- This topic has 14 replies, 7 voices, and was last updated 8 years ago by
.
-
Topic
-
Hello, about two months ago I have a problem with the knock sensor on my 2004 Mazda 3. After a cold start on the dashboard always appears check engine light.
Check engine light (CEL) appeared only at cold starts when the ambient temperature is low. After four restarts of my engine CEL disappears and everything is OK… until the next day! Anyway, I’ll probably have to change the knock sensor!
After scanning error code was detected – “p0328 – Knock Sensor 1 Circuit High Input (Bank 1 or Single Sensor)”. When CEL lights on the dashboard car is working normally, only the gas mileage is higher than normal.
Often (if I didn’t restart the engine several times) I just drive my Mazda with CEL on the dashboard. In the workshop technicians told me that the car operates in “limp mode” when CEL is on, and PCM fed too rich fuel mixture.My question is there any chance to damage my engine if I drive into “limp mode”? Can I still drive my car with these problems?
-
Replies
-
The knock sensor is there to prevent detonation. Detonation can break piston lands and spark plugs. If what the shop is telling you is correct then the computer enriches the mixture in an effort to insure detonation doesn’t occur. Also, I’d guess, it pulls timing. This will give you poor gas mileage and less power. Use high octane gas and drive like grandma and you should be good. But why not just get it fixed?
The question is whether or not detonation is going on or not. If the EGR system is operative there may not be any. With a fully warmed up engine and sources of noise off (radio, cabin fan) you might hammer the pedal to the floor a few times and listen for any faint rattling sounds.
You do NOT want to continue driving a car that is rattling or the engine can be destroyed.My vote is to fix the problem even if there is no rattling.
I’m still not solved the problem because I’m not sure if the sensor is bad or the problem is elsewhere! 🙂
I have another question:
Over how many RPM risk of detonation (knocking) in the engine is the highest? I don’t usually load the engine too much and I don’t drive my car more than 3500-4000RPM (4k in extreme cases!) on the highway.Knocking can occur at any RPM depending upon the load. You could be creeping up a hill at 25 MPH turning only 1500 RPM and the engine can still suffer spark knock.
This might be offset some by running higher octane gasoline. Around here premium runs about a quarter per gallon more so that cold be weighed against the cost of repairing the knock sensor problem.
I’m cautionary on this because as a mechanic I’ve had to tear into engines that were damaged due to spark knock. Some were not feasibly worth repairing due to the severity of the damage.
One car shredded a piston and tore up the cylinder wall. The car was showroom clean and the owner chose to just dump the car and buy a new one.
It seemed a shame to scrap such a nice car so I bought it myself on the cheap from the dealer who was just going to unload it, rebuilt another engine for it, and it became my family car for about 15 years.I personally would advise against it. It could lead to ultimately engine replacement. If you are mechanically inclined, you can replace it yourself. Either purchase a repair manual for the vehicle (always a good idea to have one anyways, well worth the $30 or so) or have it done by a trained technician. Granted it may not cause severe engine damage instantaneously and you can go a while with it bad yet it will cause damage over time. Personally I would rather spend $50-$300 repairing it then $5,000 for a new engine. Also, if you do it yourself, do NOT drop it! They are very sensitive and dropping it will destroy it. I encountered that lesson the hard way. Good luck in your decision.
well, I will try to ask another question about KS.
Is there a little chance the knock sensor actually is not damaged? Why after a four consecutive re-starts of the engine (when engine already is warmed up) “check engine” disappears? Does mean the knock sensor works normally on warmed up engine?
Somewhere I’d read after four restarts of the engine if the ECM does not detect malfunction in KS, it just clear error from memory and the car began to work in “normal” mode. If KS is really damaged should CEL lights on the dashboard always?Voltage is supplied to the knock sensor. When the senor detects vibration the output voltage varies. If the engine computer doesn’t detect this variation the code is set. Now there are certain parameters the engine has to meet before this error is sampled. So, is the knock sensor operating normally? The correct answer is that if a code for knock sensor goes away then the knock sensor meets whatever criteria programmed into the computer.
[quote=”Mazda3″ post=128971]well, I will try to ask another question about KS.
Is there a little chance the knock sensor actually is not damaged? Why after a four consecutive re-starts of the engine (when engine already is warmed up) “check engine” disappears? Does mean the knock sensor works normally on warmed up engine?
Somewhere I’d read after four restarts of the engine if the ECM does not detect malfunction in KS, it just clear error from memory and the car began to work in “normal” mode. If KS is really damaged should CEL lights on the dashboard always?[/quote]“Knock Sensors generate a voltage when vibration is applied to them utilizing the piezoelectric effect. The generated voltage is proportional to the acceleration of the vehicle. Due to the vibration, a counter weight inside the sensor is applying pressure on the piezo element, and this pressure creates an electric charge in the piezo element which is the output signal of the sensor. They are tuned to engine knock frequency (typically 6-8kHz). Once signs of detonation are detected (i.e. knocking), the knock sensor sends a voltage signal to the engine management computer which retards the spark timing slightly to avoid detonation.”
If the sensor is malfunctioning, that would cause the CEL to trigger. I presume it is a short inside of the sensor itself. For the CEL remain on consistently there would have to be a permanent failure of the part. Being that it is intermittent, there could be an issue with the piezo element inside the sensor which is triggering the CEL. If you are unsure of the diagnosis you had received, disconnect the negative battery cable for a few minutes. This will clear all codes from the ecm. When the CEL comes back on, use a scan tool to diagnose the problem once again. If the same code comes up then the sensor is definitely bad and you have two choices: replace it or continue to drive and risk possible engine damage.
