Idle issue

Clown9

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Might as well ask for some help

So back story, I own an automatic 07 Mustang Shelby GT (not GT500). I bought it used with about 69k miles on it.

I self installed FRPP hot rod cams, intake manifold, and throttle body. Had Bama tune for that while I waited to have the next set of mods installed.
Next I took the car to a shop to have Pypes LT headers, short H-Pipe, and high flow cats installed as well as 4.10 FRPP gears. Once again had a new tune from Bama for this set of mods.
Car ran great for a while. But as of the last few weeks the idle has been not so good.
I have the idle set at 650 and the car goes anywhere from ~580 all the way up to ~800.
So it will idle around the set rpm but every few seconds it will jump in rpms then it will dip stay around 650 then go up and then down and so on and so forth.

In an attempt to fix the issue I swapped back to the older tune from Bama that ran almost flawlessly before and the same issue was going on so I went back to the newest tune.

I cleaned MAF sensor and air filter and it sort of ran better but not much. I replaced MAF afterwards and pretty much the same.

Next I swapped out the spark plugs with the updated Ford oem plugs (a fantastic job to diy btw). Also changed the coil on plugs with MSD Blasters.
This was more so to get the whole spark plug job out of the way than anything else but either way it still didn't help the problem.

Have had car go through idle relearn thing multiple times with parking break and ac and such and car idle still jumps around after each relearn.

I read a lot online on forums about exhaust leaks and vacuum leaks. I jacked up the car and resealed around all the clamps on headers, mid pipe, and cats. That was the single thing that did the most but car idle still jumps and dips anywhere from 100-150 rpms.
Next I checked for vacuum leaks around the hoses on the passenger side from the valve cover to right before the throttle body, the PCV valve thing, the hose behind the intake manifold, the hose right above the PCV hose, the hose going to the fuel rail, the valve covers, the intake manifold seals, and from my limited knowledge nothing seemed out of the ordinary.
Car does die when disconnecting the PCV hose on the drivers side.

I tested battery and alternator. Battery tested at 12.55V and with car on it tested 14.65V

I will also add that during all of this not one single code ever came up. When I hook up the tuner it does not detect any codes other than P1000 which is understandable since I disconnected the battery the other day to do the spark plug job.
Another thing I will add is that when I turn the key to the on position (not turning the car on) if I wait a bit the CEL will blink 6 times. Said light has never blinked while car is on.
I have the Bama Revx tuner and have done datalogs but I will say I really don't know what I'm supposed to be looking for.

I honestly don't know what to do at this point.
Any help or guidance would be much appreciated
 

Marble

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Put the OEM coils back on. Don't spend a bunch of money throwing parts at the problem.

Almost all of the time this problem turns into a tuning issue. Bama proceeding won't be able to help. Probably will need custom tuning. Weather changes can also make small issues with tunes magnify.

It could also be a dirty throttle body.

Best of luck!!
 

Clown9

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I can change the coils back *but* the issue was present even with the oem coils.

Throttle body is only a couple months old.
I forgot to mention it but I did check yesterday and it was shiny clean.
 

RocketcarX

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A tune does not "go bad", if the car was running correctly and developed this issue after some time the problem is obviously something else.
Throwing parts at the car complicates things. Pull codes, look at vehicle data and go from there.
Check it for vacuum leaks as well.
 

702GT

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I can't imagine using anything but an OEM coil for a street car. The only reason to use anything but OEM is gonna be high performance, custom, or track only (mostly for sponsorship.)

650 idle is really low for the hotrods LSA. Remember that when you cam a car (particularly in respects to NA) your efficiency gets pushed to the right (higher up the rpm band). 650rpm is rough on the alternator and AC (not so much as to component wear but performance). It really sounds to me like your car is hunting for idle. Why it was perfect before and not now, I have to agree with Marble. The weather or even altitude (DA) could affect it. When I had Comp Cams 127020's I used to go in the tune and set the idle to 630rpm when I'd be parking it at a car show (half the fun and show of having a cammed car is the lope of the exhaust, after all lol). But on the street for DD, it was annoying to be that low. AC didn't blow as cold, constantly hunting for steady idle, rpm dips when rolling to a stop, ect.,. So I always kept my street idle at 780 (tuner wanted 850, but I wanted to keep as much lope as possible without dulling the AC and having it hunt for idle. 780 seemed to be a pretty mean spot for lope too.

