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Engine shudders

(2000 Ford Ranger)
in Jackson, MI on October 19, 2010
When i come to almost a complete stop the engine shudders and sound like it wants to stall but smooths out. This doesn't happen but only once in a while. I'm not getting any codes. I did just fix a code of P0171, had a hole in the EGR tube. My engine still wants to shudder sometimes. I have replaced MAF sensor, PCV and plumbing, fuel filter,plugs and wires. Should i replace the Idle Air control?
Displaying 2 answers & 3 comments
Popular Answer
on October 19, 2010
Is this an automatic or manual transmission? An automatic transmission vehicle with this symptom could be caused by a torque converter that is not releasing, or a transmission that is not downshifting as needed.

As you get to a stop, you have been coasting a bit, and very little fuel is required to run. So it is likely otherwise an air flow issue as you suspected, like a vacuum leak or unmetered air leak (check air box and hose), or the idle air control valve you mentioned.

Pay attention to the first thought though if it's an automatic.
on October 19, 2010
Automatic Transmission. No vacuum leaks had it smoked tested . I doubt the torque converter is acting up. This happens when i"m almost stopped to put it in reverse to park my truck never happens going down the road and coming to a stop. and doesnt happen all the time.
on October 19, 2010
Certainly may not be, but especially since it does not happen all the time, a torque converter that is not releasing or is staying partially engaged (the torque converter clutch (TCC) shows engagement in percentage when monitoring) can cause the idle to get so low that it will shudder, and then possibly it releases in time.

The best move is to have a good repair shop have a look at it; I am only offering opinion based on what i've seen over the last many years while operating a Ford service department and working on the vehicles. Having a diagnostic tool hooked up and performing different appropriate tests, while monitoring the parameters and actively engaging and disengaging various components (like the TCC) is the only way to really tell what's going on. Good luck in finding the cause!
on October 20, 2010
if the iac motor is the issue, try taking the wires off while the engine is running. the motor should idle very slowly about 500 rpm. if it stalls, then have the throttle body cleaned out, base idle adjusted to spec and yes, i would replace the iac valve.

Roy
on October 22, 2010
I pulled the wires off the IAC today. Rpms dropped down to about 500 like you said but didn't stall. I did notice yesterday and today when i drove it that i'ts getting worse and its
shuddering when i turn corners. could this be a serpentine belt issue or a power steering issue? Just changed the belt 3 monthsago. Fluids full
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