Problems with my "new" 5.0HO

copo123

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Hello! I have some issues with my idle and low pedal acceleration is a bit jerky.
I have 70mm tb, smoke tested intake, changed all the vacuum tubes, tried 3 different IAC valves and nothing, right now im running with a blocked iac.
With oem iac it idles right, but it jerks during acceleration, while it jerks it fluctuates on the vaccum gauge i have.
With replacement "Walker" iac it idles at 2000rpm.
With replacement oem but 96-00 PN it idles perfect first minute, then 2000rpm.
Tried resetting the TB with the gauge and 0.93 same, tried with 0.96 and same.
With iac blocked or disconnected it backfires from exhaust on deccel badly.

Here´s a video of the vaccum gauge.
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ttocs

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The only reason I have heard of blocking off an IAC is for when you are setting the idle. I never heard of someone driving with it blocked. My tuning knowledge is limited but I thought while you were driving the IAC opens up to a set %open and then when you let off the gas it slowly closes to control the idle. Taking that out of the equation could be part of the problem.

The high idle would point to a vac leak. A cigar and a smoke test can tell you the truth to if it is. I have seen where the leak was found to be around the butterfly of the TB that was not sealed right and allowed air to get in after the maf so it could be the new TB that is causing the problem. What brand?
 

joemomma

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Looks like a BBK TB? Aren't those prone to idle issues?
 

96blak54

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A bad throttle position sensor will throw a high idle. An out of adjustment tps will throw a bad idle.
 

Musturd

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I would start with a base idle reset before throwing more parts at it . The throttle body most likely isn’t the issue. I ran the same one on my car with no problems before switching to fox style .
 
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copo123

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thanks everyone for reply, the base idle reset procedure was done and nothing changed. Im thinking that the bbkrap tb is the issue, living in a country that there is no parts for this car, so ill be buying a oem tb from there.
I smoke tested and i cant see any leak.. that vacuum numbers are right? i think need to be 25 on idle at least, sometimes i have 20 other ones i have 10. First american car and still learning.
Oem used 5.0 iac disconnected is closed
Oem used 3.0 iac disconnected is closed
Walker new 5.0 iac disconnected is open.
The only one if i apply 12v to it and see movement is the oem used 5.0 iac. The other ones click but i cant see any movement at all.
Sometimes the car runs very great, but the other it runs like 150hp car.
Thanks :)
 
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copo123

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if i use the oem used 5.0 iac the car idles perfect, but in acceleration i feel power-no power- power - no power
 
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copo123

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Bbkrap... Smoke tested today again, and see it leaks from the tps... Aplied some rtv and car runs more great, but when i do some throttle and let off, it hangs at 1500rpm and slow down to 700, maybe time to make some restictor plate?
 

ttocs

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my hanging idle problems were due to my pro product TB. When I switched to an edelbrock it fixed it.

the restrictors are just a band aid but if you don't feel like dicking with getting the hole perfect this makes it easier.

 
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copo123

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maybe someone can help me, i uploaded 2 videos one koeo and one koer of the errors i get. But in the beggining i get 11 i think, i dont understand :\


 
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copo123

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UPDATE!

the "new" oem TB arrived, installed and adjusted as ford performance pdf, sometimes it doesnt idle at cold, in warm idles perfect. But driving i experience some hiccups like he is accelerating itself and the vaccuum gauge tell me that is changing in vaccuum. I dont know what to look for... Probably maf? its got recently cleaned but same issue.

I have 4 different iac and with all is the same.
Ignition set at 10
New water pump,thermostat, plugs, wires, msd distributor,msd coil, full bbk exhaust with shorty headers, other than that is stock.

For example, yesterday when i install the TB the car doesnt idle and he dies at cold, allways, but today it was idling perfect on cold and warm.
But in early warm it was idling at 450-500rpm then in a sec it was setting the idle at 750 and then perfect. Probably some water temp sensor?

The only thing that can change the vaccuum in "cruise" i think is the IAC or i am wrong?
Thanks everyone.
 
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copo123

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Another thing.. im searching on some gt40 used heads, any site to look for? need to ship overseas... here its impossible to find ones.
 

Musturd

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Personally unless the gt40 heads are like free . I’d go another route . Even Chinese casting afr enforcers over gt40’s .
 
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copo123

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This car is going to put me crazy.
I dont know where to look. Sometimes drives good and iac do their job, sometimes runs like crap, i doesnt idle at cold, if i give 10% pedal it fluctuates the rpm 500rpm high, then normal, then high..
Looked to temp sensors are in working order, something is triggering the iac 5v and then 0, then,5v then 0v. What to look for? Ecm?
 

Jon95GT

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How old is your distributor? Over the summer I experienced running issues with my Mustang like loss of power, hesitating, missing and it turned out to be a bad hall effect sensor in the distributor.
 

ttocs

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I discovered a problem with mine during a remote tuning session that could be a similar problem here. I am running a holley HP EFI and during a remote tuning session the tuner noticed that my throttle position sensor was showing %5 throttle was being added even though I was outside the car, and then it would fluctuate up/down when I tapped on it. I thought the TPS was bad and replaced it, fired the car up and it showed 0% so I set up another appointment. 30 mins into this session it started to do it again and when I grabbed the harness and moved it around/jiggled it that the % changed. The harness had gone bad and when it was cold it was still tight enough to read properly but when it got hot, then it got looser and changed the reading.

Next time your having issues pop the hood and while the motor is running try to grab/pull/tug/push on ANY wire harness/sensor connection that you can find and see if the motor changes at all.
 

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