5.3 Check engine light??

[the boy]

Hey the check engine light came on in my truck today, its saying multiple misfire and running lean on bank #1. The truck is a 2004 silverado 5.3 Z71. anyone have this problem before, im just wondering what i should check first?? Thanks

[05silver]

Hey the check engine light came on in my truck today, its saying multiple misfire and running lean on bank #1. The truck is a 2004 silverado 5.3 Z71. anyone have this problem before, im just wondering what i should check first?? Thanks

if it has the old style intake gaskets, they are leaking, spray brake cleaner around the intake and listen for the idle to change and locate ur vacuum leak.

[the boy]

it does almost stall sometimes when idleling.

[the boy]

is it bad if the check engine light is flashing????

[kam2265]

Flashing SES light usually means the engine is misfiring.

[Madd Maxx]

The flashing SES means that the misfiring is serious enough to cause catalytic converter damage. If it continues to flash you need to address the problem soon or you could experience a possible cat meltdown.

[the boy]

Is the change in idle when i spray the brake cleaner gonna be really noticable???? So i just spray it on the top joint of the intake where it meets the heads right??? could the leak be on the underside of the intake???

[txarkitekt]

If there is a leak, the brake clean will get sucked into the leak, causing a surge at idle. And yes, you'll notice it.

Also try other things: Have your truck scanned on HPT possible. Look at your fuel trims. Check plug wires/plugs. Check coil packs. Move the driver's side to the pass side. Does the lean condition move to Bank 2? Injectors could be a prob as well. Fuel filter?

There are several things to try--good thing is that you can troubleshoot without spending money.

[the boy]

So i checked the intake today and no sign of it leaking, so i tried pulling each wire off the coils 1 by 1 to see if it would make a difference, each wire i pulled made the truck idle worse which is to be expected. but i checked the codes again and it had a new code: P0131 oxygen sensor circ low voltage bank 1 sensor 1. not sure what that means but it also showed the same codes as before P0171 sys to lean bank 1 and P0300 randon multiplyer cyld misfire detected. Could it be the O2 sensor on the driver side??? It idles pretty rough kinda like it has a bigger cam.....also i cleared the codes with my superchips flashpack and it ran pretty good for a bit but the engine light is now back on.....What should i try next??

[RedHeartbeat]

02 sensor.