(Fixed!) High Idle

Hi all,

I just finished some work on my 2000 5vzfe 3.4 TRD 4x4 Tacoma with MT.

- Two new cams (took one off wrong, and dropped one, so replaced out of caution)
- Adjusted valves
- Timing belt
- Water pump
- Thermostat
- Crank and cam seals
- New injectors (intermotor brand, look to be OEM manufacturer)
- New coils
- New wires
- New plugs
- Cleaned throttle body
- Cleaned MAF
- Cleaned IAC
- Coolant flush
- Oil change

Previously after 30 seconds or so, my truck idle would drop from 1000-1300 down to 750. Now at the exact same time, instead of dropping, my idle increases.

What’s going on?

 

Have you verified that there's no vacuum leaks, connectors and vacuum lines are in their proper places, and no engine light on?

 

I'll take re-learn for $1000 Alex

 

No CEL. How can I re-learn? I tried pulling the EFI fuse for a minute.

 

It should relearn on it's own if everything is correct, only other thing is I've read some people had some issues with throttle bore wear causing high idle after throttle body cleaning.

 

Cleaning IAC, give it a few a days relearn. How do you do this, drive it.

 

Thank you. I’ll let it relearn and then check for vacuum leaks and throttle body wear.

I did test the ohms on the IAC and MAF while waiting for the truck to cool down a couple times. Both of them tested good.

I did resurface the upper and lower plenums with a bristle roloc disc. I checked it for flatness with a sanding block and it seemed probably flat. Is it possible a leak at the plenum or throttle body would cause this problem? I reused both plenum gaskets and the throttle body gasket and IAC gasket. The gaskets all looked in good condition.

I guess I should just relearn first before tearing anything apart.

Side note, while I was burping the cooling system of air I saw my temp gauge go over halfway for the first time ever. I turned off the engine when that happened. Where on the temp gauge is the needle pointing when the truck is too hot, and it may be causing damage? Is any non-ref area ok? Or should I not drive it when it’s over the halfway mark?

 

Did this just begin after you started it w/ battery disconnected? If so and the ecm was cleared, it will normally idle high for about 3-5 minutes. Then it will drop.

 

It began after all the work I described above which included removing the battery.

I unplugged the battery for an hour. I plugged the battery back in. I idled the truck for 7 minutes. The idle rose after maybe the 5th minute of idling. I drove around a bit and noticed at one stop sign in 1st gear and clutch pedal in, it idled at 1200. When I got home it was at 1750 idle in neutral. The whole drive I did was 10 mins after the idling (17 mins total). I just drove on city streets no faster than 35.

 

Should I adjust the idle position on the throttle body? Maybe now that my truck is all tuned up the engine is so strong it idles higher?

 

It should not need adjusting unless someone has messed with it before, did you by chance have the TPS removed at any time, it is adjustable and has to be properly adjusted if removed and reinstalled. Also make sure your throttle body doesn't look like this.

 

I did not disconnect the TPS. I did disconnect the MAF to clean it.

Woah thank you for that pic. I heard about throttle body wear but had no idea it could look that bad. I looked at mine when it was off and didn’t notice anything that bad. If I take mine off again I’ll look at that closer.

One thing I noticed is every time I pop the cap off the radiator and try to add more coolant, I can continue to add coolant and burp air and lower the coolant level. I haven’t even driven the truck once without being able to add coolant after. I think this means I’ve been driving around with low-ish coolant level and air in the system. So that’s one possible cause of my issues.

It’s also possible I forgot to hook up a hose or I hooked up a hose to the wrong spot. There are so many damn vacuum hoses and since I did the timing belt and the valve adjustment I disconnected pretty much everything.

I’m a little bit worried I damaged my IAC by cleaning it. Well anyway I’m out of coolant now so I’ll just get some more coolant and see if the coolant is the issue first.

Is there a way to test the strength of my vacuum to see if that’s the issue?

 

Not really, smoke test is the easiest way to rule out vacuum leaks but if there's bad enough to cause a high idle usually you can hear it.

How much total have you put in so far, if you end up putting in more than the total capacity of the system then I'd be concerned of a leak somewhere.

As long as you didn't force it I don't see how cleaning it could have caused damage, does the computer seem to be in control of the idle otherwise?

 

I think I put in about 2 gallons. I don’t know how much I drained. I checked for oil and coolant leaks. I don’t think it’s leaking. I think I just never fully burped the system. This is only my second cooling system flush.

 

Total capacity is 10.7 QT according to owners manual so that should be about right.

 

https://www.tacomaworld.com/threads/high-idle-problem.691056/
https://www.tacomaworld.com/threads/annoyingly-high-idle.688542/

good info here

 

Thanks all. I managed to get Techstream installed and hooked it up to my truck. It showed that my truck is still verifying certain sensors and whatnot are working. Some passed and some are still being tested.

I only let it warm up a tiny bit and idle. It started closer to 1200 and then moved up to 1500.

I noticed my throttle position value is at 10% even when my foot isn’t on the pedal and the transmission is in neutral. Is that normal?

These are all at coolant temp only 163F:
- Injector 3.2ms
- IGN advance 15.5 deg
- IAC duty ratio 35.9%
- CALC load 17.64 %
- MAF 9.45 gym/sec
- Engine speed 1563 rpm
- Coolant temp 163 F
- Intake air 52 F
- Throttle pos 10%
- O2S B1 S2 0.350 V
- AFS B1 S1 3.25 V
- Short FT #1 -0.04 %
- Long FT #1 -0.04 %
- TOTAL FT #1 1.012
- O2FT B1 S2 99.15%
- AF FT B1 S1 0.99
- Ignition 64

 

Fuel trims look good so that would tend to rule out a vacuum leak. Can you see TPS voltage?, I'm pretty sure TPS should be 0% with the throttle closed.

 

Mine reads 10.5% closed. That ain’t it....

 

Essentially, if you know the throttle plate is closed, and there are no obvious leaks beyond or at it, you should look into the iac valve. You don’t have the AC or defrost on, correct? Those will increase the idle as well.