1993 Chevy Corvette engine misses

VETTE

MEMBER
1993 CHEVROLET CORVETTE
V8
2WD
AUTOMATIC
85,000 MILES

Hello, My 93 Corvette generally runs very well. Lots of power and nice take off. The engine does miss between 45 and 50 mph. I notice if I am accelerating hard it goes right thru 45 and 50 just fine but it does not like to go down the road between 45 and 50. Seems to get worse if I use a fuel other than a 92 octain. Also I notice if I drop the automatice transmision down to drive instead of the overdrive, and increase the rpm, it does not miss. Could it be a problem with vaccuum advance?

Saturday, July 4th, 2009 AT 2:18 PM

1 Reply

DR LOOT

MECHANIC
2,311 POSTS

Well, this isn't my specialty, but since your post has been here so long, I'll give it a try.

When you drive a fuel injected car at partial throttle in the range you mentioned, it tries to use the oxygen sensor to to lean out the mixture for optimum economy. When you give it more than 2/3s throttle, it goes strictly by the fuel map in the computer and doesn't try to lean it out. In this situation, the engine runs quite a bit richer. Your engine miss is probably either a misfire or detonation. Lean mixtures detonate and misfire easier that rich ones. So, I would look at either your oxygen sensor or your knock sensor. A bad knock sensor would let the computer advance the spark too far and create detonation which would be less pronounced with 92 octane gas. So my first choice would be the knock sensor. However, it's probably easier to change the oxygen sensor, and it's more common to have problems with the oxygen sensor, so I would start there. Your car will probably run better with a new oxygen sensor, anyway.

Good luck.
Dr. Loot's Assistant

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Monday, August 3rd, 2009 AT 9:58 AM