Idle speed

Chancey · Feb 14, 2020

Hey guys. I have a 2013 GT500. Basic bolt ons and tune. VMP 69mm throttle body, JLT 123mm CAI, 2.4 upper pulley w/idler, cooler plugs, custom canned lund tune with ngauge device. Installed mods a couple months ago. All is well, runs REAL strong. Put 2,000 miles on her like this. Now suddenly the last couple of times I drive it, idle speed is staying from 1,000 to 1,100 rpms. Does it at random (but increasing in frequency to more often than not). It will only go back to the normal idle of around 700-750 rpms after you sit for about a full minute after coming to a complete stop. Then today, it would stay around 1,000-1,100 rpms even after I let it sit after stopping. Still runs strong. Any ideas from you vets out there? Thanks.

Catmonkey · Feb 14, 2020

See if you can pull any codes. That's a weird one.

Chancey · Feb 14, 2020

Catmonkey said:
See if you can pull any codes. That's a weird one.

No codes thrown or stored catmonkey.

Chancey · Feb 14, 2020

Ive been readind that an unseen vaccuum leak or idle air control valve maybe? Gonna do some further checking tomorrow and at least eliminat vaccuum leak.

Catmonkey · Feb 15, 2020

There is no true idle air control valve on these cars. It's all a function of the throttle body. But some open vacuum port could let more air in than the throttle body is programmed to regulate. Most of the potential vacuum leak sources are going to be the barbs on the rear and the passenger side of the supercharger.

Jam421 · Feb 15, 2020

After you check vacuum sources, CAI clamps, MAF & TB Connects...You may want place your SCT on the seat. That happened to me was after mods but I was in the 90 day Lund warranty period. When it happened again I data logged for a short bit then revved a few times until it settled down. Lund did a tune TB revision and it was gone. Lund may charge you $50 but they should identify the cause.

PM-Performance · Feb 15, 2020

Have your tuner revise the dash pot decay rate settings I think it is.
As soon as you tel the tuner what it is doing, they will know what to correct

gm kilr · Feb 15, 2020

Should have bought Ford cobra Jet throttle body so much better more money but you get what you pay for

Sent from my iPhone using svtperformance.com

Mojo88 · Feb 15, 2020

Try a thorough spray cleaning of the MAF (appropriate cleaner, of course). I was having issues like this and a good MAF cleaning fixed it right up.

Chancey · Feb 15, 2020

Thanks fellows. Gonna get lund to check it out come monday. No obvious vac leaks of any kind.

5.8 Venom · Feb 15, 2020

Mojo88 said:
Try a thorough spray cleaning of the MAF (appropriate cleaner, of course). I was having issues like this and a good MAF cleaning fixed it right up.

^ This, especially if you have a "wet" oiled air cleaner. I had a wet K&N that fouled the MAF and made the idle irregular.

Norton · Feb 15, 2020

Catmonkey said:
See if you can pull any codes.

Step 1 ^^ (Check for codes.)

Mojo88 said:
Try a thorough spray cleaning of the MAF (appropriate cleaner, of course). I was having issues like this and a good MAF cleaning fixed it right up.

5.8 Venom said:
^ This, especially if you have a "wet" oiled air cleaner. I had a wet K&N that fouled the MAF and made the idle irregular.

Step 2 ^^ (Clean MAF.)

Chancey said:
Ive been readind that an unseen vaccuum leak or idle air control valve maybe? Gonna do some further checking tomorrow and at least eliminat vaccuum leak.

Catmonkey said:
There is no true idle air control valve on these cars. It's all a function of the throttle body. But some open vacuum port could let more air in than the throttle body is programmed to regulate. Most of the potential vacuum leak sources are going to be the barbs on the rear and the passenger side of the supercharger.

Step 3 ^^ (Look for vacuum leaks.)

PM-Performance said:
As soon as you tel the tuner what it is doing, they will know what to correct

Step 4 ^^ (Consult tuner.)

gm kilr said:
Should have bought Ford cobra Jet throttle body so much better more money but you get what you pay for

While I agree with the sentiment about getting what you pay for, there's nothing cheap about CFM/VMP throttle bodies. They've proven reliable for hundreds of us.

