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Hey I've been having quiet a few problems with my run around car.
I have resolved most of the problems myself but am stuck on this one and am wondering if anyone can help me out.
It started with the car not starting properly (cranks but won't fire) then I discovered if i put my foot flat on the accelerator it would fire, rev to about 1500rpm and then die. However this problem was very temperamental and it seem to have a mind of its own (starting fine every now and then) also if i was persistent when it didn't want to start, for some reason it just comes good, and after various attempts just start fine or, start, sit at a very low idle(even though my foot was still on the pedal and build up revs until it idled fine)
I manually pulled the codes and I got the code for the idle control valve.
Being only a runabout I didn't want to spend excessive amounts on it so I managed to get a second hand one. This however did not fix the problem.
I continued to drive it with the starting problem when I noticed my thermo fans were coming on too early and my check engine light was again coming on.
I once again pulled the codes and got the code for the coolant temperature sensor.
I bought a new one and installed it last night while doing a service on it. I have now started and stopped it a number of times and the starting problem seems to have been fixed.
However, and this is what has me stumped. I pull up to the lights after driving for a while and the idle is very up and down. When i actually pull up it increases and decreases rpm by about 100rpm quickly. The car is shuddering and almost sounds like its missing. I again pulled the codes and have the code for idle control system malfunction.
I am sick of spending money to fix it when it either doesn't fix it or seems to create another problem.
I'm sorry it's so long but it's the only way I could explain it properly and I don't know if all these problems are related. I'm not so much a Subaru man but this is my daily that is suppose to get me from a to b reliably.
If anyone has any suggestions/advice it would be much appreciated.

your second hand idle control valve could be faulty. If you still have your old one clean it with carby cleaner (don't remove the part that unbolts also known as the solenoid) and put it back on you may find it works again. Or if you don't want to go to those lengths pull the hose of the end of the idle control valve and spray the inside with carby cleaner. let it sit for a little while and start your engine (it might take a little while to start then blow copious amounts of smoke) and while your engine is running without the hose on the idle control valve hit it with more carby cleaner. This will make clouds of smoke as well but should clean your idle control valve.

TOONGA

Hi and welcome to AUSubaru

The IACV fault code doesnt nesseccarly mean the the ICAV is faulty, it could be that something else is causing erratic idle, like a vacuum leak. But because the ecu is having trouble controlling idle, it assumes the IACV is at fault.

Try cleaning the air flow meter by blowing some electrical contact cleaner on the hotwire element. Use the aerosol can cleaner that doesnt contain lubricant.

Hi and Welcome

I would like to know what faults you started off with and how you resolved them. Can you please make a list (of the check engine codes) and give brief description on what you did to fix it.

I would also like to ask, what sort of air filter are you using? and have you recently changed it?

Have you done a service recently and also a compression test?

Did you replace the whole IACV or just the sender unit? same with the Coolant Temp sensor (or the Temp Gauge sender?)

Cheers,
Paul

I have had the old idle control valve off and put a second hand one on. Since a vacuume leak was mentioned I took it off again and made a new gasket for it because I realized the other one was pretty stuffed. I cleaned my airflow sensor and also sprayed some brake cleaner on various hoses and parts around the throttle body to see if the rpm would pick up indicating a leak. This didn't happen so I don't think I've got a leak.
I also tested the resistance across my injectors and it seemed normal.
I ran the test with the green wires under the dash and then checked the codes again.
This time I got code 24: idle control system malfunction and code 31: throttle position sensor circuit.
I haven't had any dramas starting it since I replaced the coolant temperature sensor so I guess that fixed that.
The idle being erratic like I said before when I pull up to the lights ect doesn't happen every time. Sometimes I'll pull up and it's going up and down by almost 1000rpm before it settles to going up and down by about 100rmp after I come to a stop. Other times it will be as if nothing is wrong and idles fine.