Hey folks, new to the forum. I have a new to me Ram 1500 and am having some issues with low rpm hesitation, especially pronounced going uphill in OD and even 3rd. I have read quite a bit about this and am trying to narrow it down. I'm fairly certain it is not the transmission as I just finished rebuilding that. First suspect is the TPS. Key on engine off I am reading about .69v. Getting a steady 5v from the PCM feed line. When I open the throttle, the voltage increases and doesn't jump around. My concern is that it maxes out at 3.8-3.9v. From what I've read it should be more in the 4.5-5v range. Do you think it is faulty? I'm trying to prevent playing guess and check with the parts store and my bank account. I have some other items that I will be checking as well for signs of wear (plugs, cap, rotor, TB, IAC, o2 sensor, as well as potential vacuum leaks). Thanks for your input and all the great info. Been lurking for awhile and decided it was time to jump in.

Not sure if this showed up in the signature.....1999 Ram 1500 4x4 5.9l 46RE QC

 

What are you using to read the voltage? Analog meter is best, as it reacts instantly to changes in voltage. Various scanners and such reading data from the PCM simply do not update quickly enough to show if you have weird spots in the sweep.

Your voltages are good. Anything over 3.5 at WOT is what you need.

How is your fuel pressure?

 

I'm using a digital voltage meter. Not sure I have the tools to check fuel pressure. Didn't have much time to tinker with it last night. I am hearing a slight whistle sound (almost like a turbo) coming from the throttle body area. I need to take that apart, clean it, and replace the gasket.

 

While you're in there do a good cleaning of the IAC port an the plunger itself. This might help with the low rpm hesitation.

 

Will do. I did pull the IAC off the other day and it was pretty dirty. I cleaned it and put it back in, but like you said I'm sure the port is in need of a good cleaning.

 

Digital gauge bounces too much to be accurate for TPS test. (been there......)

 

I was able to borrow an analog meter and test the TPS. No bouncing, so I feel like that is good. I started pulling plugs and they were pretty well worn. Gap was .45-.50 and they were a a white-ish color (lean?). A couple had some corrosion/chipping on the insulators. They were champion coppers. I replaced them with ngk coppers and took it for a test drive. Seems to have fixed the hesitation issue. Will probably still adjust the tv cable a little to do some final tweaking. Thanks for the help and input, I appreciate it!

 

Almost forgot, I did take the throttle body off to clean that. It had some carbon build-up. I replaced the gasket and torqued it to 200in/lbs per the FSM.

 

Be sure to reset the PCM when all is said and done, let it relearn how to run the engine.

 

I may have spoke too soon. I pulled the battery cable for a few hours to reset the PCM. After about 50 miles the hesitation is coming back. I think it's still running lean. I checked the fuel pressure and it was good (50psi at idle, 46psi at key on, and it hilds pressure after turned off). Hooked a vacuum gauge to the manifold and have about 18 hMg. I think this should rule out a clogged cat. Did notice the pcv valve is cracked so I will replace that. My friend has a snap on machine that will read the spark plugs (oscilloscope?). The voltage on about half the plugs was double to triplw what it should be (25-30k vs. 10k). I plan on replacing the distributor cab and rotor button. He was saying if the rotor gap is too large, the coil would have to deliver more volts to get spark and cause it to run lean. We hooked a scanner up to read the O2 sensor. It was showing lean at idle, but seemed to be functioning properly when we would raise the rpms. Thoughts?