Error codes 42 and 34 - Knock sensor and Fuel Temp

[IAmAlive]

So i have a standard 1990 300zx NA with pretty high mileage, so obviously its gonna start having some problems. the ecu gave me codes 34 and 42, which are the fuel temp circuit and the detonation (knock) sensor. advice on whether i should relocate the knock sensor or bypass it with a resistor? and what to do to check the fuel temp? And also, my gas mileage has been a lot worse then usual. i only get roughly 100-120 miles per tank, and its getting a rough start in the mornings, i have to give a little gas to even get it started. Possibly bad spark plugs? All the injectors tested 10 ohms.. And when i start it up or accelerate too hard, i can hear the belt squeal a bit, and also a hissing and deep gurgle from possible the right side of the car when accelerating. I know these are tender cars in a sense, so i just want to make sure i get things fixed the right way.

-Brand new to the forum, so i apologize on the long post. Any help would be VERY appreciated!

[Ace2cool]

Relocate. Buy it here, as this is the cheapest price for a quality relocate kit. I just got mine in and it's great quality.

http://www.yugobernie.com/inventory.html

And usually if the Fuel Temp sensor code is popped, the sensor is bad. Needs to be replaced. Verify the connector is free of corrosion, and if cleaning it doesn't help, then replace it.

As far as gurgling, that's most likely your coolant gurgling in the heater core. Burp the radiator. Park the car on an uphill grade (a steep-ish one,) and (with the radiator cold) open the radiator cap, and remove the bleed screw. warm the engine till the thermostat opens and coolant starts circulating. The level should drop. keep it topped off. Revving the engine helps circulate the coolant faster. Don't bounce it off the limiter, just a quick blip of the throttle.

[IAmAlive]

Thanks a bunch. And as for the hissing noise, is it probably a vacuum leak? Its only when i accelerate. It's rather noticeable and the noise reflects when I drive by other cars or houses etc.

[t.mcginley.jr]

I just replaced my fuel temp sensor and had the same code. It's only $26 from Z1:

http://www.z1motorsports.com/product_in ... ts_id=1731

When the fuel temp sensor is bad, you will get crappy gas mileage. Also the bad knock sensor retards the timing which doesn't help mileage either. You can get an OEM Nissan knock sensor on ebay for ~$35. You should replace the subharness to since it can be the source of the code, not just the sensor. Z1 sells an upgraded subharness for only $20:

http://www.z1motorsports.com/product_in ... ts_id=6565

As for relocating it, I just bought the KS, subharness, and a longer bolt from Lowes so I could bolt it to the back of the plenum.

[t.mcginley.jr]

Also, taking off your MAF and cleaning it with MAF cleaner or electrical contact cleaner is always a good idea with high miles.

[IAmAlive]

Is it safe to burp my radiator if I found a leak under the driver side dash? My foot started slipping off the clutch this morning and I looked down to see a nice slimy mess all over accelerator and other pedals. And the windshield was getting a thin coat of slime/fog inside. Heater core leak?

And thanks for that link, my wallet thanks you! how long will the relocation take probably?

[Ace2cool]

Relocate shouldn't take long. You bolt the new one on, and plug it into the stock harness where the old one was plugged in.

And yes, that's a heater core leak. MAJOR PITA on these cars.

As far as the hissing noise? Not sure. Can you tell approximately where it's coming from?

[IAmAlive]

Well when I drive by other cars or houses etc, I hear a sort of hissing or fast clicking kind of sound from the outside of the car, mostly the right. Either from the exhaust, or the front side of the hood. But it's only when the car is in gear and revving and not parked. Sort of hard to explain. And along with a wonderful squealing on start up and in high rpms.

[t.mcginley.jr]

And yes, that's a heater core leak. MAJOR PITA on these cars.

ASK ME HOW I KNOW!! I just got my new heater core in, still gotta put the dash back on and button everything up though. I think I'm somewhere around the 12 hour mark so far. If you don't need it right now you can just bypass the heater core by connecting the 2 hoses coming off the back of the engine to create a loop.

Does the weird noise only happen when you're driving? or just when its revving?

Squealing = bad/loose/wet belts or bad bearings (idlers or auto-tensioner)

[IAmAlive]

12 hours? Dear god. Yeah I think the bypass sounds like a better option at the moment. And I found a coolant leak coming from the tank behind the front driver side door.. I think from the bottom lining of the tank? Or a pipe further up I can't spot.

