2001 dodge ram 1500 v6-rough idle

I Can't seem to figure out what the problem is. Changed the plugs ,wires, cap ,rotor,fuel filter,air filter,pvc valve.I have checked all the vac lines. The rough idle is still there just as strong. No check engine lights. no codes when scanned. Almost feels like it is missing a cylinder.The whole cab shakes, but the exhaust sounds smooth.Motor and tranny mounts are good also. What could it be? Anybody ever came across this problem?


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So whenever the engine is revved above idle, the problem smooths out?

I don't understand why it is not setting a missfire 'code', the way you described it.

It should set a code P0300, random cylinder missfire detected, with any vacuum leak, false reading exhaust HO'2 sensor, or a contaminated mass air flow sensor. This also could be caused by a exhaust leak prior to any HO'2 sensor.

Code P0301 is a missfire detected in cylinder #1.

Code P0302 is a missfire detected in cylinder #2, and so on, through cylinder #4, P0304 in a 4 cylinder engine, cylinder #6 P0306 in a V6, and P0308 for a missfire detected in cylinder #8 in a V8 engine. They continue, as in a V10, P0310 cylinder missfire in #10 cylinder.

Maybe a problem with the ECM?

These are some other problems I have found in Dodge trucks.

The coil wire, or coil power connection. Both V6 and V8 models. These may, or may not set the P0300 code although.

A disconnected, or cracked manifold Vacuum line to the EVAP system, at the intake manifold. Runs too lean, and also set's the code P0300.

Faulty fuel pump wiring, and/or fuel pump relay. This usually set's no codes. Replace this and the EEC relay at the same time. IIRC there was a change from 'resisted' to 'diode' protected, or opposite made a few years ago.

The power steering pressure switch, in the high pressure hose, mounted by the power steering pump can rupture, and send power steering fluid through, between the wire and it's insulation, down the harness to the left side HO'2 sensor connector, flood it, and it will give a false reading.

In all, I hope this helps.

Not likely, but still a possibility. I have not had to replace one yet on a truck like yours.

No codes, It seems to smooth out at a higher rpm.

It sounds like you have a real lean condition in a cylinder, or bank of injector's with no codes. Could it be a clogged injector, or a bad injector o'ring sucking additional air? Have you checked the compression?

check the injectors, I messed with it some today and can hear a high pitched wistel out of one of the injectors. I don't know if it's sucking air,that is what it sounds like. would it suck air without leaking fuel if the o rings were bad?

That's the first thing that I thought of, but wouldn't that have thrown out a p0171/174 code? Very strange indeed.

Yes it can suck air, at the lower seal without leaking fuel.

I will have to check out the injector. It does throw a code if I unplug it and the engine seems to get worse. It possibly is that injector oring.

Something to check, although a long shot, open the throttle blades and look into the intake plenum with a flash light. If there is oil covering the bottom of the intake, the plenum gasket has failed. It is a very common on the V6, and 5.2-5.9 V8. If it has failed it will cause oil consumption, pinging under light loads and rough idle.

I have a V8 1999 Toyota Landcruiser I am checking out for a misfire. It is setting a code (P0307) for a misfire in cylinder #7. The ECU is showing more misfires in cylinder #8, with no code set. It should be setting the code P0308 for cylinder #8, but it is not.

I have swapped the plug on coils to other cylinders, and checked the compression. The spark plugs, and coil boots, and electrical connections look great. It is still setting the same code P0307 only. The Iridium spark plugs have been in for only 15,000 miles, and look as if it is burning evenly in all cylinders. So evenly clean I would think it should not be setting any codes at all, let alone for one cylinder only.

All of the injectors are pulsing equally, and I do not hear any vacuum leaks. Tomorrow I am going to check the injector seals with unburning propane injection, to see if the misfire in gear under load smooths out. That is if I can figure out exactly how to do this by myself safely. I will also do a fuel pressure/volume test, along with unplugging the injectors, and running a OHM test on each one. I will post back what I find wrong.


Geez, all I did was an oil change yesterday, with the required 7 quarts of Castrol GTX 5W30, and a Wix oil filter.

Well today, I checked all of the fuel injectors, and they Ohmd the same. My test equipment said they should Ohm between 13.4 and 14.2 Ohms, they were all at 0.017K Ohms. They all were pulsing the same, around 3.28MS at Idle, and up to 8.46MS when the engine was revved, at a steady RPM of 1000 in gear, they all read around 5.48MS, including cylinder #7.

The fuel pressure at idle was 33 PSI, this was checked at the fuel rail. Well within spec, of 28 to 34. It jumped up when revved, so a clogged fuel filter, or bad fuel pump, or fuel pressure regulator, is out of the equation.

I shot propane, and carb spray at the fuel injector seals, with no improvement found. Right above this cylinder is where the fuel enters the fuel injection rail. My only other option was to pull the fuel injector out, and bench test it for flow. He needed the vehicle tomorrow, and I needed time on 2 others.

I also tried swapping spark plugs in cylinders yesterday.

All I could suggest, was put some fuel injection cleaner in the fuel tank, maybe a couple of times, to see if it will take care of it.

I hope that is it's fix, as it has compression, spark, and maybe just not enough fuel.