03 Dodge Ram Hemi Engine Can Hardly Idle

I just replaced all the spark plugs on my 2003 Dodge Ram 1500 Hemi 5.7 engine, and it still barely idles on it's own at 600 rpm. To keep the engine from dying, I need to constantly press on the gas pedal to raise the rpm, if not it drops to 600 rpm immediately. I installed Champion 3570 Platinum Power plugs. The PCM is not throwing any codes. This makes things really difficult to troubleshoot. I did a scan using my OTC Genisys Scanner with the key on, and the engine off. Here are the results. I hope someone can understand it:

2003 Dodge Ram 1500 Hemi Engine Troubleshooting

Using my OTC Genisys Scanner
Key On Engine Off

Engine coolant temp - 3.13 volts
Engine coolant temp - 95 degrees
Intake air temp - 3.34 volts
Intake air temp - 86 degrees
APP Sen 1v - 0.43 volts (no change when the gas pedal was depressed)
APP Sen 2v - 0.24 volts (no change when the gas pedal was depressed)
Accelerator pedal position (0) (no change when the gas pedal was depressed)
Ambient temp - 1.73 volts
Barometric pressure - 30.53
Cat Modeled Temp - 83 degrees
Cam, Crank Difference - 0.90 degrees
Cam sync at start - In sync
Cam sync state - Out sync
Closed loop timer - (0) usec
Current fuel shutoff - disabled
Elec Throttle Control - (3) (no change when the gas pedal was depressed)
Fuel level percent - 40
Fuel level sensor - 2.24 volts
Injector pulse width cylinder # 1 - 41.36
Map sensor - 4.57 volts
Map vacuum - 0.06 inHg
S/C switch 2 - 4.55 volts
TPS 1 minimum volts - 0.49 (no change when the gas pedal was depressed)
TPS 1 volts - 0.86
TPS 2 minimum volts - 4.56
TPS 2 volts - 4.16 (Looks like this may be a problem)
Target idle speed - 12800
Voltage sense - 172.00 volts

Well according to my OTC scanner, the TPS 2 volts at 4.16 appears low. The minimum volts should be above 4.56 volts. My question is: Where and what is the TPS 2. With the key on engine off, when I press on the gas pedal, shouldn't the voltage value change. There is no change when I press on the gas pedal slowly to the floor, then back off on the gas pedal slowly all the way out. Any help will be greatly appreciated. Thank you, Tommy.

The spark plugs can do jack if the distributor coils aren't getting the power to them. It happened to my Miata. The distributor coils had a hole burned through the rubber insulation from the wires arcing or whatever.

Actually, I don't even know if the Hemi engine has distributor coils, just saying.

Think the plugs may be your issue. The hemis just like plain copper plugs

Copper is the way to go. It's odd though.. my truck idles at 550-600 no problem.

Were you having these issues before the plug change? All the coil boots seated correctly? No mix up on the wires? Just trying to get some background info.

The engine was running bad, very bad before I replaced any of the spark plugs. The plugs that I removed were Champion RE14MCC4. These plugs were operating fine for approximately 50 thousand miles. The new plugs are Champion 3570 Platinum Power. The new plugs are gapped at 45 thousands. Most of the plugs that I removed were at 60 thousands, and one plug shown below was at 73 thousands. The plugs from the front 4 cylinders were not as bad as the plugs from the rear 4 cylinders. We did take the truck in to the Dodge Dealership to replace all of the plugs a few years back. My feeling is, they did not replace the plugs at the back 4 cylinders. We all know how hard it is to get to the plugs at the rear 4 cylinders, especially the plugs on the driver side. I had to get my son to replace the plugs at the rear 4 cylinders due to my back problems. However, my son suggested placing a wooden plank across one fender and an "A" frame ladder at the other end of the plank. As you can see in the picture below he then layed down on the job to replace the spark plugs. So, when it is time for you to replace your spark plugs, this method makes it much easier to do. The big problem for me is, no codes are popping up. This makes it very difficult to troubleshoot. The engine just barely idles at 600 rpm, however, I have to assist by constantly steeping on the gas pedal to keep the rpm up, if I don't step on the gas pedal, the engine will die. I'm thinking my problem is inside the throttle body. Here's what I will be doing today. I will remove the induction tube assembly. I will then remove the sensor from that assembly and plug the sensor back into the harness. I'll then have someone try to start the engine so I can watch what is happening at the throttle body plate. I could be wrong, but I think the throttle plate is closing cutting off the air supply. If the engine starts, then I will manually play with the throttle plate to see if the response gets better. I friend of mine asked if it is possible that water got into my gas tank. That would account for the way the engine is running without thowing a code. The only way that water could have gotten into my gas tank was when I went to the gas station to put gas in my gas tank. Perhaps the tank at the gas station was near empty and I got comtaminated gas from the bottom of their tank pumped into my gas tank. In any case, if the engines performance improves when I play with the throttle plate, then that tells me the problem is electrical. Let me know what you think about this. Thank you, Tommy.

