recently huge drop in power
08-29-2003, 07:28 AM
#1
recently huge drop in power
I am not sure what is wrong with my car but recently the power has just dissappeared. I am not sure what it is, right when 3000 rpm hit my car had majr torque steer. Now I can keep my hands off the wheel if I wanted to. The engine kind of hesitates for a second the it climbs right before 3000 rpm. I think I hear a leak in my exhaust when I barely push on the gas, would that create a major power loss? But it seems like I am only getting like 200 miles per gallon of gas. I have 77,000 miles, could it be my spark plugs doing this? Can an exhaust leak cut down fuel milage and lots of power loss?
08-29-2003, 08:49 AM
#3
Senior Member
Join Date: Mar 2002
Posts: 271
OK.. jokes aside, check your ECU and see if it throwing any codes. I had a intermittently bad Knock Sensor and my 50/50 (city/Hwy) mileage dropped from about 23-24 MPG down about 19-20 MPG. After the knock sensor replacement - I am back at 24-25 MPG. The ECU (if any) could be a good diagnostic tool for your problems..
08-29-2003, 09:04 AM
#4
you have a bad knock sensor and/or a bad front bank O2 sensor...Congratulations!
pull the codes from your ecu, if you have 0303 and/or 0304 you have a bad knock/o2 sensor...fix the o2 sensor first, reset ecu, and recheck codes in a few days...if 0304 is still there, change the knock sensor
ebay is the cheapest knock sensor place... www.ebaymotors.com ,search for Maxima Knock sensor 80-110 bucks
www.buyoxygensensors.com is the cheapest place for o2 sensors 50-65 bucks
pull the codes from your ecu, if you have 0303 and/or 0304 you have a bad knock/o2 sensor...fix the o2 sensor first, reset ecu, and recheck codes in a few days...if 0304 is still there, change the knock sensor
ebay is the cheapest knock sensor place... www.ebaymotors.com ,search for Maxima Knock sensor 80-110 bucks
www.buyoxygensensors.com is the cheapest place for o2 sensors 50-65 bucks
08-29-2003, 10:31 AM
#7
Dyno plot says I have the most area under the Administrator curve
Join Date: Jul 2001
Posts: 7,060
99% chance that your knock sensor is blown. The knock sensor just LOVES to fail between 70-80k. I'm at 78k and mine has been blown for the past few thousand miles, but it's bypassed. And the knock sensor code is a "ghost" code meaning it won't light the SES.
Read the ECU FAQ sticky on how to check codes.
Search in the 4th Gen forum at the test site for the 0304 code or "knock sensor" and you should find a zillion threads discussing it and how to fix it.
Read the ECU FAQ sticky on how to check codes.
Search in the 4th Gen forum at the test site for the 0304 code or "knock sensor" and you should find a zillion threads discussing it and how to fix it.
08-29-2003, 11:40 AM
#8
Senior Member
Join Date: Mar 2002
Posts: 271
Originally posted by SteVTEC
99% chance that your knock sensor is blown. The knock sensor just LOVES to fail between 70-80k. I'm at 78k and mine has been blown for the past few thousand miles, but it's bypassed.
99% chance that your knock sensor is blown. The knock sensor just LOVES to fail between 70-80k. I'm at 78k and mine has been blown for the past few thousand miles, but it's bypassed.
08-29-2003, 11:44 AM
#9
Member
Join Date: Apr 2003
Posts: 67
Classic KS symptomology:
I keep this information handy just for such occasions:
Once and for all: a bad knock sensor WILL NOT trip the check engine light, you must extract the codes from the ECU to determine if your sensor is (potentially) bad (code 0304). Some other hints as to a bad KS: poor acceleration below 3000 RPM (I was getting tired of being left behind at stoplights by Honda Civics).
If you don’t already own a Haynes or Chilton manual, get one. In addition to telling you how to extract the codes and locate the KS, there is a wealth of useful information for the do-it yourselfer. I am very cheap, but this an area well worth spending the $20 or so (I bought mine off of EBAY for $10 shipped).
