Pacman

Got the good o'l code 34, bad knock sensor. There were topics on this before but didn't have answers. I'm getting horrible gas mileage, failed smog since I was runnin' rich, idle a little shakey, and the car dies on start up (especially when its cold outside). But, on the other side of the coin, my engine isn't pinging and the CEL isn't on, just the LED on the ECU. I went to Kragen and there charging $310 for a new one, thats insane and I'm going to other places to get pricing.
Now, heres my questions, where is the sensor, is it the little thing on the block just below the head (between cylinders 2 & 3)? If not where is it, pictures would be nice.
If it is what I described, I have it on the '91 motor, can it be replaced in the '95 motor? Thanks for your help.

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axiomatik

I don't know where it is, but you should make sure it's wiring isn't damaged before ponying up that much money for a new sensor. check an online fsm for location.

Pacman

The FSM I have online just tells me what it does basically. Doesn't tell me anything about the location. I think its a little black circle on the block on the passenger side. Is that correct, if so, I can take it off the '91 motor. Also, how do I test the wiring.

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sr240mike

http://zhome.com/ZCMnL/PICS/detonati...ionSensor.html

This should help you diagnose the problem.

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mrmephistopheles

fucks sake.. if you're going to replace a knock sensor, just get one off of a newer Altima.. Go to the junkyard, find a KA block from a new Altima, and get the knock sensor.

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Pacman

I know you're a mod, but calm down. Theres no real good topics on this that I searched. Now, you can help me by helping me identify it. Is it this part (click link, go to the last three pics, is that the knock sensor?):
Knock Sensor?

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In search of a Zenki S14 right side (passenger) fender and straight hood that are rust free.

aznpoopy

knock sensor is 120 bucks from everythingnissan.com brand new. no clue why kragen or any other autoparts store would charge $300 for one...

idlafie

Pacman...Good ol' Code 34...bad knock sensor..will not cause your horrible gas mileage, poor idle, running rich, dies on startup condition. All these conditions could be the result of a poorly tuned & poorly maintained engine. The reason the LED light on the ECU is on is because your motor is kicking a diagnostic code. Your Check Engine Light may not be coming on because the bulb may either have been disconnected OR burned out. Your Code 34 is probably due to a bad ground wire..check the ground connection on the driver side engine block towards the rear directly above the Oxygen sensor.

Usually when you have horrible gas mileage, poor idle, running rich & dies on startup condition, it's usually a combination of things, such as:

1). Either a poor connection to Engine Coolant Temperature Sensor or a defective Engine Coolant Temperature Sensor.

The purpose of the ECTS is to inform the computer of the engine's temperature so that fueling and ignition timing can be modified for all temperature operating modes. In addition, it is used to allow the computer to go into closed loop once engine temperature is high enough. In some models, it is also used to turn on the radiator fan. It also can be used for sensing an engine approaching an overheat condition. As this condition occurs, the computer would open the idle control valve and raise the idle in order to move more coolant through the engine and the radiator fan would turn on to cool the radiator down.

In the case of our KA motors, it is also used to regulate smog emissions on startup. When the KA motor first starts up, the ECU dumps more fuel into the intake manifold to warm up the engine & catalytic converter quicker. It does this merely to reduce emission gases caused by the combustion process. Once the motor reaches normal operating temperatures, the ECTS tells the ECU to cut back on the amount of fuel being dumped into the intake. If the wire to the ECTS, (or the ECTS itself), goes bad, then the ECU has no way of knowing that the motor has reached normal operating temperatures & continues to dump more fuel into the intake thinking the motor is still cold.

2). A defective Oxygen sensor - the attached link gives an excellent explanation as to how an oxygen sensor works.
http://www.autosite.com/garage/encyclop/ency13b.asp

3). A cut vacuum line or no vacuum to the fuel regulator or a defective fuel regulator. Here's another good link which gives an excellent explanation as to what the fuel regulator does:
http://www.stcloudchampionauto.com/pdf/57_PressReg.pdf
Symptoms of a defective fuel regulator are stalling immediately after starting the motor, mis-firing under load, or poor starting when warm.

4). Carbon buildup in the intake manifold, fuel injectors, IAV valve AND last but not least, the EGR valve/system. A leaky EGR valve can & will cause a poor/bad idle & bogging on acceleration.
Easiest way to clean out the carbon buildup is to use a can of Seafoam:
http://members.nuvox.net/~on.roz/cars/z28/seafoam.html
Pour it in the gas tank next time you fill up your car with gas. That should clean out your injectors & intake manifold. Another option is also to take a can of carburator cleaner, remove the intake & spray the carb cleaner directly into the intake manifold. Remember to save some carb cleaner for the EGR valve & IAV valve.

Best bet is get your hands on a Factory Service Manual & give your car a complete tune up. Change the air / fuel / oil filters along with your PCV valve, change your distributor cap & rotor along with your spark plugs. Inspect your spark plug wires along with all your vacuum lines on the motor. Check & adjust your timing along with your idle...you'll need a FSM to do those. Once you check, clean & adjust all of the above, I can pretty much guarantee you that your motor will idle a hell of a lot better than it is now.

Anyhow, I hope the above helps you to get your car running better. Apologies for the long post.

