Wondering if I created a problem or if it’s just circumstantial?

May 24, 2019
Ontario Canada
I normally run premium Costco 91 octane alcohol free fuel for the LeSabre. Although the 3.8 was engineered to run on 10% ethanol and you can run it on 87 octane, I like the added fuel mileage and theoretical higher detergent levels of the premium fuel. I basically run this all year long and then once a year, I run 10% ethanol Regular grade Costco to absorb any moisture that might have collected in the fuel tank over the last year. I did this last week and about two days afterward I got a flashing check engine light that then turned solid while I was heading back home. The car did not strand me but has a slightly rougher idle and acceleration from a standstill and is a little sluggish off of the line until she gets going. It is easy to notice because this car has a wonderful torque curve and a remarkable smoothness about it befitting to a car with the Buick name on it. I decided that the time has finally come for me to order my own OBD II reader and so I have one of those Bluetooth “BLUE DRIVER”s being shipped to me and I should have it by Monday. I suppose my question is do you think switching from a years worth of premium back to 87 would have caused this since I know the car’s computer is designed to adjust for different octane levels. Or maybe it is just a random thing and the OBD reader will give me more info if I need to replace something like a MAP sensor etc. Notice in the photo I attached here with all of the dash functions that everything has been operating normally. When I first saw the light, my first instinct was to look at my dash readings and everything looked fine including oil pressure, temperature, RPMs etc. could be that the car’s computer is giving me a heads up that something needs adjusting or replacing? Does anyone have any theories as to what it could be? I guess that’s a loaded question and it could be just about anything? FYI, I am the second owner of a soon to be 23-year-old car that has been treated like royalty all its life and gets quite a few offers whenever I take it to get any kind of service. With only 90,000 miles on the odometer, your girl should have quite a few years left in her. I am not a senior citizen but I i’ve always driven like one so there’s that too. 🙄

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Yeah your ethanol slurped up some water.

Maybe in future throw a gallon of E10 87 in with every tank.
Coincidence. From what you describe, something has let loose in the emission system, probably due to age. When cars sit awhile and aren't used for driven hard much, things tend to get alittle upset when heated up again. Your statement: "Or maybe it is just a random thing and the OBD reader will give me more info if I need to replace something like a MAP sensor etc. Speaks volumes.
The OBD II reader is the way to go, anything else is a guess. My guess FWIW is the EGR valve is sticking. Our '03 Park Ave had the same symptoms as your LeSabre at approx. the same mileage and it was the EGR valve that needed to be replaced. Not expensive and an easy part to replace.
Although I wonder if you had built up water in the tank, the solution to that would've been to run E10 all along. That 3.8L does not need premium nor ethanol free gas. I've had 3 vehicles with that engine and none did.

You've not mentioned what is factory vs replaced, but at that age, I'd have replaced the spark plugs and wires at least once, and although some people call those a bulletproof engine, they have a couple of weaknesses, the upper and lower intake manifold gaskets, as well as the plastic intake manifold itself if it is not the newer design with an insulated, smaller EGR return tube that keeps the intake manifold from overheating, getting brittle and falling apart to cause a coolant leak at the throttle body passage. Some people just plug off the throttle body passage to avoid the issue in the future but in Canada it could be useful to keep it for de-icing purposes. Due to this, at the very least I'd check the oil ASAP, as it can eventually cause hydrolock and damage the engine.

As others have already mentioned, no point in speculating rather than using a scan tool to pull codes, then if the codes are not clear enough, a tool showing live data running.
If the check engine light was flashing, that means it was misfiring bad enough to do damage to the cat. Now to just scan it to find out what’s causing the misfire.
I don’t follow the logic for you to use e10 once per year... If you’re worried about moisture use a gas line antifreeze to rid the system of any moisture. Ethanol attracts moisture, so unless your using it all the time I’d skip this routine in the future.

A simple scan from and OBDII should get you headed down the path to fix it.

Just my $0.02
I don’t follow the logic for you to use e10 once per year... If you’re worried about moisture use a gas line antifreeze to rid the system of any moisture. Ethanol attracts moisture, so unless your using it all the time I’d skip this routine in the future.

A simple scan from and OBDII should get you headed down the path to fix it.

Just my $0.02
Meh, gas line antifreeze is usually just methanol instead of ethanol and it also attracts moisture (which is how it works). Granted, coming in a little jug it is less likely contaminated with water in the first place.
Everything on the car is original from new except for the coils which were replaced at around 35,000 miles. At 45,000 miles, I decided to go ahead and do the replacement for the intake manifold along with the lower intake manifold gaskets. These were all of the newer design and are superior to the original GM manifold and gaskets and I believe even better than the GM replacement original design. I went ahead and did this proactively given the natural course of events that happens due to this poor original intake manifold design. I replaced the PCV at around 70,000 miles “just because“. Fuel filter was replaced at 75,000 miles and was mercifully simple because it sits along the rocker panel and not inside the fuel tank. (I wonder if this was one of the last generation cars to have a fuel filter outside of the tank?). I will do the OBD check this coming week and follow up here with what I find. I will also investigate the EGR valve so thank you for the suggestion there. One of the good things I have noted about owning this vehicle is that it has been remarkably expensive to maintain an even high-quality aftermarket parts or not all that costly. The entire intake manifold replacement procedure ended up costing me very little in parts and I think it’s due to the sheer vast number of vehicles that GM put this engine into and for how long it was in production.
Low Miles. I would run the tank dry first before you go start replacing any parts. Chances are the ethanol blend picked up some water off of the bottom of the tank and ran it through your engine. Go back to premium and mid grade once it is close to empty.

After you check the codes, do a reset and keep driving it to see if any of them return.
1. Scan for codes and use the appropriate diagnostic strategy to determine the issue and fix.
2. Start using 87 octane - all it needs
3. Run a bottle of PEA detergent fuel system cleaner (gumout, techron etc) just before every oil change goes a long way for fuel system maintenance
Likely a misfire and resulting stored code, unrelated to your fuel choice. Fuel would effect all cylinders typically and I bet you've only got codes for 1 or 2.

As others have said, your fuel choice is costing you money in the long run - I'd bet you get the same fuel economy on regular fuel and only slightly less on e10 and at a minimum, not enough increase in mpg to justify the added cost of premium.
Well my BlueDriver came and I must say it was the easiest thing to hook up to the LeSabre. Here are some screenshots of the reports he gave and it looks like it so it’s showing a misfire on cylinder two. Sometimes the check engine light stays solid but I took it for a short neighbourhood drive today and it started flashing again and I still have a subtle but consistent hesitation when I first hit the Excelerator and then the engine appears to drive normally. Here are some screenshots of the OBD scan findings. The original owner replaced the coils on the car sometime ago but I have no idea what the quality or brand wise. If I end up replacing a coil, should I replace all three or just the one for cylinder two? Also, I priced the ignition coils for this car on Amazon and I can get either a Delphi brand or an AC Delco professional/gold brand. The AC Delco is actually more expensive but it looks like the Delphi is still US made. Or does any of my hair splitting make a difference really?


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Well, I did a little more research at Amazon and discovered that the AC Delco professional a.k.a. gold branded coil is made in Poland and the Delphi unit or Delphi branded unit is made in China. Wondering if there are coils made for this engine anywhere in North America?


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