rough idle? / low idle? bad fuel or maf?

**eggy790** · 15 March 2010, 09:40

hi guys

tanked up on the way to work with v power and noticed at the first set of lights that it was idling 100 or so rpm lower and quite rough and with the loud exhaust you could hear it in the exhaust note also, didnt sound healthy...

althought once you take off it drives perfect.

did it 3 or so times on the 10 mile trip, and then it stopped then did it once more in work car park when cooling down.

any ideas what this is? bad fuel? as i haqd just tanked up or something else.

cheers

99greenwagon · 15 March 2010, 09:58

Quote:

Originally Posted by eggy790

hi guys

tanked up on the way to work with v power and noticed at the first set of lights that it was idling 100 or so rpm lower and quite rough and with the loud exhaust you could hear it in the exhaust note also, didnt sound healthy...

althought once you take off it drives perfect.

did it 3 or so times on the 10 mile trip, and then it stopped then did it once more in work car park when cooling down.

any ideas what this is? bad fuel? as i haqd just tanked up or something else.

cheers

bad fuel is unlikely,i had the same symptoms,it was spark plugs. the prime suspects for this is maf or plugs.

**eggy790** · 15 March 2010, 10:17

plugs have only done 3.5k miles - nggk pfr 7bs

likely to be the maf then?

any harm in driving till it gets worse so i can pin point it better?

cheers

powerwrx · 15 March 2010, 11:37

could be a dodgy batch of fuel seen as you just filled up before it happened, daft question but are you sure it was v power you put in? i put normal in once and it ran ****e, very hesitant at times.

or maybe your car was choking on the price of the V Power you just put in

JDM_Stig · 15 March 2010, 11:45

Quote:

Originally Posted by powerwrx

could be a dodgy batch of fuel seen as you just filled up before it happened, daft question but are you sure it was v power you put in? i put normal in once and it ran ****e, very hesitant at times.

or maybe your car was choking on the price of the V Power you just put in

Or they have put the wrong fuel in the V power tank at the petrol station maybe

**eggy790** · 15 March 2010, 12:02

well im sure i put v power in.. i put in 20ml of nf race formula before it.

its my local petrol station, they have v power on eveything pump, except i normally use pump number 8 religiously lol this time i used 7

i'll see how it runs, if it continues after another tank i'll get a maf off my other car and swap them and see if it changes

powerwrx · 15 March 2010, 12:09

do you normally use nf formular? could be that

**eggy790** · 15 March 2010, 12:15

ive used it for the last 10 tank fulls with no problems

**eggy790** · 15 March 2010, 12:23

p.s. could nf really cause something like this in such small quantities? its mapped for v power.

i just put a bit in for safety as i have loads of bottles at home from when i had my classic

dunx · 15 March 2010, 14:07

It is more likely to be bad fuel, many have none left, you may have got the slime out the bottom of the tank.

I use a different octane booster, but mine has idled poorly recently.

dunx

**eggy790** · 15 March 2010, 14:22

ok no worries, got half a tank left, so will tank it again.

dunx: how does yours idle? its been rough before i.e. shaking but never changed the sound of the car from the exhaust.

this time it revs 100rpm lower at about 500 and sounds like a missfire .. the exchaust note changes every 3 or so secs . kinda wierd

dunx · 15 March 2010, 14:27

That may (?) be a touch of MAF but get rid of this tankfull and see how it goes....

Mine just idled a bit lumpy and slow.

dunx

P.S. plug gaps can cause issues too !

**eggy790** · 15 March 2010, 14:29

ok no worries, i'll keep an eye on it

cheers

K30FOY · 15 March 2010, 17:41

Id say it was the MAF, only coz mine is doing the same (2002 WRX), does throw a CEL on now and again though. But other times, its fine.

joz8968 · 15 March 2010, 17:53

Quote:

Originally Posted by 99greenwagon

bad fuel is unlikely,i had the same symptoms,it was spark plugs. the prime suspects for this is maf or plugs.

lol

**shawn r** · 15 March 2010, 22:21

having problems too, hessitation while boosting, are you getting any of that? starting to think mine is the maf.

Stevesbluewrx · 16 March 2010, 02:57

Must be a bad time of it with the cars at the mo. Possible change in weather maybe?

Mine is doing it but also cutting out when you come to traffic lights or traffic.

Also Ed, maybe worth checking plugs before you pass out at the price of a new MAF. NF can foul the plugs big time over a period of time.

I'm about to change my MAF for the 3rd time in a year!! Great.

Steve

**eggy790** · 16 March 2010, 08:39

hmm i'll have a look at the plugs steve but i dont use a lot of nf for it too foul the plugs, well i would have thought they wouldnt.

i'll run the next 2 tanks without it and see if it clears up.

shaun: not having nay problems or hesitation during boosting though, just idle

just out of interest , how much is a maf for these cars?

o and no CEL lights .. yet..? should i expect one when it gets worse?

K30FOY · 16 March 2010, 08:53

MAF's are expensive new from Subaru (£200+), got a price from CES exhausts £109!! Dont go for Ebay new MAF's, I tried one and it gave up after 2-3 hours. Got a refund though.

Stevesbluewrx · 17 March 2010, 06:54

Quote:

Originally Posted by K30FOY

MAF's are expensive new from Subaru (£200+), got a price from CES exhausts £109!! Dont go for Ebay new MAF's, I tried one and it gave up after 2-3 hours. Got a refund though.

Thanks for the warning. Was just about to order one.

Did mention to the better half about going SimTek........the rest I won't repeat.

Steve

Stevesbluewrx · 17 March 2010, 06:56

Quote:

Originally Posted by K30FOY

Id say it was the MAF, only coz mine is doing the same (2002 WRX), does throw a CEL on now and again though. But other times, its fine.

Can you recall the CEL light code at all?

Cheers
Steve