Any mechanics here?

[sylvest]

I have a 2003 Silverado with a 5.3L V8. It has been idling rough on cold starts and keeps throwing a check engine light saying it is running lean. I changed the fuel filter and ran lucas fuel system cleaner through it but the light remains. Is anyone here a professional mechanic who is good at diagnosing things and could help me out without costing me an arm and a leg?

Thanks in advance

 

[Dave328]

Absolute first thing on these engines is to make sure the throttle plate is clean. Take an old tooth brush and some carb cleaner to front and back and the bore too. If you have the electronic throttle body just have somebody work the pedal with key on engine OFF so you can clean real good.

 

[sylvest]

I took it off and cleaned it out with carb cleaner and a tooth brush

 

[Dave328]

Next is to look for unmetered air. Meaning a vac leak after the mass airflow sensor. I don't remember if those intakes had warpage issues. Let the truck warm up at idle, then slowly/carefully spray carb spray all along the base of the intake,flange of throttle body,injector rail. Pretty much anywhere air could be possible entering the motor. You'll know when you find it, the idle will fluctuate when you hit the spot.
I'm a little rusty on GM, been out of them for about 6 years. Good Luck!

 

[SpeedRacer]

Do you have a more exact code for the CEL? Is it just one cylinder running lean, or a general code?

Dave's definitely on the right track though I think!

 

[mrmojo32]

Couldn't it be the mass air flow sensor?

 

[SpeedRacer]

Couldn't it be the mass air flow sensor?

Could be, though that would generally throw a MAFS specific code.

 

[sylvest]

The 2 codes are " Lean right bank" "lean left bank"

 

[paddle007]

Do you have a more exact code for the CEL? Is it just one cylinder running lean, or a general code?

Dave's definitely on the right track though I think!

Intake gaskets leaking are common with the 5.3 engine. The warmer it gets the better it runs. It's not a biggie to replace the gaskets.
While it is apart you or your mechanic should check the knock sensors and associated connectors as corrosion appears because of water intrusion into the coonector. It not a happy time when you have to pull the intake off AGAIN to fix the knock sensor code.

Have somebody hook a smoke machine to your intake and check it while it is still cold. A smoke machine pumps out about 3psi of smoke ladened air and will roll out of any leaks.

Ever wonder why we charge $75.00 per hr? Our older out of date machine cost us a grand 7 years ago.

 

[SpeedRacer]

Did a VERY little bit of research, looks like the intake manifold gaskets are a common issue, and cause the same symptoms and codes you are experiencing. Not a definite answer, but worth looking into.

 

[sylvest]

thanks guys

 

[DesmoDucRob]

Let us know what you find out. I've got an '00 model with a 5.3, and I'm anxious to know the diagnosis.

 

[sylvest]

Ive done some more looking around on chevy forums and stuff and people seem to be saying intake manifold gaskets. Apparently the older ones from GM were orange and the new ones are green and work a lot better.

 

[MALIBU12]

Also check your EGR valve .

 

[SpeedRacer]

Ive done some more looking around on chevy forums and stuff and people seem to be saying intake manifold gaskets. Apparently the older ones from GM were orange and the new ones are green and work a lot better.

Well in that case it sounds like a cheap fix!

 

[sylvest]

Well in that case it sounds like a cheap fix!

HAHAHA thanks for the help on that one

 

[hdsprstr]

perhaps maybe check on the O2 sensor. Seen that throw that code before.

 

[LS1RX7]

Also check your EGR valve .

Theres no egr valve.

Definitely the intake gaskets, I did a set today as a matter fact. Every year the cold weather makes the problem more pronounced and we get a surge of them. I've done 3 or 4 already this year. If you are somewhat mechanically inclined you could do it yourself and save some dough. Pretty easy job, there's no coolant running through the intake either, you can remove the throttle body and leave the coolant hoses hooked up so you don't lose any coolant. I think an 8mm and 10mm socket and a flathead and pliers is all you need. Oh yeah and a fuel line disconnect tool.

 

[paddle007]

perhaps maybe check on the O2 sensor. Seen that throw that code before.

Typically on a engine with a bank 1 and bank 2 oxygen sensor, a faulty sensor will affect only one bank of the engine. It can be baffling when an engine pops up with four fuel fouled black spark plugs or four white glazed over spark plugs and the opposite four are perfect.

 

[peterf225]

My truck is doing the same thing but my light comes and goes. It only happens when it's cold. BTW I have a 03 chevy z71 with the 5.3L.