hi guys i need your help jumped in the impreza (my99) this morning and it started fine but after about a mile it started too miss badly under acceleration and the tick over was dropping between 25orpm and 800rpm, i have changed the MAF BUT ITS STILL THE SAME any suggestions please.

 

Dealer/speciallist and get it on a diagnostics machine, far cheaper than replacing the maf (new I take it?) O2 sensor, coolant temp sensor etc

Tony

 

have you checked your HT leads or your coil packs.

 

yes mate all checked..... its all ok when cold but when the temp rises if you put your foot down there is a lot of missing

 

have you run it low on fuel? it might have dragged some crap through from bottom of tank and just need some engine treatment putting through and/or new air and fuel filters just some of the cheaper possibilities for you to try! good luck fella hope its nothing too serious

 

Its going to be far cheaper to just get your car put on a diagnostics machine at a dealer/speciallist, this could cost you coil packs, and those aint cheap
Dealer..... (or dearer if you just keep replacing items)

Tony

 

Split or loose boost hose??

I presume you don't put your foot down when it's cold and wait until it's at normal operating temp. If you're struggling to get it above 3000-3500rpm and it starts missing and spluttering like a goodun then it will be boost hose, equally that could also cause rough tickover.

If it's ticking over rough and doing nothing more than missing a bit when hot then it could be O2 sensor as you've already changed the MAF. MAF and O2 sensors don't always throw a cel when faulty. It needs plugging in to a laptop or diagnostic kit to see if the O2sensor is registering.

Coolant temp sensor normally causes startup and rough running problems when cold then car runs OK when hot.

 

to be honest dont boot it much at all. the garage i have it at now have checked the coil pack and its ok so they are looking at the o2 sensor as we speak they dont think its the boost hose, it is ticking over when hot and only a small miss, but when trying to go over 40mph its missing like f*ck

 

I don't know about 40mph but what rpm is it missing at??

If they have checked all the boost hoses what about the Air bypass valve where it bolts onto the intercooler, is it bolted down properly. Vacuum pipes, are any of those split or leaking?? Have a look underneath the intercooler at the solid pipes that bolt onto the intercooler ports for the Y pipe. A customer of mine had a leak from one of those because it wasn't bolted down to the intercooler properly either.

If your garage isn't a Subaru's specialist they may not pick up on things like that as they won't really know Subaru's. I've known Subaru dealers to miss stuff like that as well, but then they aren't specialists either.

 

Coolant temp sensor?

 

Sorry to jump in this thread, any ideas/pics where the coolant temp sensor is on a 2003 sti?

Cheers anyone