The ECU is located behind the center console on the drivers side. It is accessible by removing the plastic cover panel right next to the gas pedal. The ECU is a metal box with a screw on the side covered by a piece of tape. Peal back the tape to get at the screw. With the ignition in the “On” position, turn the screw all the way clockwise, hold for at least 2 seconds, turn it all the way counterclockwise. Your CEL will now start flashing out any codes stored in the ECU. The codes are two digit numbers. The first number is signaled by long flashes, there will be a two second pause, and the second number will be indicated by a series of short flashes. Long-long-long-pause-short-short-short-short = 0304 (KS fault). There may be more than 1 code in the ECU, they will be flashed out sequentially and the whole sequence will repeat. To clear the codes from the ECU, follow this sequence: clockwise, hold, counterclockwise, hold, clockwise, hold, counterclockwise.
A good KS will measure ~550 k-Ohm resistance between the left pin of the KS and ground. You can check the resistance without removing the KS by following the harness to the connector. The connector has two pins, only one of them hooks up to the KS, so try them both. The act of whacking on the KS with your wrench can (temporarily) start it working again, so checking the KS once you removed it may not give you the bad reading you suspect. Hint: the connector is not the green one closest to the KS (1995-1996 models – most likely 1994-1999), it is a few inches closer to the front of the car. A heat shielded wire leads into the bottom of it and there are two wires coming out the top, one clear and one black.
Low cost knock sensor sources: The dealer will charge you $160 or so for the sensor. I purcahsed a Nissan OEM sensor off of EBAY for $90 shipped. I have seen them for as little as $80 and routinely for $100-$110. Search for both “Maxima knock” and “Nissan knock” to make sure you get all the possible matches. You can get a Bosch sensors for $115 shipped from http://www.nissanpartstore.com/nissan_knock_sensor.html I prefer OEM parts when possible and have no information on the Bosch.
Two good article on KS replacement:
http://www.skippynet.com/maxima/knocksensor.htm
http://www.motorvate.ca/mvp.php/507
Modifications to the Skippynet method
The article suggest using a 14” (or longer) ¼” socket extension to reach the KS retaining bolt. I found that using a 9” extension made it much easier to get the u-joint onto the KS bolt. To save money, I used two 3/8” drive extensions with a 3/8 to ¼ adapter, a ¼” drive u-joint and a ¼” 12mm socket (most of which I already had). Skippynet suggest using a 12mm flex socket, but being cheap I used a separate socket and u-joint so that I would have a more useful general purpose tool left over than the 12mm flex socket (better yet, I borrowed the u-joint and saved another $8). A 3/8” u-joint is a slightly bigger animal and in my opinion would make it hard to get the socket onto the bolt. It was not at all difficult to loosen the bolt using this setup. I had also borrowed a 16” extension and found it very difficult to get the socket onto the bolt head (I gave up after about 2 minutes, so it probably could have been done).
Once the bolt was out, I used a magnetic pickup to retrieve it (and eliminate the possibility of dropping it into the engine cavity where as you will find out soon, is not a very friendly place). With the bolt removed, you can pull the knock sensor out of the cavity by the harness and replace it. Next, I put the bolt into the new KS and used a small piece of tape to hold it in place while I stuffed it back into the engine cavity (again to eliminate the chance of dropping it in there).
Now the difficult part: I don’t see how you can locate the bolt into the hole and get it started without stuffing your hand under the manifold (others have done it using a claw type pickup to position the bolt). If you have very large hands, you might try enlisting a girlfriend or your mom as others have done. I was able to get my hand in there and get the bolt hand tight, then it was just a matter of using the 9” extension/u-joint setup again to do the final tightening. Your hands will get cut up a little doing this, but no worse than I am used to with other auto repairs.
I was able to replace the KS in both cars in less than 1 hour including test drives using this method. The real key is using the skippynet socket extension method to crack the bolt loose. Once you have jammed your hand into the engine cavity you will realize how difficult it would have been to get a wrench on the bolt and loosen it.
I keep this information handy just for such occasions:
Once and for all: a bad knock sensor WILL NOT trip the check engine light, you must extract the codes from the ECU to determine if your sensor is (potentially) bad (code 0304). Some other hints as to a bad KS: poor acceleration below 3000 RPM (I was getting tired of being left behind at stoplights by Honda Civics).
If you don’t already own a Haynes or Chilton manual, get one. In addition to telling you how to extract the codes and locate the KS, there is a wealth of useful information for the do-it yourselfer. I am very cheap, but this an area well worth spending the $20 or so (I bought mine off of EBAY for $10 shipped).
