old 3L throwing code PO174

[BeaterMan]

My 99 3.0 has been stumbling almost surging lately and yesterday the CEL came on and i got po174- bank 2 lean. I'm sure i know how to diagnose this but just want to make sure i'm not forgetting anything to inspect.

i'm gona check the o2 voltage output seeing its only bank2 and i have no missfire codes ect.
i also thought i'd check the injectors, wires and plugs.
my logic is telling me that if i had a intake leak, that would produce a missfire- correct? i was also thinking i could put the bank 2 o2 sensor on bank 1 and if it were bad then bank 1 one would read lean correct?

any insight would be appreciated thanx
-mike

 

[Runnin'OnEmpty]

i had both banks running lean once, after i pinned everything out and checked voltages and resistances, i had no problems with any of the readings.

this code kept coming up time and time again, im not sure how, but it wound up being the coil pack

replaced the coil pack and have not had any codes in the last 22,000 miles of abuse. how that works, i don't know but it cant hurt to check

This is a new one on me, and I'm filing it in my brain cell for
future reference. OBD II can be a strange puppy sometimes.....

Mike, that's a good plan. If you swap O2's and still get the bank2
lean code, then it's probably an intake gasket leak. Sometimes a
minor leak won't cause a misfire.

 

[BeaterMan]

i checked the output voltage of the o2 sensor and it was lazy but still functioning. i checked the plugs to see if the engine was really running lean or the computer just "thinks" its lean. Plugs indicate normal combustion. I did change that one o2 sensor being it was lazy to react to rich/lean mixture changes and it kinda helped but not enough. My next thoughts were vacuum leak on the driver side but a full can of carb cleaner later and i'm not finding any. I did have someone tell me the PCM could be upset and confusing itself but that is gona be the very last thing i check. I havn't performed an injector balance test either- can't afford one of those injector pulse testers. I have a friend who is a master mechanic at supershuttle so imma see if i can get sometime to go up there and use their scantools and special equipment.
thanx for any further insight- mike

 

[wahl_7s]

I don't know, is it just me. It seems every time I come to this forum and others somebody has a 174 lean code(including my daughters truck '01) what's going on? I changed a bunch of stuff and nothing I've done fixed it! And all of a sudden it fixed itselfNot even kidding!

 

[Ranger44]

A lazy Ho2S isn't going to cause a lean code.

Ignition wouldn't really do it either....if it's not firing right, then the air/fuel mixture wouldn't burn properly.....causing a rich condition....

A vacuum leak won't either. It'd most likely show on both.

Now an exhaust leak???? Maybe. If one side is leaking near or before the O2 sensor then it's going to pick up on more oxygen, telling the computer that it's running lean. Then a lean code pops up. Whether you realize it or not between the puffs of an exhaust leak, air is being drawn into the exhaust.

Now....other causes??? Fuel injectors....a noid light will only tell you if the injector is firing. A stethoscope is very useful and can basically tell you the same thing and more. Better yet it's only about $6 out of your pocket. Listen to the injector clicks. See if one is clicking more slowly than the others.

Actually now that i think of it.....that engine should be bank fire. Check the wiring harness for damage, shorts, or corrosion.

These are all just guesses. I cannot properly diagnose the truck without being there and seeing/hearing it for myself.

Good Luck!

 

[BeaterMan]

Ranger44 thanx for the input, i'll go check that out here in a few. Could a egr do this? when i apply vacuum to the egr the engine putters but never dies. anyways i got the day off tomarrow so i'll really get into it. thanx again

 

[Ranger44]

I didn't see the surging part.

Unmetered air is getting in somehow? IAC acting up?

Carbon can do some very nasty things. Check the egr tube for carbon buildup.

 

[BeaterMan]

I pulled the egr off and it looks fine, no excessive carbon build up. iac seems to be working well since the idle is completely fine. i'm starting to get lost with this. I ran the vehicle for quite a while cruzing around town, got home and pulled the "lean" bank plugs and they still look like normal combustion. there are no vacuum leaks at all. i know its possible but i'm hoping not the PCM is what comes to mind next?????? any help would be appreciated. -mike

 

[Runnin'OnEmpty]

I pulled the egr off and it looks fine, no excessive carbon build up. iac seems to be working well since the idle is completely fine. i'm starting to get lost with this. I ran the vehicle for quite a while cruzing around town, got home and pulled the "lean" bank plugs and they still look like normal combustion. there are no vacuum leaks at all. i know its possible but i'm hoping not the PCM is what comes to mind next?????? any help would be appreciated. -mike

Mike, probably not the PCM, not for a lean code.

I still think it's connected to a vacuum leak.
What about the PCV valve....? or the vacuum
'tree' with numerous hoses connected.....? or
maybe the brake booster hose or check valve?

All this stuff is located toward the driver's side of
the intake (bank 2), so maybe it's something simple......

 

[jwranger96]

when mine was throwing this code it was because the hose that went into the charcoal canister was cracked, dumb i know but thats what caused it...