Fuel observation

cantdecide · 13-03-2008 4:55pm #1

Anyone know why my car, which has an intermittant slight splutter that I've never fully resolved, runs best of Statoils petrol? Went to Texaco just now and filled up just to prove my theory (been watching the trend for months) and left with a noticeably increased splutter.

hellboy99 · 13-03-2008 4:59pm

Dirty/watered down petrol by the sounds of it, get some redex in your tank (may also need to get injectors cleaned). You ever let your car go to empty and what rpm does car idle at ?

cantdecide · 13-03-2008 5:19pm

I mean it's there most of the time to varying extent (sometimes not at all) and I don't believe it's fueling problem. I've used up a couple of bottles of redex already with no effect, I've changed fuel filter and I never let the fuel run too low. I've never resolved this properly but I want to get the throttle body cleaned and maybe replace the fuel pump.

My observation is that the splutter is least noticeable with Statoil's petrol, for some reason. Can someone explain?

hellboy99 · 13-03-2008 5:35pm

What car do you have ?

cantdecide · 13-03-2008 5:50pm

'98 A6 2.8 117k. (serviced recently, btw) had car for last 10k and problem is there to some extent since I've had it. It's not that bad but I know it could be improved.

hellboy99 · 13-03-2008 6:08pm

Does it misfire ?

cantdecide · 13-03-2008 6:21pm

At it's absolute worst it will almost backfire, like just a putt sound and a momentary blip in power but it has done that twice maybe in the last year. It can go from a period of weeks of near perfect running to a week of slight missing under acceleration and slightly lumpy/ blippy idle, back to near perfect running again. Howver it's generally very well behaved when filled at the local Statoil.

Saabdub · 13-03-2008 6:34pm

If the 02 sensor isn't working properly it can go to its default setting which makes the fuel/air mixture overly rich, this can lead to the engine bogging down and rough idle. The sensor only only comes on after the car has reached operating temp, so it can affect performamnce after the first idle. If you have an OBD sensor you could see if its throwing any codes. Also check the service history and see if the 02 sensor has every been replaced. The usually last about 80-100k.

Saabdub

cantdecide · 13-03-2008 6:41pm

Saabdub wrote: »

If the 02 sensor isn't working properly it can go to its default setting which makes the fuel/air mixture overly rich, this can lead to the engine bogging down and rough idle. The sensor only only comes on after the car has reached operating temp, so it can affect performamnce after the first idle. If you have an OBD sensor you could see if its throwing any codes. Also check the service history and see if the 02 sensor has every been replaced. The usually last about 80-100k.

Saabdub

Did the AFM but no O2 sensors. I've had it plugged in twice but each time everything was ok apparently with only fault codes for the knock sensor.

hellboy99 · 13-03-2008 6:43pm

Always stick to the one filling station, also is your car a 12V or 30V ?

mickdw · 13-03-2008 6:51pm

Is knock sensor not there to help change engine mapping/timing to adjust to different fuel grades. Just pulled that from back of my head so I maybe totally wrong but if im right, Is that not the problem...Knock sensor?

hellboy99 · 13-03-2008 7:00pm

Could be the cam timing is off as you have had the problem for a while.

cantdecide · 13-03-2008 7:00pm

Car is 12V.

That is always what I thought, too but I have been told from several sources, from mechanics to discussion boards that this being wonky wouldn't make a discernible difference.

cantdecide · 13-03-2008 7:01pm

hellboy99 wrote: »

Could be the cam timing is off as you have had the problem for a while.

If this was the case, wouldn't it be running bad permanently and consistantly??

mickdw · 13-03-2008 7:09pm

cantdecide wrote: »

That is always what I thought, too but I have been told from several sources, from mechanics to discussion boards that this being wonky wouldn't make a discernible difference.

Are you talking about knock sensor? If its giving a fault code, Get it checked/sorted

hellboy99 · 13-03-2008 8:12pm

When you got it serviced was the plugs and coilpack changed ?

cantdecide · 13-03-2008 8:42pm

Plugs yes, coilpacks no. I think I know what's coming next:D Again, if this was the problem, it shouldn't be the case that the fuel I use causes it to get better or worse.

hellboy99 · 13-03-2008 9:06pm

cantdecide wrote: »

Plugs yes, coilpacks no. I think I know what's coming next:D Again, if this was the problem, it shouldn't be the case that the fuel I use causes it to get better or worse.

You will always get varied preformance & milage from different filling stations, but as you said in an earlier post, "intermittent slight splutter that you never fully resolved" so it's not just a fuel problem.

What all was done and checked when you had it serviced ?

meathstevie · 13-03-2008 9:09pm

From my own observation : the Statoil lorry delivers to Tesco in Finglas after or before delivering at Statoil a mile further out the North Road.

Fuel observation

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