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5.0 IAC issues


Ramcharger90

Well-Known Member
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V8 Engine Swap
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1990
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Manual
My 92 mustang 5.0 with a power dyne blower develops an issue with the IAC ones a year where the rpms will go up to 1500 at an idle or after a downshift will stay at 2500 and keeps the engine at that speed while driving. I can accelerate past that rpm but won't drop below that speed. Voltage on the tps is correct and has a new one. If I replace the iac it will be fine until next year but I can't imagine all of the motorcraft iac will go bad that fast. I know they got issues with the cheap ones. Any idea?
 
My 92 mustang 5.0 with a power dyne blower develops an issue with the IAC ones a year where the rpms will go up to 1500 at an idle or after a downshift will stay at 2500 and keeps the engine at that speed while driving. I can accelerate past that rpm but won't drop below that speed. Voltage on the tps is correct and has a new one. If I replace the iac it will be fine until next year but I can't imagine all of the motorcraft iac will go bad that fast. I know they got issues with the cheap ones. Any idea?
It only does it once a year?

Wonder if something with the blower is fucking them up
 
It only does it once a year?

Wonder if something with the blower is fucking them up
No Idea, it runs fine for awhile then I will get the same issue once a year then I will replace it. Sometimes you can get it to stop doing it If you shut it off then restart it, but it will start acting up again either after a while of stop and start or the next day after driving a lil.
 
No Idea, it runs fine for awhile then I will get the same issue once a year then I will replace it. Sometimes you can get it to stop doing it If you shut it off then restart it, but it will start acting up again either after a while of stop and start or the next day after driving a lil.
Hmm.
 
I’ve never bothered to buy a Motorcraft one when I’ve had a problem. I bought the one from Autozone that had the “lifetime“ warranty. If/when it developed a problem I just took it back and said warranty it. Even replaced one or two in the parking lot. It’s on top and two bolts plus a wiring connector. 30 seconds to swap, plus a couple minutes inside demanding a replacement. Annoying, but whatever. Now that I have a commercial account I just call and tell them to send it for warranty, guy comes and brings the new part and I hand him the old one and all is well. Simple stuff like that I find annoying, but that’s about it. Who cares how often it goes bad if I can swap it in 30 seconds and someone is dumb enough to warranty it for life. See how long I keep a vehicle running like that, lol. My vehicles are lifetime warrantied through Autozone… :icon_rofl:;missingteeth;
 
I wonder if one of the race guys would know?

@Maritime Drag Racing any ideas? I can't remember the other person's handle.
 
I have had a fair number of issues with iac valves, including one that was bad (sticky) right out of the box new. I would try a different brand.
 
I wonder if one of the spacers would help. I put one on the ranger like 3 years ago or so, I don't remember why, but that IAC hasn't gone bad since.
 
I’ve never bothered to buy a Motorcraft one when I’ve had a problem. I bought the one from Autozone that had the “lifetime“ warranty. If/when it developed a problem I just took it back and said warranty it. Even replaced one or two in the parking lot. It’s on top and two bolts plus a wiring connector. 30 seconds to swap, plus a couple minutes inside demanding a replacement. Annoying, but whatever. Now that I have a commercial account I just call and tell them to send it for warranty, guy comes and brings the new part and I hand him the old one and all is well. Simple stuff like that I find annoying, but that’s about it. Who cares how often it goes bad if I can swap it in 30 seconds and someone is dumb enough to warranty it for life. See how long I keep a vehicle running like that, lol. My vehicles are lifetime warrantied through Autozone… :icon_rofl:;missingteeth;
I had an 89 F250 i got 5 or 6 valucraft starters out of them over the course of about 1.5 years. Finally they cut me off. Come to find out it was a flywheel issue,
 
I had an 89 F250 i got 5 or 6 valucraft starters out of them over the course of about 1.5 years. Finally they cut me off. Come to find out it was a flywheel issue,
I never bought the ValueCrap. Don’t forget, I worked for Autozone years ago. I saw ValueCraft stuff fail right out of the box so often for awhile any time we sold a starter or alternator, we tested it right out of the box before selling it to someone. My preference has been the Duralast Gold when I can, Duralast (the red box) if I have to. Sometimes like brakes I will go as high on the scale that I can. If a part dies partially quickly, I try to investigate and see if the problem is on my end. Sometimes it’s just junk quality. Like my clutch slave cylinder in the F-150. I killed like 4 of them in 4 years. At that point the transmission came out (M5OD) and got swapped to what I wanted (ZF5). I swapped my blown slave from the old trans for a replacement slave for the new one which was heavier duty but unfortunately a “new and improved” hose retaining deal that wouldn’t hold the hose. Well, there’s now a stainless retaining deal I made with dad’s help bolted to the bellhousing that holds it together.
 
I never bought the ValueCrap. Don’t forget, I worked for Autozone years ago. I saw ValueCraft stuff fail right out of the box so often for awhile any time we sold a starter or alternator, we tested it right out of the box before selling it to someone. My preference has been the Duralast Gold when I can, Duralast (the red box) if I have to. Sometimes like brakes I will go as high on the scale that I can. If a part dies partially quickly, I try to investigate and see if the problem is on my end. Sometimes it’s just junk quality. Like my clutch slave cylinder in the F-150. I killed like 4 of them in 4 years. At that point the transmission came out (M5OD) and got swapped to what I wanted (ZF5). I swapped my blown slave from the old trans for a replacement slave for the new one which was heavier duty but unfortunately a “new and improved” hose retaining deal that wouldn’t hold the hose. Well, there’s now a stainless retaining deal I made with dad’s help bolted to the bellhousing that holds it together.
I just bought the VC cause it was all they had in stock. Otherwise yeah i usually buy atleaat duralast assuming i buy from AZ
 
thats a common issue on forced induction. especially if you run hot. there used to be a little adjuster deal that sandwiched in there with a screw like a carb back in the day for bigger cams and forced induction....similar to this https://lmr.com/products/how-to-install-mustang-idle-air-control-adjuster-86-93






there is the gm style that i seen alot the last few years....but that is mostly for aftermarket ecm guys...




 
I did order the spacer for the IAC hopefully that will fix it until I can get around to doing the Trick flow top end kit I have for the car. I like the blower and all but I don't want to spend the money on a vortec so I would rather just refresh the block to a 306 or go 331 stroker and call it a day. I don't want to go to crazy with this car it's a cruiser. Maybe cowl hood stay 4 lug but go disc in the back. I'm saving the big bucks for the Model A roadster and a 25 Buick I wanna build down the road.

If I find a termi motor or coyote with a Whipple I would do that but.... $$$$$$$
 

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