Sc2002cavy

Just picked up a 98' firebird ls1 car with a cammed Ls2 swapped into it. It's making no sense rightnow. I'll start by laying out the symptoms then what I have done so far.

My torque pro says the car is idling at 850rpm, but it's at 1200 tach shows 1200 as well.
no throttle response
rev down takes about....forever
no power until 4K and even then it's meh at best.
Both the cam position sensor codes , high voltage and low voltage

So far I have put in a new cam sensor.
And re-wired the cam sensor.

in starting to think the car has not been tuned for the ls2. But even the factory tune would know what RPM the engine is at. I'm just chasing my tail at this point.

Any ideas? Thanks fellas.

.

G Atsma

I'm thinking someone messed with the tune, and really messed it up!

2xLS1

iTrader: (25)

You are wasting your time if all you have is torque pro.

Sc2002cavy

okay so update on the car. It is a 2002 iron block gen III not an LS2 like I had been told. don't know displacement yet. There is a cam sensor in the block at the back under the intake. previous owner cut the harness at the plug back there and spliced in wires to run to the front of the motor for the ls2 sensor he then spliced those wires for the new plug.

some new questions.

Is there a benefit to running a ls2 style cam sensor? I am trying to understand why he would do the ls2 cam sensor.

How do I know if the car should be using the ls2 cam sensor or the one at the back of the block?

2xLS1

iTrader: (25)

Cam might not have a reluctor on the back of the cam. If that is the case then you have to use a reluctor on the cam gear. You can pull the rear cam sensor and look down the hole while turning the engine over and see if there is a reluctor. A 1x reluctor is a 1x reluctor regardless of it's location. There is also the possibility there is no reluctor on the cam gear where the sensor is wired.

2xLS1

iTrader: (25)

And a missing cam sensor signal has little to no effect on a running engine. It can cause an extended crank when starting. Once running the PCM knows when to sync the spark timing and injector pulse.

Sc2002cavy

Thankyou for the replies 2XLS1

I am going to plug in the rear sensor and see if the code goes away.

If the cam sensor only serves to start the car then I can safely assume that my other issues(throttle response low end power ect.) are being caused by the tune and not the cam sensor?

If so then I can have the car tuned even with the code present?

kingtal0n

iTrader: (1)

if it loses the cam signal, i think it will wind up in batch fire mode. because it will never find cyl#1.

2xLS1

iTrader: (25)

The CMP sensor determines whether a cylinder is on a firing stroke or on an exhaust stroke. As the camshaft rotates, the reluctor wheel interrupts a magnetic field produced by a magnet within the sensor. The sensors internal circuitry detects this and produces a signal which the PCM reads. The PCM uses this 1X signal in combination with the Crankshaft Position (CKP) sensor 24X signal in order to determine the crankshaft position and the stroke. This diagnostic monitors for a loss of Camshaft Position sensor signal.

As long as the PCM receives the Crankshaft Position sensor 24X signal, the engine will start. The PCM can determine top dead center for all cylinders by using the Crankshaft Position sensor 24X signal alone. The PCM uses the Camshaft Position sensor 1X signal in order to determine if the cylinder at top dead center is on the firing stroke, or on the exhaust stroke. The system attempts synchronization, and looks for an increase in the engine speed indicating the engine started. If the PCM does not detect an increase in the engine speed, the PCM assumes an incorrect synchronization to the exhaust stroke, and re-syncs to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.

kingtal0n

iTrader: (1)

How would it know the difference between a poor cranking injection PW and a misfire due to incorrect timing. Also, don't most computers try to start in batch fire mode anyways? Isn't the initial squirt of gas to all cylinders and it double lights? I know some V8 mercedes do.


I believe you it will start. But guessing the sequential aspect? I think thats a myth.

subeone

iTrader: (5)

you dont need the cam sensor on a ls for it to run.. and it will not default to batch injection.. lol.

All the cam sensor really is used for is for startup.

once again, I side with 2xls1.

kingtal0n

iTrader: (1)

I can't imagine a computer program that can run sequential EFI without a cam sensor working. If this was true, why didn't we have sequential back in 1983? We had batch, why not just guess the compression stroke like you are saying now? 50% chance guys. Come on. Sequential EFI came after the cam sensor, depends on it. Sounds like a myth to me, don't worry though- this is why I am here. To make sure if its a myth or not, lets wait and see. Somebody's bound to show up and know for sure, say where is our Pantera fellow? He probably knows

im not saying its impossible I just never encountered this. Mega squirt for example wouldn't do this, I never read anything like this. I would have remembered.

Sc2002cavy

Fixed it!
hooked up the rear cam sensor and boom shes running great and fires right up. No idea why that timing cover was on a gen III iron block. but whatever.

Now I just need to figure out the injector size and engine displacement so I can get it tuned. This whole 1200RPM idle crap is getting old.

joecar

The PCM does not need the CMP signal to actually run the engine...

if you read what 2xLS1 said above, the PCM measures the crank's acceleration on each ignition event, and from this it can easily determine which stroke/phase each cylinder is on (it's not guessing, it's measuring crank acceleration or lack thereof);

the 24x CKP reluctor is encoded, this allows the PCM to know which cylinder pairs are approaching TDC, it needs this signal to run the engine;

the PCM uses the CMP signal to sanity check the phase, if it disagrees, a CMP DTC is thrown
(i.e. ignition events correlated to CKP have more relevance/priority over CMP);


it does not need to use injector batch mode and/or ignition waste spark;


the reason that batch mode and waste spark were used the 1980's is because their CPU's were not fast enough to keep up at higher RPM's.