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944 Turbo ignition advance doesn't change

 
Old 08-02-2017, 04:13 AM
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WPO
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Default 944 Turbo ignition advance doesn't change

OK

I'm posting this on behalf of a friend of mine who has mind-blowing problem with his 1988 944 Turbo.

A bit of background:

Ignition advance of the car does not change. This has been confirmed when the car was on rolling road and it doesn't change ignition advance under load. So as a result the header is bright red and the car does not boost higher than 0.2 perhaps or so. So it appears that the car is in "safe" or "limp-home" mode? Correct?

What has been tested and changed:

All hoses have been pressure tested for leaks. No leaks were found.

DME and KLR have been tested. Known good units were changed from another car and same problems persists.

New TIAL wastegate has been installed. ( yes the right way )

Reference and speed sensors changed to new units.

AFM has been tested as per Clark's garage instructions.

Crossover pipe has been checked and it wasn't collapsed. (added and thx to V2Rocket for reminding me about this)

Basically all sensors which are possible to test have been tested and wires beeped. Testing has been done with a multimeter - no access to an oscilloscope.

Turbo has been reconditioned.

So what on earth can cause a problem that the ignition advance doesn't change? Which are the components that the DME / KLR uses to sense that advance needs to be changed? Or is it something else which causes the car to be in the "safe" mode?

The car runs nicely w/o boost but it just doesn't go anywhere as w/o advance it doesn't boost properly.

Turbo was reconditioned / pressure testing of hoses etc. were done before it was known that the problem was the advance as obv. turbo / hoses have nothing to do with the ignition advance.

We're really scratching our heads here with this one. Props and infinite bragging rights to the guru who points us in the right direction from here!

Last edited by WPO; 08-02-2017 at 01:11 PM. Reason: added a missing item in the list
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Old 08-02-2017, 08:22 AM
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odonnell
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How is this being tested - with a timing light?

Also test the TPS. If it's stuck on an idle or WOT map, the timing table is a 1 dimensional array of values. That would be an easy multimeter test.
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Old 08-02-2017, 08:27 AM
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Originally Posted by odonnell View Post
How is this being tested - with a timing light?

Also test the TPS. If it's stuck on an idle or WOT map, the timing table is a 1 dimensional array of values. That would be an easy multimeter test.
Hi and thanks for the message, appreciate it!

Yes timing is being checked with a timing light on a rolling road. Advcance doesn't change.

TPS has been tested with a multimeter as per Clark's instructions. http://www.clarks-garage.com/pdf-manual/ign-03.pdf

As per this everything should be OK but a faulty TPS would explain the problem. This is easy enough to retest so we might do that again.
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Old 08-02-2017, 08:56 AM
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Here's another test:
http://www.arnnworx.com/catalog/inde...id=2&chapter=2

I also was wrong in my last post about there being a WOT switch, apparently that's only on NA cars.
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Old 08-02-2017, 10:58 AM
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Have you change the knock sensor? If the KLR is detecting knock, or perhaps if it's getting no signal from the knock sensor, then it might try to retard the timing all the way...
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Old 08-02-2017, 11:47 AM
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aside from the knock sensor capabilities there is no "limp mode" on a 944 turbo ECU.

this is the stock ignition profile of a 944 turbo...what are you seeing on the timing light?

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Old 08-02-2017, 12:23 PM
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Originally Posted by Van View Post
Have you change the knock sensor? If the KLR is detecting knock, or perhaps if it's getting no signal from the knock sensor, then it might try to retard the timing all the way...
Yes to this.

The learned adjustment should also be able to be cleared and checked immediately afterwards to see if timing advance is restored, at least temporarily.

T
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Old 08-02-2017, 12:44 PM
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I will check from my buddy what the timing was.

By limp mode I meant that (as per my understanding) there is a mode which keeps the boost limited along with limited advance?

Is there a way to check the KLR apart from changing the unit?
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Old 08-02-2017, 12:58 PM
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I wonder if your crossover pipe from exhaust manifold to turbocharger has collapsed internally (dual-wall pipe), a known issue on some 944 turbos.

Extreme restriction in that pipe would cause sluggish response, low boost and make the manifolds heat up red hot under load.
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Old 08-02-2017, 01:10 PM
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Originally Posted by V2Rocket View Post
I wonder if your crossover pipe from exhaust manifold to turbocharger has collapsed internally (dual-wall pipe), a known issue on some 944 turbos.

Extreme restriction in that pipe would cause sluggish response, low boost and make the manifolds heat up red hot under load.
V2Rocket, yes that is a good point and I forgot to add that to the list above. Crossover pipe has been checked and it wasn't collapsed. At the time we were almost certain that this is the case but alas - no avail

This problem is really driving us mad. Well on the positive note at least the car becomes more and more familiar step by step
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Old 08-02-2017, 01:45 PM
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Originally Posted by WPO View Post
I will check from my buddy what the timing was.

By limp mode I meant that (as per my understanding) there is a mode which keeps the boost limited along with limited advance?

Is there a way to check the KLR apart from changing the unit?
The ignition timing signal runs through the KLR and the KLR will alter it under certain conditions. You can bypass the KLR for testing -- if the timing still doesn't move, then that would rule out a lot of possible causes. If it does move when you bypass the KLR, then I'd focus on the KLR itself, its harness, and the sensors connected to it (knock, tps, etc.). Don't go crazy without the KLR in the loop, just rev it enough to see if the timing now moves. Here's a thread with the pins to bypass...

https://rennlist.com/forums/944-turb...lr-bypass.html

You might also check the blink codes at the diagnostic port in case they are trying to tell you something...
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Old 08-02-2017, 01:59 PM
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Originally Posted by Tom M'Guinn View Post
The ignition timing signal runs through the KLR and the KLR will alter it under certain conditions. You can bypass the KLR for testing -- if the timing still doesn't move, then that would rule out a lot of possible causes. If it does move when you bypass the KLR, then I'd focus on the KLR itself, its harness, and the sensors connected to it (knock, tps, etc.). Don't go crazy without the KLR in the loop, just rev it enough to see if the timing now moves. Here's a thread with the pins to bypass...

https://rennlist.com/forums/944-turb...lr-bypass.html

You might also check the blink codes at the diagnostic port in case they are trying to tell you something...
Thanks Tom!

We'll try to bypass the KLR and then we'll see what happens. Next time the car is being tested we'll check the blink codes if there's anything sensible there.

I'll keep everyone posted accordingly.
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Old 08-02-2017, 02:11 PM
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Originally Posted by WPO View Post
Thanks Tom!

We'll try to bypass the KLR and then we'll see what happens. Next time the car is being tested we'll check the blink codes if there's anything sensible there.

I'll keep everyone posted accordingly.
I'd also mark the timing belt cover and pulley (white out works well) and put a traditional timing light on it while giving it revs, etc. I'm sure they've double-checked, but I'd want to see it for myself before believing it.
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Old 08-02-2017, 02:25 PM
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Originally Posted by Tom M'Guinn View Post
I'd also mark the timing belt cover and pulley (white out works well) and put a traditional timing light on it while giving it revs, etc. I'm sure they've double-checked, but I'd want to see it for myself before believing it.
Pulley has been marked with white marker. Oddly enough timing changes when the car is revved without load, but once the car is under load on rolling road the ignition doesn't change and the header becomes glowing red.
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Old 08-02-2017, 03:18 PM
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anti-lag?
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