My 95 STI is running really rough when cold, when you try to pull away it almost stalls, you have to give it a few revs just to get it moving. It carries on running rough with loads of hesitation until it gets up to proper running temp. I am going to change the plugs cause they haven't been done for a while. If this doesn't work, where else should I start looking?

 

Water temp sensor. The ECU relies on this to tell it what the water temp is in order to provide the right amount of warm-up enrichment, idle, boost etc...etc...

If this is faulty then you will experience rough cold running and possibly cold start-up issues too.

 

i agree with the gent above-my car was idling lumpy and especially from cold-i did a check 4 error codes and it came up water temp sensor so changed it mon and all is well now-mine was also using more fuel-i dunno if u think yours is

 

Go for the spark plugs and gap them correctly and this will sort your problem, too many people go too indepth when its not required (as above)

 

TBH it is so crap on petrol I don't bother to check how many MPH it's doing just fill it up when it's empty. Thanks for your help, don't suppose you have part number to hand, and is it easy to get too and change?

 

Granted plugs can affect cold running but failing plugs usually fail all over the range, from cold running to high speed running also.

change the water temp sensor 1st before the plugs (it will be quicker also than changing 4 spark plugs on a flat 4 in the scoob)

 

I just changed mine this week was stalling when cold but ran as good as normal when at working temp, put new ones on gapped them for 0.65 and everything is now fine, so cheep option take off windscreen washer bottle and regap all plugs takes 20 mins tops and no cost (if you have sparkplug socket and t-bar)

 

part no 4 coolant temp sensor is 22630AA041 if u want genuine subaru part-i wont lie 2 u mate its a bugger 2 fit,its located by no3 cylinder and there isnt a lot of room down there-good luck tho and i hope u get things sorted-bye the way it might b worth checking 4 error codes 1st

 

Thanks for all your advice. I tried the plugs a few weeks ago and although it ran a bit smoother it didn't fix the cold running problem. Finally got round to changing the Temperature sensor this morning and it has fixed the problem. Now starts much better when cold and runs smoothly. It was a right bugger to change but all it cost me was £9 for second hand sensor and some skin off my hands. Interestingly it wasn't showing the temperature sensor as a fault, infact it wasn't showing any faults.
Thanks again!!!!!!!!!!

 

Glad it's sorted