starts to miss on hills

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  imidazol97 Member Posts: 27,154

  October 2019 edited October 2019

  What kind of Buick is this? What year? How many miles on it? What maintenance items have been replaced?
  
  If it's a 3800 Buick engine, a common maintenance item is spark plugs and spark plug wires. Replacing the plugs with the correct AC Delco plugs, not some other brand, gives the best results. AND the spark plug wires need to be replaced with quality wires that are OEM level--not replacements in a pretty color with a big picture of a zooming race car on the box. Well, I overstate, but I'm sure people get the idea... Stick with OEM.
  
  The low engine speed in higher gears as more power is needed and the throttle opens and more fuel goes into the cylinder makes it harder to fire the spark plug. A weak plug or poor wires easily fail on an occasional shot and you feel a miss. When the car downshifts, the engine speed is higher and the resistance in the plug circuit is less and the miss is gone.
  
  Another factor is that on some applications, the transmission stays in torque converter lockup, in 4th or in 3rd, and you feel the misses or just uneven engine firing more. The computer is programmed to resist unlocking the torque converter or downshifting to 3rd sequentially for higher fuel economy.
  
  One thing to try is to keep you foot on the gas at an uphill approach at lower car and engine speed, then touch the brake pedal lightly to unlock the torque converter. The engine speed will increase and you won't feel the spark plug/wires miss like before.
  
  Or keep the selector in 3rd and approach a similar hill at a lower speed keeping the engine tach at about the same speed as the missing occurs when hitting a slope in 4th gear. The missing plugs or wires usually won't show up in 3rd under similar low engine speed load because the actual engine power required is less due to the gear ratio.
  
  There are other things that can be happening, but this is where I start. With the simplest.
  
  I can't emphasize enough the problems caused by using off brand, not AC Delco, plugs over the decades I've been owning leSabres and reading Buick forums. Spark plug wires are often overlooked. They're good for 100K roughly, then I replaced with AC Delco wires, there are two levels, either works. Be careful to run them as the originals were clipped in to avoid cross over misfiring.
  
  And last the problem may be noticeable but not fatal, if it's what I'm guessing on the engine I suspect you might have. in fact, I recall my 93 leSabre was given a computer update which changed the lockup engine speed for the torque converter. It locked up and transmitted engine roughness at the low engine tach speeds when in 4th gear and under a slight load. So I believe it didn't lock up until about 50 mph after that. Earlier it locked up at 40 or under IIRC. That was long time ago.
  
  Good luck.
  
  
  
  

  2014 Malibu 2LT, 2015 Cruze 2LT,

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