Knowledgeable people. Knock sensor?

95_XR7

Registered User
Ok, I've posted video's before, and everyone agrees that the car seems to not have as much power as it should. I'm also dealing with poor gas mileage, and extremely rich smelling exhaust.

My question...I was readig that a knock sensor that's bad can cause the car to run rich. Do you think this could be my problem? Any way to test one, or would I have to replace it and see if it makes a difference?
 
Well if I understand a knock sensor correctly it basically retards timing once a knock is noticed. I have read before the computer and knock sensor are much more sensitive on the late model SC's. IMO I dont believe its your problem, unless it thinks there is a knock and is retarding the timing all the time:confused:. Have you pulled codes?
 
If a knock sensor is bad, it won't pull timing. Therefore, the motor is more prone to knock by collisions of flame fronts in the combustion chamber. It would take fuel to rid of that, so there isn't a way for it to be rich.

Is the car stock or has it been tuned for modifications with a computer chip? O2 sensors could be bad. Check your codes. If there isn't a CEL coming on, it may still be in memory. Check it out.
 
If a knock sensor is bad, it won't pull timing. Therefore, the motor is more prone to knock by collisions of flame fronts in the combustion chamber. It would take fuel to rid of that, so there isn't a way for it to be rich.

Is the car stock or has it been tuned for modifications with a computer chip? O2 sensors could be bad. Check your codes. If there isn't a CEL coming on, it may still be in memory. Check it out.

Alright, wasn't sure if it could be bad and make the EEC think it's knocking, therefore pulling timing, etc.

The car has been tuned by Dalke and has a chip. O2 sensors are brand new, and the only codes are due to the EGR being blocked, and the wire mod making the fan run all the time. I'm kinda just throwing stuff out there as it comes to mind.
 
Fan mod to so it runs all the time?... what outside temperatures do you have right now?

If that car is not getting above 175F its going to run pig rich.... thats why its such a BAD idea to just run that fan all the time. Dave would have lowered the fan on temps in that chip so you can run a 180 properly, so get that system fixed.

Anyways, I'll get off my soap box now.
 
Fan mod to so it runs all the time?... what outside temperatures do you have right now?

If that car is not getting above 175F its going to run pig rich

No, it won't. That is only partially true if his car was tuned with "X" amount of timing and fuel at 180* and he has a peak current temperature of 160*. Then it will be richened slightly. That's at WOT, too.

At idle or part throttle, which is what he is speaking of, the same air/fuel is maintained regardless of the temperature. Once the motor is warmed up, then it will lean out slightly.

Needless to say, this is splitting hairs.
 
I've had the problem with running rich for awhile. Even when it was 80*+ outside it was running rich enough to smell gas. As of right now, it's about 30-40* out, but the car is kept in the garage, and warmed up before I drive it. The plugs are black, but aren't too bad. According the the scanner I hooked up (My brothers Snap-On MT2500) the timing is advanced only 8*

The car's idle isn't the smoothest (which also made me think knock sensor.) and I noticed sometimes it seems as though the fuel pressure may be bleeding off by the way it starts. According the the pressure gauge I hooked up, this is untrue.

Also, motor mounts are solid, and in perfect condition.
 
MAF element cleaned. Vacuum and boost leaks are a negative. Changed plugs, wires, 02 sensors. etc.
Actually, if you wouldn't mind me asking, what is the code for an early style MAF? (found on top.) Just an idea, but won't an old style MAF used on a new car cause it to run richer?
 
MAF element cleaned. Vacuum and boost leaks are a negative. Changed plugs, wires, 02 sensors. etc.
Actually, if you wouldn't mind me asking, what is the code for an early style MAF? (found on top.) Just an idea, but won't an old style MAF used on a new car cause it to run richer?

What have you done to the car since David tuned it?
 
Replaced the exhaust, center section back. The car has a stumbling problem that I somehow solved. Besides the problems listed here, and that...it runs perfect.
 
What kind of thermostat do you have? I had one of those fail safe ones.... It locked open after a month or two.
 
What kind of thermostat do you have? I had one of those fail safe ones.... It locked open after a month or two.

I honestly have no idea. All I know is that the car is definitely producing some heat. It'll toast you if you aren't careful. :D
 
No, it won't. That is only partially true if his car was tuned with "X" amount of timing and fuel at 180* and he has a peak current temperature of 160*. Then it will be richened slightly. That's at WOT, too.

At idle or part throttle, which is what he is speaking of, the same air/fuel is maintained regardless of the temperature. Once the motor is warmed up, then it will lean out slightly.

Needless to say, this is splitting hairs.

Well I didn't know that. So I guess its ok to run my cooling fan 100% of the time even when its -20 out... Guess I'll go do that fan mod myself then.

Thanks Cmac
 
Well I didn't know that. So I guess its ok to run my cooling fan 100% of the time even when its -20 out... Guess I'll go do that fan mod myself then.

Thanks Cmac

You and your sarcasm.....HAAAAA:)

Go ahead, it won't make any significant difference. He stated the problem existed even after it was warrmmeed uuuuuppp.

Apples n oranges..............
 
Alright, wasn't sure if it could be bad and make the EEC think it's knocking, therefore pulling timing, etc.



If you are running so rich that you can smell it, must be well over stoich, and running that way, may foul your plugs. I am surprised you do not throw a code saying you are running rich.

One thing I have done to my chip is lower the transition temp to 120 F to switch to the 'base fuel table'. (vs the 'cold fuel table') This idea I got from EECTuner forum @ yahoogroups.com
(from memory default is 150 or 180 F?)

Switching to NGK O2 sensor from sparkplugs.com increased my mileage 1-2 per mile (my wideband sensor shows my NGK O2 sensors with a A/F = 14.7 at idle, and the new Bosch O2 were at 14.3, and very happy getting an extra mile to the gallon.)


For more SC reading pleasure:
http://www.sccoa.com/forums/showthread.php?t=87577&highlight=KNOCK

http://www.sccoa.com/forums/showthread.php?t=92420&highlight=CODE
 
You mentioned something about an older style MAF? You could get a rich condition if the amount of air the MAF is reporting to the computer is higher than the actual amount of air going into the car. Since the earlier MAF is smaller.....

Do you have a newer style MAF you can throw back in?
 
You mentioned something about an older style MAF? You could get a rich condition if the amount of air the MAF is reporting to the computer is higher than the actual amount of air going into the car. Since the earlier MAF is smaller.....

Do you have a newer style MAF you can throw back in?

Sorry for that. I have a C&L 76mm MAF, but I'm using early style electronics. Can the electronics cause a rich condition? (The car came with these.)
 
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