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We read the blink codes and it gave 2-2 i.e. knock sensor monitoring. We checked the grounds and one KLR ground was not good (KLR pin 12) and we thought this was the problem and fixed the ground and drove the car. Same problem persists. Knock sensor is not fastened at this point but this shouldn't cause such problems, right?
Checked also the other grounds and TPS ground was bad (KLR pin 23) and fixed this. Same problem persists. This didn't give a fault code though?
Now the car doesn't give any fault codes but the problem is still the same? It boosts around 0.2 and starts to "whizzle" after that? It looks like the problem isn't with the ignition advance though? One guy guessed that perhaps valve springs are broken and it blows pressure out after the car starts to build boost? Is this a realistic scenario? Would be quite odd if this is the case?
We tried bypassing the KLR completely by adding jumper between the pins provided in an instruction and same problem persists. Also I've forgot to add that it's been tried to block the wastegate with a plate and the same problem persists.
Also the car is not running lean, a bit rich actually so that's not the problem. Fuel pressure hasn't been checked though at this point as the mixture isn't lean.
Attached dyno graphs before and after and here's a video of the problem: https://ufile.io/jstx9
Most likely we're missing something pretty obvious but what?
Before<br/>
After
Last edited by WPO; 08-06-2017 at 05:07 PM.
Reason: typos and added info
On the knock sensor, is it torqued to spec? Check the resistance of the sensor and harness at the KLR by pulling the connector off the box and checking how many ohms you get between pins 11 and 13. Original knock sensors should show about 300k ohms +/- and the later style about 1M ohms +/-. If you get an open or closed circuit or something way off from those two specs, then test again at the sensor to see if it's the sensor or the harness.
Separately, if you blocked off the wastegate and built .2 bar boost max, then that suggest something more mechanically wrong (rather than engine management things). Have you run a compression check? Do you have big exhaust leaks? Have you pulled the J-boot off the turbo and confirmed it spins smoothly without tons of play and/or damaged fins? Do you have a large vacuum/boost leak somewhere? Is the bypass valve stuck open?
How do you know it's not lean?
FQS is a little rotary switch on the end of the DME, but sounds like you have bigger fish to fry right now.
On the knock sensor, is it torqued to spec? Check the resistance of the sensor and harness at the KLR by pulling the connector off the box and checking how many ohms you get between pins 11 and 13. Original knock sensors should show about 300k ohms +/- and the later style about 1M ohms +/-. If you get an open or closed circuit or something way off from those two specs, then test again at the sensor to see if it's the sensor or the harness.
Separately, if you blocked off the wastegate and built .2 bar boost max, then that suggest something more mechanically wrong (rather than engine management things). Have you run a compression check? Do you have big exhaust leaks? Have you pulled the J-boot off the turbo and confirmed it spins smoothly without tons of play and/or damaged fins? Do you have a large vacuum/boost leak somewhere? Is the bypass valve stuck open?
How do you know it's not lean?
FQS is a little rotary switch on the end of the DME, but sounds like you have bigger fish to fry right now.
Knock sensor is currently loose and not torqued in place. Wires were beeped and found to be OK. Does this cause problems if it's not in place? KLR has been measured and the sensor is new - I don't remember what the exact numbers were but they were within spec.I can remeasure this to be on the safe side though.
Compression was tested today and it was ~10bar. Exhaust is not leaking anywhere and the x-over pipe is not collapsed and cat is not melted and muffler is not stuck.
Turbo has been reconditioned with new bearings etc. so that is not the issue for sure. I'm not sure about the bypass valve though? How do I check this? Wastegate is a new TIAL unit so that's not an issue.
What mechanical could cause such a condition for the engine? It is as if somehow the once the car is supposed to build boost the pressure escapes from the cylinders and the mixture burns in the header. Broken valve springs?
The car starts fine, runs OK w/o boost but as soon as it's supposed to make power it makes none and the header becomes glowing red - like ignition timing would be really late but I'm not sure about this anymore? I know that the car is not lean as the AFR was measured during dyno runs and it shows the car being a bit on the rich side.
The shop said that the car was in said that they pressure checked the system and found no leaks. Haven't obv done this myself but have to trust them with this.
As said the car ran fine until it was tracked lightly (not pushing it super hard) and on the way home it was noticed that it doesn't build any boost and the problems started. No mechanical sounds, nothing was noticed during the run though? All of a sudden it just doesn't make power anymore.
