Tractorman

Observing soot at the end of the tailpipe is normal for this era of truck, especially if you have larger than stock injectors. Disconnect the compressor discharge plumbing from the turbo and inspect for an oily mess. Then, disconnect the exhaust band on the exhaust side and inspect for the same. It is possible. The hone pattern intentionally put into the cylinder walls is used as a mild abrasive to condition the outer wear surface of the piston rings for the first 1,000 miles or so of driving. During this period of time, the best mating of the rings to the cylinder wall will occur, resulting in the least oil consumption and least engine blow-by. Using a slippery synthetic oil during break-in reduces the effectiveness of the abrasive characteristics of honing the cylinder walls - it will have a more likely effect of polishing the piston rings and the cylinder walls, resulting in more oil consumption and more engine blow-by. Try performing the oil cap rattle test for the poor man's method of checking engine blow-by. John

I would wait for him to drive the truck for at least a month plus a few hundred miles before I would consider it repaired. Many people who experienced death wobble have posted the repairs here on this site, only to experience the death wobble again weeks, or even months later. John

👍! John

Same method that I use. I have the engine running as well to allow the power steering to put a maximum amount of force to the linkages. Years ago, I set the caster to 4 1/2° positive. It was the best single steering performance improvement on my truck. John

It almost sounds like the "high idle" is being activated. If you drive the truck with the coolant sensor disconnected, does the idle rpm stay where it should? John Some time ago, I did some research regarding this. It seems to be a bit of an anomaly that occurs on some vehicles when static electricity generated from the rubber part of the harmonic balancer jumps to the oil pan as a spark. The good news is that there is no cause for concern. John

How does the track bar look. How are you testing the track bar or steering linkage? John

P0122 - Accelerator Pedal Position Sensor Signal Voltage Too Low Are you familiar with the W-T ground reference modification? If so, have you done the modification? This modification addresses a potentially poor ground splice for the ECM and many other components. It addresses other wiring issues, as well. The wiring diagram below shows how many components use this splice. Here is the link to the Ground Reference Modification. I recommend to read thoroughly before beginning any work. https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation/engine/electrical/ground-reference-vp44ecmpcmpdc-plus-tc-lockunlock-r567/?&tab=comments#comment-177452 John

Since only the ECM controls idle rpm, I think that you are going to have to provide some information regarding what your truck is and what repairs and symptoms that triggered high idle rpm. Details matter. John

This is just my opinion here, so do not take this as fact. I have never been real concerned about maintaining a maximum specific AC voltage from the alternator. Nobody ever talks about this when diagnosing problems with vehicles that are not 2nd generation Dodge Cummins trucks. Why would they be an different? I am still running my original Bosch alternator (changed brushes twice, bearings once), but still have original diodes. I have checked for AC voltage at least three times in the last ten years. The readings have never be below .05 volts AC. However, I still am running with my original ECM, PCM, and a second APPS. The original APPS lasted for 289,000 miles until it failed (interestingly, with the same code as yours). The APPS I am now running is a Timbo and it has currently logged about a 113,000 miles. So, I can't say that this is absolutely not your problem, but I don't think that it is. Did you use a mulitmeter to check the idle validation switch activation when you loctited the throttle set screw? John

That is a good way to test. Will be waiting to hear back. Also, have you verified that the mechanical set screw for the throttle cable is in good condition and that the throttle cable always returns to the mechanical stop when operating the throttle? John

Interesting. I copied mine from my 2002 FSM, however your P0121 description actually seems more related to the symptoms that are occurring. What is the source of your information? John

You could do that - it could confirm what your scanner is saying. Also, you mentioned that you are getting the P0121 code. P0121 (M) Accelerator Position Sensor (APPS) Signal Voltage Too Low APPS voltage input below the minimum acceptable voltage. You could check this voltage (5 volts supply) at the same time to see if it is fluctuating while the symptoms occur. The condition of wiring and wiring connections (both positive and negative) are crucial on these trucks - so, yes, it is possible for this to be the problem. John

This doesn't mean that the APPS is faulty - it just means that there is an output signal at idle when there shouldn't be. Need to know where it is coming from. More troubleshooting needed. Since I don't know what your level of skill is with electricity, I will just start with the basics. Let's say you wanted to check the condition of the crossover cable by using a voltage drop test. First, you would need to understand what would be normal for the test results. There are two batteries (wired in parallel) and a starter on your truck. The starter will draw at least 400 amps when cranking. This means that 200 amps will be supplied by each battery. Consequently, when the starter is operating, the positive and negative cable of the driver side battery and the positive (crossover cable) and negative cables of the passenger side battery will be handling 200 amps each. By design there will always be a voltage drop during the starter operation - there has to be, otherwise current would not flow. The maximum allowable voltage drop in a complete positive circuit is generally .5 volts and in a complete negative circuit is generally .2 volts. The positive circuit has a higher allowable voltage drop because there are usually more switches and connection points than in a negative circuit. Voltage drop measurements can be taken at different points with a voltmeter while the circuit is under an electrical load. Voltage drop tests taken without the circuit under an electrical load will show results that are meaningless. So, back to performing a voltage drop test on the crossover cable. This usually works best using two people. One person will be in the cab and will crank the engine as instructed for a specified period of time. Be sure to be safe - truck in neutral / park and park brake set. Remove the fuel pump relay (in the PDC) for the VP44. This will allow the engine to crank continuously without starting. Set your voltmeter to a manual DC voltage scale of two decimals - example: battery shows 12.67 volts DC on the meter. Do not use the floating scale. Place and hold the positive lead onto the passenger side positive post of the battery (the actual post, not the clamp). Place and hold the negative lead onto the eyelet at the other end of the crossover cable. Your meter should read 0 volts. Instruct the other person to crank the engine for 10 seconds (no interruption). A reading of .1 volts or less during engine cranking indicates that the crossover cable is in very good condition. A reading of .7 volts (for example) during engine cranking would indicate that the cable needs to be replaced. This voltage drop test allows you to see the true condition of the crossover cable while over 200 amps are passing through - a real life situation. John

It sounds like you have confirmed that a false signal is being generated in the APPS output circuit. It would stand to reason that the engine rpm's would increase if a signal is present. Back to a previous statement of mine that was meant as a question - are you using the starter for a heavy electrical load when performing your voltage drop tests? By the way, my throttle APPS output always showed zero at idle on the OBDLink scanner. John