94Q at 90k miles

Post by **DAEDALUS** » Wed Oct 15, 2003 10:28 am

It's not corrosion causing the problem; if it was, then the sensors wouldn't ohm fine at the main engine harness. All connectors have a rubber seal to help keep out moisture. Not 100% effective, but they help.

Post by **Q451990** » Wed Oct 15, 2003 10:28 am

Corrosion would be my guess too... a lot of water can collect in the valley during engine cleaning, coolant leaks, etc. In fact, if I remember correctly, the connector contacts on "Q1" back when I replaced the sensors were green. I didn't replace the harness - this was way before NICO or even the Yahoo board. I later had the harness replaced at T3.

For protection, my thought would be to load them up with di-electric grease. The connectors plug directly to the knock sensor, so elevating them wouldn't work unless you somehow solder the connectors directly to the sensors - I don't know how you'd do that... I don't remember rubber seals in the harness to sensor connections, but I could be wrong - seems like they're the same as the fuel injector connectors.

Heath

Post by **Chally** » Wed Oct 15, 2003 10:28 am

The grease is a great idea, just check out boat motors, all their connectors are filled with grease. I did the same with mine.Another problem is the rubber boot, that seals the harness to the connector, deteriorates & breaks. This is where the grease helps to keep the moisture & crap out, for a bit longer at least.

Post by **Q45tech** » Wed Oct 15, 2003 10:28 am

Still believe it is all those summer after engine turned off overheats as the 220F underplenum may easily exceed 300F in the 5-15 minutes after parking.

If you change them every 6 years/70k, when you do your plenum hose replacement........it only adds $75 per year prorated.

My plenum was last done at 200k 3.5 years [58k ago].

By the way the 97-01 Q and most Nisaan use the same type KS we have seen similar failures in 97 and 99 Q. I30, Qx4.

Post by **natsoundup** » Wed Oct 15, 2003 10:28 am

Are there obvious signs that you have bad knock sensors.... this is new territory to me.

The 90Q has 160k miles and just runs like a top. I have had the car 10 years and haven't had to change them, but I don't know much about this.

The 94Q has 84k miles and I have no indications that they've been changed...no dealer records anyway...

I have been trying to research this area, but there doesn't seem to be a lot of info on it..

Post by **louiegz** » Wed Oct 15, 2003 10:28 am

You guys in Georgia have it good with Q45tech around. I wish I had someone like that in New Jersey. Hey, not to sound like and idiot, I'm new to NICO, but what is the plenum? What does it do? What happens when your plenum is bad? Will my 94Q with 67000mi need this soon?

Post by **Aus94Q45** » Wed Oct 15, 2003 10:28 am

Regarding the changout on the harness, is this a separate strand that clips into the main harness, or is it soldered into the main harness? Obviously the new wires clip onto the KS units, but what is on the other end? Has anyone placed heat sheild material around the harnesses. As Dennis points out, the KS's and wires sit in an area that gets very hot in the summer and remains hot long after you turn off the car. Over time the heating and cooling make the harness hard and brittle . . . .

Post by **Q451990** » Wed Oct 15, 2003 10:28 am

The harness is actually a sub-harness that terminates at the right side of the plenum beside the injector harness. It's right near the throttle cams on that side. I'm not sure that there's a way to shield the sensors since they bolt onto the block, so the heat is pretty much a direct transfer. Insulating them on the bottom (say with exhaust gasket material) would keep them from doing their job, since they couldn't "hear" as well. As far as the harness, I'm not sure if shielding it would help. The wires don't seem to get stiff, but the connectors on the sensor end get corroded...

Heath

Post by **Q451990** » Wed Oct 15, 2003 10:28 am

louiegz wrote:...but what is the plenum? What does it do? What happens when your plenum is bad? Will my 94Q with 67000mi need this soon?

:pface Plenum is just a fancy word for intake manifold - I'm sure there's some difference, but for the most part the terms are interchangeable. It's the big aluminum "Spider" that sits on the top of your engine with the Infiniti symbol.

The plenum itself doesn't go bad (unless something really weird happens and you crack it - never heard of that) - it's all of the hoses under there, and the knock sensors, and KS harness, and the injectors, that will give you trouble. When people say a "plenum job" it means they're removing it to get to some or all of these parts. At 67K and 10 years you're probably looking at coolant and PCV hoses at some point in the next year or two. Just use a flashlight and check in the valley for coolant or oil from time to time. Either a hose failure or knock sensors will let you know when it's time to pull the "damn spider" as they call it at my local dealership.

Heath

Post by **Q451990** » Wed Oct 15, 2003 10:28 am

natsoundup wrote:Are there obvious signs that you have bad knock sensors.... this is new territory to me.

The ECU will store a knock sensor code that can be read by turning the screw on the ECU. Your service manual will tell you how to read the codes. Consult or a code scanner will also tell you. There's a way to ohm test the harness with a multi-meter as well, but I'd have to go look that up.

As far as symptoms you can feel while driving... I'd say just a general reduction in power, and a "bucking" at about 40MPH under a load that disappears when the transmission downshifts to 3rd.

Heath

Post by **Q451990** » Wed Oct 15, 2003 10:28 am

Here's a new thread for the Ohm test...

http://www.nissaninfiniticlub....42356

Post by **louiegz** » Wed Oct 15, 2003 10:28 am

Thanks Q451990! That was very helpful.

Post by **elwesso** » Wed Oct 15, 2003 10:28 am

Only way to tell is to do the ECU test, or have a consult done... Also, another good test is bad low end power..... I cant break traction from a stop.....

Also.... Dennis... Will this knock sensor be the right P/N.... http://cgi.ebay.com/ebaymotors...33557

It says its for Nissan, but I remember the part number being listed here somwhere, and I think thats it... Could you confirm??

Post by **Q451990** » Wed Oct 15, 2003 10:28 am

That's the one for the 90Q, I assume it's the same in 1994.

Heath

Post by **elwesso** » Wed Oct 15, 2003 10:28 am

So if I buy this its gonna work??

If the price difference isnt much by the end of the auction, Ill just get them from Joe for convenience sake!

EDIT: Auction ends in an hour, so Ill wait for the next one!

Post by **nuQ** » Wed Oct 15, 2003 10:28 am

********You guys in Georgia have it good with Q45tech around. I wish I had someone like that in New Jersey. *******

LOUIEGZ,,,,,THERE IS A VERY GOOD GUY IN JERSEY THAT IS A MASTER INFINITI TECH, NOW OWNS HIS OWN SHOP-----CHEAPER!!!!

KEITH VANMETER OF VANMETER AUTO IN MANTUA NJ. HE DID MY CHAIN GUIDES, PLUGS, OIL PLUGS, WATER PUMP, DROPPED MY OIL PAN,,,ETC. HE DID A FIRST CLASS JOB ON MY 90Q. LOOK HIM UP FOR ANY REPAIRS. IF YOU TELL HIM YOU HEARD ABOUT HIM ON THIS SITE, SURE YOU'LL GET A GREAT DEAL!!! LET ME KNOW IF YOU HAVE ANY QUESTIONS ABOUT HIM, OR HIS WORK. WOULD BE GLAD TO HELP!!!!!! JEFF

Post by **louiegz** » Wed Oct 15, 2003 10:28 am

Thanks for the help, Jeff. Very helpful. He's quite far, but it sound like it might be worth the trip. Next time I have to do my brakes, I'm due for new rotors and that can be expensive at the dealer. I'm also due for my tension rods. Any one know a good place in Northern New Jersey?

Lou

94Q at 90k miles

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