Common Reasons Your Mercury Mountaineer Wont Accelerate

If your Mercury Mountaineer won’t accelerate, that is a serious cause for concern.  There are a lot of different reasons that can cause this.  Diagnosing the issue can be narrowed down by whether the engine is still revving when you push the gas or not.  There is a section for each scenario with likely causes for each.

Before looking into anything else, if your check engine light is on, get a code scanner and see what trouble codes are stored in the computer system.  They can provide valuable insight as to what the problem may be, and really help you narrow down the problem.

 

Not Accelerating Diagnosis Mercury Mountaineer

 

Mercury Mountaineer Won’t Accelerate:  RPMS Go Up

If your Mountaineer won’t accelerate, but the RPM’s go up it’s usually not going to be an engine related issue.  Somehow, the power that your engine is creating is not making it to the rear wheels.  This is typically a transmission related issue.

Here are the most common cause of acceleration with the RPM’s going up:

 

1.  Transmission Fluid Low

If your Mountaineer is too low on transmission fluid, it’ll will no longer be able to transfer power to the rear wheels.  The power goes to the torque converter, and that’s the end of the line.  You should check the transmission fluid immediately.  This is the number one cause of not accelerating but the RPM’s Go up.

Low Transmission Fluid Signs

 

2.  Bad torque converter

The torque converter is responsible for taking the mechanical power of the engine and converting it into hydraulic power.  If the torque converter has gone bad, it will no longer be able to do this job.  No power can get to the transmission.

Bad Torque Converter vs Bad Transmission

 

3.  Drivetrain No Longer Connected to Wheels

If you’ve broken a drive/axle shaft, your Mercury Mountaineer’s transmission has no way to turn the wheels anymore.  If this were the case, there would not be any movement whatsoever from the vehicle.  You also wouldn’t feel the slight jerk your Mountaineer as you put it into gear.

 

4.  Bad Transmission

If something has gone wrong in the transmission, your Mountaineer may not be able to accelerate any more.  If it can no longer shift, it could be caused by a solenoid/valve body has gone bad, clutch packs, debris, and much more.  Automatic transmission are very complicated.

 

5.  Clutch

Although the manual transmission is going away, if you happen to have a Mountaineer equipped with one, a bad clutch can cause it not to accelerate.  The clutch is responsible for making a direct connection between the engine (via the flywheel) and the transmission (via the input shaft).

When the clutch can’t hold on anymore, it’ll start to slip.  Slipping means that it loses its grip on the flywheel and it feels like you’ve pushed the clutch in.  This will usually happen at highway speed, under heavy acceleration.  It only gets worse as the clutch disk slips, burns up, and can handle less and less torque.  Eventually it’ll only move in first gear or not at all.

 

 

Mountaineer Won’t Accelerate:  RPMS Stays Put

Mercury Mountaineer Won't Accelerate

If your Mountaineer won’t accelerate, but the RPM’s do not change, that is an indication that there is an issue with creating power.  The issue is going to be something affecting the motor.

Here are some common issues that can affect the motor:

 

1.  Clogged Catalytic Converter

If the catalytic converter gets too clogged up, it’ll keep the motor from accelerating properly.  It’ll “bog” after a certain speed.  Maybe it’ll drive 20 miles an hour just fine, but after that it just doesn’t want to accelerate whatsoever.  This can also be a sign that it’s not getting enough fuel as well.

Mercury-Mountaineer Catalytic Converter Diagnosis

 

2.  Bad Fuel Filter

A bad fuel filter will not let enough fuel into the Mountaineers fuel injection system to support operation above a certain demand on the engine.  It just can’t provide the fuel pressure.  If this is the case, like the catalytic converter, it’ll feel like everything is fine until you hit a certain speed, and then it’s going to bog down again.

Mercury Mountaineer: Bad Fuel Filter → Symptoms and Diagnosis

 

3.  Timing Chain or Belt

The timing chain (or belt) is responsible for keeping the upper valve train synced with the crankshaft.  This is vital for spark timing.  If the timing is off a little and the engine still runs, the timing belt may have skipped.  If it has jumped too much the Mountaineer may not even fire.

 

4.  Vacuum Leak

Your Mountaineer’s engine creates a vacuum as it runs.  The amount that is created is carefully thought out during the engine design process.  When there is too much vacuum, it creates a situation where air is not coming in and being read by the MAF sensor, which causes the vehicle to run wrong and not accelerate.  The MAF sensor also may not be functioning correctly.  If this is the case, it’ll almost always throw a trouble code.

Mercury Mountaineer: Bad MAF Sensor → Symptoms and Causes

 

Conclusion:  Mercury Mountaineer Not Accelerating

As you can see, there are a lot of reasons that your Mercury Mountaineer may not accelerate.  Good luck diagnosing yours.  If there is anything that you can add, please feel free to leave a comment.

 

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