My 2008 TL-S has a surging idle. It normally idles at 800 rpm, but every 7 to 15 seconds surges to 1100 and then immediately back to 800 rpm. Does this even with the AC off.

It appeared to start after I removed and reinstalled the IMT (intake maniforld tuning) valve actuator located above the power steering pump. Tried reinstalling the actuator with the gears in different positions but no change.

Also tried the idle learn procedure.

Any idea what could be causing this?

 

Happened to me when I messed with the intake as well

I tried to clean the throttle body with some carb cleaner and it did this for like two weeks. After a while it just went away by itself...

 

You might be able to fix that with a can of sea foam.

 

Yes, Seafoam will reinstall something that was installed wrong or help the ECU learn quicker.

 

A bad o2 sensor or trapped air in the coolant system can cause an idle surge. Try running a diagnostic and see anything comes up, then reset the computer or pull the negative battery terminal for a few, reinstall, start the car, go for a short drive and see if that helps.

 

I just had the same thing happen with our Odyssey. it was the idle air control valve. while it is doing that surge disconnect the IACV and wait a moment. shut off and reconnect. then restart. you will now have a check engine light but hopefully the IACV will have been reset and all will be good. if it keeps coming back you may need to replace valve.

make sure your radiator is topped off. that can trigger the surge as well

not even sure the TL has an IACV but just sayin

 

Air in the coolant? Nope. If an 02 is so bad as to cause a surge you'll likely have a code and a light.

 

Think you answered your own question when you said it started after you took your imrc out and back in improperly.

 

Dbw doesn't use an iac valve.

 

Lol

 

Fellas,

I've had something similar happen after I had my runners and IM ported and polished.

The car starts and idles fine but on cold starts the idle will surge up to about 11-1200 only when placed into drive. It will even stay there and roll out of the neighborhood. I've noticed it slightly surge when warm but it's not as apparent.

I don't get any codes so am thinking it's a slight vacuum leak. I've had my check fuel cap warning come up twice in the last few months too. Any ideas?

 

I had this issue... Fixed it with new spark plugs and a can of seafoam. Hope yours is just as easy.

 

I've only got 37k miles...doubt it needs seafoam or plugs this early. It started after PnP but didn't act erratically until after the fuel cap warning.

 

fuel cap warning = vacuum leak.

 

Can you elaborate bud; do you think it's from the PnP work?

I had the runners and IM PnP'd about a year ago and haven't had an issue until 9-10 months afterwards when the fuel cap warning came on.

I was thinking maybe that plastic IM gasket loosened up over time with heat and needs tightening. I'll have to take a look over the weekend.

Cars under extended warranty but stealership wants to troubleshoot it first saying the fuel cap isn't covered under warranty but other portions of the evap system are.