Champion201

Hey guys, its been awhile. First off, 2005 VHO, 6.0, Radix MP112 and its not showing any codes on my Scan Gauge 2 or GM Tech Tool.

Anyhow, awhile back, at times my truck was running a little rough at idle so I hooked up my Scan Gauge 2 and noticed the TPS would drop low at times, so it was suggested by a mechanic to replace the TPS, which I did, just the TPS, not the entire throttle body unit, and it appeared to be fine for awhile. I also replaced a couple vacuum caps just in case.

Recently it started acting up again, rough idle at times, so I cleaned the MAF by just spraying it with MAF cleaner and while I was at it I cleaned the throttle body and figured that would take care of things, nope. It seemed to idle rougher at idle more often and died twice so I took it to a local Good Wrench garage. They had never worked on a super charged motor so they did the normal. They suggested maybe the MAF got damaged from the spraying, even though I didnt touch it with anything, so I had it replaced, this seemed to fix the issue but 2 days later it started doing it again.

Back to the dealer, he double checked the throttle body and discovered it was still dirty inside so he removed it and cleaned it. At the same time he noticed the intercooler pump was not pumping and thought maybe that could be causing the issue so I called Super Charger Online and ordered a pump. At the same time I told Brian what was going on and he said it was probably the vacuum cap on the back of the J-Tube but I don’t have a cap on the back, just 3 hoses that appear to be fine. Then he stated that it was probably the vacuum cap on the back side of the manifold so I replaced that. He also said that he does not believe the rough idle issue has anything to do with the intercooler.

BTW, both times they hooked up the tech tool and couldn’t find anything out of the norm because it ran fine while there. I also took the tech for short rides and it ran fine so I thought all was well.

Anyhow, 2 days later it appears to be running fine but at times it feels like the idle is a little rough but not real bad but that’s kind of the way it acted before.

Its driving me crazy, what else should I check?

Champion201

Could this time just be that my truck computer is just relearning after the throttle body got its good cleaning? There was a slight "Lip" of carbon built up on the inside top that was cleaned off?

trxmxzx

iTrader: (7)

Lazy o2 sensors? My truck did this in colder weather- idle down to 350 rpm at points- changed out the Delphi sensors for Ac Delco my problem went away.

Just a thought good luck

Champion201

Thanks, it seems to do it more after it's ran for awhile. I'll check the price of the sensors and probably just replace them just to be sure

Champion201

I believe I've replaced them all but can anyone tell me how many vacuum plugs there are?

CanadaLY6

Ive has something simmilar happen to me years ago.

You could try putting a manual fuel pressure gauge on it and seeing if the fuel pressure is dropping when its running rough.
If that's the case it might be a case of bad fuel pump on its way out.

gagliano7

Could also be a coil going bad. Use an infared temp gun when it is idling rough and check the temp of each primary . The one that is way off will be the cylinder with the problem.