help me

gixxer

gixxer

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ok here it goes.
lincoln ls 3.9 120k
drove 140 miles yesterday. turned car off and started back up after a potty break and had a rough idle. drives fine. so 100 miles later my cel came on so i stopped and checked it with a scanner. codes are as follows.
p0174-bank 2 running lean
p0172-bank 1 running rich
p0304-cylinder 4 misfire
p0302-cylinder 2 misfire

so my thought is coils. i replaced the coils. and same results.
so i searched like an lvc pro:p checked for vacuum leaks=none.
checked all my connections on my injectors=they're fine
replaced all plugs.

could this be a bad injector? maf is fairly new and the last 2 times it went bad i had way different results than whats going on now. any other suggestions? and i thought the coils going bad might have made the computer run one side richer than the other so i have disconnected the battery for a few hours.
 
Why are you on your third MAF sensor? Normally, they last the life of the car. Is your intake/filter stock or modified?
 
Vacuum leak

Vacuum leak after the MAF to cause the lean both banks. Check all connections. The V8 has the EGR not PCV like the V6. I'm not familiar with the EGR system, but the V6 gets the same codes with the PCV hose splits. Check the EGR system.
 
idk about the maf sensor. its been replaced under dealer warranty. and i cannot find a vacuum leak for the life of me. im gonna hook it up[ to a tester tommorrow and see what that says.
 
tireman said:
Vacuum leak after the MAF to cause the lean both banks. Check all connections. The V8 has the EGR not PCV like the V6. I'm not familiar with the EGR system, but the V6 gets the same codes with the PCV hose splits. Check the EGR system.
Click to expand...

Actually, both the V6 and the V8s have both EGR and PCV systems. The V8 doesn't have a PCV valve, but it still has PCV (Positive Crankcase Ventilation).
 
Thanks Joegr

I wasn't sure what the V8 had in it. Hey Joegr, I just read what you wrote about how the air conditioning system worked, nice explanation. I can tell you really know your stuff. Merry Christmas!
 
ok fellas. i definitely dont have any vacuum leaks. but something i noticed a week ago and now i just realized again. when my car is idling i have one exhaust pipe thats steams a hell of alot more than the other one. one almost doesnt steam at all and one steams a bunch.(because of the cold weather) could this be a clogged cat or something? also i tapped this little silinoid with a ratchet that is attached to the tb and my idle went up until i revved it. anybody know why?
 
gixxer said:
also i tapped this little silinoid with a ratchet that is attached to the tb and my idle went up until i revved it. anybody know why?
Click to expand...
That sounds like the idle air bypass (Idle Air Control (IAC) in LS parlance)--it's what allows air into the intake when the throttle plate closes. When it goes bad, you'll get a rough (or no) idle if it fails closed (which has been normal in my experience). It sounds like yours is sticking open, and that's your vacuum leak--it's allowing unmetered air into the intake, literally bypassing the MAF sensor. On my Explorer, I used Berryman's Chemtool whenever it would stick, but that finally stopped working and I replaced it. IIRC, it's not particularly expensive nor is it particularly difficult to replace.
 
IAC valve

Yeah, take off the IAC and clean it out with carb cleaner and see if that fixes that problem. They get carbed up over time. If this does not fix it, they are $50 a quick change out.
 
SoonerLS said:
That sounds like the idle air bypass (Idle Air Control (IAC) in LS parlance)--it's what allows air into the intake when the throttle plate closes. When it goes bad, you'll get a rough (or no) idle if it fails closed (which has been normal in my experience). It sounds like yours is sticking open, and that's your vacuum leak--it's allowing unmetered air into the intake, literally bypassing the MAF sensor. On my Explorer, I used Berryman's Chemtool whenever it would stick, but that finally stopped working and I replaced it. IIRC, it's not particularly expensive nor is it particularly difficult to replace.
Click to expand...

All air going through the idle air bypass valve is metered through the MAF (unless the hose to the valve is disconnected).
The way the solenoid valve works, it is normal for idle to affected slightly if you tap it. It sounds like his IAC is okay, but the advice to clean it is still good.
 
just got car back from the shop. they say my cats are bad. apparently one has nothing left in it so it is causing the running rich code. does this sound like bs or is this a possibility? its an expensive fix for it to not be the problem. also has anyone put regular universal cats on there ls? im told i can only use oe replacment ones because of the way they bend
 
Bringing this Thread back from the crypt ....So does anyone have any answers for gixxer’s last question? This is very similar if not exactly similar to what I’m experiencing...especially with the steam/smoke being more prevenently exiting out of Left side/ driver side exhaust muffler? Any thoughts before I dump money into buying a new IAC or EGR
 
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