Have what i think is a misfire when the car is started from cold,pops and bangs as tho its only running on 3 cylinders,after about a mile it clears and runs smoothly even on boost, but the same thing will happen next morning or a couple of hours later when started. Any ideas,also shows no faults with ecu check cheers mark

 

come on fellas, somebody must have an idea,getting desperate

 

What year car is it?

 

faulty temp sensor?

 

Same happened on my sti 95 Turned out to be the lambda sensor

 

pretty sure its not the temp sensor had one go, different symptoms,the car is a 95 wrx , lamda sensor sounds an option any ideas how to check

 

i have an sti 99 GF8 and apparantly the misfiring on my car was due to the dump valve

 

havent got a dumpvalve on mine so counts that out

 

have you check the leads and pluggs?

 

To check Lambda sensor, read posts #8, then # 6 of this thread... https://www.scoobynet.com/general-te...tic-codes.html

 

information very informative will check tomorrow ,thanks, if knackered then to decide expensive or cheap version

 

Well, the cheapo ones work... but could fail in 6 months (according to one well known specialist, anyway). Whereas the OEM one - in my case at least - lasted c.15 years! Okay, so quite a lot of money at c.£200, but once fitted, it'll outlive the car...

 

tested the lamda,signal on multimeter stayed at constant reading, take it that means it is no good

 

Yep. If working fine, then the meter's digital display should cycle up and down between 0.1V and 0.9V (my recent new OEM one cycles between 0.04V and 0.82V) - it should be obvious to observe.

So yes, you need a new Lambda, whatever. BTW it won't harm your engine, as when they fail, it runs rich anyway. But get a new one asap, as obviously you're wasting fuel whilst it's not working.

 

thanks for help,the multimeter i used i was told is not accurate enough will have borrow a digital one and check it

 

Well an analogue one's needle would swing back and forth, if Lambda was okay. But yeah, hook up a digital one. It'll prob read low to mid without cycling i.e. static, anywhere between c. 0.3 - 0.5V

 

back to square one, lamda working fine,try to explain problem better,starts fine wether hot or cold,when cold runs uneven pops and bangs until about 5 minutes later when all returns to normal, no uneven running ,idles fine boosts fine and drives well,also no excessive fuel consumption

 

Right, so effectively, your car is 'missing' when warming up to normal operating temp. Seems to suggest a weak spark having trouble able igniting the warming up rich fuel/air mixture. Could be plugs... could be coilpacks ...