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Discussion Starter · #1 ·
I'm trying to figure out why my R's power feels so sporadic. Some days it'll push me back in my seat, but sometimes it feels dog slow. Slower acceleration, and occasionally sporadic - solid acceleration, momentary pause, resume acceleration.

Here in CA we're relegated to 91 octane gas. Last year I experienced where my normal fill ups at Chevron produced very consistent good power, but fill ups with 91 octane at the "cheap" gas station on the corner caused a notable performance drop. I even checked with the county office of weights and measures, and they checked the octane of the gas and confirmed it was 91 octane. Weird eh?

Lately the car is running kindof sluggish with Chevron 91 octane. I'm open to the possibility there might be some sensor problem, but I just had it in the dealer and they replaced the MAF sensor for some other symptom. No check engine lights, and they didn't get any other failure codes.

My prime suspect is octane and the anti-knock sensors causing the engine to throttle back. Easy to test - find some >91 octane gas and fill up.

Anyone else experienced similar problems, and are there known fixes>

-Boyo
 

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Re: Power woes... Octane, oxygenated gas, sensors, what else? (boyoconnor)

I have only been buying 91 Shell down here and filling up with 100 every once in a while to get the mix better than 94. After that, the car rocks. Other than that, no issues.
 

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Re: Power woes... Octane, oxygenated gas, sensors, what else? (boyoconnor)

I was test driving a buddy's R, and it was similar. Very slow, much slower than my tuned T5. It was also cutting off once in a while at 2000-2500 rpm, like it had a fuel pump or pressure sensor problem. MAF was checked by the dealer, and was fine. I logged data from OBD2, but did not find anything special with the low sampling rate. Then I gave it a reset cause could not figure out anything else. It got faster but was still sputtering at times. The car was running Shell 91 octane, and the temp was at low sixties. We will need to look under the car, since it has been in close contact with the ground and the subframe was dented and changed. maybe O2 sensor or something in the exhaust system has been also damaged or loose.
 

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Re: Power woes... Octane, oxygenated gas, sensors, what else? (boyoconnor)

Quote, originally posted by boyoconnor »
Lately the car is running kindof sluggish with Chevron 91 octane. I'm open to the possibility there might be some sensor problem, but I just had it in the dealer and they replaced the MAF sensor for some other symptom. No check engine lights, and they didn't get any other failure codes.
I would suspect the winter blend that we are still being force fed.

Quote, originally posted by boyoconnor »
My prime suspect is octane and the anti-knock sensors causing the engine to throttle back. Easy to test - find some >91 octane gas and fill up.
Uh, I think you mean find some 100 octane racing unleaded gas.... That (100 octane racing unleaded) will definitely cure the performance blues.
 

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Discussion Starter · #5 ·
I'm thinking more a blend of 91 and 100 to get up to 93-94. No real need to run pure 100 octane (fun though it might be).

Interesting about the damaged subframe...very similar symptoms. And I did have a chance encounter with an aluminum ladder at speed a year ago.
It went right under the middle of the car with a huge crunch - but no visible damage. Dealer inspected it but couldn't find anything that would keep it from being road worthy. Doubt they inspect the wiring closely...worth checking out.

Come to think of it I had a Porsche 914 (OK, don't laugh...) that did something like this to me once while entering a freeway. Traced it back to a loose coil wire. Ran smooth at constant speed, sputtered under acceleration. Hmmmmmmmmm....

-Boyo
 
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