Check Engine light comes on with 10% Ethanol

[Air_Speed]

Okay, lately, most gas nearby stations have switched to a 10% ethanol mix, but whenever I fill up my Volvo 850 with that, the check engine light comes on almost immediately. The dealer read the codes and said it is an intermittent knock sensor code.

However, when I travel out of the area and fill up on other brands of gas, notably Shell, the light goes off completely. As soon as I put an ethanol mix in, the light returns.

I wouldn't worry much, except that the car also starts harder (cranks a while), runs rougher, and my MPG goes from about 28 on non-ethanol, to about 23 with ethanol in the mix. I don't entirely blame the fuel, but I suspect the car is somehow just having trouble burning it as efficiently. My cavalier gets a very slight decrease in mileage as well (3-4%), but runs equally well on either.

Does anyone know how to solve this problem? The dealer is suggesting a new knock sensor. Will that really fix it, or just get rid of the check engine light? I want my car to run smooth again and get the mileage it should.

What gas is available in NY with less or no ethanol? I normally use Sunoco, Hess, and BJ's, which all have the 10% sign on their pumps here. There are NOCO, Kwik Fill, Mobil, Valero, and Gulf stations nearby that I haven't checked out. Any suggestions?

Thanks!

 

[Craig in Canada]

I'm just taking a stab at this, but you might have a combination of factors.

It's possible that the "winter gas" in your area has slightly lower AKI for whatever reason - ethanol or not. This is what was delivered to some huge local depot and perhaps everyone is drawing off of it. Who says that the fuel "outside of your area" is ethanol free?

What AKI range is your Volvo speced for? There may be a range - recommend X, minimum Y. Perhaps age, carbon buildup, and less-than-spec fuel are resulting in a situation where you are below the minimum effective AKI your ECU can accomodate.

Try filling up one grade up (ie. from 87 to 89) and see if that changes anything, or top off your current tank with something like 91. Run a good fuel system cleaner like Amsoil PI or Redline SI-1 to try to remove some carbon if that isn't part of your routine. (Someone will probably suggest MMO. Although I don't use it, I should probably get that out of the way).

Severe engine timing retard would also explain the mpg drop, as would the switch to "winter gas".

In my area Shell V-Power 91 is the only option labeled as 0% ethanol but this is not the best fuel for my vehicle performance (both power and economy) in my experience.

 

[StevieC]

All bet you your Oxygen Sensor(s) are weak... Saw this happen on a Mitsubishi.

 

[Craig in Canada]

Originally Posted By: StevieC
All bet you your Oxygen Sensor(s) are weak... Saw this happen on a Mitsubishi.


Even though the OP said the code was specifically "knock sensors".

 

[StevieC]

A knock can happen from an improper fuel to air ratio. If the engine was running too lean because the 02 is weak this can cause a knock and a knock code as the timing isn't setup for an expected lean condition.

Just because it is a knock code doesn't mean it is a knock sensor or timing related.

 

[lexus114]

Well if your using regular unleaded in that baby,that could also be some of the problem.But since your ecm is throwing a code that means the sensor it self may be failing.

 

[jmb106]

Originally Posted By: StevieC
All bet you your Oxygen Sensor(s) are weak... Saw this happen on a Mitsubishi.

+1

 

[Air_Speed]

It's actually rated for 91, though only Sunoco sells that grade near here. Usually, I get the 93 grade from Hess or BJ's, or 91 from Sunoco.

This was happening back in summertime too, it just wasn't until a few recent trips out of state and back that I noticed the difference.

Would changing the O2 sensor (if it is weak) help this? I also did try a few runs of Redline SI-1, and also some Valvoline fuel injector cleaner, but neither one didn't seem to help anything.

Actually, it was Shell V-Power (either 93 or 91, I don't remember) that made the light go away. I got it from several different stations in Pennsylvania and Ohio, but none of them gave me any problems.

I also did get some gas from a Getty in Ohio, and my check engine light came on with that too, so it's not just gas in my area, but some are better than others, I suppose. I really never payed much attention to gas brands or what they added to it until this started.

 

[StevieC]

You should be able to change Octane levels in fuel without affecting the engine to the point the check engine light comes on unless the car specifically is rated for Premium only. Any normal passenger vehicle is setup to run on anything available on the continent it is being sent to.

Trust me your O2 sensors are weak enough to cause the problem but not enough to set the CEL that they are malfunctioning.

Replace them. (Pre cat only) and have your ECM reset.

 

[OilNerd]

Originally Posted By: Air_Speed
What gas is available in NY with less or no ethanol? I normally use Sunoco, Hess, and BJ's, which all have the 10% sign on their pumps here. There are NOCO, Kwik Fill, Mobil, Valero, and Gulf stations nearby that I haven't checked out. Any suggestions?


Try the Kwik Fill at 2270 Walden Ave, Cheektowaga. Unless they've changed things in the last two months, you should be able to get straight gas there. NYS requires pump labeling for ethanol blends over 1%, so if there's still no pump label, it's just gasoline.

 

[Air_Speed]

Thanks for the suggestions. I ordered a replacement front oxygen sensor. Hope it does the trick!

OilNerd, thanks for the tip on the NYS law ... I'll be filling up on 0% ethanol in the meantime, but apparently that's just masking the real problem.

 

[Craig in Canada]

Originally Posted By: StevieC
You should be able to change Octane levels in fuel without affecting the engine to the point the check engine light comes on unless the car specifically is rated for Premium only. Any normal passenger vehicle is setup to run on anything available on the continent it is being sent to.



This is why I asked him for the rating on his vehicle. My "normal passenger vehicle" specifies a minimum of 89 and calls for 92. Another less-normal vehicle I owned called for 93 with a minimum of 90 IIRC.

From the extra information he's provided (already running premium, used fuel system cleaners) I agree it sounds like it's more than just the fuel...

 

[sciphi]

Good to know there's still pure gas in Buffalo! I visit there a few times a year, and hate filling up with E10.