Van

I made this video a few years ago when I had the problem:


The buzzer is hooked up to the cycling valve... because I first thought that wasn't actuating the wastegate.

One difference with your car Michael, mine wouldn't die when overboost protection kicked in... but it wouldn't boost again until the computer was reset.

Also, like you're finding, with my car is wasn't an intermittent problem - it was very repeatable.

Ky944TurboNewbie

The car is completely stock.

My mechanic has been doing the test drives so I am not certain about which gears it is happening in. However, he refers to the fact that you can feather the gas and it will drive miles at about 40-45 mph so I assume he is triggering the symptoms in 3rd gear.

Ky944TurboNewbie

Van,

That is not like my problem. I was having the issue initially at low rpm's and very intermittent. Since then, my mechanic has done the test driving and he has been more aggressive. He has been able to get it to happen regularly.

Before I took it in to the mechanic, I made a video of my issue. It loses power like it all of the sudden ran out of gas. My gauges all work properly as it is dying. I have rpm's, and my boost gauge is moving when I pump the gas showing there is not a problem with the DME relay and everything is still getting power. It just dies.

We now know it will keep running if the gas is feathered ever so slightly, but under any load, it kills the engine. We also know that letting it die and popping the clutch will get all back to normal.

My mechanic has never seen anything like it and has been calling around looking for answers also.

Here is my video.

http://s1227.photobucket.com/albums/...t=9a58d3bb.mp4


Since my car is dying, and has done this intermittently in low rpm's, does that mean it isn't overload protection?

Ky944TurboNewbie

I don't have an aftermarket boost gauge to verify the boost levels. At this point I don't have access to another AFM to swap. I don't have access to chips either. Not many 944's around and the only Turbo I have been able to source is for sale at a small dealership 40 miles from me. Not sure they will let me take it for an extended test drive though.

Van

Yeah, what your car is doing is completely different. You had no boost at all (boost gauge was at 1 - which is atmospheric pressure - neither vacuum and nor boost), so it's not "overboost protection".

That looks more like a massive intake air leak. I've had symptoms similar to that when a hose clamp hasn't been tight enough and a rubber boot has blown off of the throttle body or intercooler.

Could you have a stuck flap in the AFM or something? Maybe the flap is stuck open, so even at idle it thinks more air is going into the system than normal... so it's delivering more fuel... which is causing it to run too rich and die.

Ky944TurboNewbie

I am considering picking up the car from the shop and test driving with more video to show what the mechanic is seeing with higher boost / rpm's. Let me know if that would be useful.

fast951

Based on your video, it appears that "it" kicks in the moment you hit atmospheric pressure (0-1psi). Is this correct? If it is, are you seeing LOTS of black smoke out of the exhaust?
For the overload protection to kick in (which I'm doubting if the answer to my question is negative), then the AFM is sending a VERY high voltage. It will cause the engine to run VERY rich and could trigger overload. However, if you are not seeing black smoke, then I'll loot at other possible causes than overload.

Does the problem occurs at PT, WOT or both? Can you monitor the Idle and PT signal at the DME?

Ky944TurboNewbie

John,

"It" (whatever it is) did kick in right when hitting atmospheric pressure. However, that was intermittent. Maybe once every 20 miles and more frequently when it was cold. Now "It" kicks in at WOT and between 4 and 5k rpm's consistently. But "It" still dies the same way. I think you are right to refer to my problem as "It". I am not sure what "It" is either.

Not sure about the black smoke. I recently put in a new fuel pressure regulator because it was running really high fuel pressure and rich. I put in plugs then also as the ones in the car were fouled from running so rich. I should be able to get a good idea of whether or not it is still rich as it has fairly new plugs. Not seeing "Lots" of black smoke though.

I have the problem infrequently at PT, and consistently at WOT. How would I monitor the Idle/PT signal at the dme? Do I need to run leads off the terminal and watch a multimeter?

Thanks,

Michael

fast951

You can remove the back of the DME connector and attach one of the VM leads to the IDLE switch, the second lead to GND. At Idle, IIRC you should have continuity to GND. Once you go to PT (or WOT) it should change state.
The WOT test is the same, but one lead is connected to the WOT switch. When you go to WOT (or over 60% throttle) it should have continuity to GND.

If for whatever reason, the incorrect TPS state is being triggered incorrectly, you can narrow down your search.

I'm thinking you are getting IDLE switch when you should not. Need to verify/deny this theory.

DME #2 - Idle contact
DME #3 - Full Load signal.
DME #16, 17, 19 or 28 can be used for GROUND.