If you will be removing the intake tube inspect and clean some items that are behind the intake.
1- Throttle body, may involee removing it completly to get a good clean.
2- The IAT sensor, its located on the intake tube. Clean it until it is bright shiny and blue. I cleaned mine and it made a world of a diffrence in the idle.
3- PVC valve, its located on the left side of the throttle body. remove and inspect and clean it. If it is in proper working order the ball inside will move around freely.

By the looks of your plugs, you are running rich. Cleaning the IAT may help that. These are precautions i take every thime i change oil. Its cheap to do these 3 cleans, under 5 bucks and will help the effecincy of the motor. If cleaning these dosnt help, look into maybe new coils.

By the looks of it, I would seafoam it.
I would check for vacum leaks also.
Im no an expert at it but im sure the value would change on the throttle positioning sensor when you press and depress the pedal. Maybe need a new sensor?

brian3180 said:

If you will be removing the intake tube inspect and clean some items that are behind the intake.
1- Throttle body, may involee removing it completly to get a good clean.
2- The IAT sensor, its located on the intake tube. Clean it until it is bright shiny and blue. I cleaned mine and it made a world of a diffrence in the idle.
3- PVC valve, its located on the left side of the throttle body. remove and inspect and clean it. If it is in proper working order the ball inside will move around freely.

By the looks of your plugs, you are running rich. Cleaning the IAT may help that. These are precautions i take every thime i change oil. Its cheap to do these 3 cleans, under 5 bucks and will help the effecincy of the motor. If cleaning these dosnt help, look into maybe new coils.

By the looks of it, I would seafoam it.

Click to expand...

Yes, I removed and cleaned the throttle body with a clean cloth. I got all that black stuff off the throttle bore. I cleaned the edge of the throttle plate as well. I did look at the pcv valve. The ball inside moves freely. I looked at the IAT sensor, it looked clean to me. What did you clean your IAT sensor with? Thank you, Tommy.

Ok, here's what I did. I disconnected the negative battery terminal. I removed the air filter box cover and tube. I disconnected the IAT wire connector from the sensor. I then removed the intake manifold air box plenum. I removed the IAT sensor from the plenum box. Plugged it back into the harness. I used a plastic tie strap to secure the IAT sensor near it's original location. I hooked up the negative battery terminal. I had my daugther turn the ignition switch on for 10 seconds, then start the engine. The engine will idle at 600 rpm on it's own for a short time then die out. When we press on the gas pedal and tried to keep the engine running at 2000 rpm it tends to cut out and drop back to 600 rpm. It will do that everytime we try to keep the engine running at 2000 rpm, unless we keep pressing on the gas pedal. I did notice that the throttle plate will close completely, once at the 600 rpm idle, that is if you don't keep your foot on the gas pedal to keep the engine running. I did try to manually operate the throttle plate, it wouldn't let me. Something has to be wrong between the PCM and the iac. I don't think that the problem is between the APPS (acceletator pedal position sensor) and the PCM. If there was a problem there, we wouldn't be able to raise the engine rpm at all. Now, the question is, what test can I perform to see where the problem lies. If I understand how the basic system works, doesn't the pcm send a signal to the iac sensor inside the throttle body which controls the air flow which then keeps the engine at a specific idle. With that said, what is making the engine rpm drop down from 2000 rpm to 600 rpm everytime we try to raise the rpm? I'm sure there is someone out there who knows what my problem is. I really appreciate your support. Thank you, Tommy.

