GM LS7 problem - need urgent help

[V8 Vum]

Guys, I REALLY need your help...

I have a 'special' LS7, 'special' because I believe it was a non-production version with forged pistons etc straight from the factory as a 'left-over' (2007) from a run for motorsport.

The ECU supplied seems to have a very small stamp between the vanes with the letter E98. I thought most were supplied with something liake an E40?

I cannot find any reference to the E98 if that what it is on the net. This ECU came with the fuse box, and two relays (1 x pump + 1 x A/C)

Why am I asking? Good question... The engine is up and running now - it starts and idles but totally ignores the FBW throttle-pedal!

The Throttle-body has a silver throttle plate. (I believe some used for motor-sport have gold ones), and reacts to me gently pushing the plate open to returnb to closed.

I have checked all the connectors for bent, pushed in or broken pins, and none of the fuses has blown.

SO... is this the right ECU/Throttle-body/Throttle pedal combination? I have no idea...

Please help!!!!!

[LawrenceF]

Any chance your battery was low when you started it? Has it stored any fault codes?

[JontyR]

Has it been flashed so that it works without the normal key etc?? I'm guessing that it may have as I thought this would just shut the engine down...but running without throttle might also be a symptom

[V8 Vum]

Actually come to think of it, when I first tried to spin the engine (with the pump wiring disconnected) so I could build up some pressure to start with, the battery ran down very quickly. I plugged in the booster and did it again and all was fine....until I started the engine and found the throttle not working.

Would this have kicked the ECU into limp mode?

cheers

[davepoth]

Silly question - is the throttle pot working properly?

[V8 Vum]

JontyR said:

Has it been flashed so that it works without the normal key etc?? I'm guessing that it may have as I thought this would just shut the engine down...but running without throttle might also be a symptom

Not sure what you mean by this mate? Can you ellucidate?

cheers

[V8 Vum]

davepoth said:

Silly question - is the throttle pot working properly?

That is the problem ....how can I tell?

Kyle, bless him, is going to send one of his to see if it makes a difference!

[LawrenceF]

I believe it will give up on the pedal and store a code if the battery is really low when you try and start it? Disconnect the PCM from the battery and give it a good charge and try again or check your codes.

[V8 Vum]

It has been disconnected for alt least a day. but with the same result...however I now am the proud owner of a wifi OBDII transmatter and iPhone REV app, so I will see what I can see and reset the ECM.

cheers

[JontyR]

V8 Vum said:

JontyR said:

Has it been flashed so that it works without the normal key etc?? I'm guessing that it may have as I thought this would just shut the engine down...but running without throttle might also be a symptom

Not sure what you mean by this mate? Can you ellucidate?

cheers

As I am aware the standard ECU has a security code built in, and so when ever the engines are used in other cars....the ecus need flashing to remove the code.

[LawrenceF]

JontyR said:

V8 Vum said:

JontyR said:

Has it been flashed so that it works without the normal key etc?? I'm guessing that it may have as I thought this would just shut the engine down...but running without throttle might also be a symptom

Not sure what you mean by this mate? Can you ellucidate?

cheers

As I am aware the standard ECU has a security code built in, and so when ever the engines are used in other cars....the ecus need flashing to remove the code.

That wont affect the throttle operation tho.

[V8 Vum]

The engine and trans came for Jeff Schwartz in the States, so it would be highly unlikely that he would nit have flashed the ECU. Indee the engine I believe has been dyno'd, and JS tells me the same ECU and throttle pedal were used during the Dyno run.

I recon this p0641 error I am getting may be the source of the problem...diagnosing and fixing is another subject though!


cheers

Keith

[stevieturbo]

V8 Vum said:

The engine and trans came for Jeff Schwartz in the States, so it would be highly unlikely that he would nit have flashed the ECU. Indee the engine I believe has been dyno'd, and JS tells me the same ECU and throttle pedal were used during the Dyno run.

I recon this p0641 error I am getting may be the source of the problem...diagnosing and fixing is another subject though!


cheers

Keith

Try and get in touch with Richard/EFI Live, or Monkfish/Wortec.

or perhaps Gardner Douglas as they use these engines in their kit cars.

[Magic919]

That looks like a TPS voltage error, so it would suggest it is indeed related to your problem.

[ringram]

Are you sure its not E38?
Thats the factory ECU for the LS7. E40 is for earlier 24x crank reluctors. (LS7 is 58x)
Anyway, check your TPS works properly. Its built into the Throttle motor connector.
Its not uncommon for the connectors to go a bit awol.

If when you fire it up it holds idle etc then its likely the throttle works as the ECU controls the blade for idle etc. Maybe take a look at the throttle when you fire it up and make sure it moves. In which case check the TPS wiring aspect of the connector etc. Check the voltage coming off the wires. Looks like thats where the problem is.

[Boosted LS1]

OP where are you based? I have a flashed Ultima Ls7 E38 here which we could try if you're not to far away. Otherwise I'd suggest Ringram and his Efi Live package.

[V8 Vum]

IT IS an E38 I found out!

[V8 Vum]

Right Guys, and with your useful advice - I have got to the bottom of the problem - but raises another!

Checking the voltage on the ref circuit I found 1.4 volts!
So through a process of elimination I found that no sensors seemed to be the culprit????

Then I hd a flash of inspiration and disconnected the alternator plug...and voila - 5v ref sprang back into life!

...and the engine started and revved!

..So, what the heck is going on with the Alternator field duty and turn on circuit?

Any bright ideas?

cheers

[LawrenceF]

Good stuff, is it a stock alternator? How many wires does it have in the plug?

[V8 Vum]

It is a 2 pin plug - Orange(red to me) and grey wires as per ECU diag.

With ign on but engine not running:

Plugged in - 5 Volt reference pulled down to 1.4 v measured at the TAN wire to pedal
Unplugged - 5 volt unaffected!

I don't know what the alternator is unfortunately - but it came as a package from Jeff Schwartz with the LS7 engine.

I will have to try to find the ID stamp.

cheers