VT LS1 Timing Issue

[hsv472]

Hey all, Having trouble pinpointing an issue with my VT Clubsport.
My Issue:
When the engine gets hot (heat soaked) which takes about half an hour of driving it runs like a real slug. around 1500-3000 rpms its really bogs down and surges and has absolutely no power. Full throttle or more revs it goes as it should.
On a cool day if i don't stop in traffic it will take a lot longer to start playing up. It can be running fine and then if I stop in traffic for a few minutes it starts. Its like something is failing due to heat. And once it starts it doesn't stop till engine cools down completely.
I've had this issue for 12 months now and hasn't thrown a code.
Parts replaced:
New plugs, leads, O2 sensors, fuel filter. I have cleaned injectors, throttle body, iac, maf. Checked for vacuum leaks plus more

Now today I took it for a drive with the scanner hooked up to look at fuel trims, tps, cts and all looked fine.
Now i believe I have found my issue but i need to work out what is causing it.
Looking at timing once it started to act up here is what I found

Idle - 14 degrees btdc - thought it should be alot lower than that
half to WOT - i loose all readings for everything??
1500 - 3000 at 1/4 throttle its a bit spasmodic, but i did see it go to 5 degrees btdc quite a few times.
So long story short and sorry for the long post but what is causing my timing to be all over the show? Any help guys would be awesome as I am so over driving this thing and it really makes me sad lol

[Micks]

Going by what you have replaced, I would have the PCM thoroughly checked out & would not rule out a faulty OS there either!

[hsv472]

Yeah I'm leaning towards the pcm or knock sensors. Would really like to know if anyone has experienced anything like it.

[Micks]

If the knock sensors were outta range would certainly throw a code & won't inhibit timing normally.

[swingtan]

14° timing at idle is normal, but it should not remain at 14°. The idle timing should vary as the PCM attempts to control the idle speed.

If the car is fine when cool, but off when hot, I'd be checking a few other items.

• Wiring: check the PCM plugs. reseat them and clean them if needed.
• IAT: check the IAT readings. The PCM will adjust timing depending on the IAT. If it gets a bad signal, it will perform incorrectly.
• ECT: check the ECT as well, again the PCM will vary timing if the ECT signal is wrong.
• OBDII: check for both PCM error codes and for freeze frames. ODBII codes can clear on key reset, but the freeze frames should remain.

That should do for a start.

[Micks]

Simon good point about the iat, more than likely be a damaged loom as the sensors are very robust.

[hsv472]

OK I took the intake manifold off today and this is what I found
There was water in the hole on the front knock sensor. I would imagine that when the engine gets hot the water turns to steam and condensation on the rubber lid and water runs down inside knock sensor. I'll buy a new set of knock sensors and loom and give that a go

[Micks]

Yeah LS1 was bad design for knock location. Some peeps recommend changing the loom too & can buy them in a kit. Also smear a little silicone around the grommet when you put them back in.

[hsv472]

Yeah I'll be replacing the loom too. I broke one of the connectors whilst removing them. Hopefully this will fix my problem. Pretty confident it will!!

[macca_779]

Yeah they do that. But not necessarily what's causing your issues. I've seen worse

[Micks]

Yes doubt that too as you are Not getting enough timing! The knocks inhibit advance on detonation only, yours are not throwing codes either. Still a good idea to change them though.

[hsv472]

Ok, new knock sensors and loom installed and hasn't fixed my problems.
What I have found is when the engine bay gets hot ie. idling in shed for 20 min or so I can't get readings from the pcm with my scanner. The hotter or longer you leave it running the worse it gets. At idle I can get some readings but if I put any sort of revs on it it comes up "no data" for everything. The refresh rate on the screen is also really slow. When the car is cool I can get every sensor readout no problems at all at any rev range.
So now what? Bad pcm earth or pcm failing when it gets hot?
Suggestions?

[macca_779]

Check your engine grounds.

[hsv472]

Checked all the grounds and they were all in really good nick. Cleaned them all up and the battery terminals (battery is a month old) any way . Might have to look into getting PCM checked??

[Micks]

If the knocks & the looms been changed & you have discounted Simon's suggestion of a faulty IAT sensor or loom. Reckon your leaning back to my post #2 perhaps?
Let us know the outcome?