If your vehicle is idling at anything over 1000 RPM, this is known as ‘idling high’. A high idle can cause all manner of problems with your vehicle, including increased fuel consumption and engine wear. So, why is your Dodge Ram 2500 idling high?
Almost all automatic Dodge Ram 2500 models have an idle-up feature. This allows the driver to manually set a high idle level. If you did not set a high idle level yourself, then the issue could be with a broken idle control system, a vacuum leak, an overheated engine, or a damaged ECT sensor.
There is no one reason why your Ram 2500 may be idling high. Unless you have experience working on vehicles, it may be tough to identify the problem and ultimately fix it too. Most problems will need identifying by a qualified mechanic (preferably a Dodge dealership).
High Idling In A Dodge Ram 2500
All automatic Dodge Ram 2500 have an idle-up feature. This allows people to automatically set their vehicle to a high idle speed. This is meant to rapidly increase cylinder heat. It should be used sparingly. It is unlikely that this is the reason why your Ram 2500 is idling high, though. The idle-up feature has to be manually activated, and you have to go through a bit of rigmarole to turn it on.
If your Dodge Ram 2500 is idling high and you haven’t been fiddling about with the idle-up feature, then the problem is likely to be caused by a damaged component or system in your vehicle.
The best method for diagnosing high idle issues in your Ram 2500 is to use an OBD-2 scanner. This is a small device that plugs directly into the vehicle’s computer. It will read any error code stored in your vehicle’s computer, telling you the exact parts of your vehicle that are damaged. This is how a trained mechanic would diagnose any vehicle issues.
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There are dozens and dozens of reasons why a Dodge Ram 2500 may be idling high. Vehicles are complicated, and there are a lot of working parts. Giving a comprehensive list of reasons why your Dodge Ram 2500 is idling high is almost impossible. However, some reasons may be more common than others. Here are the most common reasons for a Dodge Ram 2500 idling high:
Faulty Idle Control System
The Dodge Ram 2500 has an idle control system. At the heart of this system is a small valve, known as the idle control valve. The valve controls how much air is flowing into the engine. The valve, in combination with your vehicle’s computer, controls the idle speed of your vehicle.
If the valve breaks, or becomes clogged, it doesn’t work properly. This can lead to a high idle speed.
In rare cases, the fuse for the idle control system can break. This can cause the same issues. Replacing the fuse should fix the problem.
Faulty Throttle Position Sensor
A Throttle Position Sensor (TPS) is responsible for monitoring the position of the throttle valve and sending this position info to the computer. When this sensor malfunctions, wrong or no data is being sent so the computer tries to adjust the air-fuel mixture and ignition timing the best it can with the info it has.
Faulty TPS can sometimes make the engine idle high when the computer thinks that the throttle is in a different position than it really is.
When this happens there are other issues that the truck can experience, like sluggish acceleration, stalling engine and erratic engine behavior. Since this is a crucial sensor to the overall health of the engine performance, it is important to get it diagnosed and replaced as soon as possible.
Vehicle Computer Issues
Nearly everything your vehicle does is controlled by a central computer. If there is a fault in the vehicle’s computer or any of the sensors that feed it information, then this could lead to a high idle speed.
Any vehicle computer issues are temporary, normally down to a software glitch. If the problem seems to be happening all the time, then it may be a problem with the sensors rather than the actual computer.
The only way to diagnose this problem is to use an OBD-2 scanner. Any issues with the vehicle’s computer should generate an error code.
Many Ram 2500 high idle issues are caused by an incorrect amount of oxygen flowing into the vehicle’s engine. When you have a vacuum leak, the vehicle’s computer believes that more oxygen is flowing in than actually is. This will cause it to increase fuel levels to balance things out. Of course, things don’t get balanced. You just end up with a high idle and a vehicle that burns even more fuel than normal.
Vacuum leaks should be easy to detect. You will need to inspect all of the vehicle’s vacuum hoses (your vehicle’s manual should tell you where they are). You are looking for any holes or cracks in them.
