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Ethanol and Rough Idle?

 
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Old 18 Mar 2010, 11:46 am
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Default Ethanol and Rough Idle?

Every once in a while after I've filled the tank I'll notice a period of 'rough idle' when sitting at a light or in traffic. The RPMs normally idle around 750, but surge quickly to 1000, drop to 500, and then settle back at 750. It will do this in cycles as you are idling. It doesn't stall, but shudders like it wants to.

I usually use the same few gas stations, but I've noticed that every time I experience this problem it's after I've used a different station. If I get the gas the evening before, it's doing this the next day. When this happens, I'll go to the gas station I usually go to and refill the tank and the problem goes away.

This happened again this week and I noticed that the gas station I used had Ethanol added to the gas. The station I usually frequent is Ethanol Free. I've been attributing it to certain gas stations (thinking contaminants or something), but didn't think about additives.

Has anyone else experienced problems with gas w/Ethanol and idling? I've seen that it could affect mileage, but didn't know if it could cause other types of problems too...
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Old 18 Mar 2010, 12:56 pm
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Default Re: Ethanol and Rough Idle?

Quote:
Originally Posted by NewPTCruiserInPA View Post
Every once in a while after I've filled the tank I'll notice a period of 'rough idle' when sitting at a light or in traffic. The RPMs normally idle around 750, but surge quickly to 1000, drop to 500, and then settle back at 750. It will do this in cycles as you are idling. It doesn't stall, but shudders like it wants to.

I usually use the same few gas stations, but I've noticed that every time I experience this problem it's after I've used a different station. If I get the gas the evening before, it's doing this the next day. When this happens, I'll go to the gas station I usually go to and refill the tank and the problem goes away.

This happened again this week and I noticed that the gas station I used had Ethanol added to the gas. The station I usually frequent is Ethanol Free. I've been attributing it to certain gas stations (thinking contaminants or something), but didn't think about additives.

Has anyone else experienced problems with gas w/Ethanol and idling? I've seen that it could affect mileage, but didn't know if it could cause other types of problems too...

I have been getting worse mileage from the BP station verse the Mobil station. I'm convinced it's ethanol related. I don't get a rough idle though. Maybe it's time for some plugs and wires if your PT is really sensitive to the ethanol, unless maybe the computer has to readjust or something????
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Old 18 Mar 2010, 04:29 pm
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Default Re: Ethanol and Rough Idle?

Smarter people than I have figured out that the higher percentage of Ethanol in the gas, the worse the mileage. We fuel at the local Mobil in St. Petersburg, FL. When they shifted from Ethanol-free to 10% Ethanol, our vehicle mileage dropped by just about the same precentage. This happened in a diverse collection of vehicles: an '04 PT (N/A auto.), BMW Z-3, and an old BMW motorcycle.
While reading forums, I've noticed many PT'er voicing problems with BP. Can't address that as the only time I've used BP is when we've been in Georgia & can't find a Mobil. BP in that state seemed fine. The brand of gas that HAS caused some problems around here is Citgo.
Forum member Dino has great suggestion: new plugs and wires. The factory wires tend to be less than spectacular. A change of plugs & wires cured our rough idle/surging problem. NAPA wires good. Check this forum for information as to the procedure.
Good luck....drive on!
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Old 18 Mar 2010, 05:12 pm
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Default Re: Ethanol and Rough Idle?

From all I have read the ethanol is a not so good addition and usually will drop the miles per gallon and cause the car to run rough again from what I have read they add a lot of filler to the gas and then hit it with the ethanol to get the numbers back up to93-or whatever around here it is Casey's that is big time on the ethanol stuff---me id try to run a few tanks of no ethanol and see if that helps
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Old 18 Mar 2010, 07:14 pm
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Default Re: Ethanol and Rough Idle?

I second the idea of plugs & wires - the ethanol may be just enough different to cause the ignition problems...
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