Help With Check Engine Light - Lean

[Kody]

’02 Silvy, 5.3, 110k miles - check engine light has been on for a few weeks now. Runs fine, little rough at idle – almost unnoticeable – until just recently, sometimes when I stop at a light the revs drop a few hundred rpms and come back to normal repeatedly. Had local auto parts do a scan and they said it is “lean all over”, which I’m assuming means both banks. Unfortunately I did not get the exact codes from him. Since then I have run a tank of premium w/ fuel injection through, unhooked the battery, cleaned my K&N filter, took the mass air flow sensor out and cleaned, also put new plugs/wires in and PCV valve in. Light never went off…

 

Before I take it into the diagnostics shop, just wondering if there is anything else obvious that anyone recommends I check first?

 

Thoughts appreciated.

[renegadeking]

does the truck still run weird? maybe you fixed the problem and you just need the light turned off.

[Kody]

no change in how it runs, and the light hasn't gone off yet?

[cwendel4]

Don't know if your year has the fuel pressure regulator on the fuel injector rail or not. If it does, check the vacuum line attached to it. If fuel comes out or you get a strong fuel smell, change it. The regulator also has a filter on the base of it.

It is easy to remove, pry off the clip and lift out.

If the filter has trash this could be the source.

 

Also, take it back and get the codes. A tune up won't fix a bad set of O2 sensors.

[caddytech10]

'02 Silvy, 5.3, 110k miles - check engine light has been on for a few weeks now. Runs fine, little rough at idle – almost unnoticeable – until just recently, sometimes when I stop at a light the revs drop a few hundred rpms and come back to normal repeatedly. Had local auto parts do a scan and they said it is "lean all over", which I'm assuming means both banks. Unfortunately I did not get the exact codes from him. Since then I have run a tank of premium w/ fuel injection through, unhooked the battery, cleaned my K&N filter, took the mass air flow sensor out and cleaned, also put new plugs/wires in and PCV valve in. Light never went off…

 

Before I take it into the diagnostics shop, just wondering if there is anything else obvious that anyone recommends I check first?

 

Thoughts appreciated.

 

If you have a P0171 and a P0174 that means both banks are running lean. The two most comon problems I see are bad MAF sensors and intake manifold gaskets leaking. If you or someone you know has a scan tool or a hand held programmer with a datalog feature, you can spray carb or intake cleaner (with the engine running) around the intake gaskets while looking at the fuel trim numbers you will see the fuel trims go into the negative numbers it there is a leak (example 22% and then drop to -12% while spraying). For the MAF you can look at your grams per second value on a scan tool. It should be around 5gps at idle.

[Kody]

Thanks for the responses... I took it to autolab and had the diagnotstic done... It was the intake manifold gasket. The replaced it and cleaned the fuel rails, tb, injectors, etc since it had been running rich for so long... Got charged a pretty penny, but she's home.