I replaced my rear valve cover with a new one (3.5) and my old one and the new one both have the pcv valves and when I started back up after the swap, it runs very lean at idle. There aren't any vacuum leaks that I can detect and all hoses are tight.
So I did some troubleshooting
I disconnected the MAF and that makes it very rich at idle.
I tried a different OEM MAF and the same behavior occurs; lean when plugged in, rich when unplugged.
So the MAF seems functional.
Could be the o2 sensors, but what else could it be? TPS has not been knocked out of position.
I ordered a new intake manifold gasket, right now I am just using a light coat of rtv, but that doesn't appear to be the issue either.
Any suggestions?

 

This is a symptom of vaccuum leaks.

I would plug or tap over the pcv valve.

Then start the car. If the car runs better, you have found your problem.

 

I already tried this, I should have mentioned it sorry.
Thanks though!
Also, only code I've pulled is EGR, but I've had the EGR disconnected for a while now so it's always thrown that code.

 

I have used a propane torch to find vacuum leaks.

open the valve, but do not light it.

Point the tip towards suspected vacuum leaks.

The engine will suck the gas in, and speed up.

Please do not smoke when you are doing this.

Also, do this outside, or with good ventilation.

 

Pretty sure it aint a vac leak man...but I'll look into that more...maybe it is actually I tried a cigarette for smoke alteration or sucking and couldn't find anything. but I guess a cigarette isnt the best method.

 

Funny thing is, when I first start her up, she purrs like a kitty...only after like 10 seconds does she start bucking and showing lean, I cannot see what the afr is until the lc1 wb warms up so I don't know if it's lean in the beginning or not. by the time the wb warms up and displays a reding, it's lean by that time...
If it was indeed a vacuum leak I'd like to think it would be showing from the very start of the car..but IDK...I youtubed some vids (eric the car guy is a good guy) and the propane method seems pretty sound, or evern starter fluid albeit mighty dangerous

 

You replaced your 3.0 rear valve cover for a 3.5 and instead of using a gasket you used RTV?? That could be your problem. Did you follow torque sequence?

 

haha no bro!! I have the 3.5 already in it its got hr pistons, hi rev cams, oil pump etc..it runs pretty good i wouldnt put a 3.5 vc on a 3.0 no way what for?! I wish the 3.5 vc were aluminum tho..like the 3.0

 

lux97max might have the answer to your problem.

you apparently used rtv for the valve cover instead of a gasket. There is your vacuum leak.
Replace with proper gasket.

 

ordered one already. but this was there even with the gasket, I removed it to inspect and in the process it kinda came apart ha. so yes Lux97max I will take your advice & see.;

 

The pcv draws engine fumes into the intake, then burned.

The system operates under vacuum.

So a substantial air leak at the valve cover might explain your problem.

 

you had the problem with the old gasket that came apart .....think about that
and have not replaced it with one that is good ..

 

the problem only happened after I replaced the rear vc, then I reused the old oem gasket when I first reassembled the im. That's when it started so I thought that I frayed a wire on an injector or something. So I disassembled again to check the injector connections and all had continuity, so I figure vacuum leak, but all the hoses were pretty tight. So i swapped the pcv valve out with the old one that didn't have any issues. The issue persists, so yea it may be that I damaged the gasket on the first disassembly. I just have to wait until new gasket arrives to make sure.

 

I rfeplaced the Inatake amnifold and it's the same...could it be the o2 sensors maybe? When I press the throttle down she runs like normal, just on idle its lean..I sprayed carb cleaner around the hoses and cannot find any leaks...funny thing is it smells awful rich on idle, like unburnt fuel..kinda puzzled here.

 

I buypassed the pvc valve altogether and plugged the intake manifold up where it was connected and now it's back to normal afr. I dont get it, it always had the pcv valve connected before...Also have a massive oil leak by the front timing solenoid. I hope I can rtv it.