the EVO has been idleing rough lately...its clearly gotten worse as the winter tears on and originally i just attributed it to the cold weather. I did contact my dealer, and they suggested that the winter additives in Massachusetts gasoline are probably causing the rough idle.

any suggestions for store bought additives for me to top off the tank to smooth things out? or is it just a lost cause?

 

Does it idle rough, even after your car's warmed up? because if it does, your timing maybe off.

I would suggest checking your timing belt, pulley inspection and then change your air filter.

Also, try some gas and oil additive, that always helps smooth things out for me.

I use the BMW formula engine additive. I've found it to be better than most additive that they sell on pepboys. You could buy those in BMW parts department, comes in white container and is $4 each.

 

winter gas dont make idle rough man
just more oxygen in the gas
you just burn more fuel

 

yeah, it idles rough well after the car's been warmed. Its only got 7400 miles on it, so i was ready to discount timing / filter issues... i guess ill have to make a trip to mitsu tomorrow...

 

thats not what i wanted to hear...maybe its another issue then...

 

well, when you say idle rough, are you saying the rpm's fluctuation slightly or is it idling higher than normal? or it dips down and shoots up?

 

no, it idles roughly...like...almost as if the eninge is under load (like when you start rolling without giving it enough gas)... the rpms stay constant (1500 when cold, 900 when warm) but the engine just seems to run roughly.


it seems though that 2 others that have gotten gas from the same gas station this week have had problems, both with 93...so maybe it was just a bad batch?

i appreciate any advice you can offer.

 

if you got a bad batch of gas, (which means, it has water in it), your pistons would of cracked by now and you probably couldn't have started your car at that gas station.

Federal regulation wont let gas station have crappy gas filtration system. They must have about 7 filter/safety system as well as water vapor system on their tank and is checked regularly. So you'll know when you got a bad batch.

it could be that your fuel injectors are dirty, which could do this to the engine, or your air filter needs replacement, or it's just the cold weather that's doing it and it just feels like the engines running rough, because the suspension components are a lot rougher at winter in cold weather than summer weather (not very likely that you can't tell the difference between engine and suspension behaviors).

I would go to the dealer of somewhere to check your injectors and have your timing belts checked.

I don't think it's a bad gas.

Oh, and your spark plugs. They maybe dirty.

 

alright....thanks for all the advice... i'm going to visit Mitsu in the morning and see what they find... its good to go in with some ideas of what it could be though, so i appreciate your help.

thankfully i still have my warranty (knocks wood)

 

well the worst case senerio would be that one of your piston is cracked because water got into it, or you have cams...

but I hope it's just simple cleaning up.

try one of those fuel injector cleaner from pepboys for 2 full tanks and see if they make any difference...

good luck.

 

i would avoid going to gas stations that JP Noonan delivers to. You will see the trucks if you are in Boston or south. Their gas sucks. Avoid filling up if a truck is delivering when you are there. Try to find a station that gets deliveries from their own trucks ie. Mobil stations that have Mobil trucks delivering fuel.

Gas is one of the most important things to this car. You have to be super **** about where you purchase it. Mass sucks, and there are tons of crappy no-name suppliers. Fill up only at big corporate stations you can trust.

I have had good luck with the Shell 93 on my last few outings.

 

most of those corporation buy the leftover from BP and Exxon.

what's different about the gas from different companies are the formula of their additive to the gas.

so it's basically the same gas batch, but it's treated a bit cheaper. That doesn't make it a bad gas. Just not as good as the one with super additives on it.

 

Sorry to jack the thread but if the gas station has one pump for all 3 grades and I pick 93 and the person pick 87 before me, will I get some of that 87 in my tank?

 

You'll get some 87 along with your 91. The amount is so small though that it has zero impact.

 

i always use shell V-power (93) and have had good luck...the last 2 tanks though i have realized that im low right near home (where the exxon is) and filled up there for convenience...i dont think ill be doing that anymore