Almost resurrected an old thread until I saw it's not preferred...I'm a little new to this forum but searched as much as I could and did find a lot of useful information so thank you in advance to all who contribute.

My 2000 WS6 is an all stock motor w/ M6 - 76k miles.

I had some intermittent starting where on occasion it would fire on the 2nd or 3rd crank. In the past 6 months I've replaced plugs, wires, crank sensor and finally the camshaft sensor using OEM sensors. I took the car for test drive. The issue came maybe 5 minutes into normal driving conditions. At about 35mph the tach needle dropped to 0 and the car was still cruising but firing poorly...almost like how it feels if you have a plug or two fowled. Upon reading I noticed that the sensor controls timing on cylinders 2 and 8 so that would make sense that it feels that way. At random the needle will pop back up to where it should be reading.

My next step is to pop the manifold back off and check grounding but prior to doing so, would there be any other external checks? My thoughts revolve around fuel injection or ignition coils. Checking the grounds seems like an intimidating task but if that's what it takes then so be it. Because of the random issue, I feel strong that it is related to grounding, which I will need to do some heavy reading in this forum on how to efficiently and properly find the bug.

 

A 2000 LS1 does not have individual cylinder timing control. Your issue definitely sounds ground related. As you said, the back of the cylinder head is the 1st place, but also don't forget the ground from the chassis to the block. I've seen issues because that ground wasn't making good contact. Could always add another while troubleshooting.

 

Thank you - if anything that helps to feel more confident in the problem being a ground. Noted to give attention to the chassis-to-block ground. I like the idea of adding another while troubleshooting, definitely can't hurt.

 

No codes or check engine light?

I would inspect grounds as suggested also the wiring and plug to the cam sensor. I'm guessing the car sits a fair bit. Any chance of rodents getting to the wiring? Anything else happened that may have affected any wires/ connections?

 

Check engine light is on for camshaft POS - I wanna say it's the P0343 code.

As the 3rd owner, I know the guy before me barely drove it - in fact I want to say he only put maybe 100 miles on the car in the 10 or so years he had it. So to your point, it's very possible something would have gotten into the wires. I haven't done heavy digging for visual inspection on the grounds yet but I think it's very possible I will find something. The car has always been garage kept and still is. No rust and never driven in rain/snow.

I did inspect the harness and pins when I put the new sensor in and it looked okay which is why I'm more willing to bet its going to take some poking around the meter and moving some things around to check for interruption in the resistance. I think a good start is to check the aforementioned grounds.

 

Yeah, in a garage is where mice, etc. can have a blast dining on wire insulation and whatever else.
I would look at as much of the harness as is accessible.

 

Update to my issue with some more details from my previous interactions with the car. More forum searching has been extremely helpful in diagnosing so hopefully the additions to this thread will also help someone in the future.

When I purchased the car an E check was needed, however at the time it would not pass. In doing so, I had a local race shop install new O2 sensors, new throttle position sensor, repaired instrument cluster, and flash computer tune. At this point I passed E-check. The car ran well for the time being but then encountered an issue with starting. The motor would turnover but not fire, until at a max of 3 attempts. Eventually I received the code which I believe was P0335 - related to Crankshaft Position Sensor. At this time in July 2019 I replaced the crank position sensor (ACDelco 213-354 GM OEM Sensor) and installed new plugs and wires (8.5mm LS wire set from Summit SUM-887828 in conjunction with new NGK-TR5GP plugs gapped @ 0.040"). I then took the car back to the shop to have the crank relearned and code cleared. I was given news that the car did accept the relearn procedure, however, if the issue comes back and the tach needle drops to 0, it's likely the Cam Position Sensor. Low and behold on the way home this issue came back. The car would misfire for a short time and tach read 0.

Over the winter I removed the intake manifold and installed the cam position sensor (ACDelco 213-363 GM OEM Sensor). In doing so, I also purchased a new LS1 intake manifold as my original one was cracked and experienced a vacuum leak. New FELPRO gaskets on both intake manifold and throttle body. I installed a new Duralast Thermostat and housing assy (#37987) as well as a new battery. All the while, I have been looking for any electrical shorts or breaks in wires or insulation and haven't found anything damaged or shorting out. I also have a hard time believing it may be an electrical short due to it's predictable nature, but my eyes are open to the potential of that being the case.

