Any body experience this issue. Got a new LTZ Tahoe for my wife so now I'm driving her 02 Z71 Tahoe. Parked my 01 Z71 Silverado. We always put 89 octane in the 02 Tahoe. I put 93 in it the other day thinking it was a good idea to help clean out the lines... but it caused the idle to fluctuate badly. It ran ok during acceleration but really rough during idle. It did this throughout until I refilled with 89. Just curious. I did this all the time with my 01 Silverado and it never caused the idle to fluctuate. Any ideas...?
93 octane caused rough idle
- Thread starter ray_z71
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kandywhips504
Full Access Member
bad gas??? maybe had moisture in it?? happened to me last week, at idle it almost wanted to kill and the rpm's would jump up and down bad, but also could have been it got really cold that night and my fuel pump didnt like it
oomindwarpoo
Full Access Member
No point in wasting the extra cash on premium, not gonna gain anything, the compression is too low.
Yuke2K
Full Access Member
93 Octane isn't any "cleaner" than 87 or 89. Your truck was designed to run on 87, so use it! Theres no point in running 93 or even 89 unless you're tuned for it and the engine can take advantage of it.
Octane in and of itself is simply the measure of the gasoline's resistance to detonation. Higher octane is used in cars with higher compression ratios/forced induction so that it doesn't prematurely ignite due to the higher pressure and temperature in the combustion chamber. Think of a diesel - the fuel ignites instantly from the temperature and pressure. In a gas engine, that's the spark plug's job. By using high octane fuel in a car that doesn't need it, you're just going to cause problems like the ones you're experiencing. Your engine can't utilize the higher octane effectively (read: incomplete combustion), so it's choking on it.
If you want to clean your lines out, get a can of seafoam and dump half of it in your tank, and run the other half through your intake. Your engine will thank you, trust me. That stuff is GREAT.
The fact that your Silverado ran ok with it is just proof that each engine is different. You shouldn't run high octane in a car that wasn't designed for it though. You gain nothing, except an increased risk of problems.
Octane in and of itself is simply the measure of the gasoline's resistance to detonation. Higher octane is used in cars with higher compression ratios/forced induction so that it doesn't prematurely ignite due to the higher pressure and temperature in the combustion chamber. Think of a diesel - the fuel ignites instantly from the temperature and pressure. In a gas engine, that's the spark plug's job. By using high octane fuel in a car that doesn't need it, you're just going to cause problems like the ones you're experiencing. Your engine can't utilize the higher octane effectively (read: incomplete combustion), so it's choking on it.
If you want to clean your lines out, get a can of seafoam and dump half of it in your tank, and run the other half through your intake. Your engine will thank you, trust me. That stuff is GREAT.
The fact that your Silverado ran ok with it is just proof that each engine is different. You shouldn't run high octane in a car that wasn't designed for it though. You gain nothing, except an increased risk of problems.
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by the way....Yuke2K, what is the wear pattern like on those Terra Grapplers? I want to match a set of those up with a set of oem chrome 20's. 305/??/20. How often do you rotate them? Seems like I have to rotate my current tires every other oil change (~6000 miles) to avoid bad wear patterns.
Yuke2K
Full Access Member
Yeah, just make sure you tell the neighbors not to call the fire department if you run it through your intake...it makes quite a smoke show! It's fun though. 
Yuke2K
Full Access Member
You know Ray, I just got them about 3000 miles ago at Discount Tire (free rotations for the life of the tires), and got a 4-wheel alignment right afterwords. I'm probably going to head back over there today and get them rotated for the first time. So far they have been excellent, but again they are new enough that I can't really tell what the wear pattern is like quite yet. I figure that if I get free rotations, I might as well take advantage and get them done every time I change the oil.
just read this post.. since i got my yuks i used 89 cuz i have doubt using 87 octane for some reason.. so now its ok to used 87 on my yuks...
for those who use 87 raise your hands pls.. i just want to see how many people who use it.. thanks
for those who use 87 raise your hands pls.. i just want to see how many people who use it.. thanks
Yuke2K
Full Access Member
I actually use 85 octane, but that's only becasue I'm up in Denver. At high altitude, we can get away with it with no ill effects.
At or below sea level, I ran 87 octane in all of my naturally aspirated vehicles. For my supercharged GTP, I ran Shell V-Power exclusively. When I get my tune from Justin, I'll be running Shell V-Power or Conoco/Phillips 91 again. At that point, my truck will be tuned to take advantage of the higher octane and make more power.
For a stock vehicle, I always follow the manufacturer's recommendations. If it says you need high-octane fuel, then by god spend the money on the best stuff you can get. If it says that it was designed for 87, then run 87. Running 89 octane isn't a big deal if you can afford it, since it's only a couple of points above 87...but running 93 octane in a car designed for 87 will do nothing to help the performance, except maybe shave a few pounds off of your wallet.
Worst case is that you end up like Ray, with a truck that's extremely pissed off at you for feeding it the wrong food.
At or below sea level, I ran 87 octane in all of my naturally aspirated vehicles. For my supercharged GTP, I ran Shell V-Power exclusively. When I get my tune from Justin, I'll be running Shell V-Power or Conoco/Phillips 91 again. At that point, my truck will be tuned to take advantage of the higher octane and make more power.
For a stock vehicle, I always follow the manufacturer's recommendations. If it says you need high-octane fuel, then by god spend the money on the best stuff you can get. If it says that it was designed for 87, then run 87. Running 89 octane isn't a big deal if you can afford it, since it's only a couple of points above 87...but running 93 octane in a car designed for 87 will do nothing to help the performance, except maybe shave a few pounds off of your wallet.
Worst case is that you end up like Ray, with a truck that's extremely pissed off at you for feeding it the wrong food.
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