97 Q45 lil power when I take off from light

[grip1968]

My Q is taking off very slow, the SES light came on and I check the code. Its P0325 1&2 Knock sensor, I also notice my fuel burn alot faster too. is this due to the knock sensor going out on me. I fill up on Monday and by thursday morning I'm on 1/4 or Empty. I not replacing the knock sensor what will it effect on my car. just curious, I love this car but it just hesitate when taking. Also I notice its making a humming noise when I have it up to 2 1/2 or 3 RPM's can the Knock sensor cause that too..

I apperciate any feedback

[paranoidjack]

100% Knock sensors. Hands down, no contest.

$150 in parts yourself or $1200 at the dealer.

zerothread?id=420801

[qship96]

There is more going on here in addition to faulty knock sensors......the defective knock sensors ARE NOT RESPONSIBLE for the "check engine"lamp illuminating.....look for additional code{s} that are stored- also the "humming" is NOT caused by the knock sensors........either is the poor fuel mileage-----you must find the other real problems in order to solve your issues.

[paranoidjack]

qship's right - check your codes, but I wouldn't be surprised if the KS's were the source of your issues.

I had an odd humming, very hard to define and I never located it. I can only think it was a result of retarded timing and its affect on the resonant vibration of something - after the KS change, the sound (and feeling at same RPM) disappeared.

As far as the CEL lighting up - this definitely needs to be read with a code reader (free at auto chain stores usually), but your faulty KS could have created a condition in which another part crossed threshhold (o2 sensors perhaps?) I had an o2 sensor CEL code that tripped relatively at the same time as my KS's, within 100 miles. After being reset several times, it would repeatedly show. After I replaced the KS's, the light has not come on in 10,000 miles.

I should note I haven't TESTED the o2 sensor, it just hasn't showed faulty since the KS replacement.

Oh - and qship - no mpg decrease with faulty KS's???
Modified by paranoidjack at 12:40 AM 10/23/2009

[qship96]

Search for an old thread of mine{around Nov 2007} detailing my round trip from Md to T3 Atlanta where I had major plenum/o2 sensors/knockers/and plugs,etc replaced and the trip fuel mileage on trip to atlanta vs trip back to md 5 days later....interesting to say the least as all parts replaced had 203,000 miles on them, except for the sparkplugs which had 133,000 miles on them!!!!!

[grip1968]

do the knock sensor cause your gas mileage to decrease, I notice that when I fill up for the week, Thrusday morning my fuel gauge be on empty or near empty. Before my Knock sensor was going bad my fuel gauge on a Thrusday morning would be a lil below half.

[Infinitiguy19]

If you read Qships answer in his topic then you would know.

But the short answer: NO.

[Q45tech]

Actually Failed KS system does decrease the cruise steady state ignition advance so it does DECREASE MPG on the highway.

[paranoidjack]

Good to hear Tech say that, as I experienced a 10-15% decrease in mpg when running on bad KS's and knew that was the case.

I think the harder you run the car (harder you push the "bog"), the gas consumption goes up in quite the non-linear fashion.

[qship96]

Actually Failed KS system does decrease the cruise steady state ignition advance so it does DECREASE MPG on the highway.

That was not my experience at all.....see my results from roundtrip Md to Atlanta where defective KS were replaced along with 133K mile old sparkplugs and 203K old O2 sensors changed......exact same return trip after having all above replaced netted .10 lower fuel mileage{ lets call it even, or NO change whatsoever on 650 mile all highway tripeach way}