Keeps throwing P0327 code...driving me nuts!

[PhantomHaZe]

I'll try and make this as short as possible.

Bought the car with mods in sig (pacesetter LT's, highflow cats, GMMG catback, SLP MAF, SLP lid) and car already had a tune of some sort since it doesn't throw the typical LT codes. Mods and tune have been on car for 5+ years.

1. Battery dies initially. I replace, no problem.
2. Few days after replacement it throws P0416 code. I replace passenger side check valve and it goes away. Great...right??
3. I install NGK TR55 plugs and MSD wires soon after. After install I wash up the engine bay a little with hose water and a degreaser.
4. A few days after, I throw a P0327 code and P0416 code (again). Obviously, I'm more worried about the knock sensor code.
5. Around this time I notice a little more vibration/rattling...under the center console a little when in Drive and slowly moving or stopped at a light, although slightly noticeable under load. Goes pretty much away in Park.
6. Eventually, get around to having a shop replace the knock sensors. I supplied the sensors (GM wholesaler online, so OEM) because I originally planned to do it myself. They said they couldn't guarantee the parts if malfunctioned and would have to charge labor again if they were the culprit. Though, they did supply the wiring pigtail and did perform the bulletin RTV sealant dam.
7. Everything seems to be great after I get it back. Power seems to be more instantaneous and smoother. They did a coolant flush and oil change as well.
8. I drive it for a week or so, no problems. Although, that rattle/vibration is still around now and then and only perks it head once the car is warm.
9. I put in the first tank of new gas since being fixed. 93 octane from QT. The next day getting on the highway going to work.....ding ding....there's that dang SES light again. My heart literally sank.
10. Finally scanned it today at Autozone. It's the P0327 code...AGAIN. And I have noticed a return of slightly less power. Doesn't seem to be knock, just the timing retard with the light being on I suppose.

Can anybody give me any insight?!?!?!?! I've searched all the boards.

Could the high flow cats be clogged and on there way out, thus causing vibration and all the air system and knock sensor codes???.....Could the LT's be causing vibration, thus the code???

I'm losing patience. The car had none of these creeks and moans when I bought the car. But right after the knock sensor code came on originally, the under console rattling started. Only to be cure by Park or a cold start.

I'm really sour on the car right now. I sold my uber-reliable Chevy Silverado of 3 years to go back to the impracticality that is a Camaro/F-body. I held off from getting my dream car for too long, so I broke down and bought it....and this is what I get.

[PhantomHaZe]

Come on...anyone have any insight? I paid over 600 bucks for this knock sensor overhaul, and it just comes back. I can't understand it.

[0rion]

firstly, as I'm sure you learned, don't wash the engine down with a water hose. #1 killer of knock sensors. If you've done it since then that could be your problem. Another issue you might have is the gasket in the cowl area is leaking and letting water drip down and get under the intake. Next time it rains raise the hood and see if the intake or anywhere near it is wet towards the back.
Those knock sensors are really easy to replace.....and relatively cheap. You can go to LS1howto.com and read the write up on swapping intakes and that's pretty much all you do. Pull the intake and replace them. No gaskets to replace and no water lines going to the intake. The only tricky part is the brake booster hose.....it runs behind the oil pressure sensor and most people end up breaking that sensor trying to snake the hose out of there.

[PhantomHaZe]

Yeah I understand all that. I have NOT washed it since it's been fixed. Is it possible that it's just a bad batch of gas? I'm just having a hard time believing that one of the sensors failed after replacing both, replacing the pigtail, cleaning everything up and building the RTV dam.

[shady milkman]

could be bad gas...however it could also be a pinched wire. or a short further back than the pigtail ....the best bet is when the MIL is illuminated open the hood and put your ear to the engine and see if you can hear any knocking. have you done a full tuneup on the car ?

another thing to think about is ..if you are running longtubes the car might have been tuned before...maybe the tuner messed with the sensitivity of the KSs also...many possibilities.

[PhantomHaZe]

I'm thinking my best bet is to just take it to a legitmate dyno shop and have yen hook it up to their hptuners software. What do you guys think?

[Spaz]

I'll try and make this as short as possible.

Bought the car with mods in sig (pacesetter LT's, highflow cats, GMMG catback, SLP MAF, SLP lid) and car already had a tune of some sort since it doesn't throw the typical LT codes. Mods and tune have been on car for 5+ years.

i think i found your problem... try putting a stock MAF on and driving it for a little and see if it keeps happening...

[NaviDyn]

An small ding under the hood from just about anything can cause vibration for those sensors. Such as whatever number 8 is. If you had say, an bracket mounted to the head, and it is slightly loose, it will tap the head/block, you wouldn't even here, but the knock sensor might.

Since you said the sensors were changed after washing.

[shady milkman]

i think i found your problem... try putting a stock MAF on and driving it for a little and see if it keeps happening...

aftermarket mafs are known to lean out the fuel mix ...but with the vibrations and such i think navidyn is on the right track.

[PhantomHaZe]

Yeah, that's all I can really think of. I soaked the sensor the first time. I know that. The mechanics said the 1 sensor was soaked in some standing water. But everything was fixed. New sensors, pigtail, gasket and RTV dam. So everyhing should be hunky dory. But with that vibration, I'm thinking t had somehing to do with it. My gut keeps telling me those high flow cats could be going out or at least one is. You can hear he rattling from he outside on each side even with my center console right where hose cats are. I'm going take a chance and put some straight pipes in and see if I get some results.

