Quote:
Originally Posted by J08M3
I've noticed a noise under hard acceleration, 75%-100% throttle starting around 3,000 RPM. It almost sounds like a slight vibration/rattle sound coming from the engine. Has anyone else noticed anything like this? I'm wondering if it's possible this is engine knock? First thing I tried was a full tank of gas from another gas station to see if there was any difference. I only use 93 octane gas. I noticed no difference between Hess gas where I normally go, and Mobil where I go sometimes. I don't have many other options near me.
Or is it possible this sound is completely normal? Anyone else notice something similar to a rattle under hard acceleration?
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I have been experiencing the same noises with my car as you have. In fact, I was having a problem with my car losing performance only when the car was making that noise. Making me think it was a knocking and pinging, hence the loss in performance, as the ECU would pull(retard) timing attempting to stop the detonation.
I have to comment that my technician really worked hard on trying to fix my car. He checked the fuel quality 1st, low and behold he found a 12-14% amount of alcohol(ethanol) mixed within the fuel. He told me that the car really was not designed to run on a higher than %10 mixture of alcohol in the fuel. For clarification sake I ALWAYS run 93 octanes top tier fuels in my car. This instance I had just filled up at a local SHELL station.
Solution: he flushed the fuel and replaced it with more 93 octane and advised me to drive the car and see if it any better. Unfortunately, I drove the car for 4 more tanks worth and the car had significant power reduction, along with surging are loss of power while the slightly audible noise persisted during the 2500 - 3800 rpm rev range.
Step 2- After continued driving of the car, 4 tanks later. The car was no better. I brought the car back for service. The decision was then made to replace the injectors, under the pretense that possibly the tainted fuel could have damaged them in some way.
Solution #2: I get the car back with the injectors replaced and the car is improved but only slightly. The noise was actually a little louder and as I put more tanks through the car it seemed to be getting worse again. FYI, during this time period I stayed away from SHELL station and used my normal Chevron usage except for my last tank, I happened to use another Shell station, coincidentally one that the dealer uses as well.
This last tank seemed to really get bad and basically it was back to its worst state and making the noise even louder while the car lost power during the noisy area in the tach.
Finally I couldn't take it anymore and brought the car back in, this time he ordered a fuel pump/filter and tested the fuel again. After testing the fuel pressure while driving under different loads , it tested fine. The fuel however was questionable to have too much ethanol ration again. I told him that I just filled up a the very station that they(the dealer) uses to fill up all of their cars. He then told me that he had to replace 335i injectors/fuel pump from fuel that he put in a customers car at that very station. This station happens to be a SHELL station once again. Not sure if this is coincidence are not but this worries me.
Needless to say, this service the fuel was flushed again and the fuel filter was replaced. Now the car has its power back and seems (so far) to be pulling smooth while transitioning thru the rev range BUT i still do here this noise coming from the engine. Now the tone has changed, almost like it is an induction noise are something. Really tough to tell.
I can say this though. I am VERY frustrated with these findings. I cannot believe that this car is THAT sensitive to fuel quality. This problem started when the car had about 1800 miles and at 6500 miles I finally got the car back to running with what seems like normal power levels and health, except for the noise that is still barely audible. To be honest I have driven the car in poor health more than in good health. Pretty sad really.
Granted there may be some link to QC problems with the fuel distributer for SHELL. The technician and myself have both done some research and there is a certain distributor here locally that could cause this problem with the local SHELL fuel as this ONE dist. handles all of the local SHELL stations. Proving this would be next to impossible though.
What pisses me off the most is for the last 12 years I have owned cars that required premium fuel. Porsche 911's/ Mitsu Evo/Mini Cooper S/ VW GTI/ etc. etc. and not one, ever had a problem with any of the 93 octane fuel that I used from my local area gas stations. Why now, why when I finally find the car that I really enjoy and love, would I be subjected to this BS. Not fair I tell you. I can say one thing though, if this keeps up my days will be numbered with my M3 though. Eventually this will start to hit my pocket book/ time/ and patience.
For the time being, I am really worried when it comes time to fill up my car. But I have been trying to stick to brands that I haven't had issues with yet. I will keep you posted as things develop. Hopefully this is my last time I will have this issue but I have a feeling this may be just the beginning.