Idle won't go below 900

[BenMoore]

Need help with this issue, bought the car 5 months ago, fp hotrod cams, cat delete, fp 24lb injectors, all new cooling system including a 4 core aluminum rad, had the x4 tuner in it with a custom tune, ok the issue, when I bought the car it idled at 740 like the tune was set to, even after all the parts and maintenance I've done to it 4 months ago, about a month ago it started idling at 900 instead of 740, thought it was the throttle body so I put a brand new stock replacement on it, no change, after all the posts about idle figure it was the tune, bought a brand new Bama revx tuner with lifetime custom tunesfrom American muscle, still won't idle below 900, I've looked everywhere on multiple forums and can't find an answer that I haven't done. Any help would be appreciated, thank you

 

[Dino Dino Bambino]

You might want to check if there's a small vacuum leak.

 

[86GT351]

Need help with this issue, bought the car 5 months ago, fp hotrod cams, cat delete, fp 24lb injectors, all new cooling system including a 4 core aluminum rad, had the x4 tuner in it with a custom tune, ok the issue, when I bought the car it idled at 740 like the tune was set to, even after all the parts and maintenance I've done to it 4 months ago, about a month ago it started idling at 900 instead of 740, thought it was the throttle body so I put a brand new stock replacement on it, no change, after all the posts about idle figure it was the tune, bought a brand new Bama revx tuner with lifetime custom tunesfrom American muscle, still won't idle below 900, I've looked everywhere on multiple forums and can't find an answer that I haven't done. Any help would be appreciated, thank you

Check for Vac Leak. Get rid of the Bama Tuner

 

[BenMoore]

Found no vac leaks, smoke tested, starter fluid tested, disconnected all lines to intake manifold and blocked off, still 900rpm, doesn't surge, coolant temp sensor reads accurate temp, ambient temp reads accurate temp, intake temp accurate, pulled tune, reset computer, still 900, BTW noticed I didn't put the cars info in the first post, 2009 mustang gt 4.6

 

[BenMoore]

Any suggestions would be appreciated, thank you for the replies

 

[MasterofDisaster]

This may be stupid, but it worked for me. My 08 idled a little high. I cleaned the TB and put some dry film teflon on the bores and blades. I had much better throttle response and the idle was once more normal.

DON'T use silicone. [A Ford master mechanic told me that it will eat your 02 sensors.]

 

[Edqe]

Check fuel pump driver module.

 

[BruceH]

Cat delete messes with the LTFT. Unless the ratio from O2 1 to secondary O2 is changed you will have issues. Unfortunately custom tune places will turn the MIL? codes off to get around a bad tune. My apologies for not remembering the proper nomenclature.

It is something I've dealt with in the past when briefly trying headers (no power difference with forced induction btw). The tune looks for a time delay between the sensors and anything that isn't stock creates a code. My hope is that you have a proper tune for Hot Rod cams. Unless the fuel injector timing is changed you will have issues. I used to keep this a secret and only help friends but I'm more generous these days, lol. @hammeron

 

[Juice]

1st, what do you mean "pulled tune"? Restored to stock?
Stock and no cats should set p0420&p0430 codes.

2nd what speed is it set to idle? If it is truely idling high, that should set some type of idle speed fault.

3rd cat delete tune issue - good luck. Not discussing this subject on a street driven vehicle.

 

[BenMoore]

Thank all of you for the suggestions and support, figured out what was going on, for some reason when I set either tuners to 740, the pcm reads that I set it to 880, couldn't be a coincidence that two different tuners and two separate companies both do it, I found that when I set the rpm lower it sets the desired lower in the pcm, so now it runs 750, still figure there's an issue with pcm cause I have other communication faults that didn't set off the mil but all trace back to internal pcm issue, BTW I'm saving up for full exhaust with cats, I know it's an issue, I just bought it 5 months ago and it had no cats already, wanted to make sure engine, trans and Drivetrain were good first before spending the money on exhaust, thank you guys for your feedback

 

[BenMoore]

1st, what do you mean "pulled tune"? Restored to stock?
Stock and no cats should set p0420&p0430 codes.

2nd what speed is it set to idle? If it is truely idling high, that should set some type of idle speed fault.

3rd cat delete tune issue - good luck. Not discussing this subject on a street driven vehicle.

Yes put it back to stock, yes I get 420 and 430 about every 4 days or so, taking care of that soon, the idle was higher than I set in the tune, figured that out when I hooked the diagnostic computer to it and read the live data, was showing the desired idle set to 880, just for test purposes I moved the idle settings down in the tuner until the pcm read 750 desired, new pcm on the way, thank you for your responses

 

[BenMoore]

Cat delete messes with the LTFT. Unless the ratio from O2 1 to secondary O2 is changed you will have issues. Unfortunately custom tune places will turn the MIL? codes off to get around a bad tune. My apologies for not remembering the proper nomenclature.

It is something I've dealt with in the past when briefly trying headers (no power difference with forced induction btw). The tune looks for a time delay between the sensors and anything that isn't stock creates a code. My hope is that you have a proper tune for Hot Rod cams. Unless the fuel injector timing is changed you will have issues. I used to keep this a secret and only help friends but I'm more generous these days, lol. @hammeron

Fixing the cat issue soon, my tune is set for my hot rod cams, fpp injectors, my cai but it's not tuned for cat delete cause it won't be deleted soon, thank you for your help