Hello All,

I'm working my way through my dirty beaten up 2002 Z06 as my first project car. Previous owner(s) were not gentle with her but did end up putting on AFR 205 heads as well as some other mods.

I came across this disconnected hose (see 1st pic) coming off the driver side valve cover near the rear of the engine bay that's just been cut and left unattended. I did some research and found it is a PCV system hose. I thought on the LS6 the PCV hose connected the intake manifold to the valley cover (see 2nd pic). Should this driver side valve cover nipple and hose even be here though? Maybe it has to do with the aftermarket heads? Should I just cap off the driver side valve cover nipple?



(Yes, she is very dirty, my apologies. She is far from show car ready but we have to walk before we can run...)

Many thanks in advance!!!!

 

It might be the air injection hose connected to a one way valve located behind the head which injects air into the exhaust manifold at start up.

 

that snake-shaped-ribbed hose is the connection from the fuel tank to the purge valve. When the engine is running, the purge valve is cycled to pull fuel vapors from the charcoal canister. Part of the emissions system, and you probably have several P044X codes. So if you are in an emissions monitoring locale, you won’t pass inspection. Your picture on the driver’s side doesn’t show the purge solenoid, but with that hose off your fuel trims are going to be all messed up, as that will be un-metered air going into the engine when the pcm commands the purge solenoid to open. Fix that and your car will run better. I will bet you may have lean codes, and misfires too. I would replace the purge solenoid and that hose, clear the codes, and then run a DRIVE CYCLE (a specific drive cycle specified by GM and you can find on the internet). Then pull the codes on the DIC to see if any came back. You will need a scan tool to check readiness monitors, but if you don’t get a check engine light and no codes after a drive cycle, you will have the engine running as good as it can be, given its overall basic health Those gray rings are the hose locks. They are actually “C” shaped, and will release if you push IN at the center of the “C”. They are easy to break, hard to find replacements.

The passenger side looks OK, the curved pigtail hose properly connects the valley cover to the throttle body (TB), and the other hose goes from the valve cover to the TB as well. Now, if the PCV orifice box is cracked under the valley cover, your PCV will pull too much vacuum. If you get the engine good and warm and crank up the rpms, say in second gear, then back off the throttle. If you get oil smoke out of the tail pipe, you are either getting a lot of piston ring blow-by, or the valley cover needs replacing. If the intake runners are oily, you may need a catch can to cut down on the oil sucked out of that hose from the valve cover to the TB.

 

yea I just saw the AIR hose It looks disconnected. You might have a DTC (code) related to that as well. It may be the code associated with the AIR system does not cause the check engine light (CEL, or MIL). If that is the case, most states will pass a car with one code and no CEL

 

Hello, thanks for your reply! I believe that the snake-shaped-ribbed hose is plugged in correctly? Pic below.



I should've mentioned that the car has an AIR/EGR system delete. It throws code P0412, which I think is for the unplugged connector/vacuum lines to the removed AIR pump. I believe the code should've been tuned out but who knows....

So at the end of the day, should I just cap the AIR hose that is disconnected? I thought the LS6 did not have the AIR hose here.

 

yes that end, going back to the charcoal canister looks ok. Is the other end open? Can’t really tell in your picture.

So what DTC”s do you have? RESET any messages on the DIC such as “door ajar”. Now Hold down the OPTIONS button, while holding, press FUEL 4 times. Release both buttons. If you press OPTIONS once, you will go into manual mode where you can scroll one module at a time. Pressing OPTIONS again will advance to the next module. Right now all you care about are the PCM Codes.

 

Here's a photo of the purge solenoid. I think in regards to the purge valve I do not have any issues.


The thread was originally regarding the disconnected PCV hose in the pic below. I was asking why this hose was here and if I can just cap it.



Thanks!!!

 

That hose is not normal. When you have the U shaped pigtail hose at the TB to valley cover, There should be a plug in that hole in the driver side rocker cover. when you have that pigtail.That hose, if is is venting is letting crankcase vapor into the atmosphere. So, your PCV system won’t recirculate gases. The crankcases on cars used to be vented to atmosphere, so really, the main problem you may have is smoke coming out of that hose when you run the engine, and unwanted crap sucked into the crankcase should the PCV orifice box inside the valley be broken. That will then pull unmetered air into the engine, and that dangling hose a good path. Stick a cork in the open end and see what happens.

I think you are going to find a lot of oil in the intake plenum. This by itself will hammer good performance, making the engine burn oil along with the gas. Doesn’t take much oil to affect performance.

Do you know anything about your tune? usually when people do cam and heads, a speed-density tune is applied. That will keep the overall engine a little on the rich side, and sometimes a lot richer. Over time that rich condition along with oil ingestion will foul plugs and carbon up piston tops. Usually, the port fuel injection keeps these engines clean,so if you have a bore scope,scoping thru a couple spark plug holes might give you some clues.