By performing the above test you can determine if the TPS and its wiring are operating properly. (note: the KLR is part of the TPS circuit, however since you already tried a different KLR, we will assume it's fine).

note: Testing the TPS while it is cold may not qualify the TPS as operational. I have seen the TPS act up one it got hot.

Ky944TurboNewbie

Ok.... This sounds like the procedure from Clarks-Garage to test the TPS. I did this test last summer and the results showed the TPS was working correctly. I vividly remember the IDLE switch working because I thought I read the results wrong. I was expecting the volts to change gradually as it approached WOT, but it was just showing continuity so it immediately changed as soon as the throttle moved. When the throttle was allowed to return to idle, it no longer showed continuity.

I think I checked the Full Load Signal also, but my memory on that isn't as clear. It is possible that I skipped it when I thought the idle signal wasn't testing correctly. However, I think I tested it because I had the multi meter and it was easy enough to check that setting while it was all apart and I had my son helping by move the throttle. I think it was tested and working correctly, but only about 90% certain on that. The full load signal will need to be tested again.

Ky944TurboNewbie

John,

When you say the TPS is part of the KLR circuit... Is there anything that would be reset in the TPS by cycling the key or letting the engine die?

Would there be any benefit to seeing if the car is generating any blink codes?

fast951

The FULL LOAD signal comes from the KLR. So yes, if the KLR or the wiring is questionable, you may lose this signal. Since you already tested a different KLR, I would concentrate on other variables first.

I would monitor the full load signal at the DME while driving, to see what it does when the problem occurs. Another test is to monitor the Idle signal while driving, if for whatever reason you get Idle signal when it's not supposed to be there, you'll catch it.

At this stage, you are identifying all the variables at play when the problem occurs. Then rule things out by elimination.

Having used the Motronic Monitor for the past 8-9 years, I tend to forget how much of a PITA it is to diagnose these issues when doing it manually.

Good luck, and make sure someone is riding with you when monitoring the voltmeter.

Ky944TurboNewbie

Ok... Picked the car up from the shop. We weren't able to sort it out yet, but I wanted to have it for the weekend to experience the problems under boost first hand. This happens when under WOT in 2nd gear. I haven't tried to do this in other gears as I only had the opportunity to drive in town.

When the car reaches about 5k rpm's, it will loose power and want to die. if you push in the clutch, it will continue running down until the engine dies. If you give it gas. It will drive normal as long as you keep the gauge for boost below 1 bar. Once you reach atmospheric pressure, it kills the engine.

Cycling the key or pushing in the clutch and letting the engine die will reset everything. If you pop the clutch, it will drive normal again. If you cycle the key, it will drive normal again.

Something is triggered to cause the engine to refuse to provide boost. It is reset when the engine stops completely. Will drive poorly as long as below boost.

Here is a video... (Problem happens at about 25 seconds)

http://s1227.photobucket.com/albums/...t=84ed12a0.mp4

Van

I've had too much to drink to fully think it through... but, I can tell you that on my turbo, if I plumbed the wastegate line directly to the banjo bolt on the hard pipe - so the WG was always getting full pressure to open - my car would still build 1.2 bar on the absolute gauge (.2 bar boost).

When your boost drops so suddenly at 5k rpm, either you lift, which lets the BOV vent it away, or you have some other intake leak venting the boost away - but, it's not the wastegate that causing the lack of boost.

Now, when you try to accelerate, and you can't build any boost pressure, that's weird. Again, my first thought would be intake leak. But then I have no idea why letting the engine stall and popping the clutch would reset it. If it was an electronic issue, I'd think that you'd have to cycle the key to reset it. Since you don't have to reset the key, the DME/KLR should still be running on their same maps/settings.

Does it always happen at exactly 5k RPM? What if you drag the brake with your left foot so you build more boost, but at a lower rpm? Or if you accelerate slowly (not wot) to above 5k rpm?

I have a hunch that it might be boost related... somehow, at full boost something is blowing open (BOV? Intercooler boot?) and it's causing a breech in the intake system. Then, the vacuum or suction caused caused by restarting (with the throttle body closed) pulls the breech back into place which lets you build (some) boost pressure again.

Any change in brake pedal feel while this is happening?

Ky944TurboNewbie

A breach in the intake system makes sense. I was also having the intermittent problem at low rpm's and low boost. Just happens much more frequent at full boost. I have only triggered it three times this evening. Each time was near 5k rpm's.

What are the items that could breach and reseal when returning to idle?