****Today*****

The car starts cold with no issues. The engine runs great as it idles toward operating temperature ~200°F. Once it reaches this temperature (about 13 min of idle) the motor will misfire and tach needle reads 0. This happens for about 1 min 30 sec. After that, the tach goes back to it's idle RPM and can be driven. Additionally, if I were to go WOT - wide open throttle - the engine shuts off. It can be started immediately after with no issues, but the ECU obviously does not like going WOT. After a few days my check engine light has finally came on (not sure on code yet - but willing to bet it's related to cam/crank synchronization)

To eliminate some more variables my next steps are to check the thrust bearing play with dial indicator and pry bar to see if the crank thrust (thrust bearing) is worn. Could be losing signal as the wheel moves away from the pick up. I also want to do some more homework on the cam sensor circuit itself in conjunction with the ECU to see if I can probe out something that is causing this malfunction.

 

The cam sensor is not "critical" on an LS1; I have run with the sensor completely disconnected. The only symptom is that the engine only starts about every 2nd time. It will not cause a misfire.
On the other hand everything related to the crank sensor is critical. There are posts here about people going through 2 or 3 crank sensor until they get one which works perfectly, although the AC-Delco ones seem to be much more reliable that the no-brand ones.

 

My buddies Turbo 6.0 killed the thrust so bad it ruined the crank and the block. It was still running fine.

 

Maybe a data log might be in order?

 

Yes sir! It is on the to-do list. Haven't gotten some time to dig since last week but the crumby ohio weather coming in should give me plenty of time in the garage.

What I wish I could pin point and understand why the misfire and tach loses signal when the engine reaches operating temp. And it only happens for 90 seconds....then we're live again and showing idle rpm. It's like clockwork after every cold start. Doesn't matter if I'm driving or idle, the tach loses signal soon as that temp reaches ~200-~205°. Would love an explanation on how temperature and signal loss are related - but maybe before I dig deeper, let's see what the DTC reads first. As mentioned, the light just came on last time I drove it.

 

Good to know...I wouldn't mind taking it out and see how it reacts. It may come to that eventually. Wouldn't the check engine light stay on if that is the case? The light wouldn't bother me that much, but I think the fellas at E Check would for the next couple times it needs it. I've already went down the rabbit hole on trying to get collector plates...always something...

 

Update - no play in the thrust bearing, cleaned all grounds and contacts. Still looking to hook up to an oscilloscope and get a better idea. Read a few threads showing the reluctor wheel could be in backwards, however, the motor is stock and this problem is somewhat new. Still scratching my head on how the engine operating temp kills signal on the tach then after 90 seconds it's live again. I should mention when the tach goes live again I do receive misfires, but they are very subtle and at random. Oh and now codes P0336 with P0300 are showing up (CKP signal / Misfire).

As mrvedit had suggested, could have gotten a lemon crank sensor - can't hurt to try another.

Also going to hook up to ECU with stock tune just eliminate that variable.

 

Check out this thread:

https://ls1tech.com/forums/pcm-diagn...f-voltage.html

It indicates how sensitive the crank sensor is; even needing a clean mounting surface. I've seen other threads where the OP goes through several crank sensors before he finds one that works. I suspect that a marginal reluctor wheel position makes the crank sensor even more sensitive to getting a particularly good one.

 

Thank you, sir! This is actually very helpful. Today I will pull the starter and carefully re-install the crank sensor, inspecting and cleaning the surfaces that it mounts to.

As a new update I swapped PCMs with stock tune to check the computer isn't the problem but the issue continues to exist. Saturday I pulled the intake off to check the PCM grounds on the back of the driver side cylinder head. Cleaned all surfaces including the washers and the bolt. As I was putting the intake back on, it must have bumped the oil pressure sending unit and it cracked - I've been warned time and time again to watch for that. What are those things like 10 feet tall??? Jeeze. Just one more new sensor to add to the list (and a new deep well socket)...

I look forward to the day I can post the solution to this problem. Thanks again for everyone's input.

 

Try testing the sensor like I did. It will at least show if they are functioning and consistent. I found the negative going pule width varied with each sensor at the same RPM.

 

Hey that's a pretty cool bench set up to test the sensor! Thank you for sharing that.

 

need some help have good cam n crank sensor not sure wiring is correct this is a gen 3 lq4 2005 silverado
cam A brown/white signal
B pink/black ground (low)
c red 12v
crank A signal
B ground low ref
C 12 volts

is this how gen 3 cam and crank are labeled at the plug or is the cam like this

 

Update - the issue has been resolved!! The wires seemed in good condition from the ECU but leading down towards the crank sensor, it was noticed they started becoming quite brittle. Measured resistance on the wires and was getting around 0.3 (should read 0). Moved them around and would watch resistance drop. Spliced in new wires in turn with a new sensor and the tach continue to read fine, without losing any power.

In turn, I did come to find out cylinder 6 continues to misfire. Checking the plug for cracks and likely running a compression test. Looking to eventually replace all fuel injectors as well. At any rate, I'm thrilled this little issue is resolved.