Hey guys,

Ever since I bought my truck a year ago, it always rumbled slightly when it was idleing. While I wish it was a cool thing because it was like a muscle car, I always worried it was something bad like the fuel injectors. I replaced my air filter, spark plugs, pcv valve and even cleaned the TB and it still did it. Today, I went to go pick up a new pcv valve, and try something that I couldnt find any information on anyone doing before; using gasoline down the vacumm line to clean the pcv system.

First, I warmed up the truck just a little since it had been sitting all night. I only let it idle for about 10 minutes, and then shut if off. Next I removed my vaccum line from the pcv, put a funnel on the end, and poured about a half of sour cream container full of gas to get ready to dump it down the line. I started the engine, and I could hear the sound of the vaccum and the idle was a little high, no check engine light though. I took the container of gas, and poured slight amount of gas in to the vaccum line. The smallest amount made the engine stutter, so I kept dumping in as much as I could every 5 seconds trying not to make it stall out. I did stall it a couple times, but it starts right back up again. I got through most the gas, and then it kept stalling alot easier, so I decided to put the line back on and take it for a drive to the auto store. The rough idle was still there, but very minor. I picked up a new PCV valve from the store and drove it home.

I did the same thing with the gas again, but this time I only used about 1/4 sour cream container. I poured some in, and then I also sprayed some CRC throttle body cleaner in the line with the engine running. I did about 5 one-second bursts during a short interval. At this point, the truck was idleing up around 1250 RPM due to the vaccum hose not being on. I started pouring the rest of the gas down the line to do a final cleaning, and I stalled it. So finally, I took the little bit of gas left, poured it all down the vaccum and connected the line to my new PCV valve.
I went to start the truck, and it ran rough for a little while and was a little hard to start. I let it idle for about 5 min, and then took it for a ride and WOW! What a difference! At stop lights, I can no longer feel the engine idleing, and it feels so much smoother. It also took .2 seconds off my best 0-60 time, which I only hit once; so it definetly improves performance.

The only bad part of this process is I did it in the garage with the door open, and it still stinks like fumes in there. You can smell the burnt oil, and the fumes from the throttle body cleaner so now I have to air that out. The truck has never ran this smooth though in the past 20k miles that Ive owned it. If you have a rough idle, I recommend you give this a try.

Next mod that I do is going to be a catch can so no oil can make it in to the intake manifold .... until then, gasoline is a very good cleaner for your pcv system.

 

Or you could just raise your idle with the SC 3865.

 

I didnt want to raise the idle. It rose from the vaccum line being disconnected I assume along with pouring gas down it. When I went to go shut the truck off it was just idling at 1250 and wasnt coming down even after reving the engine a bit.

 

to what i have understand gas in vacuum lines+ goes in crankcase ventilation= have a ton of gas in the engine oil??? flush that ASAP or you gonna spin a bearing on crank!

 

If that's true and you diluted the oil in the pan/crankcase, no wonder it's running better and feels quicker. There's no viscosity left in the oil to cause as much drag in the bottom end! :/

 

Hm, Im pretty sure that vacuum runs in to the intake manifold, because the purpose is to take blow by from the crankcase and burn it instead of just letting it escape in to the atmosphere, correct?

I did do an oil change today, and after I did that with the PCV so Im safe either way. And I checked the oil before I did the PCV (to see if I should change it or not) and the level was right below the line. Checked it before I changed the oil because I like to see how much oil I burned, and it was still at the same level. I did add a good amount of gas in the vacuum line ....

 

Where exactly is the PVC located on a 4.7 engine? I have looked but dont recognize the valve.....

 

Congrats man. I'm glad you were able to work it out. I have to check my crankcase ventilation hoses from time to time as they come off, lol. Especially the one behind the blower.

 

On the oil fill tube, on the left side a couple inches down from the cap.

 

you can turn the idle up with the superchip?