GM 5.3 Vortec Questions

[Blitanicle99]

Yeah I know this is an "Import" forum but hell I thought there has to be someone with ideas.
So yes I drive an 01 GMC Sierra with the 5.3 Vortec 327. Two weeks ago I did a Sea Foam Job on it, and last week I changed the plugs (OEM Parts) and changed my oil. Also, my lifters were ticking and I did the old trick of dropping a quart of oil out of your pan, putting in a quart of ATF (Trans Fluid) and running it for 30 minutes at about 2 grand.
Well, honestly the truck had much more pep to it and ran better and my ticking went away so that worked. But, my millage dropped significantly. I averaged 14 mpg on the highway. Now this is a stock truck, no lift, stock tires with exhaust work.

I am leading towards EGR or O2 Sensor...
Ideas? Thoughts?

Reps will be given for help.

[dorin48]

Really it could be a number of things. I'm assuming that there is no CEL which makes things more of a headache. Try having it scanned for stored codes just for the sake of it, and not to be an ass but its a 325. 327's were from the 60's

[Gutling]

your supposed to change o2 sensors after seafoam, all the nasty that comes out of your engine builds up on them. that would be first guess

[Blitanicle99]

Hmm I never new you were supposed to change the O2 sensors after you run seafoam. Thanks.

And damn I never knew it was a 325. I could have sworn I read it was a 327 but after sitting here and googling lots of junk, your right.

[jfman]

Did you know an ls1 bolts right into your truck.... Not sure it'll fix you mpg issue howerver :D

[KPowerEP3]

Did you know an ls1 bolts right into your truck.... Not sure it'll fix you mpg issue howerver :D

the 5.3 is a gen3/4 motor, it's the same as an LS1, you can use LSx Heads, cams, etc.

but, as said before my guess would be the o2 sensor, because I have heard stories of the chemicals in the smoke messing them up. Also, you could have loosened a chunk of carbon that got stuck in your EGR, and you can try to clean it.

[Blitanicle99]

Sweet. And hopefully if I get some money that can happen soon.

But I guess its between the EGR or 02 Sensor. Honestly I have never cleaned out an EGR valve before. Is it quite simple? Just literally take it apart and clean it and put back together? Or do I need certain chemicals?

[Dietcoke]

Seafoam destroys 02s.

[KPowerEP3]

Sweet. And hopefully if I get some money that can happen soon.

But I guess its between the EGR or 02 Sensor. Honestly I have never cleaned out an EGR valve before. Is it quite simple? Just literally take it apart and clean it and put back together? Or do I need certain chemicals?

It's really easy, if there's anything holding it open, you'll be able to see it blocking the pin's movement. If there is use a toothpick or something to get the solids out, and give it a little carb/TB cleaner.

[Blitanicle99]

Deal Im gonna go get some carb cleaner and o2 sensors tonight and have some fun wrenching tomorrow

[blackshine007]

Deal Im gonna go get some carb cleaner and o2 sensors tonight and have some fun wrenching tomorrow
You really need to hook a scanner up to it and at least see if your O2 sensors are at least active before you go replacing them. As far as cleaning the ports, you're gonna need more than some carb cleaner the way these cars are nowadays. Try taking a toothbrush and an assortment of flat head screwdrivers (carbon build up isn't very easy to break apart). At least with the scanner you can go to live datastream and watch what all is going on from fuel trim to MAF/MAP voltage and pressure. You can even watch and control how far the EGR opens up just to ensure that it's not clogged up. Best advise, take it to someone who has experience with it. But don't go spending money that don't need to be spent.