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Originally Posted by 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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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