You may be able to perform a backyard type test to see if the system is working. Warmed up and idling, tap a cylinder head in he area of the knock sensor firmly with a small hammer a number of times. Of course, don’t hit anything critical or get ham fisted with this.
If the engine is idling smooth and stumbles a bit when you hit the cylinder head then the KS system should be operating fine.
The KS is really nothing more than a Piezo microphone although in the automotive world it’s an expensive Piezo as compared to its cheap Radio Shack equivalent.
I am experiencing EXACTLY the same problem on my 2007 Mazda 3 as described, what was the solution to the problem, a new knock sensor? I would love to know what you have done.
[i]Hello, about two months ago I have a problem with the knock sensor on my 2004 Mazda 3. After a cold start on the dashboard always appears check engine light.
Check engine light (CEL) appeared only at cold starts when the ambient temperature is low. After four restarts of my engine CEL disappears and everything is OK… until the next day[/i]Hi Mazda 3
can you share please the solution for your CEL and Knock Sensor error?
I have the same problem on the same model… so what helped you?Many thanks
Knock sensor .The computer adjust ignition timing to be as advanced as possible without resulting in engine knock .First it advances the timing until the engine knocks . Then it retards the timing until the knock goes away . It will then search for the best timing setting for that rpm load temperature and fuel . When it finds the best setting, it stores the information in memory for future drive cycles.Its an adaptive learning to find optimal engine performance.
When the knock sensor detects detonation it will retard the engine timing till engine detonation knock , spark knock , goes away.The relearns the best timing for the fuel by advancing the timing until detonation occurs, then retarding the spark slightly until the detonation stops . . All modern automotive engines have this capabiltiy . Design engineers test an engine on a dynamometer using fuels of different octanes . Different spark advances are tested at various speeds and loads to determine the engines highest torque value.Ignition timing is best when it is advanced to the furthest point without causing detonation . detect bad ignition timing , main bearing knock or piston slap.Detonation can cause the piston to expand too much resulting in cylinder wall scuffing at the four corners of the piston skirts. From the extreme heat the aluminum melts and the piston rings stick to the cylinder wall.
Detonation is a race between the flame front and heat buildup during combustion. The faster the burn is completed , the more immune the engine is to detonation. If the the air fuel mixture burn is completed before the temperture and pressure reach the point of detonation, abnormal combustion will not occur.
Excessive advanced timing can cause ,
excessively retarded ignition timing will cause an engine to overheat but will not burn a piston . Detonantion from overheating , too lean an air fuel mixture air leak into engine cause engine to run lean and overheat . Air fuel mixture to lean .
EGR VALVE FAILING A LEADING SOURCE OF DETONATION testing of egr valve will need to be performed by manually opening valve where knock occurs 1800 to 2000 rpm . If knock goes away egr valve is at fault. To manually open valve .
Older engines, used a air cleaner stuck in the heat on position or a malfunctioning early FUEL EVAP SYSTEM.
A loose sensor bracket or some thing other vibration can also cause the time to be retarded can cause false knock senses. +++++-
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++CEL CHECK ENGINE RELATED SYMPTOMS WHEN KNOCK SENSORS DETECTS THE FOLLOWING
Knock sensor .The computer adjust ignition timing to be as advanced as possible without resulting in engine knock .First it advances the timing until the engine knocks . Then it retards the timing until the knock goes away . It will then search for the best timing setting for that rpm load temperature and fuel . When it finds the best setting, it stores the information in memory for future drive cycles.Its an adaptive learning to find optimal engine performance.
When the knock sensor detects detonation it will retard the engine timing till engine detonation knock , spark knock , goes away.The relearns the best timing for the fuel by advancing the timing until detonation occurs, then retarding the spark slightly until the detonation stops . . All modern automotive engines have this capabiltiy . Design engineers test an engine on a dynamometer using fuels of different octanes . Different spark advances are tested at various speeds and loads to determine the engines highest torque value.Ignition timing is best when it is advanced to the furthest point without causing detonation . detect bad ignition timing , main bearing knock or piston slap.Detonation can cause the piston to expand too much resulting in cylinder wall scuffing at the four corners of the piston skirts. From the extreme heat the aluminum melts and the piston rings stick to the cylinder wall.
Detonation is a race between the flame front and heat buildup during combustion. The faster the burn is completed , the more immune the engine is to detonation. If the the air fuel mixture burn is completed before the temperture and pressure reach the point of detonation, abnormal combustion will not occur.
Excessive advanced timing can cause ,
excessively retarded ignition timing will cause an engine to overheat but will not burn a piston . Detonantion from overheating , too lean an air fuel mixture air leak into engine cause engine to run lean and overheat . Air fuel mixture to lean .
EGR VALVE FAILING A LEADING SOURCE OF DETONATION testing of egr valve will need to be performed by manually opening valve where knock occurs 1800 to 2000 rpm . If knock goes away egr valve is at fault. To manually open valve .
Older engines, used a air cleaner stuck in the heat on position or a malfunctioning early FUEL EVAP SYSTEM.
A loose sensor bracket or some thing other vibration can also cause the time to be retarded can cause false knock senses. +++++-
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
- You must be logged in to reply to this topic.