In rare cases, the manifold gasket may be leaking instead. This is a much more expensive problem to fix, but it is fixable.
ECT Sensor is Damaged
The job of the ECT sensor is to tell your vehicle’s computer what temperature the engine is at. If the ECT sensor is damaged, it could feed incorrect information to the vehicle’s computer. This will lead to an increase in the amount of fuel flowing into the vehicle’s engine. This causes a rough idle.
Low Vehicle Coolant
If your vehicle’s coolant starts to run low, then your engine will start to run hot. Low coolant can cause a whole host of other problems too. Regular vehicle servicing should keep the coolant levels topped up. However, coolant can leak.
If you look at your vehicle’s radiator cap or the various hoses heading into the engine and see a reddish-brown residue, then this is likely to be a coolant leak.
If you haven’t been checking your coolant levels, grab your vehicle’s manual and read it. It will tell you exactly how to check engine coolant levels and refill it, if need be. Although, if the problem is due to a coolant leak, then this will just be a temporary fix.
Dirty Throttle Body
The throttle body is an integral part of the engine’s air intake system. It controls how much air is being inserted into the combustion chamber. There is a butterfly valve that opens and closes when you press the accelerator pedal as well as controls what RPMs the engine should be running during idling.
With time, the throttle body gets dirty with carbon deposits and other substances, particularly around the valve area. This buildup can cause blockage and prevent the valve from closing properly. This can keep the idle RPMs at high as the valve cannot close to the position it should be in.
Regular maintenance and occasional check of the throttle body can help avoid this situation. During maintenance, the air intake filter gets replaced. During this procedure the throttle body is exposed and is easy to check for buildup and a perfect time to clean it.
Damaged carburetors are the root cause of many high idle issues in a Ram 2500. Damaged carburetors may be likely letting in the wrong fuel mix, leading to high idle.
Carburetors normally have a degree of adjustment on them. In fact, your vehicle’s manual may teach you how to adjust the carburetors to deal with a high idle speed. Some carburetors are so damaged they need to be replaced, although this is rarer on the Ram 2500.
Incorrect Engine Timing
The Dodge Ram 2500 engine is a precise perfectly tuned machine. The engine timing is what keeps everything inside the engine fire at the correct moment to allow the engine to run at its most efficient state. It synchronizes all the components like the camshaft, crankshaft, valves and spark plugs to ensure the optimal combustion process.
If the engine timing is off, it will disrupt this perfect dance and make the engine run in an inefficient way or even damage engine components. Idling at high RPMs can be one of the symptoms of incorrect timing.
A worn timing belt or chain is the most common reason the timing can be off. It is important to replace the timing belt or chain about every 100,000 miles to keep it at its normal performance level.
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How Do You Fix a Ram 2500 Idling High?
Because there are so many reasons why a Ram 2500 may be idling high, it is impossible for us to tell you how to fix the problem. You should always begin by diagnosing the issue. You can either head to a mechanic or pull out an OBD-2 scanner to do this.
Some issues are easy to fix e.g. replacing leaking vacuum hoses, cleaning the idle control valve, or refilling the vehicle’s coolant. Others will require an expert. For example, we wouldn’t recommend replacing carburetors yourself.
It is important that you fix any high idle issues quickly, though. You don’t want a vehicle’s engine running constantly hot. This can damage the engine, and increase fuel consumption levels. Issues not fixed now are only going to get worse.
While Ram 2500s have an up-idle feature to allow your vehicle to run at a high idle speed, you have to manually switch this on. If you haven’t turned it on, then your vehicle could have all manner of problems with it. It may be a faulty idle valve, faulty sensors, or leaking air hoses.
It is hard to work out why your Ram 2500 has high idle issues, and even harder to fix the problem. It is recommended that you speak to a qualified mechanic. It is the only way to properly fix the issue.
Valik loves tinkering in the garage and is currently restoring a 2000 GMC Sierra 1500 truck. He also writes about the progress on this blog. When not in the garage, Valik is also a web developer and a blogger. I know, strange, a hand in two completely different worlds. And that is the way he likes to keep it.