Try bumping your idle up and see how it does.
 

Pentalab

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On my 2010 auto, in PARK, idle was 700.
In RVS ( with foot on brake) it was 650.
In DRIVE ( with foot on brake) it was 600.

Ran like a top, idle on the aeroforce gauges barely budged, even in DRIVE, and that was with twin 62mm TB, LT's, high flow cats, Roush M90 blower, K+N filter. Oem cams though.. + 94 tune.

The last time VMP tuned it ( abt the 3rd tune from them), amongst other things, he also tweaked the idle up a bit.

In Park, it's now it's now 850
In RVS, it's now 800. ( foot on brake)
In DRIVE, it's now 750. ( foot on brake).

I also noticed I can no longer tweak the idle on my hand held SCT-X3 tuner. Before, I could tweak the idle up / down. Although it's still displayed on my X3, VMP has shut down the idle function, I can no longer tweak it. Even the new idle settings don't budge.

On cold start up, idle is higher than normal. After aprx 15-25 secs high idle drops down to normal. That's to get the cats up to temp. Even the plane jane ford oem tune does that. All cars do that... including my 2011 Fusion.

I don't believe cranking up your idle will do much of anything, but try it for a few days. You had zero idle issues.. then all of a sudden the idle is hunting about. You have some other issue going on in there, and I don't think it's tune related. Exhaust leak, vac leak, could also be a front / rear O2 sensor.

Other than the idle issue, how does your car run when just driving around, or mashing the gas ?
 

Clown9

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Throwing parts at the car complicates things. Pull codes, look at vehicle data and go from there.
Check it for vacuum leaks as well.

I don't believe cranking up your idle will do much of anything, but try it for a few days. You had zero idle issues.. then all of a sudden the idle is hunting about. You have some other issue going on in there, and I don't think it's tune related. Exhaust leak, vac leak, could also be a front / rear O2 sensor.

Other than the idle issue, how does your car run when just driving around, or mashing the gas ?

I would definitely pull codes from the car if it gave any. Only code I get is P1000 and that is because I disconnected battery to do the spark plugs. One thing I did write up there is when the key is flipped to the on position after a bit the CEL will blink 6 times. Do not know what that means and like I said car gives no codes.

As I wrote in the original wall of text, I would look for data but I do not know what exactly I am supposed to be looking for :/

Already checked for vacuum leaks, unless there is a place I am missing? It may be I checked wrong? Is there a proper way to do it?
I went about all the places I mentioned above with a sprayer bottle filled with water spraying hoses, intake manifold, and valve covers to see if water was being sucked in and nothing.

As far as how the car drives when stopping it obviously shudders because of the low idle and when giving it gas after a stop it hangs (low idle I presume) but after that car runs completely fine.
It's really only the dipping and jumping idle that I have an issue with since the car never did it before.

I can't imagine using anything but an OEM coil for a street car. The only reason to use anything but OEM is gonna be high performance, custom, or track only (mostly for sponsorship.)

Try bumping your idle up and see how it does.

When I get home today I'll put the oem coils back on and I will set the idle to either 780-800 depending on what the tuner gives me as an option
 

CammedS197

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Agree with the set idle. Me cammed I have at 700. Also from one tune to another you can get idle surge. When I got tuned I did logging no AC and got that dialed in for driving and clutch in and then we did with AC on and we did the WOT logs first then focused on the daily driving portion.

Later down the road after doing longtubes and H pipe tuned for 93 from 87 (need for hurricane season lol) we had a small issue from tune to tune. Just commanded tq is all. Throttle wanted to close some at 5500rpm. Just an example that one tune to another can have minor changes. Especially idle surge. Very common thing especially at low idle.
 

sman247

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I had those cams and could go anywhere less than 840 rpm at idle or it would surge. Also learned the hard way about aftermarket coils with this platform, never again. It's definately not a tune issue or you would've had the issue from the beginning as stated above.
 

Clown9

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Alrighty, I have completed the task at hand.
Removed the MSD coils and put the OEM coils back on.
Set car's idle to 800.
Here are the results


Also, just curious, how old is the battery?

Battery is a little over five years old. Tested it at 12.55 volts at rest and 14.65 volts with car on.
 

RocketcarX

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A volt meter won't detect the issues our alternators usually suffer from. You need to test it with a machine that can do a diode ripple test. It can charge the battery and still be bad.

