wrxsti280

iTrader: (6)

Heres the story, any help greatfully received.

my car has been stood for some 4 and a half months, garaged, whilst bits and bobs have been done to it, the battery has had to be charged back up to get it started, but the upshot of it being that the car has had a full decat exhaust from turbo back as well as some other bits but nothing else engine related as of yet. the car was running pretty much 100% before being stood and worked on, but now, it seems to be running rough. the car does not pick up as early in the rev range as it used to, but when it does come on boost, it absoloutley flies, defo quicker than before. im assuming that this is down to the reduced back pressure from removing the cat on the downpipe, but when on boost the better flow of gases coming out.

the car seems to stutter when cold, as if not firing properly, there was a bit of what i guessed was piston slap, as it was quite noisy on start up and once warm disappeared to leave nothing more than the constant ticking of injectors. however, when the car is properly warmed up, the engine seems to rock from side to side every couple of seconds or so, there is no pattern to it that i can see, but every few seconds it goes from side to side and the exhaust makes a funny popping noise when the engine does this, this is what is worrying me, as ive never noticed it before.

if someone more mechanically minded can shed some light on this it would be appreciated.

cheers
steve

_________________

wrxsti280

iTrader: (6)

anyone????????

dan83590

Eh up Stokie!!

What 'bits and bobs' did you add on matey?

wrxsti280

iTrader: (6)

exhaust, bit of bling polished covers for fuse box and maf, then the rest of it was stripping interior and sorting out all the cables that run to rear of car and covering with convoluted tubing. got a fuel pump to do, along with injectors and some other engine stuff, but dont want to mess with it anymore until i get this problem sorted

dan83590

Did you alter the lambda sensor at all?

Have you read the ECU error codes?

wrxsti280

iTrader: (6)

not touched the lambda as it is in the headers on mine, and got no engine light on, so im a bit lost, the only thing that has been disconnected and not reconnected is the cat on fire sensor

dan83590

See what codes are stored on the ECU first, then go from there. If only to eliminate things...

wrxsti280

iTrader: (6)

there arnt any codes as the check engine light isnt on, thats why im a bit stuck with it, at least i assume the light has to be on if there are codes stored

wrxsti280

iTrader: (6)

anyone else got an ideas????

all help and advice greatfully received

NUTTYNICK

Have you tried fresh petrol?

MY,k436suy

As above, it may way help.
I'd do an ecu reset and then go from there, cleaning all the likely suspects such as maf, boost solenoid etc. Clean and check plugs, check coil pack(s) etc, there's plenty of options to help eliminate your problem which won't cost a penny.
Johnboy.

dan83590

Double check the codes by connecting the blocks under the steering wheel, there may be some stored code that may help diagnose the prob. If no codes are present then lots of sensors will be been eliminated. There on it's already been said. Wouldn't have thought it is the Boost Solenoid as you say it is boosting okay. Stagnant fuel is easy to check if the car runs, just run the fuel low and fill up. From there I'd check/replace your plugs, make sure the gap is perfect (meaning double check the gap with a gauge, don't just throw them in from the packet). Then look for cracks or arcing from the coils and if necessary replace all 4. Clean/replace the MAF sensor. Check BOV operation, none standard BOV's can seriously affect tick over and fuel/air mix.

Something in the above replies will be at fault. Unlikely to be anything not already mentioned.

Scooby-kid

Remap after full decat?

Scott.

dan83590

If a new map was needed the car would probably be over-boosting at WOT and the car would cut the fuel supply momentarily.

debbiesonic

iTrader: (7)

How long have you ran it for? Remember, if the battery went flat, the ecu will have reset, and will now be "learning" again.
I would take it for a longish drive before you jump to any conclusions.

dan83590

The ECU would have reset itself to factory settings, it doesn't have to learn everything again!!

debbiesonic

iTrader: (7)

They are always a bit lumpy after a reset, Idle can vary, throttle response and spool up are compromised.
Up until the time when the ECU has found the optimal settings, rather than safe settings. The ECU it is learning and adjusting!!

dan83590

I refer you to my last answer...

debbiesonic

iTrader: (7)

Meaning? Do you think it returns to factory settings and then nothing happens?

It returns to the base map, and then begins to learn, in which time it constantly adjusts. Which in turn can lead to slightly erratic running conditions.

wrxsti280

iTrader: (6)

it's running on fresh petrol, it has had a new maf less than 100 miles ago, it had new plugs at same tile, coilpacks have been replaced about a year ago, the more i think about it, the more im thinking it is down to the change in exhaust pressure, and the fact that the ecu is learning again after the battery going flat and resetting it, im gonna leave it as is for a bit, take it for a long run and go from there, hopefully any problems will iron out

dan83590

Exactly that, but without the erratic bit. It may not run at its very best as the ECU would alter itself to best match our lower octane fuel (it's a WRX STI right?), I think describing it as 'erratic' is a bit much. I did plent of ECU resets with my car and not once did it run erratic, if anything it drove slightly quicker until it retarded the ignition a tad.

I still think it's one of the things I mentioned earlier, and if I'm wrong and the problem just goes away by itself...... I'll dance down street naked!!

myblackwrx

iTrader: (1)

Have you actually checked for codes (did read the thread and can't see any mention of you doing it) just becasue the CEL isn't on doesn't mean there isn't a fault,i had a water temp sensor need replacing which didn't bring the CEL on and i unplugged the MAF whilst the car was running,no CEL but the Select Monitor when plugged in registered it as a fault code.

The ecu isn't learning diddly as the parameters are already defined,swapped my ecu for a later model ,drove it for ½ hour (various speeds all legal though) perfectly fine.

dan83590

The OP says the car has been stood for a little over 4 months. Is that long enough for fuel to varnish? Could that ruin an injector?

debbiesonic

iTrader: (7)

Well yes, erratic may be too strong of an explanation, but i've certainly had plenty that idle a tad rough after a reset. It only takes a run out (which at the end of the day, only costs the price of the fuel) to see if it cures it.

As for the ecu not learning didly... Of course it is. Base map is the safe generic ignition map, as you drive it advances the ignition curve, up until it senses any pre-detonation, then retards it slightly. It's just how they work.