A little engine info first:

Built block
HKS 1000cc
Fcon (everything)
JWT TT
HKS Ignition amp
Iridium one step colder plugs

Obviously there's more to the engine but I figured this would be the areas concerned with inconsistent idle.

Sharif did the build and tune in August. I'd ask him but he is at Sema and I'm impatient.

It has always idled perfect at 1000rpms until about a week ago. What is happening now is that it dips below 1000 and slowly moves back and forth from about 750 to 500 occasionally dipping below 500. Vacuum is good, oil pressure is good, fuel pressure is good, A/F is about 12 at start up and 14 once warmed up. After warm up idle is still inconsistent. I live in OK and the weather started to get a lot cooler the same time poor idle began to occur. Could this simply be the issue or somthing more serious?

Thanks

Judson

 

I think SEMA ended on Friday.

 

I don't think he will be back in the office until tomorrow. Yes I am impatient.

 

changes in outside temps?

 

When the idle surges,it is searching for the porpper A/F to run at idle. This happens sometimes when the air intake and water coolant temp adjustments need to be tweaked a bit. This would steady the idle A/F a bit. DO you also have an A/F feedback set up on the car?This would also help.
Or it could be a vacume leak.

 

I have the knock amp. I'm assuming this is what you mean by A/F feedback. I don't think it's a vacuum leak as the guage reads around 18 like always.

Westpak,

As far as temps are concerned it is now around 40 in the mornings and mid to high 60's during the day. Before the idle trouble temps were well over 70's for lows and highs later in the day were 80's and 90's.

 

Dont worry My car did the same thing, it a easy fix and as far as I know it wont hurt anything. He should be able to fix it.

 

its worse on the 05s for some reason too.


the drive by wire is the issue with it all. the stock computer still controls the opening of the throttle body. the 05s actually switch to air flow sensors not 02 sensors and they are really touchy. they will overcorrect it back and forth. the stock computer still thinks its doing something so it will slightly open the throttle body back and forth to compensate, even though it has no control on the fuel.

 

The Fcon has water temp and intake temp maps, so it being colder out could cause it to be in cells that maybe too rich until it warms up and gets to the cells it is used to being in.

 

Sorry I left out my car year it's an 07.

Jeremy,

Does your comment still apply?

 

^ Colder air = denser = requires more fuel

From this description I would guess it leaned out a bit at idle due to the colder air. A quick adjustment to intake-temp compensation should have you fixed up. Until then, keep an eye on AF in boost to make sure it didn't lean out as well.

 

I am back. I will call you tomorrow and go through this with you. Nothing to worry about at all.

 

Glad you made it back safely. Thanks for the reply. Talk to you tomorrow.

 

Were you able to fix your inconsistent idle? If so, what was the fix?

I seem to be having some inconsistent idling as well. Dips from 1000 to about 750 rpm. Temps here starting to drop too.

 

if the target AF ratio is set up right, you shouldnt have any issues with the idle at all...

if you dont have the knock amp/wideband installed yet, maybe now is a good time to add it

 

How did you get a JWT kit on your 07?? Full custom??

 

07 G35 coupe still single intake

 

Ahhhh right. Thought the Z, G sedan, and coupe all got the HR motor. Forgot that the coupe got the stiff arm until the G37's came out.