first its an automatic. when i start my car it jump up to 2000 rpm and sometimes it stay there intill i put it in park or drive. then it drops down to 1000 rpm. then when im driving at 35 miles per hour it stays at 1500 rpm. dont know which gear im in but when ever i hit 40 it shifts. if it 38 miles per hour it wont shift the rpms stay at 1500 too. only shifts at 40 at that gear. is that normal cuz i dont know?

 

hmm 1000 rpm is a pretty steep idle. i have an 02 auto too btw and on cold starts it should idle higher for a little bit, until the engine gets up to operateing temperature. but generally it will sit at 1200 or so until it gets to temp or i put it in gear and then i start idleing at 600-700

 

wow i figured i would get more help on this one. i love how when someone has a real problem people just ingnore you. thanks for the info Intnz.

 

Has it occurred to you that maybe we don't have the answer? I know I don't have the answer, hence the reason why I haven't helped. I'm sure others would like to help, but there is a chance that none of us have the answer.

 

this happens every time i try to ask a question though. i know some people wont know but every one on here? comeon now. people are smarter than me here. i dont know anything about cars. and the things people type on this forum amaze the hell outta me. i just get pissed when i ask something no one replies, then a month down the road someone else ask the same thing. everyoen answers them. sorry i'm trying to quit smoking and its hard. i feel like killing someone right now. so i apologise.

 

many times its just because the same questions get asked a lot. The search feature does wonders instead of getting mad at us. Start off by cleaning the IAC if that doesn't work here are some questions that have been asked on the same topic with other ideas as well. I would start with the IAC though. Vacuum leaks are other possibilities. Have any mods been installed right before this started to happen... also a lot of times people don't see every thread I didn't notice this until now

https://mustangboards.com/modular-4-...high-idle.html
https://mustangboards.com/v6-tech-fo...92-prblem.html
https://mustangboards.com/v6-tech-fo...-probs-v6.html
https://mustangboards.com/modular-4-...e-problem.html

 

I wouldn't call 1000 rpm a high idle. Mine is a stick, so I know what gear I'm in. Any help I may provide is from my observations with my car, which has a basically stock drivetrain. YMMV.

When I start my car, the RPMs jump to almost 2000 rpm and usually quickly fall to about 1200. This is normal. Once the engine warms up, idle will drop to about 980-ish. Any lower than that (i.e. I let the clutch out without giving the car gas) and it starts chugging and will eventually die.

In 4th gear while driving at 35-38 miles per hour, I am usually around 1500 or so rpm. I don't like shifting to fifth until I'm traveling at least 42 miles per hour, or the rpm drops to about 1000 or just below and the engine starts feeling a little rough. So your auto probably is set to shift into overdrive at about the same point.

If you think your car is having a problem in light of this information, start with the IAC like Dave said. I'd also recommend checking the PCV valve and making sure the MAF is clean while you're inspecting stuff anyway -- just be sure to check out one component at a time, test drive, let the car cool down, and repeat if you're trying to isolate a problem.

EDIT: INtZ, did your car always idle at 6-700? That seems low unless it's attributable to some mod or another... then again, I have never even been in a mustang with an auto.

EDIT AGAIN: I paid a little closer attention today as I was out driving, the idle does drop to about 800 or maybe even a little less once the engine is warm. Maybe this will help you decide if your car is okay or not, good luck!

 

srryabout being all pissy. im trying to quit smoking and im taking it out on everyone. what does you car idle at 35 mph? mines 1500 rpm. and only shift at 40. that was my main question i wanted to know.

 

ya my cars always idled around this range but now thinking about it im sure your idle might be different depending on altitude. the higher the altitude the thiner the air is so might idle higher but im just throwing out ideas

 

mines about 900 something at idle. Mine usually isn't steady at 2000+ rpms unless I'm on the highway so going around 70-75. I'll check what mines at on 35mph tomorrow on my way home if no one answers before you. I would guess probably around 1300. Since yours stays there I would clean out the IAC just to see if that fixes the issue. It can't hurt

 

your speed dosent have a whole lot to do with what gear ur in bc if your on a hill it will be a bit diff
im mean i have a 5 speed but it all depends

 

how many gears are there in an auto mustang? i never noticed. to take the iac off do i have to remove the intake as well? i have the stock one. and i havnt seen the iac in a while i forget where its located at. that you all for you help. and i still apologize for being an *******.

 

i think its 3 with overdrive

 

the auto is a 4 speed.

 

PCV valve is where?
IAC i thought i knew what it was, where is that?
should i go and get one of those haynes books?

 

Passenger-side valve cover. There is a black rubber tube running to it from the intake/manifold area.

It's on top of the intake manifold, and is connected with wires to the ECU.

Haynes or Chiltons, your choice. And yes.

 

thanks for the info. i got one of those books but it doesnt go into much detail on the 99-04 3.8 motor. it is helpful. ill most likey try to clean the iac tomorrow seeing how they dont show the titans on tv in my area. but the book says not to clean it with carb cleaner or anything.

 

The Haynes manual has the IAC in part 4, fuel & exhaust. And yeah, don't use carb cleaner on it. It'll mess up the coating on it.

 

whats better haynes or chiltons...

 

I've been using the Haynes manual with no complaints.

I've thought about buying the Chilton's as another resource to have handy. The Chilton's looks thicker...