The video isn't working for me, what were the results?
 

Clown9

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Ah, I see.

All the video was was the car idling after what I did and the CEL blinking with the key on
 

Marble

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You said the throttle body was new...What is on the car? If it's anything but the original, get rid of it.

If the engine is hunting up and down at idle and after slowing down, it's tuning. It could be something else, butt I doubt it. It had to do with air metering and a calculation that was input by a tuner that under certain conditions is great.

I haven't had experience with bama but they are not a custom tuning house. They do okay with lots of cars, but are not spot in like custom dyno tuning places.
 

Clown9

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You said the throttle body was new...What is on the car? If it's anything but the original, get rid of it.

If the engine is hunting up and down at idle and after slowing down, it's tuning. It could be something else, butt I doubt it. It had to do with air metering and a calculation that was input by a tuner that under certain conditions is great.

I haven't had experience with bama but they are not a custom tuning house. They do okay with lots of cars, but are not spot in like custom dyno tuning places.

TB is the FRPP twin 62mm
Th first wave of mods I did along with the FRPP intake manifold and FRPP Hot Rod cams
 

Pentalab

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A volt meter won't detect the issues our alternators usually suffer from. You need to test it with a machine that can do a diode ripple test. It can charge the battery and still be bad.

The video isn't working for me, what were the results?

IF the battery reads 12.55 vdc with eng off, that's normal. With eng on it should read 14.4 to 14.65
If eng on, and it still reads 12.55, then the alternator is DOA, outputting nothing. Diodes typ fail shorted.
If one or more diodes fail shorted, you will then see AC ripple on a Digital voltmeter. Switch the DVM from
DCV to ACV, to see any AC ripple. Normal AC ripple will be extremely low, like a few Milli volts.

Beware though, not all DVM's will indicate the AC component that is superimposed on a DC system. For the
DVM to function properly when doing the above test, a capacitor is switched into the dvm, one in each leg.
The pair of caps BLOCKS the dc component , and allows the AC component to pass through. Caps block DC, but allow AC to pass through them.

My B+ K DVM doesn't have the blocking caps when in AC mode. When trying to do the above test, it will see the 14.4 vdc and the display will indicate 14.4 vdc, when DVM on switched to read ACV.... so a few Milli volts of AC can't be read. My Fluke 87A DVM does have the pair of block caps inserted when switched to read ACV, so it works just fine for the above test. I forget what the max AC ripple is acceptable, before you can conclude that 1 or more of the 6 diodes inside the alternator is shorted. ( 3 phase alternators use 6 diodes. Older, ancient single phase alternators will use just 4 diodes).

High levels of AC ripple are bad news. That will fry a battery very quickly. Batteries don't like any AC component on them. Your ECU / stereo won't like it either. Stuff like halogen headlights are a non issue, they are just a resistive load.
 
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Clown9

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I have a DVM. A blue point eedm596c.
Switched the thing to read AC volts and placed the positive lead on the positive post on the alternator and the negative lead on the engine block.
The thing read at ~.04 volts and dropped down to .028 after a few seconds. Did this three times and each time the same.
Also tried it on the battery and it started at .06 and promptly dropped to the .028 reading.
 

Pentalab

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I have a DVM. A blue point eedm596c.
Switched the thing to read AC volts and placed the positive lead on the positive post on the alternator and the negative lead on the engine block.
The thing read at ~.04 volts and dropped down to .028 after a few seconds. Did this three times and each time the same.
Also tried it on the battery and it started at .06 and promptly dropped to the .028 reading.

.06 vac = 60 millivolts
.04 vac = 40 millivolts
.028 vac = 28 millivolts.

I think those readings are in the typ normal range with a good alternator. I will try and dig up my old notes on this, which depict the max allowable.

With eng off, your readings should drop to 0.000 AC volts.
With eng on /off, polarity of leads should make no difference, there is no polarity per se, when using a DVM in AC mode.
 

07gts197

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Your cel flashing at key on engine off is normal.

If you want to try logging more I would recommend also logging maf flow, fuel rail pressure, tps voltage, throttle position absolute (actual), throttle position commanded and knock sensor activity if you can. I dont use my x3 for logging so I dont know if you can log all those functions or not. I can on Forscan Lite, which I highly recommend if you need a obd2 scanner for other vehicles.
 

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