Chancey · Feb 15, 2020

gm kilr said:
Should have bought Ford cobra Jet throttle body so much better more money but you get what you pay for

Sent from my iPhone using svtperformance.com

The ford cobra jet tb is good as well, but the VMP 69mm is not less expensive or a cheaper throttle body.

Chancey · Feb 15, 2020

Norton said:
Step 1 ^^ (Check for codes.)

Step 2 ^^ (Clean MAF.)

Step 3 ^^ (Look for vacuum leaks.)

While I agree with the sentiment about getting what you pay for, there's nothing cheap about CFM/VMP throttle bodies. They've proven reliable for hundreds of us.

Completed steps 1 and 2, did a basic check of all vaccuum hoses and connections, but I need to get a mirror and go a bit deeper on the area behind the SC tomorrow. My fat fingers dont play well in the tight spaces there! After Im confident of zero leaks, gonna get with lund again monday. Thanks again, Ill post what I find.

biminiLX · Feb 16, 2020

It’s usually the TB.
I really wanted my car to idle down to 800-900rpm to hear the cams chop, but even after multiple changes it still idles 1000-1100.
Good to check the basics as above, but it may need some TB tune tweaking.
-J

PM-Performance · Feb 16, 2020

Chancey said:
Completed steps 1 and 2, did a basic check of all vaccuum hoses and connections, but I need to get a mirror and go a bit deeper on the area behind the SC tomorrow. My fat fingers dont play well in the tight spaces there! After Im confident of zero leaks, gonna get with lund again monday. Thanks again, Ill post what I find.

trust me, just tell Lund what is going on and suggest dashpot decay rate review. They will know what to look at. This is not uncommon at all.
As soon as I told them this with mine, the next revision corrected it. I went through this with my SN95 as well with a prior tuner and fought back and forth with him. When he couldnt figure it out I had another tuner fix it.

It may not be exactly the same since these do not have iACV, but that will trigger with them and they will know what to fix. They like to keep that value high as they think it is going to stall the car if it drops too fast or low. I asked multiple times until they fixed it and said I would deal with stalling if that happened. Since then it has been perfect. I knew it was not an issue though because the car was fine before them tuning it from another tuner. So I knew it was a tune setting

Norton · Feb 16, 2020

PM-Performance said:
trust me, just tell Lund what is going on... They will know what to look at.

+1. Once you eliminate the easy stuff, this is solid advice. (Not sure how I missed concuring/quoting previously.)

Chancey · Feb 16, 2020

PM-Performance said:
trust me, just tell Lund what is going on and suggest dashpot decay rate review. They will know what to look at. This is not uncommon at all.
As soon as I told them this with mine, the next revision corrected it. I went through this with my SN95 as well with a prior tuner and fought back and forth with him. When he couldnt figure it out I had another tuner fix it.

It may not be exactly the same since these do not have iACV, but that will trigger with them and they will know what to fix. They like to keep that value high as they think it is going to stall the car if it drops too fast or low. I asked multiple times until they fixed it and said I would deal with stalling if that happened. Since then it has been perfect. I knew it was not an issue though because the car was fine before them tuning it from another tuner. So I knew it was a tune setting

I plan to speak with Alex at Lund monday about it for sure. Thx man.

Robot_trainer · Feb 20, 2020

Vacuum leak, MAF, tune or any combination would be my first choices

Catmonkey · Feb 20, 2020

If you're coasting to a stop in and out of gear, the PCM strategy uses the dashpot settings. If you're sitting still idling, it's using the idle control. If your car is able to reach the programmed idle using programmed parameters, it's going to stop trying to adapt and is ikely to idle higher than intended as a default because the PCM can't figure it out. It could be a tuning issue or attributable to a vacuum leak. I think most tuners are going to have you do some sniffing around for the latter as opposed to spending time on the tune.

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