The ECU is located behind the center console on the drivers side. It is accessible by removing the plastic cover panel right next to the gas pedal. The ECU is a metal box with a screw on the side covered by a piece of tape. Peal back the tape to get at the screw. With the ignition in the “On” position, turn the screw all the way clockwise, hold for at least 2 seconds, turn it all the way counterclockwise. Your CEL will now start flashing out any codes stored in the ECU. The codes are two digit numbers. The first number is signaled by long flashes, there will be a two second pause, and the second number will be indicated by a series of short flashes. Long-long-long-pause-short-short-short-short = 0304 (KS fault). There may be more than 1 code in the ECU, they will be flashed out sequentially and the whole sequence will repeat. To clear the codes from the ECU, follow this sequence: clockwise, hold, counterclockwise, hold, clockwise, hold, counterclockwise.
A good KS will measure ~550 k-Ohm resistance between the left pin of the KS and ground. You can check the resistance without removing the KS by following the harness to the connector. The connector has two pins, only one of them hooks up to the KS, so try them both. The act of whacking on the KS with your wrench can (temporarily) start it working again, so checking the KS once you removed it may not give you the bad reading you suspect. Hint: the connector is not the green one closest to the KS (1995-1996 models – most likely 1994-1999), it is a few inches closer to the front of the car. A heat shielded wire leads into the bottom of it and there are two wires coming out the top, one clear and one black.
Low cost knock sensor sources: The dealer will charge you $160 or so for the sensor. I purcahsed a Nissan OEM sensor off of EBAY for $90 shipped. I have seen them for as little as $80 and routinely for $100-$110. Search for both “Maxima knock” and “Nissan knock” to make sure you get all the possible matches. You can get a Bosch sensors for $115 shipped from http://www.nissanpartstore.com/nissan_knock_sensor.html I prefer OEM parts when possible and have no information on the Bosch.
Two good article on KS replacement:
http://www.skippynet.com/maxima/knocksensor.htm
http://www.motorvate.ca/mvp.php/507
Modifications to the Skippynet method
The article suggest using a 14” (or longer) ¼” socket extension to reach the KS retaining bolt. I found that using a 9” extension made it much easier to get the u-joint onto the KS bolt. To save money, I used two 3/8” drive extensions with a 3/8 to ¼ adapter, a ¼” drive u-joint and a ¼” 12mm socket (most of which I already had). Skippynet suggest using a 12mm flex socket, but being cheap I used a separate socket and u-joint so that I would have a more useful general purpose tool left over than the 12mm flex socket (better yet, I borrowed the u-joint and saved another $8). A 3/8” u-joint is a slightly bigger animal and in my opinion would make it hard to get the socket onto the bolt. It was not at all difficult to loosen the bolt using this setup. I had also borrowed a 16” extension and found it very difficult to get the socket onto the bolt head (I gave up after about 2 minutes, so it probably could have been done).
Once the bolt was out, I used a magnetic pickup to retrieve it (and eliminate the possibility of dropping it into the engine cavity where as you will find out soon, is not a very friendly place). With the bolt removed, you can pull the knock sensor out of the cavity by the harness and replace it. Next, I put the bolt into the new KS and used a small piece of tape to hold it in place while I stuffed it back into the engine cavity (again to eliminate the chance of dropping it in there).
Now the difficult part: I don’t see how you can locate the bolt into the hole and get it started without stuffing your hand under the manifold (others have done it using a claw type pickup to position the bolt). If you have very large hands, you might try enlisting a girlfriend or your mom as others have done. I was able to get my hand in there and get the bolt hand tight, then it was just a matter of using the 9” extension/u-joint setup again to do the final tightening. Your hands will get cut up a little doing this, but no worse than I am used to with other auto repairs.
I was able to replace the KS in both cars in less than 1 hour including test drives using this method. The real key is using the skippynet socket extension method to crack the bolt loose. Once you have jammed your hand into the engine cavity you will realize how difficult it would have been to get a wrench on the bolt and loosen it.
08-29-2003, 01:19 PM
#13
Senior Member
Join Date: Mar 2002
Posts: 271
Originally posted by SprintMax
didn't 3 people already said the Knock Sensor doesn't throw a code?
didn't 3 people already said the Knock Sensor doesn't throw a code?
08-29-2003, 03:14 PM
#15
spanishrice...
used sensor-> http://cgi.ebay.com/ebaymotors/ws/eB...&category=6763
New Sensor-> http://cgi.ebay.com/ebaymotors/ws/eB...category=33557
used sensor-> http://cgi.ebay.com/ebaymotors/ws/eB...&category=6763
New Sensor-> http://cgi.ebay.com/ebaymotors/ws/eB...category=33557
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