Sudden MPG loss!!!
Safety Car
Joined: Mar 2015
Posts: 3,638
Likes: 245
I haven't pulled plugs just yet.... I will also give QCVette's battery idea a try. Usually I always fill up at Costco because the fuel is a little cheaper. I asked several attendants there and they all say their fuel is BP fuel. I also saw a BP truck filling their tanks so I am pretty confident. Just the same though, I have gone to a proper BP station and didn't notice any change.
Also, I should clarify that both cars didn't start this at the same time.... only the same mileage. The '98 is 20,000 ahead of the '99. Both cars exhibited this behavior at approx. 75,000-80,000.
As to the suggestions about O2 sensors.... can an O2 sensor be going bad without giving a code? Like perhaps the readings aren't quite out of the acceptable range, but their really close?
I would like to thank everyone so far who has been responding.... it's nice to be able to bounce problems like this off other owners who have had similar issues
. I really hope we can figure this out!!!
Also, I should clarify that both cars didn't start this at the same time.... only the same mileage. The '98 is 20,000 ahead of the '99. Both cars exhibited this behavior at approx. 75,000-80,000.
As to the suggestions about O2 sensors.... can an O2 sensor be going bad without giving a code? Like perhaps the readings aren't quite out of the acceptable range, but their really close?
I would like to thank everyone so far who has been responding.... it's nice to be able to bounce problems like this off other owners who have had similar issues
. I really hope we can figure this out!!!
Safety Car
Joined: Mar 2015
Posts: 3,638
Likes: 245
Has anyone experienced a noticeable drop in MPG? I have a 98 and 99 (both coupes)... around 75,000 to 80,000 miles, both cars went from averaging 26-30 MPG on the highway to now struggling to get 24 MPG. I have stainless exhaust cat-backs on both cars along with bigger/cold air intakes, but the significant drop happened long after that work was done. PLEASE HELP!!!!.... my green, efficient American 8-cylinder is turning into a gas hog!!!
Perhaps even try shell gasoline and see how things turn out.
Worth a try.
Safety Car
Joined: Mar 2015
Posts: 3,638
Likes: 245
I haven't pulled plugs just yet.... I will also give QCVette's battery idea a try. Usually I always fill up at Costco because the fuel is a little cheaper. I asked several attendants there and they all say their fuel is BP fuel. I also saw a BP truck filling their tanks so I am pretty confident. Just the same though, I have gone to a proper BP station and didn't notice any change.
Also, I should clarify that both cars didn't start this at the same time.... only the same mileage. The '98 is 20,000 ahead of the '99. Both cars exhibited this behavior at approx. 75,000-80,000.
As to the suggestions about O2 sensors.... can an O2 sensor be going bad without giving a code? Like perhaps the readings aren't quite out of the acceptable range, but their really close?
I would like to thank everyone so far who has been responding.... it's nice to be able to bounce problems like this off other owners who have had similar issues. I really hope we can figure this out!!!
Also, I should clarify that both cars didn't start this at the same time.... only the same mileage. The '98 is 20,000 ahead of the '99. Both cars exhibited this behavior at approx. 75,000-80,000.
As to the suggestions about O2 sensors.... can an O2 sensor be going bad without giving a code? Like perhaps the readings aren't quite out of the acceptable range, but their really close?
I would like to thank everyone so far who has been responding.... it's nice to be able to bounce problems like this off other owners who have had similar issues
. I really hope we can figure this out!!!
Thread Starter
Advanced
Joined: Jun 2007
Posts: 63
Likes: 12
From: Altamonte Springs FL
I got sent on a business trip today, so it'll be a few days before I am back home, but I will definitely check a few plugs when I get home.
While I am thinking about it, a co-worker suggested that some cars use a sensor to look at engine temperature to run the engine more rich while cold.... sort of like a choke on a carbureted engine. Anyone heard of something like this on a Corvette motor? The thought was that the computer mistakenly thinks the engine is cold. Might be reaching a little, but it's as valid as anything else I suppose.
While I am thinking about it, a co-worker suggested that some cars use a sensor to look at engine temperature to run the engine more rich while cold.... sort of like a choke on a carbureted engine. Anyone heard of something like this on a Corvette motor? The thought was that the computer mistakenly thinks the engine is cold. Might be reaching a little, but it's as valid as anything else I suppose.
Pro
Joined: May 2014
Posts: 670
Likes: 46
From: Indiana
Engine Coolant Temp sensor provides the data you speak of, but I doubt that both cars sensors would go south at same time.
I suspect either summer blend fuel and/or you've got some higher ethanol content fuel.
I suspect either summer blend fuel and/or you've got some higher ethanol content fuel.