Last edited by WPO; 08-06-2017 at 07:28 PM.
Reason: added a few things..
Knock sensor is currently loose and not torqued in place. Does this cause problems if it's not in place? KLR has been measured and the sensor is new - I don't remember what the exact numbers were but they were within spec.
Compression was tested today and it was ~10bar. Exhaust is not leaking anywhere and the x-over pipe is not collapsed and cat is not melted and muffler is not stuck.
Turbo has been reconditioned with new bearings etc. so that is not the issue for sure. I'm not sure about the bypass valve though? How do I check this?
I know that the car is not lean as the AFR was measured during dyno runs and it shows the car being a bit on the rich side.
The FSM says to check the torque on the knock sensor if you get 2-2 (as well as the resistance).
Reconditioned turbos have been known to fail, especially on the track. By saying "that's not the issue for sure" you have exponentially increased the odds of that being the issue. Check it.
The FSM says to check the torque on the knock sensor if you get 2-2 (as well as the resistance).
Reconditioned turbos have been known to fail, especially on the track. By saying "that's not the issue for sure" you have exponentially increased the odds of that being the issue. Check it.
Very good
I will bolt the knock sensor down as specified and let's see what happens.
Reconditioned turbos have been known to fail, especially on the track. By saying "that's not the issue for sure" you have exponentially increased the odds of that being the issue. Check it.
I'm starting to wonder if the turbo is actually turboing! I'd think a 3-1 would set tho.
I'm starting to wonder if the turbo is actually turboing! I'd think a 3-1 would set tho.
When the car was at the shop they were also scratching their head with what is wrong with the car. At that point the turbo was taken out and it was reconditioned even though there wasn't anything wrong with it.
So the car had exactly the same issue with the "old" turbo as with the reconditioned (same but bearings changed etc.) turbo.
The car doesn't give any blink codes but still it doesn't boost at all. Next timing will be checked - not sure if that's the problem though as it gave ~10bar of cylinder pressure when it was pressure tested yesterday.
Knock sensor was installed in its place and torqued down properly. Same thing. New knock sensor that is.
Starts to feel like it is something mechanical as there's nothing wrong with any of the sensors. This thing drives me crazy
Is it possible for cat to be the problem? It's been out and it's not melted or collapsed but is it possible that something blocks the exhaust once there is pressure / car is running? Nothing is loose in the cat though?
Not to be critical, but how much experience does this shop have with the 951 and/or in general? Easy to say from my arm chair I know, but it shouldn't be 'that' hard to figure out a consistent no-boost situation like this.
As for the cat, I doubt you can tell by looking at it. Try a test pipe...
We'll try the car without cat & muffler and let's see what happens. That's at least a much easier alternative to check before checking the timing and taking the turbo out.
This car is really turning into a nemesis
edit: my cousin stuffed his teacher's car's muffler full of apples as a revenge because he got detention. Note to self: check muffler for apples.
He also glued the window wipers in the windshield with superglue. I haven't tested the wipers on the 944 yet. Perhaps they are also stuck
You might fit your compression tester to the O2 sensor bung and see what your backpressure is like, I do not know a "good" reading for a 951 but probably under 5psi at 2K RPM, probably less.
I was thinking more about a melted cat but it'd also be good to test at the sample port and the psi should be low enough so the connection could be made by jamming a hose on there and whipping it with mechanic's wire.
I believe my first post on this was to check the cat but the response was that it was all OK. If they didn't use a scope to look at the substrate inlet, it was not properly checked.
Just drop the downtube from the turbo and fire it up. No need to run it very long to find out if it's ok.
Cross-over pipe was checked already earlier with a scope and it's not collapsed.
Also the car was ran today without cat and muffler and it keeps the same whining noise at ~0.2 bar as earlier. Turbo was checked - ok it wasn't out of the car but it really feels like new and spins freely with no play.
Timing was checked and it came out..surprise..surprise. Good. Mark in the distributor and flywheel aligned like they should.
This thing really drives us mad. As said earlier the car doesn't give any blink codes.
What is a mechanical issue that can cause this? Cylinder pressure was ~10bar or so valve springs are not broken as it wouldn't give such good cylinder pressure?
Any ideas? Should we check the cylinder head next? Most likely cam gear hasn't spun as cylinder pressure is OK?
08-06-2017, 04:48 PM
Check it.
