Engine Stutter

[australia]

just bought a 1992 ls400 with 93k. ran great for first 1000k, but put 91 octane instead of 93 and now i have a stutter at about 65mph after running engine for a liitle while(30min.). added ber. gas treatment but no help. have not added any new gas yet, but need to soon. is this an injecter challenge, bad gas,filter.HEEELP! engine idles at 800rpm, but one time it stuttered and dropped for a second; just like it does at 65. overall acceleration still great. thanks for any ideas.

[obergc]

Could be a dirty throttlebody, had similar problems with a 93 with 100K. Developed erratic idle and occassional what felt like a miss at partial throttle, ran fine wide open throttle. Put a can of BG 44K fuel injector cleaner in it and cleaned the throttle body and smooth running returned immediately. I believe the throttle body cleaning helped the most.

Curt

[VBdenny]

I'd fill it as soon as possible with premium. The computer is compensating to prevent engine damage from detonation. Like the Caillac Northstars, these engines do not run very well on low octane fuel. Since my wife usually has the car in NJ where they put the gas in your car, I put an extra sticker on the filler car that says PREMIUM so some flunky gas station dude doesn't screw up. The fuel system cleaner never hurts either. I use Valvoline Fuel System treatment ($10US) about twice a year.