Engine Popping Under Load

[Kanin]

Hi,

I hope someone can help.

Todd you still around?

Under load engine power drops and it starts popping do not understand what is wrong. Alo no power with full throttle in low revs.

Looked for the obvious:

- MAF changed

- No air leaks detected

- Coil packs checked and changed any cracket

- O2 sensors working

- Changed the Cam Shaft sensor

- Tried to change the variocam+ solenoids which did not have any effect

running out of ideas what could it be?

Thanks,

Kanin

[tholyoak]

Kanin,

Certainly sounds like the valve lift isn't being actuated.

The important part of your problem is you are using an aftermarket controller to actuate the valve lift solenoids. I would make sure that the controller is still providing the ground output when the maps call for solenoid actuation and that the other terminal on each solenoid is getting a constant 12V. You can verify the solenoids are working by simply applying 12V across them and listening if they click.

-Todd

[Kanin]

Hi Todd

Thanks for quick response.

If I remember correctly I think they are getting a +12V from the second relay. The piggy back activating grnd activates the second relay. When checking the solenoids they seamed to be getting the +12V when they are supposed to. This remind me I did not check the grnd on them so could be a problem with the grnd.

Let me do some digging tomorrow and get back to you and I will also check that the solenoids are working.

Kanin

[Kanin]

Hi Todd

Quick question.

Will the solenoids click even when taken off the car?

thought I will take them off and check them.

- Kanin

[tholyoak]

Yes, they are simply 12V actuated solenoids. Send me a pm if you want to discuss further.

-Todd

Edited May 3, 2010 by tholyoak

[Kanin]

Hi again

Thought I would give you all an update.

After several attempts I have not been able to solve the problem. Even after changing the timing solenoid lift solenoid, MAF sensor and visit to the Porsche specialist. Yesterday night 1am in the morning after reading many threads here I stumbled on the AOS problems and thought I would check and guess what the hose between the AOS and Throttle Body is full of Oil.

Ordering a new AOS and cleaning the intake tomorrow and hoping this solves it. In my case the symptoms were so different from what I have heard before. The power loss in the engine was drastic like hitting the rev limiter. When driving slow and easy no problems. As soon as I pushed it would almost loose all acceleration and power. I even had miss fires.

In any case I am hoping this is it. I may have more than one problem but first things first. I am hoping I can confirm that the problem is solved in a couple of days.

- Kanin

[Wayne R. Dempsey]

Hmm, that might be the problem, but you can remove the hose from the air oil separator and the throttle body and plug both ends to test. I would also think that you might have a vacuum leak that is causing problems, have you checked all of your connections? I had similar problems, but it was a MAF calibration problem (see my engine conversion article for details on that). See if closing off the throttle-body connection to the air-oil separator makes a difference - I tried this when I was having issues with my 3.4. Also check the 12V on the variable valve timing solenoids (both of them) when the car is running. For more info on checking for vacuum leaks, use a smoke machine like the one shown here: http://www.pelicanparts.com/techarticles/Boxster_Tech/21-FUEL-Vacuum_Leaks/21-FUEL-Vacuum_Leaks.htm

Hope this helps,

-Wayne

[Kanin]

Thanks for input Wayne - great article by the way it is in my favorites now :)

I had the car running spot on untill this happenned. The MAF signal is modified thorugh a piggyback system and should as such at least go back to what it used to be. In any case I think I need to take this step by step and eliminate the problems I find. AOS first and then air leak as you suggested.

Will keep you posted on progress.

- Kanin

[Kanin]

Hi,

Finally got the time to change the AOS. Also cleaned the throttle body and Idle control valve. Blue smoke is gone and the car is much more responsive however it did not help me with my original problem. It still looses power and exhaust starts popping as soon as I put load on it. It must be linked to Variocam+ but no idea what it could be. I Will try to check for air leaks again. Maybe MAF signal calibration as wayne suggested.

If anyone has any suggestions I am open for those ......

- Kanin

[Wayne R. Dempsey]

Did you verify the signal to the Variocam+ solenoids?

-Wayne

[Kanin]

Hi,

Yes checked and it did get the signal at about the right rpm when iddle. Why I thought it may be linked to mixture or MAF signal problem. However not sure what happens when on the road. I guess the easiest is to disconnect the variocam+ solenoids and see if it changes anything. Ok I will try that tonight probably a good way to eliminate them.

The background is that the car was with a body shop for a month or so. I was getting a GT3 style bumper on the car. When I got it back it was like this. Not sure what happened. I have already changed the MAF sensor as I thought dust may have had something to do with it.

- Kanin

[atomicmedia]

The background is that the car was with a body shop for a month or so. I was getting a GT3 style bumper on the car. When I got it back it was like this. Not sure what happened.

FBDO syndrome...

[Kanin]

FBDO syndrome...

FBDO??? Sorry did not get that .... I may be making a fool out of my self but thought I would ask any way :)

Finally got to test the car with the Varicam+ solenoids disconnected and it ran even worse than before. Maybe a wild guess but does any of you have some experiance if a bad flywheel with missing teeth could create this kind of problems? I still have the old original flywheel from th 2.5 engine.

Will now investigate the MAF signal through the piggy back system and see if the output is right.

I have also decided that I will be starting the 7.8 DME upgrade as it is very dificult to troubleshoot with the piggyback system. Now collecting all the parts I need and should hopefully be able to start the project next week.

- Kanin

[atomicmedia]

Ferris Bueller's Day Off

sorry I *thought* I was being funny...