My check engine light came on and I got it checked out- the diagnostic showed a knock sensor code and I ended up having to replace the detonation sensor and rear exhaust gas sensor.
I've got a '99 with 31,000 on it and I thought the car felt sluggish for about a month or so before the check engine light came on.
I got the work done by a pro but I want to know from you experts out there more about these sensors and what they effect....I'd be grateful for anyone's take on this stuff and any teaching is much appreciated!
Also, is it unusual for a fairly new and low mileage max like mine to have this problem? I bought it used and I wonder if it was driven particularly hard? I vaguely recall my wife's '98SE having a check engine light at around 30K too and I think hers had something to do with the fuel line being clogged or something like that....Anyway, unless it's my imagination the car seems quicker now...?
I've got a '99 with 31,000 on it and I thought the car felt sluggish for about a month or so before the check engine light came on.
I got the work done by a pro but I want to know from you experts out there more about these sensors and what they effect....I'd be grateful for anyone's take on this stuff and any teaching is much appreciated!
Also, is it unusual for a fairly new and low mileage max like mine to have this problem? I bought it used and I wonder if it was driven particularly hard? I vaguely recall my wife's '98SE having a check engine light at around 30K too and I think hers had something to do with the fuel line being clogged or something like that....Anyway, unless it's my imagination the car seems quicker now...?
It should feel quicker after getting those replaced. Your car wasnt able to advance the timing to the optimum point, or accurately measure air/fuel ratios with the Knock Sensor and rear O2 sensor bad.
Member who somehow became The President of The SE-L Club
Chances are you didn't need a knock sensor. If the 02 sensor was bad, that itself may have caused the car to ping or knock which made the knock sensor work over time, thus throwing the KS code as well.
Your mechanic should have replaced the 02 sensor, reset the ECU and sent you on your way. If the Knock sensor code came back, then that should be changed next.
Probably could have saved you some $$$ if you asked here first.
Your mechanic should have replaced the 02 sensor, reset the ECU and sent you on your way. If the Knock sensor code came back, then that should be changed next.
Probably could have saved you some $$$ if you asked here first.
The rear O2 sensor has nothing to do with controlling A/F ratio. The ECU compares the readings between the front (which is used to regulate A/F) and rear O2 sensors to keep track of catalyist efficiency.
(I did a little reading since my first post
)
(I did a little reading since my first post
)
Member
Quote:
Originally posted by njmaxseltd
Chances are you didn't need a knock sensor. If the 02 sensor was bad, that itself may have caused the car to ping or knock which made the knock sensor work over time, thus throwing the KS code as well.
Your mechanic should have replaced the 02 sensor, reset the ECU and sent you on your way. If the Knock sensor code came back, then that should be changed next.
Probably could have saved you some $$$ if you asked here first.
Hmmmm. I don't think so....Originally posted by njmaxseltd
Chances are you didn't need a knock sensor. If the 02 sensor was bad, that itself may have caused the car to ping or knock which made the knock sensor work over time, thus throwing the KS code as well.
Your mechanic should have replaced the 02 sensor, reset the ECU and sent you on your way. If the Knock sensor code came back, then that should be changed next.
Probably could have saved you some $$$ if you asked here first.
If your knock sensor is bad, it will never set off the check engine light. NEVER. However, if you put the ECU in diagnostics you will see the code 34. If your all is ok, you will see code 55.
As stated above, the ONLY purpose of the rear O2 sensor is to make sure the cat is working. It has NO control of engine performance. However the front O2 sensors sure do.
I just changed my knock sensor after having the trouble code 34 reappear and reapper for over a year. All is well know (code 55) and the lower RPM pull is stronger.
Funny thing, I hooked the knock sensor to my oscilloscope and when I tapped it with a screw driver, it did create a voltage spike on the display.
BTW, If you OVERTIGHTEN the single bolt for the knock sensor you may make it too sensitive, and if you UNDERTIGHTEN it may not be sensitive engough.
Senior Member
Quote:
Originally posted by MaxVQ
BTW, If you OVERTIGHTEN the single bolt for the knock sensor you may make it too sensitive, and if you UNDERTIGHTEN it may not be sensitive engough.
Now I'm curious, what's the correct torque setting?Originally posted by MaxVQ
BTW, If you OVERTIGHTEN the single bolt for the knock sensor you may make it too sensitive, and if you UNDERTIGHTEN it may not be sensitive engough.
Quote:
Originally posted by iwannabmw
Now I'm curious, what's the correct torque setting?
...of course, you'd have to remove the upper and lower intakes to get a torque wrench on that thing...Originally posted by iwannabmw
Now I'm curious, what's the correct torque setting?
...ouch...
Senior Member
Quote:
Originally posted by mzmtg
...of course, you'd have to remove the upper and lower intakes to get a torque wrench on that thing...
...ouch...
You mean there's an easier wayOriginally posted by mzmtg
...of course, you'd have to remove the upper and lower intakes to get a torque wrench on that thing...
...ouch...
Just wanted to thank you all for your input. I've carefully read and am making some sense of it at least. Luckily I bought an extended warranty on my baby (brought the interest rate on the loan down) and having the mechanic replace both sensors only cost me a $50 deductible, so I guess replacing both at the same time was actually a better deal for me. And I know it was a pain to get at one or both sensors b/c it took 3+ hours and at one point I had about 4-5 guys around my engine.
Senior Member
Quote:
Originally posted by mysuperblack
Just wanted to thank you all for your input. I've carefully read and am making some sense of it at least. Luckily I bought an extended warranty on my baby (brought the interest rate on the loan down) and having the mechanic replace both sensors only cost me a $50 deductible, so I guess replacing both at the same time was actually a better deal for me. And I know it was a pain to get at one or both sensors b/c it took 3+ hours and at one point I had about 4-5 guys around my engine.
They followed the service manual instructions to change the knock sensor. That calls for removing the intake manifold. If you have small hands and are stubborn, you can change it in 15 min. Doesn't matter since you weren't footing the labor bill.Originally posted by mysuperblack
Just wanted to thank you all for your input. I've carefully read and am making some sense of it at least. Luckily I bought an extended warranty on my baby (brought the interest rate on the loan down) and having the mechanic replace both sensors only cost me a $50 deductible, so I guess replacing both at the same time was actually a better deal for me. And I know it was a pain to get at one or both sensors b/c it took 3+ hours and at one point I had about 4-5 guys around my engine.
Damn! So after all that work done replacing those two sensors I took the car for a long trip and on the way home today BOOM! The DAMN check engine light came back on! S#%T! The car's riding smooth as silk and now I'm wondering what the hell else is wrong! I'm hoping that at worst the mechanics installed one of the two incorrectly or maybe it was a defective unit. Otherwise I'm looking at something else to replace! This IS NOT SUPPOSED TO HAPPEN WITH THESE CARS!!!!!!!