There are a lot of mods and sorting them out to get a great running car is often tough, as you may be trying to fix the mistakes of others.

 

Thanks for all the great info! I ordered the $12 plug on Amazon for the driver side valve cover

I was planning on pulling the intake manifold this winter to clean it. Probably install an oil catch can afterwards.

I do not have history of the tune, the PO didn't give me much. It does have AFR 205 heads, an LG-G5X3 cam, and LG long tubes w/ cat delete. Planning on getting a mail-order tune after I get all these odds and ends sorted.

Thanks!

 

why get a mail order tune? Before you do that, I think you need to find out what you have first. The po probably did not do the tune, and a good shop will have records of what was done. Ask him where it was taken. The shop will also know some history on the car and what was done. Sometimes home done mods can be a challenge to get right. For example, putting high comp heads on an 80k mile engine is asking for tons of blow by the rings. If they were letting some go past before the mods because of normal wear, then higher compression will make this worse. Piston skirts can wear, and this causes the edges of the rings to wear, reducing ring sealing. That’s normal wear.

If the car was dynoed , then asking if the shop will give you a break on a dyno run. They can tell you what is going on real fast. First, though, I think you should clean the intake and at least make sure the spark plugs are not fouled. If you know some one that has a scan tool, it would be good to know if you are getting random misfires that are not frequent enough to throw a P0300 DTC. If the car has to idle too fast to keep running, maybe a sign of a vacuum leak.

My Z06 is an ‘02 as well. I replaced the valley cover because the plastic orifice box was broken and my PO bonded it back with body filler, closing off the metering slit. When you pull your intake, pull the valley cover too and inspect that orifice box.

If you don’t plan to track the car a catch can won’t help a lot. If you have oil in the intake, it will probably be from your underperforming PCV. Catch cans do a good job of catching oil carried in from the rocker cover because the oil tends to flood that area at sustained high rpm’s. For s street car, the oil in the blow-by gases are very fine mist like droplets that a catch can can’t separate very well. They end up being burned, and leaving oil residue in the intake.. A catch can is a crude oil separator. There needs to be a noticeable pressure delta to slow down the droplets so they will get caught. You can’t get that much change in the PCV system.

Do you have a P0103 DTC? I think that code is an indication of a speed density tune. IIRC that DTC is MAF high circuit Frequency. Since a S-D tune does not use the MAF, it tosses that Code. Isn’t Chicago an emission compliance place?

 

I was thinking a mail-order would be cheaper, but going to a dyno sounds like a better option. Still learning as I go.

Replaced spark plugs last week, they looked fine but I wanted a fresh set in. I have a BlueDriver Bluetooth scan tool, but don't know if that can read a P0300 code

Other codes read by the BlueDriver are P074 (clutch switch, unsure if related but on my list of to-dos), P0412 (because of the deleted AIR system I assume), and yes P0103. I think the best guess is that it's a speed density tune and the codes were not tuned out? Unsure though because I have no cats and am not throwing any codes for that. I was under the impression that the tuner will tune the codes out, no CELs, and your car will pass emissions. Illinois is OBDII test only, no sniffer or visual inspection.

 

if the plugs aren’t badly fouled, that is good news. p0103 pretty much confirms a s-d tune, so a mail tune will be of no use and intro a new set of probs. a p0300 is random misfire. if the misfire rate is below a certain rate, the counter will reset and you will have fish-bite misfires but never a p0300. your blue driver prob does not read individual misfires, as that is an advanced power train diagnostic.

so, fix the pcv stuff, clean the intake. call LG and ask them what idle speed to expect from the cam you have, and heads. If your idle is higher, look for vacuum leaks. Without a good scan tool, though it is a guess about what your performance issues are. Also, if you can get the dyno sheets from the tuner and compare with what LG would tell you what to expect from their cam. You probably should be above 400 RWHP, which would put you in C6Z06 performance territory, except torque. Cubic inches always wins that one.

At that you should have a pretty fast beast and if it is not, then compression tests and blow-down tests, looking at fuel trims, ignition,etc.

BTW, in your original first pic, it looks like the #5 plug wire is touching the header. Not good, if true.

Your clutch DTC is missing a number. A P0174 is a lean bank 2 code, if that is the DTC you are seeing.

 

That's definitely going to be my plan of action.

I meant to write P0704.

Also, I forgot that the PO gave me a SCT Xcal2 programmer. I plugged it into my OBDII to see if there were any tunes that I could flash but I received "Error 12 - FS_E RR" and "Error 16 - CLAS S2_ERR" I know this programmer is super old but it's what I was given.

 

You have all the makings of, please excuse the old school phrasing, a hauling *** car there. Those headers are among the very best, and for a 205cc intake port, the AFR heads are also 1st rate. Since LG doesn't publish cam specs,, except to the purchaser, I can't comment on the cam. But it sounds, number wise, like at least a middle to upper end range of cams. Good luck...