[BrettR]

Did you test the IAC valve by jumping E1/TE1?

I tested it and the rpms get LOWER a bit... On this video go to 3:52

he says the idle speed should get higher.

 

[BrettR]

I tested it and the rpms get LOWER a bit... On this video go to 3:52

he says the idle speed should get higher.

Also, if I pull the plug off the IAC nothing changes and the engine light does not come on.

 

[Apples555]

When you jump the pins with the engine hot, the idle should go higher for a few seconds, then drop to lower base timing. I can record a video of mine if you need. If they don't go higher, IAC valve is not functioning.

 

[BrettR]

Hopefully that takes care of it. I'm not a big fan of throwing parts at a problem, but on the other hand it's good maintenance to replace cap/rotor every now and then. I'm surprised to hear NGK wires would be arching after just a couple of years, that seems pretty atypical.

And yeah I typically also spring for OEM parts as I figure it's worth paying a bit extra for a bit less hassle and worry.

Thanks. Please take a look at the post about testing the IAC valve...

 

[BrettR]

When you jump the pins with the engine hot, the idle should go higher for a few seconds, then drop to lower base timing. I can record a video of mine if you need. If they don't go higher, IAC valve is not functioning.

Sounds like the IAC valve I just got from the junk yard is bad but it looked ok... Would this cause the stuttering idle? When I remove the IAC plug nothing changes with the idle as far as I can see and the engine light does not turn on.

 

[Apples555]

If idle doesn't increase when jumping E1/TE1, your IAC is not functioning. Faulty IAC could definitely cause bad idle, because IAC is responsible for letting in enough air to keep the engine running with the throttle closed.

 

[BrettR]

When you jump the pins with the engine hot, the idle should go higher for a few seconds, then drop to lower base timing. I can record a video of mine if you need. If they don't go higher, IAC valve is not functioning.

This part just controls the idle speed in regards to the temperature of the motor right? It isn't a "necessary" part for the functioning of the motor? If I just press the accelerator a bit when cold, I get the same effect right?

 

[Apples555]

This part just controls the idle speed in regards to the temperature of the motor right? It isn't a "necessary" part for the functioning of the motor? If I just press the accelerator a bit when cold, I get the same effect right?

At idle the accelerator isn't pressed. Bad IAC might stall at stoplights etc.

 

[94RollaDad]

Brett's right though, the role of the IAC is to let a measured amount of air through at idle to increase or decrease idle, and you can accomplish that with the accelerator too. In fact modern gas engines don't have IACs, they have electronically actuated butterfly valves in the throttle body, so the ECU will "push the accelerator" so to speak when idle needs to be increase.

 

[BrettR]

If idle doesn't increase when jumping E1/TE1, your IAC is not functioning. Faulty IAC could definitely cause bad idle, because IAC is responsible for letting in enough air to keep the engine running with the throttle closed.

Brett's right though, the role of the IAC is to let a measured amount of air through at idle to increase or decrease idle, and you can accomplish that with the accelerator too. In fact modern gas engines don't have IACs, they have electronically actuated butterfly valves in the throttle body, so the ECU will "push the accelerator" so to speak when idle needs to be increase.

When I pull the plug completely off the IAC, it's no difference idling or driving. As for now, I might just leave the IAC as is. Not working, it doesn't seem to affect the car's performance. In the winter I'll just hold my foot on the pedal for a few minutes.
Wires: After watching a few Youtube videos to learn how to check resistance, I checked first the resistance of the wires and they're all good. Not sure about the insulation though. The mechanic I said I'd taken it to said the wires were arching.
Cap & rotor: One video showed using fine sandpaper to sand the rotor and cap points. I had just used steel wool. So I did it again and used 320 sandpaper and it did a better job. This made the idle stuttering almost gone but not quite. (The tip of the rotor was rusted to the point of having little tiny holes noticeable after sanding.) I imagine the tolerances are not so great now. I'll keep my new order of cap, rotor and wires and see how that goes. Should run better. I can always send the wires back and get my $95. One guy on another post said his OEM wires have lasted 350K miles!
As is now, the car is running great with the OEM distributor and having sanded the connection points.

 

[BrettR]

 

[DrZ]

I would think disconnecting the IAC would turn the check engine light on. Does the light work and come on when you first turn the key to ON like it should?

