Rough idle at start up

[quote:dfb02b4171="Service Writer"]Start at the beginning and find the codes in the pcm and we can go from there.[/quote:dfb02b4171]

We have replaced the Gas filter, cleaned out the throttle body and put a new air flow sensor and it still won't idle. Any suggestions!

Thanks.
Mike

What did you determine was the problem with your 1999 Taurus. Mine had the same problems and I did about the same repairs and no improvement

For the last year or so, I've had intermittant issues with my car sputtering and idling rough when restarting. Happens when I restart after running into the store, etc. and only when the engine is warm. It did it again on Friday and now will not start at all after sitting for over a day. All other times would start fine after the engine sat for 3-4 hours. Checked fuel filter & pump and looks to be ok. Checked spark on plugs and getting spark on all 6 plugs. Any thoughts. Had it in to the dealer a month ago for an alternator and had the codes read and no codes were stored for anything releated to the issue I'm having as I asked them since I was paying the fee.

IDLE SPEED
Idle Air Control (IAC) Valve Assembly
IAC valve assembly is used to control idle speed and provide a dashpot function. IAC valve assembly meters inlet air around the throttle plate through a by-pass within the IAC valve assembly and throttle body.The PCM determines desired idle speed or air by-pass and signals the IAC valve assembly through specified duty cycle. The IAC solenoid is built into IAC valve assembly. IAC solenoid responds by positioning the IAC valve to control amount of air by-passed. PCM monitors engine speed and adjusts IAC duty cycle to achieve desired RPM. IAC valve assembly is not adjustable and cannot be cleaned.

Always look for the simple things first. When was your last set of plugs or tune up?

I tried the new IAC and $52 later, no difference in performance. Still holds the RPM too high when you take your foot off the accelerator, acting like the cruise is on but then when the brakes are applied, it will idle down at a light and sometimes, not every time, will die at low idle.

[quote:a6b3506c4d="Dave H"]IDLE SPEED
Idle Air Control (IAC) Valve Assembly
IAC valve assembly is used to control idle speed and provide a dashpot function. IAC valve assembly meters inlet air around the throttle plate through a by-pass within the IAC valve assembly and throttle body.The PCM determines desired idle speed or air by-pass and signals the IAC valve assembly through specified duty cycle. The IAC solenoid is built into IAC valve assembly. IAC solenoid responds by positioning the IAC valve to control amount of air by-passed. PCM monitors engine speed and adjusts IAC duty cycle to achieve desired RPM. IAC valve assembly is not adjustable and cannot be cleaned.[/quote:a6b3506c4d]

Thanks. Plugs were changed around 50K. Would be surprised if it were the plugs as there appears to be no sense of ignition in any cylinder but you never know. Is there anything to try to see if fuel is making it to the injectors or fuel rail? Haven't gone that far, just know fuel is making its way out of the fuel filter on its way to the injectors but haven't confirmed fuel is making it into the cylinders. I've had my share of car trouble over the years and this is the first time I've had a car do nothing but just turn over. About 8 inches away from the engine as the fuel line come up from under the vehicle, there is a silver component that looks like a regualtor. I was unable to get the fuel line off this part to see if fuel was getting this far.

Your getting unmetered air by the sounds of it...high idle and the two codes. The brake booster uses vacuum when you press it taking away some vacuum.

Check for a vacuum leak such as around the intake manifold and the pcv hose. Being 10 years old, I wouldn't be surprised if the pcv hose was deteriorated, but check any vacuum source going into the engine.

The little "silver thing" you see it the fuel pressure regulator. Just beyond the regulator on the fuel rail should be a "pressure tap" with a cap on it. Here is where you connect a guage to check your fuel pressure with "key on" and "key crank". You will also need to check for spark at the plug wires and injector pulse at an injector connector. Both of these are checked on "key crank".

Had same problem with my 1988 crown vic low milage 34k It was in fact unmetered air getting in part time thru a vacuum line to a canister(tab/tad) under the ac compressor that came off. Any vacuum leak will cause this heart ache.

I have to put in my little bit here.....
Ford products since 1992 have a special coating in the throttle body to prevent sludge buildup. These throttle bodies should NEVER be cleaned. The coating actually seals the outside diameter of the throttle plate so that intake idle air is metered through a calibrated hole in the throttle plate. Cleaning or backing off the idle stop screw will damage the throttle body, and as far as I know, there is no repair for it other than replacement.



We have replaced the Gas filter, cleaned out the throttle body and put a new air flow sensor and it still won't idle. Any suggestions!

if the problem started after you changed the spark plugs retieten the the mass air intake the big thing on top( the gasket under it may be damaged.) i had the same problem here 1 year ago. did every thing you did this is the problem. no one esle is thinking human error i made a mistake.but man enough to say it.maybe you did to.or the gasket is bad but this is what is wroung. some time it helps to retrace your steps. glad i could help.