I have a brand new VX Diag Tech 2 emulator from Amazon, and I want to use it to assess the sensors and other running conditions of the engine. Before I try to set it up and plug it into the car, I would like to confirm that this will not cause my tune to automatically be lost. I have an LS2 with an LS3 top end, a good sized cam, and LT headers in my '04 CE coupe, so it's pretty critical for me to retain the tune for that setup. Can anyone definitively calm my fears?

 

Your tune won’t be lost !!

 

Ok, the Tech 2 emulator is up and running now, and it seems to display real time data quite nicely as the engine is running. There are zero misfires shown on any cylinder for the 4+ minutes run time. It is showing 4% engine load at idle. It idles at around 900 rpm +/- 50.

The first thing that jumps out at me is that the throttle plate angle shows 10-11% at idle. Is this normal? If not, then how do I adjust or recalibrate it?
2004 CE Coupe, 6MT
LS2, LS3 heads and top end
Good size cam that idles nice and choppy, but unknown specs.
LT catless headers, 3" X pipe, and Corsa Extreme.
PO stated it dynoed 452 at the wheels.

So a couple of things I want to check:

First, how do I look at the cam and crank angle sensors to see how they are working while the engine is running? I'm now chasing a hard start issue, so I'd like to see that info. There are no DIC codes for the PCM.

Second, the engine seems kind of laggy when I push the throttle. I know I need to first diagnose and fix the fuel pressure drop , as it goes to zero almost instantly when I shut off the key. (I just put a brand new GM fuel pump module in the car, so I don't think it's anything to do with that.) I can also hook up a vacuum gauge to the manifold to see what it's doing. Where else should I look besides what's listed above?

 

I like to see TPS % below 10%...6 or 7% is good...you can try cleaning your throttle body and there is NO calibration or adjustment for that...this may fix your "laggy" throttle. You will need a scope to check cam and crank sensors...there is no other substitute to check this (waveform capture below)...there are a few things that can cause the fuel pressure drop...on a 2004 maybe fuel injector, faulty cam sensor, or faulty fuel feed line check valve...you can check the injector and check valve easily with a Mityvac (picture below) hooked to the fuel rail feed for the injectors and the fuel feed line for the check valve...you can check manifold vacuum with engine running by subtracting the BARO (inHg) from the MAP (inHg)...29.9 (sea level) minus around 10.0 inHg or so which equals 19.9 or you can hook up a vacuum gauge...I always check BARO "key on engine off" to check the MAP sensor...29.9 good for sea level.


2001 good cam/crank blue- 24X crank red- 1X cam

 

I got in there today and figured out how to reach the cam angle sensor. I unplugged it, and then I decided to try to start the engine just to see what it would do. There was no difference. It took 3 short cranks, and then it fired off and idled just like it has been. The fuel pressure dropped to zero as soon as I shut it off. I have the new sensor already, so we'll see if it is the miraculous fix.

 

The Crankshaft Position Sensor is above the starter…the Cam Sensor is behind the intake manifold…which one did you disconnect ??…the engine will start with a disconnected cam sensor but NOT the crank sensor.

 

It's an LS2, so the cam sensor is next to/behind the harmonic balancer on the driver's side. That's where I unplugged it.

 

Whether CMP on an LS2 or LS1 car would still start eventually…what if you cycle the key a few times before starting ??…will it start right up ??…I would chase your fuel pressure problem.

 

The cam sensor was not the magic elixir. It acted the same after changing it.

 

If it’s an aftermarket sensor you may have a bad “new” part or it can also be a wiring issue if that wasn’t checked and a scope wasn’t used to verify you had a proper signal…it can really lead you down the rabbit hole…I’d be looking at a fuel pressure issue.

 

It's pretty simple if the camshaft sensor was not working it would cause the check engine light to illuminate or there would be a pending code that the vxdiag would show.

 

I got the cheapest one at rock auto, so I'm not opposed to buying a better one. Should I just get the "genuine GM" or is Delphi equal?

 

With your fuel pressure dropping to zero quickly when the fuel is shut off I’d chase your fuel pressure issue not the cam sensor…you ALWAYS want to use the OEM sensor if possible.

 

Since you are so worried about the camshaft sensor just get the best one you can find. You can get the OEM one. There should be none better. It will ease your mind and you will have the best.

 

Disconnecting the cam sensor puts the injectors in batch fire mode and eliminates the ability to attribute misfires to individual cylinders AFAIK. I've disconnected it on my truck and it ran exactly the same.

Random ask OP, can this device see the Magnasteer and do you see a calibration option for soft, stock, and firm?

 

Ok, I am taking the semi-nuclear option on the fuel injectors. I wanted to first pull the rail and see if I could see an injector leaking. This was a useless endeavor, because there are no retainer clips to hold the injectors in the rail. I bolted the rail back on the intake and cycled the key to be greeted with a shower of fuel from the #8 injector. I then had my wife video it on both sides of the rail. It was just #8, leaking from the top o-ring. Knowing that I was flirting with disaster by doing this, I stopped.

I called a local place and found that they will flow test and clean top feed injectors for $27 each plus tax.

So doing some quick math and some quick shopping, I instead decided to buy the Autool CT160 and clean and flow test them myself for about $100 more than having them done locally. My son has a 350Z with questionable injectors also, so the machine will pay for itself just with the Corvette and the 350Z. Yes, I could have cleaned them much cheaper using ghetto methods from YouTube, but I'd rather have the repeatable method with the Autool setup. My son also has 2 extra lower intakes complete with injectors for his 350Z, so I commandeered 8 retainer clips from his spares. They are the same style and work fine on the Corvette. I can start up by cleaning and testing the Corvette and 3 different sets of 350z injectors. I'll report back when it arrives!

 

Well, the injector test bench arrived. I have to say I am generally pretty happy with the purchase. I had one problem with the machine, in that the drain fitting in the sink bowl of the ultrasonic cleaner was loose and leaked from the factory. I thought it was the valve not screwed in enough, but of course I snapped it off with the threaded portion remaining in the machine. I actually got it out quite easily just by jamming a big flathead screwdriver in there and turning it out. I put a new valve in there that I had laying in a drawer, filled the sink back up, and it continued to leak out all over the wrong bench. I took the back cover off the machine, found the real problem, and fixed it.

Anyway, I found that the Corvette injectors had no internal leaks, but they did have several bad o-rings. Once I changed them all out, they all flowed within about 10% of each other, and ultrasonic cleaning them while heating and cycling each second for 20 minutes had no real measurable effect on flow rates or spray patterns of the Corvette injectors. They are factory LS3 injectors, by the way, rated at 441cc. So they were clean enough, and they needed new o-rings all along. I'll put it all back together tomorrow and see what it does on the car.