Idle hunting issue

[Durandal]

What would cause my cold starts to not idle high at all? Right now my cold starts the same as hot starts and idle at 900 instead of over 1k like it should. The IAC is used after it warms up right? Or do I have that backwards.

[pwpanas]

Originally Posted by Durandal

What would cause my cold starts to not idle high at all? Right now my cold starts the same as hot starts and idle at 900 instead of over 1k like it should. The IAC is used after it warms up right? Or do I have that backwards.

The IAC is open during starting and cold-engine operation. Throttle plate is sealed shut unless you press the accelerator. There should be no vacuum leaks other than the IAC. In other words, the IAC is the only path for air into the engine, so it must be open for initial idle. While cold, the idle rpm is higher (so the IAC is actually open its widest during cold idle); a/f is also richer during cold/cool engine conditions. The IAC closes a bit after the engine warmed up to reduce rpm.

[Durandal]

After more troubleshooting I'm still stuck at the same spot with a cold start idle around 500-750.

*Cleaned idle air control valve and even opened up the inside of the stepper motor which was clean. Checked the stepper motors bearings and that the spring was good. Did resistance checks on the IACV and they were reading 20.5 ohms.

*Checked coolant temp sensor resistance when cold and it was 2.1k ohm

*Cleaned air intake temp sensor and checked the reading on it when cold, it was 2.3k ohm

*Checked my coolant by measuring the voltage between the negative of the battery and the coolant at the rad cap. It read 0.13 vdc, 0.1-0.5 is supposed to be good.

Is there anything else I can try? I'm not completely sure it isn't the motor on the IACV but buying a new one just to test is $300+ Also really hoping it isn't the ECU on its way out.

*edit. After resetting the ECU and having to keep it from stalling by hold the accelerator in a bit, I managed to get it to idle by itself at 500 RPM. I went for a drive and then let it sit for a couple hours. Tried to start it up later and was having a hard time, it was turning over fine but wouldn't start. It eventually started and revved up to 2300 RPM and started to hunt from 1k to 2k again like it was a couple of weeks ago. I'm really thinking the IACV is bad.

[Durandal]

Pulled all my spark plugs today, and they were all soot black so I cleaned them with a wire brush and some brake cleaner (they are iridiums with less then 10k on them).

I tested my intercooler piping with a homemade boost tester and it wasn't leaking.

Took the car for a drive after resetting the ECU. It started up cold at 2500 RPM and slowly came back down to around 1800. While driving I noticed when the clutch is pushed in the revs bounce from 1000 to 2000 continulously. (An ongoing problem that comes and goes that i've been trying to solve)

Come back to the house and right before I shut it down the MIL and CEL come on. I shut it off thinking that I will have a code that will point me in the right direction. Put my paper clip in and turn the key and my CEL light isn't flashing just on solid with my "SLIP Cont off" light flashing. 30 mins later I try to check the codes and the CEL light is flashing steady telling me there is no codes.

I start looking into my electrical system checking the plugs at the ECU which look fine, they are tight and none of the pins are bent. (The car is pretty much stock)

Upon looking at the large bundle of wires that come through the firewall from the ECU I find this.


There four wires (3 black and red stripe one and 1 thicker black one all spliced into one black and red wire and also another 2 wires spliced into 1 where the blue electrical tape is. That's not standard I'm assuming?

I had a greddy emanage ultimate that I used to have hooked up only for the speed limit removal and speedo adjustment for bigger rims. I disconnected it awhile ago trying to eliminate possible problems while troubleshooting but it wasn't the problem. I'm thinking I could hook it back up and use it to datalog some data to troubleshoot with although I've never used that datalogging part of the EMU, hoping its straight forward.

Anyone have any ideas?

After looking at some electrical diagrams, I'm starting to think I have some grounding problems.

[pwpanas]

Originally Posted by Durandal

Pulled all my spark plugs today, and they were all soot black so I cleaned them with a wire brush and some brake cleaner (they are iridiums with less then 10k on them).

I tested my intercooler piping with a homemade boost tester and it wasn't leaking.

Took the car for a drive after resetting the ECU. It started up cold at 2500 RPM and slowly came back down to around 1800. While driving I noticed when the clutch is pushed in the revs bounce from 1000 to 2000 continulously. (An ongoing problem that comes and goes that i've been trying to solve)

Come back to the house and right before I shut it down the MIL and CEL come on. I shut it off thinking that I will have a code that will point me in the right direction. Put my paper clip in and turn the key and my CEL light isn't flashing just on solid with my "SLIP Cont off" light flashing. 30 mins later I try to check the codes and the CEL light is flashing steady telling me there is no codes.

I start looking into my electrical system checking the plugs at the ECU which look fine, they are tight and none of the pins are bent. (The car is pretty much stock)

Upon looking at the large bundle of wires that come through the firewall from the ECU I find this.


There four wires (3 black and red stripe one and 1 thicker black one all spliced into one black and red wire and also another 2 wires spliced into 1 where the blue electrical tape is. That's not standard I'm assuming?

I had a greddy emanage ultimate that I used to have hooked up only for the speed limit removal and speedo adjustment for bigger rims. I disconnected it awhile ago trying to eliminate possible problems while troubleshooting but it wasn't the problem. I'm thinking I could hook it back up and use it to datalog some data to troubleshoot with although I've never used that datalogging part of the EMU, hoping its straight forward.

Anyone have any ideas?

After looking at some electrical diagrams, I'm starting to think I have some grounding problems.

No that doesn't look right. That's definitely not an oem splice.

[Durandal]

Yah removed the tape today and there are crimp connectors and all the wires are red striped black wires which are grounds i believe? I don't know why it is the way it is though.

[pwpanas]

Originally Posted by Durandal

Yah removed the tape today and there are crimp connectors and all the wires are red striped black wires which are grounds i believe? I don't know why it is the way it is though.

Crimp connections in general are good (Toyota never uses solder - it's a less relaible connection over time on a moving/vibrating vehicle than a proper crimp). That said, I'd guess you're referring to a cheap plastic press crimp.

Regarding the wire colors in the harness, it's best to refer to the TSRM:
http://www.mkiv.com/manual/1995_elec...ual/index.html

[Durandal]

At long last I traced all my problems to a bad battery. It had never been below 12 vdc when I checked it but after doing some testing, I found that it wouldn't hold a charge much past 12.15 volts. If you charged it up to around 12.7 volts with a charger and hooked a multi meter up to it with nothing else connected you could watch the voltage drop and in about 10 minutes it was at 12.05. It would never drop below 12 volts so I never thought much of it until this test.

Replaced it with a new battery and after a test drive the voltage is reading 12.9 and not dropping. Roughly 1 volt makes all the difference in the world after factoring in the resistance of the wires.

[pwpanas]

Originally Posted by Durandal

At long last I traced all my problems to a bad battery. It had never been below 12 vdc when I checked it but after doing some testing, I found that it wouldn't hold a charge much past 12.15 volts. If you charged it up to around 12.7 volts with a charger and hooked a multi meter up to it with nothing else connected you could watch the voltage drop and in about 10 minutes it was at 12.05. It would never drop below 12 volts so I never thought much of it until this test.

Replaced it with a new battery and after a test drive the voltage is reading 12.9 and not dropping. Roughly 1 volt makes all the difference in the world after factoring in the resistance of the wires.

So it idles 100% consistently now?