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Ford Ranger RPM's slow to drop

Hi, I have a 2005 Ford Ranger 4.0 V6 2wd Edge, with around 175,000 miles. It runs great, however the RPM’s are slow to return and it seems to idle a little high for longer than you would expect when starting the engine. For example, exiting off the freeway with the clutch depressed, the RPM’s will drop from approximately 2300, pause at 1800 for a second, then drop and pause at 1100 for a few seconds before returning to idle. If stationary and rev the engine, they seem to drop back normally.

So far I have changed the IAC valve and checked for vacuum leaks (not sure how exhaustive a check it was but sprayed every joint I could find). My mechanic agrees that it is abnormal, but has suggested that we wait for it to worsen enough to throw a code rather than spend a lot of time and money replacing things that may not be a problem. Also the throttle cable appears to be functioning normally and not sticking.

Anyway, I would appreciate any thoughts or opinions.

Thanks

Tom M

There is a TSB that applies to this. tsb 05-5-10. The powertrain control module needs reprogrammed.

If this hasn’t been happening since the car was new, consider to ask your mechanic to check the engine coolant temp sensor. The ECM might be thinking the coolant remains cold, when it already has started to warm up. Problems with the throttle plate sticking in the housing or the MAF on the fritz could cause this problem too.

@TommyM2 here’s that TSB

I suggest you go to a Ford dealer and ask them to perform the TSB. Since you’re out of warranty, they’ll probably want a c note.

Thanks Guys, that sounds like it. I will follow advice and visit the dealer first. If that doesn’t help I will follow GeorgeSanJose’s advice.

Thanks again.

I’ve had a similar problem in my '98 Ranger 4-cylinder, which has been regularly serviced by our local Ford dealer. They suggest two “solutions:” first, there is nothing they can do about it, and second, don’t worry about it. Two independent shops we’ve visited for this situation say the same thing. I’ve owned it for 118,000 miles, still don’t need to add oil between changes, its performance has been fine, and I don’t worry about it anymore.
Occasionally, when it gets annoying I will put the car in high gear and let the clutch out with my foot on the brake, which brings the rpm’s down. Something similar might work with an automatic.
If this is the only problem you have with the Ranger, it’s been a great truck for you, just as mine has been for me.