So i've been battling with a slightly high idle (150-200 rpm) for a little while now.

I've tried all kinds of things, i can reset the idle air learning no problems, to the point where i can go out and do it now, first try, from memory, with my eyes closed.
Each time, it correctly drops the idle to 650, but turning the engine off and on again results in it going back to exactly where it started. Also, driving it for long enough after the reset will very very slowly cause it to go back to the higher value as well.

Anyway, my tuner seems to think (without seeing the car) that it has to be a vacuum leak after the MAF, which makes sense.

However, i'm really at a loss as to where that would be, there is only the intake tube and then the connection to the TB.


I was thinking about using a water spray around those areas to check, any thoughts on that?
The other possibility would be to get a local garage to run a smoke check on the intake...

 

the vac leak could be anywhere after the maf. at TB, manifold upper, manifold lower, etc...

Do things like clean maf, clean tb, and check for easy to catch leaks at the rubber hoses and intake pipe attachment points.

 

There is a leak detection spray you can buy, brake cleaner also works. Spray around intake manifold and hoses, idle will increase if it enters the leak, possibly stall the engine. Easy.

 

I've seen the leak detection spray, but not in the US, only in europe, ironically, it's Valvoline.

Any idea where you've seen it here?

Not sure i want to use brake cleaner, just on the off chance we have a problem, hence the preference for water or this spray if i can find some anywhere.

Lower manifold replaced, spacer gaskets and TB gaskets replaced, so i'm hoping it's something like a problem with the tube attachments.

Originally, it had this problem, i fitted the spacer, and it went away, perfect idle. It came back again after messing with the stock exhaust.

 

Use throttle body cleaner instead of brake cleaner.

 

Brake cleaner is fine, carb cleaner is the only thing i don't use as it started a fire once. Brake clean has found me many leaks and made me a lot of money, more than I used on brakes. It can discolor crappy rubber on Mitsubishis though.

What do you dyno at? Curious if spacers and HFC are worth anything.

 

Erm, i'm sure brake cleaner is just as flammable as carb cleaner, is it not?


Don't know on my specific power gains, but i know for sure that the spacer does give significant gains, independently proven. HFC over standard will always gain, same with TP's. However, both lose low down power/torque, so i went for the ART pipes to mitigate that loss and still gain.

 

u can buy the leak detector at an A/C store... i do hvac and we have bottles on bottles of this stuff.. works wonders and finds leak in no time

 

The idea here is to introduce a combustable material to richen the mix up, idle will increase will a small amount, stall with a large amount. It's not difficult and its not dangerous as long as there is no source of spark. The flash point on brake cleaner is lower than carb/throttle cleaner as well.

 

Surely an AC leak detector is for detecting escaping gas from the system? We want to detect vacuum leaks, air getting *in* the system.

Neimad, isn't a higher flash point better? less chance to the heat setting it off? Not so sure on brake cleaner making a mess of the plastics either.

 

I'm posting this same response in a few threads for this problem in the hope that someone else will benefit from it.

My idle problem is fixed, and by that, i mean the problem where it does not remember the correct low idle after turning the car off.

I did a couple of things differently during my last reset, which i'll explain below, but here's the points i used.

1) Car fully up to running temperature (required)

2) Reset performed per the book, correctly takes new idle setting (as normal each time i do it)

Two things i did/did not do this time that seemed to make the difference:

1) I turned off the interior fan before starting the procedure.

2) I did not rev the car a few times after the new lower idle had taken (even though the procedure calls for it)



I have no idea which of those two made the difference. All i know is, that it's now remembering the new idle and it's super smooth.

I had loaded a new map on the car a week previously, and i had the door open and the fans on low with the engine off for a few mins before starting it, i do have LED interior bulbs.
However, it complained of battery voltage too low and would not let me flash until i had closed the door and turned the fans off.

This has never been a problem before when flashing and whilst i don't think it's a problem directly, i'm wondering if it showed up another problem that perhaps contributed towards the issue.

The battery isn't that old but it's possible it's not as well as i thought, I'm thinking the battery voltage during the reset procedure, which is done with the ignition on but engine off, was causing a problem with the learning portion.


Short version;

* I came home and turned off the engine, fans and kept door closed.
* I ran the procedure, acquiring the lower idle, but omitting the rev testing at the end.
* Turned off the engine and shut the car up for the night.
* Everything perfect once up to running temperature the next day.


Hope this helps someone out.