Have you tried to rest the pedal?
Disconnect the negative battery terminal for 15 mins. to rest PCM.
Reconnect battery terminal.
Turn key to on position but do not start.
Slowly press the pedal to the floor I usually do about 15 secs. worth of pressing.
Then depress the pedal slowly for 15 seconds.
let sit for 15 secs. then turn ignition off.
Then start truck.

When i did this i could tell a differance in the rpm range.Maybe press the pedal a little before you turn your ignition on and not let out all the way on the pedal and shut it off with you foot still on the pedal, then try to start. If you press and depress the pedal choppy and not smooth the RPM range will be choppy. Smother is better. Im not saying it will work in every situation, but it works for me. I always like to try all my low cost options before i start getting into spending money.These arnt miracle tricks, but if they work they work, if they dont fix the problem you will know the trix for when it is running right.

brian3180 said:

Have you tried to rest the pedal?
Disconnect the negative battery terminal for 15 mins. to rest PCM.
Reconnect battery terminal.
Turn key to on position but do not start.
Slowly press the pedal to the floor I usually do about 15 secs. worth of pressing.
Then depress the pedal slowly for 15 seconds.
let sit for 15 secs. then turn ignition off.
Then start truck.

When i did this i could tell a differance in the rpm range.Maybe press the pedal a little before you turn your ignition on and not let out all the way on the pedal and shut it off with you foot still on the pedal, then try to start. If you press and depress the pedal choppy and not smooth the RPM range will be choppy. Smother is better. Im not saying it will work in every situation, but it works for me. I always like to try all my low cost options before i start getting into spending money.These arnt miracle tricks, but if they work they work, if they dont fix the problem you will know the trix for when it is running right.

Click to expand...

I did try something similar, but not like your method. I will try your method to see if it works. I'll get back to you on that. Thanks for your support, Tommy.

When its running at the 600 does it sound ok or like its not running on all cylinders?

KGBIGCOUNTRY said:

When its running at the 600 does it sound ok or like its not running on all cylinders?

Click to expand...

I'm thinking you may be right, it may not be running on all the cylinders. Not absolutely sure though. Thank you, Tommy.

brian3180 said:

Have you tried to rest the pedal?
Disconnect the negative battery terminal for 15 mins. to rest PCM.
Reconnect battery terminal.
Turn key to on position but do not start.
Slowly press the pedal to the floor I usually do about 15 secs. worth of pressing.
Then depress the pedal slowly for 15 seconds.
let sit for 15 secs. then turn ignition off.
Then start truck.

When i did this i could tell a differance in the rpm range.Maybe press the pedal a little before you turn your ignition on and not let out all the way on the pedal and shut it off with you foot still on the pedal, then try to start. If you press and depress the pedal choppy and not smooth the RPM range will be choppy. Smother is better. Im not saying it will work in every situation, but it works for me. I always like to try all my low cost options before i start getting into spending money.These arnt miracle tricks, but if they work they work, if they dont fix the problem you will know the trix for when it is running right.

Click to expand...

I just tried this method. It did not work. I followed your directions to the letter. I know I'm not getting any codes, however, I was told by a reliable source to try replacing the crank shaft sensor. Since it doesn't cost that much, I will give that a try. I'll post my results later. Thank you, Tommy.

Alright, heres whats prob happened seeing your an early hemi. Pull the valve covers and check for broken springs in the valve train. Sounds like a spring or two has broke but luckly the valve hasnt dropped.

Wow! That is a huge job. Perhaps I should do a compression test to confirm your diagnosis? Do you know if there is a special compression tester used on these Hemi engines due to tight clearances? Thank you, Tommy.

Pulling the covers is not that bad basically same thing as doing the plugs but instead of pulling the plugs out just undo the boots and coil packs and undo the valve cover bolts. Hope im wrong but its starting to sound that way. If it was a coil issues it would point out a cylinder, being as the injector and coil are working the engine is not showing a fault code. Im starting to lean towards a broke spring or keeper.

So the plugs don't have to be removed to pull the valve covers? They are brand new, I wouldn't want to break them. Thank you, Tommy.

Nope the plugs are deeper in the heads so they can stay in.

Here is a performance hemi head but will give you an idea how far down the plugs are in the head. The valve cover will just pop off and its a reuseable rubber gasket, not cork like the old motors.

Ok, I see what you are saying about the plugs being protected. So if I find broken valve springs, what is the procedure for replacements? Can I use air pressure to hold the valve up? Thank you, Tommy.