Cold idle E82

[TheWanderer]

So I got into investigating my cold idle issue a bit today.  The past week she's run ok and hasn't given me any issues until the other morning when I fired her up in -10 degree weather.

 

The info given to me prior to this lead me to believe the CTS was the cause, however I'm not so certain that is the case.

 

Here's what happened:  Went out and she fired right up, idled fine for a bit (2-3 min) then died.  When she fires up she idles high then starts to hunt right before dying.  I unplugged the CTS while running, the idle shot way up, then she died.  upon plugging the CTS back in and starting her up, she went back to what she was doing (fire up perfect, idle for 2-3 min, start hunting for it, then die).

 

So, I am wondering (and speculating) about the IAC valve being borked.  It seems as if the CTS is functioning properly, and the plug/contacts are clean.

 

Any ideas?

[Gloyale]

Sounds like MAF or an unmetered air leak affecting the MAF

 

Cold weather can make rubber hoses brittle.

 

Check the intake boot, all PCV hoses and all vac hoses for leaks/loose fitting.

[l75eya]

Stupid question, but we all make stupid mistakes sometimes; you're not out of gas are you?

[Petersubaru]

My IAC is also no good when the weather gets cold, and in very, very cold weather it is absolutely no fun driving at all until once warmed up, then it will run very smooth..the temp sensor has been exchanged and the advance moved a couple of degrees ahead... using my vacuum gauge shows no leaks..needle is study

[ruparts]

hi,

 you didn't say if you have a high idle on your cold start,  then the idle starts to decrease , then hunt , then die.  if you have no high idle on cold start  as you said 2 min i'd say the iac may be  suspect,  but , to me the symptom you described still sounds like cts.  if it doesn't send a proper cold signal to the ecm, the iac won't get the proper signal  to know what it needs to do.  the cts sends a variable signal depending on temp it sees,  they can be partially non functional,  but the iac on spfi are known to stick and therefore not accurately meter the air it passes.  they can be taken off and cleaned.  you might try that and if no results try and test your cts at different temps for readings according to fsm specs.

[TheWanderer]

Not out of gas, still 3/4 tank in her

 

She does high idle when I first start her, but not a terribly high idle (mostly depends on the temps, and if they are low enough I have to feather the gas pedal).  The second day I got her home she didnt do it, fired right up and idled normal, then when the thermostat opened she dropped down.  This was after I ran fresh gas in her and seafoam'd the engine thru the brake booster vac line.  But with the past couple days the temps have dipped down something fierce (negative numbers) and I haven't been driving her (have been starting her every morning and running til she warms up)

 

I really am suspecting the IAC is bad,

[ruparts]

hi,

  it sure could be, the iac valve on the spfi motors have a known history of sticking and being problematic.   i am talking about the valve bolted to the front of the throttle body,  it can be taken off and cleaned  to free up the spring loaded valve plunger which is what controls the air flow through it.   they get a buildup of crud like the stuff in a pcv , same air system source.  anyway usually they will respond to a good cleanup.  another thing is thermostats,, if it pops open with a sudden surge of hot water going out to radiator and cold water coming into engine, this will cause a fast change in the cts and influence the iac which may not respond that quickly.  point here is the factory thermostats are a far superior unit to the aftermarket ones and do a slow open so the motor does not see a wide temp variation (shock) suddenly,   the xt6 unit actually has a dual opening valve which lets about 1/4 the flow through at a lower temp till it's up to running temp, then opens the main valve for full flow.  the fsm says this is so the motor isn't shocked by an inflow of cold water into a warm engine,,  they say this shock can lead to head gaskets failure due to the expansion and contraction from a wide temp variation with other thermostats.   i use that unit in my rx turbo and i am sold on it. 

 # 21200 aa 080 this number might have been supersceeded by now but this from an 88 parts book.

[TheWanderer]

I talked to the previous owner this morning (been in contact with her since I bought the car actually), and she said they've replaced the MAF with one from a junkyard car.  Doesn't rule it out necessarily, but it seems they were on the hunt for the fix to this problem well before I started.

 

She (the car) seems like an ornery lil pain in my rump roast lol.  Wouldn't ya know it, I went out this morning in 5 degree weather and had nothing but trouble getting her to run right (started up, high idled, and died as soon as the idle dropped).  Drove her to work and when it came time to come home, I went out and started her up to let her warm up.  Close to 20 below out, and she fires right up, idles a bit high (to be expected), then drops down and purrs like a kitten. I am so #$@!'n stumped with this its not even funny O.o

[reedbj40]

How much coolant do you have? As stupid of a question as that may seem, my loyale was doiung the same thing. I had tested all sensors and all were in working order, but my radiator had a leak that I hadn't noticed, and I had foolishly gone without checking it. Apparently, the CTS was misreading the temperature due to low coolant level. It would start, then was flooding out, causing stalling.

[TheWanderer]

Good question   It looked full when I checked it, but could very well be low since it was sitting so long.  I also found a small puddle of coolant under the car the other morning after I had trouble getting her to idle and sat with my foot on the gas.  I need to get a pressure tester and see if the heads may be leaking a bit (no coolant in the oil that I can see though, so I'm on the fence about that)