As for the hissing kind of noise, it's generally only when driving. These cars can be very uplifting sometimes, but also very frustrating...

[Ace2cool]

The only tank behind the door is the windshield washer fluid. The filler is in the hatch.

[IAmAlive]

Behind the front driver side wheel. Sorry about the typo.

[t.mcginley.jr]

The coolant overflow bottle sits in front of the driver side wheel. As far as I know there's nothing coolant related behind the front wheel, are you sure it's coolant?

[IAmAlive]

That's what I meant. I believe it's the overflow tank then. What's the replacement procedure on that? Just buy a new tank, rip out the old and replace? Or is there a way to seal it, to last me a little while.

[t.mcginley.jr]

Its usually cheaper and easier just to buy a used one from someone. Pull the wheel off and the fender liner and you'll be looking at the overflow tank. It could just be the hose that's leaking.

[IAmAlive]

I'll see if I can find a cheap used one online somewhere.

And that high pitched hissing sound. Any idea? I only hear it if I push on the accelerator somewhat heavily. It's sort of like a slight high pitched "sss" noise. Mostly only audible when the windows are down, and it's only when the car is in gear and moving. Wish I could explain it better..

[Ace2cool]

See if you can get a passenger to record the noise and post a video.

[IAmAlive]

I'll try and get a vid by this weekend. And my fuel temp sensor just got in today. Just pull out the old and plug in the new one? Or do I need to relieve pressure? I don't want any fuel shooting all over the place..

[t.mcginley.jr]

No fuel will shoot out, no need to relieve pressure. Just unplug the connector, take the old one out the a socket (~12mm?) and put the new on in the same way. Should take 5 minutes or so.

[ThisIsSparTTa]

Bummer on having to replace the heater core t.mcginley.jr . I've seen a good writeup on the tear out, and its something I'm dreading. My A/C isn't working, and I think its possible the mechanism that switches between the heat/air is stuck, and I REALLLLLLLLY don't want to get at it.

[t.mcginley.jr]

Bummer on having to replace the heater core t.mcginley.jr . I've seen a good writeup on the tear out, and its something I'm dreading. My A/C isn't working, and I think its possible the mechanism that switches between the heat/air is stuck, and I REALLLLLLLLY don't want to get at it.

Yeah I finally got it all back together a few days ago. I looked at all the writeups before doing it and that estimate of 12-15 hours is dead on. The hardest part was actually getting the heater core box and A/C box separated and pulled out.

[IAmAlive]

So I was driving this morning and the windshield fog got to the point of not being able to see outside at all, whether the air was on or not, it got worse. Then I started to notice a fog/mist coming out of the defroster vents. Even when the air was off? Is this because of my bad heater core? I've sort of put off the hose bypass, because I've been busy.

[Ace2cool]

If it was really cold outside, it could cause fog when you run hot air into a very cold area.

[IAmAlive]

But u tried blowing cold air instead and it just continued to fog up. And it wasn't even like normal fog, it was like a thin layer of slime or something. And do you know what may be causing the smoke/dust blowing out the defroster?

[IAmAlive]

Alright bypassed the heater core and changed the fuel temp sensor. I noticed the wire running to the sensor is cut, and zip tied to the whole group of wires running to the ecu (I'm assuming) as if someone has messed with it previously. Should I just pull wires in the region til I find a matching one and splice them?

[IAmAlive]

[IAmAlive]

I believe this is the matching wire. Is that right, or too exact of a question to be sure?

[IAmAlive]

Make that 2 cut wires in the exact same region. No color similarity, but I'm no expert.. Any clues guys?

[Ace2cool]

Hm, that's a tough one. The fuel temp sensor wire is supposed to be Brown, like the second pic. Maybe the wire was bad, so they cut and spliced a new wire in, and that got broken along the way? Read from that brown wire to pin 36 on the ECU harness. If it has continuity, connect the wire coming from the Fuel temp sensor to the brown wire.

[IAmAlive]

I think your right, because the brown wire in that region had electrical all around it, possibly to keep it together with the black one, and they must have fell apart. And the black wire was zip tied around all the the other wires from the coil packs, injectors, etc. so I should just pull the floorboard and check the pins on the ecu connector for the brown wire?