Hi all

New to site but have owned my 2004 STi with PPP for over a year now. Recently car has developed a few niggles after a series of events. The problems that happen both when car is cold and warm are as follows:

• Lumpy performance around 2.5k-3.5k rpm (afterwards though performance is fine all way to redline.)
• When lifting off throttle car very jerky

Recently I had the spark plugs changed for the colder NGK PFR7B ones along with the panel filter. I left the gap at 0.8mm as was recommended to me by local Subaru garage. After this car was fine and running better than before (which it should have been given the state of the old filter!) with better throttle response especially low down.

One morning on way to work around a week after above work was done I got stuck in traffic with little petrol and light came on. Don’t usually take it so low and worrying that id run out with 15 miles of traffic ahead of me and no idea of nearest Shell station I pulled in to an Asda which only had 95 Ron on tap. Stuck £10 in and got to work fine.

On leaving work at the end of the day though I felt something wasn’t right in traffic as around 2-3k revs it felt slightly lumpy – was more evident when I got onto dual carriageway off roundabout in low revs pulling away in 2nd gear from 2.5k and it was noticeably lumpy until it got over 3k revs when was normal.
At first I thought fuel – so I stopped off at Tesco and filled up tank with 99 Ron fuel and then added some Wynn’s cleaner to help rid of any of the fuel. Ran the whole tank down and still getting the lumpiness. Today have stuck in Optimax and also some octane booster – done about 20miles on it and still there but not sure if too soon to notice.

Problem is what has caused it?

• The new Spark Plugs?
• Damaged Coil Packs fitting them?
• MAF sensor? This was all removed to fit the plugs so has something happened with it?
• ECU Reset – I know they run a limp mode after a reset as battery too was off for over an hour fitting plugs. Could something be off with this?
• The fuel - could this be all down to the 95 ron fuel? and that it needs time to clear? Alternatively could the fuel have damaged something?

I did a few searches and came up with some similar problems but no one seems to have finished the thread to say what was wrong!

 

Any ideas?

 

From what you have said i would defo say its a fuel issue, optimax is poo, id rather run on red bull Fill her up with the reccomended v-power and poss reset the ecu, see how ya go

 

sorry thats me showing my age - it was v-power i filled up with i still call it optimax!

Will reset ecu tonight - wondering if was still "learning" after ecu reset whilst the 95 ron was in there and this has caused the problem.....

 

It may well have backed off the ign advance due to the poor quality fuel.. give it a couple of tanks of V-power and normal driving, if it hasn't recified it'self by then, I'd get it to your nearest specialist (not dealer ) to have a look at.

 

Sorry thats the dis-lex-i-a kicking in again, i read 'ultima' as in BP

 

it might be worth changing the fuel filter just in case you pulled anything up from the tank when it ran low. then again some may think I`m talking out my a$$.

I would change it tho just in case.

 

Being as the fuel is sucked from the bottom of the tank anyway, you are indeed talking out of your ***

 

what was the result of this mate?/