 

[BrettR]

When I pull the plug completely off the IAC, it's no difference idling or driving. As for now, I might just leave the IAC as is. Not working, it doesn't seem to affect the car's performance. In the winter I'll just hold my foot on the pedal for a few minutes.
Wires: After watching a few Youtube videos to learn how to check resistance, I checked first the resistance of the wires and they're all good. Not sure about the insulation though. The mechanic I said I'd taken it to said the wires were arching.
Cap & rotor: One video showed using fine sandpaper to sand the rotor and cap points. I had just used steel wool. So I did it again and used 320 sandpaper and it did a better job. This made the idle stuttering almost gone but not quite. (The tip of the rotor was rusted to the point of having little tiny holes noticeable after sanding.) I imagine the tolerances are not so great now. I'll keep my new order of cap, rotor and wires and see how that goes. Should run better. I can always send the wires back and get my $95. One guy on another post said his OEM wires have lasted 350K miles!
As is now, the car is running great with the OEM distributor and having sanded the connection points.

Here's some pictures of the car. It's got a separate electrical system run off a 100w solar panel with 1500w inverter and 100 amp hour deep cycle battery. I've got a fridge for trips that runs off it. The car also pulls a 5x8 utility trailer. SO excellent when needed! Got a Sears car carrier on top for camping stuff. The motor should still have less than 100K. JDM. The barricade tape is so I'm SEEN and don't get hit!

 

[BrettR]

I would think disconnecting the IAC would turn the check engine light on. Does the light work and come on when you first turn the key to ON like it should?

Right, no engine light when pulled. lol Yes the engine light does work and I've replaced several things from it coming on but it doesn't come on when the IAC plug gets pulled...???

 

[BrettR]

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Wish I could find a driver side floor mat. All the other mats are absolutely perfect.

 

[DrZ]

There is a spring in the IAC that adjusts the idle based on coolant temperature, then the ECU will tweak the idle to try to be exactly around 700 or 750, whatever the spec is. So through dumb luck the IAC may be open just about right without the additional ECU control. It may not throw a code until it realizes the idle is not where the ECU wants it to be. With the IAC plugged in does turning the AC on affect the idle? With it unplugged does it not change the idle? That might give you a clue if it's actually working.

 

[BrettR]

There is a spring in the IAC that adjusts the idle based on coolant temperature, then the ECU will tweak the idle to try to be exactly around 700 or 750, whatever the spec is. So through dumb luck the IAC may be open just about right without the additional ECU control. It may not throw a code until it realizes the idle is not where the ECU wants it to be. With the IAC plugged in does turning the AC on affect the idle? With it unplugged does it not change the idle? That might give you a clue if it's actually working.

As stated, it sounds like the idle decreases just a bit when you junction the E1 and Te1. Then when you unjunction them, it comes back to normal idle after 5-10 seconds. Does the same thing with the IAC unplugged. Turning on the AC incrementally decreases the idle speed in tiny amounts as you increase the fan speed. Same unplugged.

 

[94RollaDad]

I thought i was well set up with roof basket and a hitch receiver with bike rack.... but clearly I have met my overlord in terms of "my Corolla IS my utility vehicle"!!

 

[JacRyann]

As mentioned earlier, measure your throttle-plate closed angle. And test and measure your TPS rotation relative to throttle-plate. There is idle-switch that must be closed (zero ohms) when throttle is released. ECU will only control idle-speed using IAC when it detects throttle is closed (via TPS). If idle-switch in TPS doesn't make contact, ECU thinks your throttle is open and it won't adjust IAC. So it doesn't matter if IAC is working or not, it won't be used.

Another very likely possibility is vacuum-leak. Someone reported stumbling and drivability issues recently and after lots of parts replacement and time, it turned out to be disconnected vacuum hose.

 

[BrettR]

I thought i was well set up with roof basket and a hitch receiver with bike rack.... but clearly I have met my overlord in terms of "my Corolla IS my utility vehicle"!!

Ha ha! I call it the "Car-V" cuz it's like an RV. I've also got a bike holder for hitch. I have to have the utility trailer for picking up millet hulls in Asheville. An 800lb pallet from South Dakota. I make and sell millet hull pillows. Best all natural pillow on earth. Millet Pillow - Millet Hull Pillows - 100% Organic!