspect as with O2 sensors, spark plugs.

Really the only method is to remove examine for minute cracks and test resistance AT 170F-240F [where they operate] I always tap them while the ohmmeter is attached [bolted to head or a metal plate] to make sure they are not intermittient.

[yodawill2000]

Hmm .. I have a 94 ODB1 ..Suppose I can put a temp gauge on it .I have a few that I used on my old trucks.Thanks , It really does seem temp related,

[yodawill2000]

Pulled the code from the ecu .Knock sensor for sure .Gonna install a real temp gauge and see if its temp or the KS's .On a cool day she runs like a Buzzsaw.Hopin' I dont have to yank the plenum