random rough idle, inconsistant IQ reading

Hello, I have a 2003 Jetta TDI Wagon, I have been having a problem with a rough idle lately, but it comes and goes. Some days it idles and runs fine, other days it idles rough and then comes out of it and then it returns later on.
Last week I had fault codes stating that the Quantity Adjuster - Upper limit reached (intermittent) , also had fault code QA- lower limit reached -intermittent (only one time so far).
The IQ had a reading of 1.8 or so, and I adapted it to 3.5. It didn't fix the problem.
Today while idling rough, the IQ was bouncing all over from 0.00 to 3.5 or so.
I can many times shut the engine off, restart, and all is fine (sometimes for a while), other times not.
Today I have the QA upper limit reached fault code- intermittent, along with a new one: 17762 Modulating piston movement sensor (G149) - intermittent.
I am not sure the Hammer Mod is what will correct this intermittent problem or not.
Please help me diagnose this problem!
Thank you.
Jeff

PS: all readings, etc. were done at operating temp.

jeffbrom said:

...................Some days it idles and runs fine, other days it idles rough and then comes out of it and then it returns later on.
Last week I had fault codes stating that the Quantity Adjuster - Upper limit reached (intermittent) , also had fault code QA- lower limit reached -intermittent (only one time so far).
The IQ had a reading of 1.8 or so, and I adapted it to 3.5. It didn't fix the problem.
Today while idling rough, the IQ was bouncing all over from 0.00 to 3.5 or so.
I can many times shut the engine off, restart, and all is fine (sometimes for a while), other times not.
Today I have the QA upper limit reached fault code- intermittent, along with a new one: 17762 Modulating piston movement sensor (G149) - intermittent......................

Click to expand...

Sounds oh so familiar, same codes, same symptoms I had.
Took me forever and boxes of parts to locate and fix.
Unwrap the wire loom from the IP where it passes by the starter and under the battery. Look for damaged wires. Mine was a small nick in the lilac/black wire.
Could also be a loose ground or bad pump I guess.

BobnOH, Thanks for the speedy reply, I will start checking the wires and connectors. I too have a feeling it could be electrical, the way it acts. Thanks for your experience! Jeff