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2004 Ford Escape Limited Tachometer fluctuation

I just bought a used 2004 Ford Escape Limited ( with a 30 day warranty). I have noticed when it is in park and idle, the tachometer fluctuates a little, between 500 and 1000 RPM’s. When I was driving it tonight I also noticed that between 35-40 mph, the tachometer fluctuates up and down and the car seems to surge a little. I put it in cruise to make sure that I wasn’t adding any pressure on the accelerator that I wasn’t aware of and it still did it. ( Not sure if this problem could be tranny related, but I should note that I had the tranny flushed when I purchased it last week.) I obviously want to make use of my 30 day warranty, so I am having it looked at, but would like some ideas before then so I know what they should be looking for. Thanks!

Possibilities:

Bad idle air control valve
Vacuum leak
Dirty throttle body
etc.

I hope the shop that flushed the trans used the correct Mercon ATF

I hope you have a trusted mechanic
If there are any stored fault codes, please post them

From the receipt it appears that they used Motorcraft ATF, which a google search showed as Mercon ATF. It was done at a Ford dealership, so they’d better know what they’re doing!

Assuming this is an automatiic, it could be seraching between gears at that speed. You could check for this by shifting to the lower gear change at those speeds and seeing if the symptom disappears.

I’m not trying to talk you out of using your warranty…you absolutely should do that. I’m only offering a possible explanation for the symptom.

“when it is in park and idle, the tachometer fluctuates a little”

Open the hood and listen closely to the engine.
If its speed is really bouncing up and down out of gear at idle then it’s highly unlikely the problem is in the transmission.
Besides the possibilities db4690 mentioned there could be a faulty temperature sensor or engine computer.

Well, a few years ago, that might mean something wrong with the ignition. I don’t know about newer cars.

As mentioned above, there are lots of things that can cause this. Probably the first place I’d look is the setting of the idle speed adjustment screw (assuming your car has one). There might have been a air/fuel mixture problem which affected the idle speed, and this screw was adjusted to try to fix it. But that is not how to fix a mixture problem. So then the idle speed screw is not set to the position the ECM assumes it should be set, and this confusion causes the ECM to try to compensate, creating surging. Ask you mechanic to verify the idle speed screw is set to its nominal position.

Well, I’ll probably be corrected, but I don’t believe many cars have an idle speed screw

Well, I took my car in for an inspection and at a Tires Plus store they said the tranny was stuck in third gear, and that I would possibly need a new tranny. Because it was still under warranty, the dealership I purchased it from agreed to service it for me and run through the problems Tires Plus noted. They called today after having it in their shop for 4 days, and said they changed the ignition coil, but couldn’t find anything wrong with the tranny. Does this sound like an honest response to what Tires Plus noted as being wrong with the car?

Ihink the Dealership hit the problem on the nose. I said 4 posts back that it probably was an ignition problem. Let us know it they fixed it.

It seems better after they fixed that. The other idling problem is something to do with my defrost. When the defrost is on and the car is idling or stopped at a stoplight,etc., the tachometer fluctuates when the defrost kicks on. Never had that happen in all the cars I have owned, but since the tachometer doesn’t fluctuate when the defrost is off, there is nothing they can do according to them.

Well, the reason the tach fluctuates when the defrost comes on is the fact that the A/C compressor runs with the defrost on.

The AC compressor is adding load too the crankshaft when you turn the defroster on. Modern cars all engage the AC system to remove moisture when defrost is turned on. A fluctuation would be normal, and even a higher idle, to compensate for the added load.

@smile13 you have the CLASSIC symptoms of a bad idle air control valve.

Take it back the dealer
Leave the car running
Get the service writer to come out
Open the hood
Turn on the defrost
When the idle fluctuates, tell the writer to keep the car until it’s fixed

Be persistent