[Spaz]

aftermarket mafs are known to lean out the fuel mix ...but with the vibrations and such i think navidyn is on the right track.

i didn't want to rule out any options...

Yeah, that's all I can really think of. I soaked the sensor the first time. I know that. The mechanics said the 1 sensor was soaked in some standing water. But everything was fixed. New sensors, pigtail, gasket and RTV dam. So everyhing should be hunky dory. But with that vibration, I'm thinking t had somehing to do with it. My gut keeps telling me those high flow cats could be going out or at least one is. You can hear he rattling from he outside on each side even with my center console right where hose cats are. I'm going take a chance and put some straight pipes in and see if I get some results.

you'll need to program the rear 02 sensors off...

also are you sure it's the cats and not the heat shields taht are rattling???

[PhantomHaZe]

The rear O2's are already programmed off. There was some sort of tune already on the car since there was no spot for them with the LT's. And the passenger side cat heat shield was half off, buti had the shop clamp it down and it hasn't had any affect on the noise.

[PhantomHaZe]

I finally had a chance to listen underneath the car a few minutes ago. The rattling seems to be coming from the driver side cat's heat shield almost resting up against the brake lines going up the center of the car. I had to rest something on the gas to keep the rpm's at 900 or so....to get the sound I was hearing. I have no clue if that would be enough to set the sensors off.

Another weird thing was the car seemed to drive really well on the way home from work....with the SES light still present. It was very smooth through the band and was pulling at least if not more hard than any other time I've had the car so far. I'm wondering if maybe it is a bad batch of gas.

I still have 3/8's plus of a tank...so I don't know if I want to run it down some more before I put a new tank in....or if I'll just do it now and put a fuel system cleaner in.

[Cutlass]

Loose knock sensors can set codes, maybe the guy didn't tighten them down enough. They should be tightened to 11 ft*lbs

[PhantomHaZe]

I just don't believe this shop would have not tightened or tightened the sensors too much. They had a very clean shop and were very reputable and had two days to do it. I would hope they check everything right. My only problem is that since I bought the parts, they couldn't guarantee their reliability even though they were the same AC delco OEM sensors they would have bought. So if I want to take it back to them to check, I'm charged all over again for labor, unless of course they didn't put them in correctly. But I assume they did. Like I said before, the light was off for almost a week after getting fixed. And didn't come on until the next day after a new full tank of gas.

I'm going to let this current batch of gas go all the way down to empty and again put in some more fuel system cleaner and see if the light finally goes away. Otherwise, there is something more at fault unfortunately.

p.s. It still seems to drive really strong though. Pulls hard.

[PhantomHaZe]

I've also just been informed that bad gas would not set off the light or any knocking as well, so it must be some sort of connection etc.

[PhantomHaZe]

I'm going to let them scan it this weekend. That way they can tell me it is either the sensor itself...or the pigtail. Hoping the scan can point to which one it is, that way they don't have take off the intake again. Plus, if it is the wiring pigtail they should be liable since it's their part. If they have to take it off again, and I'm liable for the labor again, I WILL do it myself.

I'm also planning on calling Performance By Joe, here in St. Louis. I'm going to see what they can do about a tune. I want them to tell me if it has a tune already, or if it was just a simple hand held one. I'm betting it was hand held. I ordered some non-catalytic converters online (straight through stainless pipe that looks exactly like a cat) to take care of my rubbing problem and any future cat failure.

[PhantomHaZe]

I finally got the same shop to take a look at it better. They went through some procedures and tapped on the intake and said both sensor were reading the tapping. So their conclusion was that the sensors were working fine and that either the PCM had gotten water on the inside or the y-pipe touching underneath was setting a false knock sensor code off. I don't know why false knock would set off another p0327 instead of another knock sensor code.

Either way, I went and got straight pipes (cats that have straight pipes) put in place of the cats. The exhaust guy did a decent weld job but he ended up making the y-pipe bang pretty seriously on the driver side frame just past the header collector. And I NEVER thought I'd be doing this, but I have a crushed soda can and some cardboard strapped to the pipe to stop the banging. So I have to go back to get him to fix that....maybe heating up the pipe and flattening it out a little.

Hopefully, after I get the pipe from touching the SES light and p0327 code will go away and I can then get it tuned....or maybe the tune will fix it, who knows because I sure the hell don't.

[Cutlass]

I finally got the same shop to take a look at it better. They went through some procedures and tapped on the intake and said both sensor were reading the tapping. So their conclusion was that the sensors were working fine and that either the PCM had gotten water on the inside or the y-pipe touching underneath was setting a false knock sensor code off. I don't know why false knock would set off another p0327 instead of another knock sensor code.

Sounds like a reasonable diagnosis. Hopefully fixing the exhaust will fix you knock sensor problem

[PhantomHaZe]

Sounds like a reasonable diagnosis. Hopefully fixing the exhaust will fix you knock sensor problem

I'm really hoping so. It sounds like a beast now and pulls really hard. I'll get the pipe flattened this week. Hope the light goes out. Otherwise, who knows.