Sputtering?
- Thread starter Runnah
- Start date
IAC opens an extra air passage in throttle body during cold start conditions, and closes it off once engine warms up.
when it's starting to go bad, the valve does not close off this passage, and you get low-rev sputtering/backfiring and sometimes 2000+ rpm cold idle. at higher revs even with iac pooched, engine runs fine.
there's an electrical terminal test outlined in Haynes manual to check the valve's operation. informal check is to pull the IAC once motor is warmed up...motor off. have your beautiful assistant turn key to ON posisiton (but not start engine) and if the rubber plug on end of IAC motor doesn't extend, it's pooched.
IAC failure is fairly common on high-mile 2.5 engines, enough so that used parts places rarely have em in stock. new one is $250, sorry for bad news!
when it's starting to go bad, the valve does not close off this passage, and you get low-rev sputtering/backfiring and sometimes 2000+ rpm cold idle. at higher revs even with iac pooched, engine runs fine.
there's an electrical terminal test outlined in Haynes manual to check the valve's operation. informal check is to pull the IAC once motor is warmed up...motor off. have your beautiful assistant turn key to ON posisiton (but not start engine) and if the rubber plug on end of IAC motor doesn't extend, it's pooched.
IAC failure is fairly common on high-mile 2.5 engines, enough so that used parts places rarely have em in stock. new one is $250, sorry for bad news!
a subaru drivetrain contains several thousand individual parts.
entropy affects each and every one of them sooner or later. coil packs fail (rarely) and IAcs fail (less rarely) but......
hoo da fark knows what's really wrong with your motor? we are playing click n clack onilne, trying to diagnose things from afar.
entirely possible we are 100% right about your sputtering, equally likely we are 100% out to lunch! :dontknow:
iac, coil pak, plugged cat, gremlins, spooks, and haints...any or all could be your plobrems
entropy affects each and every one of them sooner or later. coil packs fail (rarely) and IAcs fail (less rarely) but......
hoo da fark knows what's really wrong with your motor? we are playing click n clack onilne, trying to diagnose things from afar.
entirely possible we are 100% right about your sputtering, equally likely we are 100% out to lunch! :dontknow:
iac, coil pak, plugged cat, gremlins, spooks, and haints...any or all could be your plobrems
inski
New member
spray water on coil, lots of water. If idle goes to raisin you need coil. If you see arcs you need coil and/or wires. A funky IAC will cause loopy idle and/or stalling at idle or coasting, but not spuddering. Although, Did you ever fix that IAC code you had for a couple years?
Another way to check the coil is to measure resistance (ohms) across matching cyls on the coil using a digital multimeter, and that measurement should be similar to the other matching cyls on the coil. If measurements aren't similar then its yunk. I can't remember what the specific ohms reading should be, but the paired side should be the same as the other paired. I think theres even a line drawn on the coil top to show you the paired cyls.
Misfires kill cats. Misfires will show up as P0300-p0304 codes. Do you have any codes? Has your CEL ever flashed repeatedly? Flashing CELs mean you are currently having a catylist damaging misfire (says so in the owner's manual, and tech manuals). "Things that cause misfires"...theres a post on here somewhere, I remember listing them before.
Another way to check the coil is to measure resistance (ohms) across matching cyls on the coil using a digital multimeter, and that measurement should be similar to the other matching cyls on the coil. If measurements aren't similar then its yunk. I can't remember what the specific ohms reading should be, but the paired side should be the same as the other paired. I think theres even a line drawn on the coil top to show you the paired cyls.
Misfires kill cats. Misfires will show up as P0300-p0304 codes. Do you have any codes? Has your CEL ever flashed repeatedly? Flashing CELs mean you are currently having a catylist damaging misfire (says so in the owner's manual, and tech manuals). "Things that cause misfires"...theres a post on here somewhere, I remember listing them before.
-=Lobstah=-
Active member
Did you get any codes? I just remembered that these symptoms are fairly similar to fuel filler neck/valve issue that i had with my RS. Not a 100% match but similar, I had an annoying sputtering in low RPM range as well. Might be worth checking.