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'02 Taurus rpm surge


bradleyheathhays

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Have an '02 Taurus 6 cyl where the start up and idle down seem normal, but when it's put in gear and allowed to move just with engine idle it has a consistent wave like throttle surge that can easily catch you off guard and propel you too far forward. The surge happens in pulses about a second and a half apart. After you get rolling above 5mph the surge either doesn't happen or isn't noticed. Does it all the time anywhere in a drive, cold or hot. Been happening for at least 5 years now.

Any idea what's causing this?

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No check engine light but I'll hook up the code reader to see if it's showing anything.

 

I've had someone else comment on the problem...

 

'That scenario is called an idle roll or a warm idle roll. Typically what is happening is a condition that the PCM corrects and then stops and the condition repeats with correction and return to the issue. Unmetered air getting past the throttle body or a vacuum leak or some other lean or rich condition that is corrected and then the correction stops.'

 

I'll be cleaning out the throttle body and IAC today, and possibly the MAF to see if that helps the situation.

Edited by bradleyheathhays
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You know I'm not really sure about the number of valves right now. It's my mother's and I'm just getting to know the car. An insurance card says it's a model SES.

 

edit... If it helps the VIN is 1FAFP55U72G273676. One guy at a car parts store said the U in the VIN gave him enough info to know what kind of engine it has.

 

After cleaning the main throttle body I was going to clean the IAC valve but found this written on the outside... "Attention: Do not clean inside throttle body or adjust hard stop screw. Special coating on throttle plate and bore."

 

Again, this was written on the small IAC attached just after the throttle body, although it seems to refer to the throttle body itself. So is this referring just to the smaller 'body' the IAC is installed in or does it refer to the main throttle body with the large pivoting circular flap valve?

 

And whatever it's referring to, can I clean it despite this warning or should I follow the instruction?

Edited by bradleyheathhays
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Clean the throttle body and iac with a rag and come cleaner dont use a brush. Also make sure the air filter box is secure and the tabs at the bottom are not broken. If the box doesnt fit together tightly it will cause a rolling idle. Check and or replace the Pcv valve and check the elbow for being collapsed or mushy and replace if necessary. Its a 12 valve motor btw.

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