Idle running really high

[4GOTNPNY]

Hi everyone the car is running a really high idle. I’m
Stumped and need opinions. It’s a 302 mass air car. Just had it tuned at diagos drive fantastic took it racing the next day after the first pass idle spiked I replaced the iac with a used one I had it ran great on my way to work yesterday idle spiked again. I have new coolant temp
Sensor tps is adjusted if I disconnect iac the idle drops checked for vacuum leaks everything checks out. I replaced the iac again and it didn’t change anything this time. It’s a new Motorsport harness so I’m not sure what to do I want to enjoy the car for a few more weeks since it’s been down all summer but I want it running normal again

[bbriann]

Could be in the tune

[ZR]

Seen similar issue with aftermarket coolant temp sensor or broken wire in the harness.

[4GOTNPNY]

I stripped a bunch of factory intakes not long ago I will
Check one of the used ones and see if that fixed it up. The new one is a standard one

[ZR]

Not sure if still available or not but Ford had introduced a newer style sensor and pigtail for the 5.0 push rod

[Parkway Ford Lincoln SVT]

That updated sensor with the new connector is still available, Motorcraft part number DY-1145. CAN retail is $93.40, TMC club price $58.38 + shipping and HST.

[4GOTNPNY]

Still no change I tried everything I cut a brand new Motorsport harness for the update sensor and still no change I have done everything I know idles around 2500 unplug the iac and it drops and runs fine with a slight hunt iac is new there is adjusted nothing in the throttle body coolant system is burped never been stumped so bad before and I like to think I know this system really well

[ZR]

TPS voltage?

[4GOTNPNY]

.98volts

[ZR]

-any chance upper intake is sitting tipped, either it or vac port hitting intake?
-does throttle body blade have a drilled hole it's not suppose to have?
-sure egr is fully closed (if equipped)?

[CHILL5.0]

One thing I would check is your TPS. I had this same issue or very similar. Turned out it was the TPS. I'd do a base idle reset and it would be fine and then I'd drive it and come to a stop and it would be idling at 2000 rpm. It's not the IAC that is the problem it's something telling it to open. In my case it was the TPS, worn out where it mates up to the butterfly valve. When you do a base idle reset after, you set your throttle body with your IAC unplugged to your desired idle rpm while running. Then with key on engine off you check your TPS voltage. Should be at .98 volts. If it's not then adjust it to that voltage. Then you can shut key off, plug IAC back in. Disconnect battery for 15 mins and reconnect. Good to go.

[ZR]

^ Good point, similar problem bunch of years ago with a 351w in a van, intermittent mild run away that turned out to be exactly that.

[4GOTNPNY]

No egr. intake is not tipped I will go over vac lines again next week even with the iac unplugged I ran 12.20 at 110 yesterday lol no hole in the throttle body blade

[ZR]

Look to TPS / dead / inaccurate spot next.

[4GOTNPNY]

I will check the tps again this week for a dead spot I changed the coolant temp sensor with the updated version and would like to know if anyone knows the part number for the pins I hate butt connectors and would like to repin the connector so it looks factory since the harness is a new motorsport one any help would be appreciated

[CHILL5.0]

Not necessarily a dead spot in the TPS. On mine it was the 2 teeth on the bottom side of TPS that were physically worn. Like I said I would do a base idle reset, would be good for a little bit and then I'd come to a light or stop sign and be idling at 2k. So what was happening was my TPS was actually not sitting in the same spot it was supposed to be when I did the base idle reset and it was telling the computer funky readings.

[ZR]

Removed one yesterday where 1/2 throttle blade was bent. Car has had intermittent idle hang, see today if it's fully cured or not.

[maxwell6]

Just curious if you solved your high idle problem. I had a high idle problem turned out to be intake gasket was leaking. Have you had your intake off lately.

[4GOTNPNY]

had the intake off just before the tune but it was tuned no issue then started a day later

[4GOTNPNY]

anyone know the part number for the coolent temp sensor pins :)

[hammerhead]

easy way to check intake leak - with engine running spray brake clean around intake gaskets - idle will race if a leak is present - your first pass may of caused a leak..just a thought good luck - also I'm not sure about your car but some cars use vacuum for heating vents under dash - it will be hard to hear a leak - sorry don't know the part #

[maxwell6]

I had the same problem ran great the first couple pulls then high idle. Check your torque spec on your intake.

[ZR]

We've gone back to nothing but OEM Ford intake gaskets on mod motors after sealing issues with aftermarket.