ID

mrmephistopheles

Pacman, yeah that's it.
I AM calm.. it's just frustrating to see people stupid enough to pay 'rip your asshole open' prices for parts that can be had cheaply.

oh, and sidenote: get a real digital camera.

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sepulchral

um hey buddy ever go to faqs i posted a good topic, 34 means ur knock sensor is bad or wiring is bad, just get a new one and replace it under the intake manifold, you mod basher

sr240mike

With the ecu giving a code 34 the ecu pulls timing and runs richer, which could cause you to fail smog. Im also pretty sure a code 34 does not trigger a cel, it just shows up when running a diagnostic. I get most of my parts from courtesynissan since they have always taken good care of me. http://www.courtesyparts.com/Merchan...Category_Code=

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Pacman

I wouldn't pay that much for a part that could have been had easier. I need a digi cam, but the car is taking all the money away. You got a cheap one for sale?

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In search of a Zenki S14 right side (passenger) fender and straight hood that are rust free.

sr240mike

Follow the link I posted earlier and bypass it with a 5 cent resistor if you wanna be really cheap.

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Pacman

I installed the other knock sensor and harness off the old motor. The one that was on there was missing half the wire on the harness so thats what was wrong. Tommorow I will scan the ECU and see if it gives me another code. I hope this fixed it.

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In search of a Zenki S14 right side (passenger) fender and straight hood that are rust free.

Pacman

I tried to reset the ECU according to the FAQ on this site, and now its throwing code #11: Camshaft Position Sensor, #21:Ignition signal in the primary circuit is not being entered to the ECU during cranking or turning, and the original code #34: Knock Sensor. I did it exactly like what Zilvia said to, and now more codes are on the ECU. And, after trying to reset the ECU, the check engine light came on after start up. It would take it roughly 3-5 secondes after the engine was running to turn on, then after about 10 seconds it would go off for about 3 seconds and come back on. It did this 3 times. It went away after the third time, so I took it for a 30min drive to see if it would come back on. I turned off the motor and re-started it to see if it would come back and it didn't. When I got home, I re-tested the ECU and the same three codes came up. I let it sit w/o the battery connected (a good 12+hrs) to see if the ECU would reset, I haven't checked tho. Whats going on? Any help, PLEASE!!!

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In search of a Zenki S14 right side (passenger) fender and straight hood that are rust free.

sr240mike

Check the cas to make sure the connection is good and maybe clean the terminals with some contact cleaner. Follow this link to help you diagnose the knock sensor problem. Zilvia Junkie


http://zhome.com/ZCMnL/PICS/detonat...tionSensor.html

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Pacman

sr20mike, that link doesn't work.Is the camshaft position sensor the same as the crank angle sensor inside the distributor, if not wheres the camshaft position sensor? What does code #21 mean, is it a wiring thing? How do you reset the ECU, I tried over and over again ad nothing happened. Did these codes come up because I didn't reset the computer worng? Thanks

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In search of a Zenki S14 right side (passenger) fender and straight hood that are rust free.

idlafie

Pacman....
Are you following the diagnostic procedures found in the Factory Service Manual? Do you have a Factory Service Manual??
If you don't, then download one from here:
http://www.ffdet.com/members/rich/Nissan/nissan.htm
Follow the troubleshooting procedures for the Diagnostic Trouble codes your ECU is kicking & you should be able to figure out what's causing your problems.
It will probably boil down to the following:
1). Component failure
2). Bad Wiring harness or connector.
3). Bad Ground wire or ground connection.
It doesn't exactly say it in any of your posts, but it looks like you may have done so recently, did you swap out the motor in your car recently? If you did, did you swap your sensors from the old motor to the new one?
Anyhow, let us know what you find after you check the FSM.
ID

Pacman

Hey, thanks for the FSM, it helps a lot. I got some stuff on the different codes that'll help. Here's what I found; the crankshaft position sensor (code #11) may be the culprit to the ignition signal circuit (code #21). Oh, and yes, I swapped in a '95 motor in my '91 Coupe. I swapped over the distributor, intake manifold, exhaust manifold, and now the '91 knock sensor.

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In search of a Zenki S14 right side (passenger) fender and straight hood that are rust free.

Pacman

My check engine light is staying ON all the time now. In the FSM, it says that the three codes that its throwing WILL NOT cause the CEL to go on. I retested the ECU many times and only these codes show. Is there someting else I'm not seeing or doing?

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In search of a Zenki S14 right side (passenger) fender and straight hood that are rust free.

sr240mike

Do you have the right ecu for the motor?

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Pacman

Yeah, its the right one.
I reset the ECU, and code #34 went away. I still have the other 2 codes, and I think that the wiring is screwed up (on wire is exposed). I'll look at it tommorow when I have Auto again. Thanks everyone!

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In search of a Zenki S14 right side (passenger) fender and straight hood that are rust free.

MELLO*SOS

Hey I have a code 34 and was reading on your thread to see what solution you found... It sounds like something you did while replacing the knock sensor caused the 11 and 21 codes, since they weren't there before.

Anyway is your code 34 gone for good? And what about the other codes?

Thanks

edit: I solved my code 34 problem. Turned out my ECU->knock sensor wire had a short somewhere. I installed a dummy 1 megohm resistor off pin #27 of the ECU (s13) and grounded it, which completely solved the problem. I don't have a knock sensor anymore, but at least I have decent performance!