This vehicle sat for 5 years. It has a 3.4L V6 with 196K miles. After I got her running a few months ago she ran normally, high idle at start up then dropped back down after engine warmed up. Then some rats chewed up my wife harness to the fuel pump and sending unit. Fixed that and fired her back up. Idles at 900ish when started cold, then slowly climbs to 1700. If I shut it down and wait for awhile, it will rev to 1700 when I start again. Only in the morning when the motor is cool does it ever idle at normal range (which really isn't normal because it should idle high until the motor warms up, right?) basically seems like things are happening backwards now. I tried spraying carb cleaner in the throttle body, no difference. I have read several threads on this topic, but none seem to be exactly like my scenario. Most people get their vehicle to idle normally by either revving really high and letting off the gas or by turning the vehicle off and restarting. Neither one of those works for me. Any ideas?
97 4Runner high idle after warming up
- Thread starter shepnuts
- Start date
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I'd check / clean the IAC valve and throttle body. Thoroughly cleaning the valve and the inside of the throttle body solved all of my high idle issues. It doesn't hurt to clean the MAF since you'll be removing the air intake tube during the process. One tip if you decide with cleaning the valve, use an impact screwdriver like this otherwise you WILL strip the screws holding the valve to the throttle body.
You can also test the throttle position sensor. I'm sure a search will show a How-To. My idle issue was fixed before this point so I didn't bother.
Good luck!
You can also test the throttle position sensor. I'm sure a search will show a How-To. My idle issue was fixed before this point so I didn't bother.
Good luck!
Thank you very much, I will try this and report back!
Ok so now the CEL light is on and I got code P0505 "idle air system". I cleared the code and unplugged the IAC, then started the motor. It threw the same code again. From what I have read there is either a short in the wiring somewhere or the ECM is bad. Has anyone dealt with this before? If the idle air controller is unplugged and I still get the code, does that mean that it isn't the IAC?
***UPDATE***
I unplugged the IAC and started the motor. When it got to temp, the idle dropped to 900, which is closer to normal. So I guess the problem is in the IAC? I haven't taken it off to clean yet because this is my only means of transport and I'm afraid to get balls deep in this throttle body assembly and wind up stranded for awhile.
***UPDATE***
I unplugged the IAC and started the motor. When it got to temp, the idle dropped to 900, which is closer to normal. So I guess the problem is in the IAC? I haven't taken it off to clean yet because this is my only means of transport and I'm afraid to get balls deep in this throttle body assembly and wind up stranded for awhile.
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Are you sure about this? Reason I ask is because I read on OBD-codes.com that if the IAC is bad, the code will not reset when you unplug it. If the code does reset, the problem is a short in the wiring harness or bad ECM.
I know on mine that does not normally throw the p505, it will trigger the code as soon as I unplug the IAC. It will also return in about 15 seconds if I clear the code while unplugged. I guess I shouldn't say definitely, I really only know how my car behaves. It is possible that on another vehicle you could get a different response.
gamefreakgc
Elite Member
If it sat for 5 years, there's a high probability of the coolant passage being all gunked up and it's failing.
OR
There's a short somewhere in the circuit if the car is known to having wiring problems due to rats.
OR
There's a short somewhere in the circuit if the car is known to having wiring problems due to rats.
There was coolant inside the IAC that looked good, the surrounding area was clean and free of gunk or corrosion from what I could tell. I cleaned the IAC and it was pretty dirty, bench tested it and it seemed to be operating well. I traced all wires to the PCM and saw no signs of rat activity. I tested the voltage at the connected for the IAC, 12.4 V at the middle pin with the key on. How else can I test the circuit for a short? After I put everything back together it idled at 600 until I drove it around for awhile and now it idles at 1400. No CEL or codes again yet..
gamefreakgc
Elite Member
I'm not sure how to test the circuit beyond that, unless you can follow the wiring down to the ECU and test the voltage output there. Visual inspection of the wire and harness is probably the best you can do.
If all else fails it will need to be replaced. You could try checking for vacuum leaks as a last resort or maybe cleaning the Mass Air Flow sensor (MAF) but the IAC is really the only thing that controls the idle. If it's not idling right, well, that's the problem.
Edit: Just read the FSM and it said the PCV valve can also trigger the P0505 code. Might as well try it! PCV valve is $5 and the grommet is usually about $3. Worth a shot, they don't last forever!
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Thanks for your help, I really appreciate it.
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