Fed up with my car and the idle

[Turbo92PGT]

Long story short. My car idles high all the ****ing time. I cant stand it anymore. I have replaced the IAC (have 4 or 5 to swap between), even purchased a brand new one. No help. Replaced the TPS, bought a new IAT sensor and tested the ohms with my stock ford sensor. Same, so that tested good.

TPS voltage is set at .97 (.96-.99 ok i heard).

I start the car up, it will begin to idle at 1200, then slowly climb to 1500. Then after a good 30 seconds idling at 1500 it will cut out and nearly die. Then stabilize at 900. Then after a couple seconds will idle at 1200 again.

While driving I let off the gas to find the car not engine braking at all but rather speeding up slightly. So I push in the clutch and the rpm's begin to climb.

With my "dyno tune" my rpms on the freeway will hang at 4000RPM.

Recently threw codes for P1504, P0500, P0113

IAT code may be because I disconnected the IAT while it was running for a few minutes to see if it affected the idle.

If you disconnect the connector to the IAC it will drop the rpms.

The throttle body idle screw has not been adjusted!

I put it back to stock tune and it doesn't hang at 4,000 but will hang just the same.

Throttle body is stock, plenum is stock, engine is a stock 99 PI 4.6 with crower stage 2 cams. Fuel filter is new, plugs are new, wires and coil packs are new, O2 sensors are new.

Throttle body is not sticking

 

[deftsound]

this may sound dumb but are you sure you don't have a vacuum leak somewhere? What about a cold air kit? One time the filter on my cold air intake came off and i couldn't see it because it was in the fender and it caused the same idling problem...

 

[Airbeast]

Check your vref voltages at different sensors. They should be almost 5v. Mine was doing about the same thing as yours and randomly going crazy.

That p0500 is a VSS malfunction. Does your speedometer do anything abnormal?

I had a ton of water in my ECM connector under the kickpanel inside the car. I don't know how it got there but it was making the engine do all sorts of weird things and the speedometer would sometimes go crazy. I blew it out and it's all ok now. Also I would blow out your main harness connector and the 2 other connectors that are by the main harness connector.

And like said, if you have an air leak after your maf, it can cause strange idle.

 

[mineralgraygt]

that sound like a vacumn leak to me

 

[eliteJAE]

like airbeast said, check the connectors for water, if you cant blow it out, spray some WD-40 and itll displace all the water in between the contatcts.

 

[Turbo92PGT]

Well I will give that a try. Did you guys have trouble with water on the passenger side floor too then?

The vacuum is a steady 18-20 =/

My intake is just a tube with the maf and a filter attached so no missing filter!

Keep the ideas comin!

Thanks

 

[96GTstang46]

Termi? JK

If you need another hand, hit me up....

 

[Airbeast]

Yeah I don't know how it got there, but the connecter to the ECU inside the cabin was full of water. Everything else was dry. You should also check your sensor voltages. Mine were going all over the place. I spent all day tracing and checking wires. The OHM meter wasn't showing any abnormalities either despite the water. Finally just pulled the connector to the computer to check the wiring. That's when I discovered the water and all was solved.

http://forums.stangnet.com/showthread.php?t=733651

I'd check the three connectors on the rear right of the engine bay. The big one and the two that go to the oxygen sensor/vss sensor harness. Then check the inside connectors to the ECU. I'd also check your VSS connecter on the transmission because they are likely to get some water in them and it can't leak back out since it's pointed up. I'd remove the sensor and make sure it's dry. I'd rent borrow a compressor to blow out the big connector since it can't be pulled up and flipped upside down. Took a lot of air to get mine dry. The WD40/Silicone spray trick works well on the ones that you can flip upside down but water is heavier than oil so it will stay in the big connector.

 

[the98stang]

vacuum leak for sure. Use a butane torch to find the leak. The idle will increase when the butane enters the intake.

 

[nyuk98gt]

Turbo92PGT:

Is this a new problem or has it been doing this since the dyno tune? Does it idle high with the stock tune? (You said it hangs at 4k RPM but I assume that this is while freeway driving (so same thing it does with the dyno tune)). Idle drivability can be a bear to tune (trust me).

I like the butane (propane) torch method of checking for vacuum leaks. Rule out hardware issues first and then start looking at the tune.

Chris