I own a 2007 Ford Taurus with about 108k miles on it. When I first start the car, the rpms stay very high (2000) or so for about25 seconds. Once I start the car, until it gets all the way warm, the rpms want to stick around 1300 until I’m stopped for a few seconds, then they jerk downwards hard to almost 400 and come up to around 700. After the car gets warmed up, it no longer sticks when I brake, but then when I’m stopped it lurches shakes and jerks between 400 and 1000 rpms. Occasionally it will die ( maybe twice a week) but then starts right back up again. I have replaced
Air compressor
Idle air control valve
Throttle body sensor
I replaced the throttle body sensor yesterday and it seemed to drive better but it only lasted for about 12 hours then the next time I started the car it’s doing it again. I really need some help here. The only solution I’ve found so far is that it jerks just a little less when I’m in neutral.
Thanks
I would say that your IAC is carboned up and causing the sticky idle.
This is what it should look like.
To be sure my diagnosis is correct, locate it under the hood,start the car when it’s cold and acting up, then tap on it with a screwdriver handle. If this changes the idle…it is sticking.
This procedure will dot cure the problem, but you will be able to pinpoint that it is the IAC.
You may be able to remove the two bolts that hold it and clean the passages up, then bolt it right back down.
But for $50 I would just replace it.
Yosemite
I just tried this after letting it sit for about 6 hours (it’s like 40 degrees outside) I just replaced my IAC LIKE two weeks ago. I forgot to add that it’s worse when the heat is on. I even disconnected the IA C while it was running just to make sure and it immeadiately killed the car.
Collin
Then I would start looking for a vacuum leak. It is a little early, but the rubber vacuum lines do dry out from the heat under the hood and the environment.
Yosemite
How about the temp sensor? It sounds like the computer does not know what temp.
This definitely sounds like a problematic IAC. Or something wrong with what controls the IAC. How does your IAC work? Is part of it immersed in the engine coolant? Or is it’s position controlled by the ECM?
Next guess is a sticking throttle valve; i.e. the butterfly valve. Usually the best way to clean it and make it work correctly, smoothly, is to remove the throttle body and clean it spic-n-span on the bench. But there are throttle body cleaners I think that you leave the TB on the engine and spray into the air intake. Might be worth a try, although I’d b a bit worries that might damage a maf or map or iat sensor.
Third is line is like Yosemite says above, some kind of air leak into the intake manifold. You could start off by simply measuring the intake manifold vacuum with a vacuum gauge, see what that tells you. Something like a power brake booster diaphragm leaking could produce this symptom, and that should show up with a vacuum gauge measurement.
My IAC position is hooked up with a plug and is controlled by the ecu. If it helps at all, the problem is much worse when I turn on the heat AC. Also, I have a working charged new air compressor but my car will not blow out cold air. When you turn the temperature control on the dash it does absolutely nothing.
Collin
I pulled the throttle body today, it was dirty as hell, I’m letting it dry from the spray.will update later collin
Not sure what you mean by
"problem is much worse when I turn on the heat AC"
It sounds like your IAC is the modern type, where the ECU (aka ECM) measures the coolant temperature via the ECTS, then controls the IAC directly via some kind of electrical servo motor. It’s a pretty common thing for those servo motors to go bad or even more likely, the mechanical linkage gets gummed up and the servo motor doesn’t have the force to overcome the friction. Usually that is obvious once the IAC is removed and on the bench. I’m presuming you’ve already done that, and the IAC seems to be working smoothly.
You plan to give the throttle body a good cleaning is definitely a step in the right direction. Did you notice if the throttle valve mechanism was a little sticky, esp near when it is all the way closed? That could be part of the explanation.
Re your AC problems, I’m don’t know much about AC. There’s lots of stuff that can go wrong w/the AC system, besides the compressor. If I had that problem the first thing I’d be suspicious of what that the venting and blend doors were not operating properly. Sometime you can poke your head up under the dash, maybe use a combination of mirrors, like dentals mirrors, and see if any of those doors are stuck, not working.
Those doors are often operated via electrical control by similar servo motors used on the IAC, and suffer the same problems, gumming up and not able to overcome the friction. The most reliable kind of vent and blend door mechanisms operate by cables, and the next most reliable operate using vacuum motors. The least reliable seem to be the servo motor type. My early 90’s Corolla uses cables, and never had a single problem with the door operation to date. My early 70’s Ford truck, the same. Never had a problem in 40+ years with the heater doors.
If you have vacuum motor controlled vent and blend doors, for those to work properly there has to be a good steady supply of vacuum, so you might actually have a vacuum problem, and that could explain the lack of AC, as well as the weird idle.
My blend doors are operated by cables. I checked then. They are both non functional. Teeth on the motors are ground down. I cleaned the throttle body, it was very gunked up but it didn’t help much. I took it to a mechanic today, his plug in scanner was not able to read anything in my ECM. But i did find out that I’m getting almost no electrical current from my rear spark plugs and wires. The engine is misfiring, causing this stupid idle problem. I’m going to replace them Friday.
Well, at least you know why your AC isn’t working. That’s a pretty common problem reported here. Best of luck getting to the bottom of the misfire problem. Sounds like you are on the right track.