[coolfog]

'07 Solstice GXP w/AT.
Coming home from work yesterday on the freeway (~70 mph & 3600 RPM), accelerated fairly briskly to get around a big rig and the car just fell flat on its face and barely gained any speed!... backed off letting traffic pass then accelerated easy to pass and the motor seemed fine. But put my foot into it and it just craps out!
However, from a stop (in the "I" gear), I can hammer it and it will run up through the gears at 14psi boost!

• temp @ 196°F
• all fluids at proper levels
• NO CEL

Hopefully someone can help me figure this out?!

Thanks!
John

 

[kgschlosser]

I would get a code scanner on it. Your automatic trans could be going into limp mode, when it does this I believe it limits the torque coming from the engine. The check engine light will not light up when this happens, plugging in a code scanner that is capable of reading transmission codes would reveal if there is a problem there.

For hoots and ha ha's I would replace the Valve Timing Solenoids, they are known to cause grief with the automatics, they may be on the edge of being bad and it could cause an issue like you are having. They will be within specification so the ECM will not throw a code, but they can be on the edges of the spec and causes something wierd with the engine and the TCM doesn't like it. Another symptom that may show up is hard down shifting.

 

[The_Ghost]

Valve Timing Solenoids

aka Camshaft or "cam" solenoids for intake and exhaust...

 

[grandpop07]

If you have never checked the O-rings on the MAP sensors and the EVAP solenoid, you should. You seem to be experiencing some of the symptoms that arise from pressure by-passing them and giving bad information to the ECM, etc., and there may not be a code thrown (you may or may not get a P0106 code). I speak from experience. There has been quite a discussion over the the past 2 years on the board. My "fix" for this is removing the items above to inspect the O-rings for deterioration (replace them if they are doing so) - if they appear to be OK, apply a bit of silicone grease to them and reinstall the units. I did this twice over a year and half and had excellent running. A third removal (after the same symptoms occurred again) I again removed the parts, re-greased the O-rings and added a small amount of Teflon tape to the underside of the units (do not let any tape extend down to the O-ring area) and re-installed. The car has been starting/running exceptionally well ever since for about 10 months or so inspite of the cold weather we've had here in Georgia in the past couple of months. While this may not fix your problem, it will insure that the O-rings are not contributing to it - and it costs practically nothing to do it, primarily some labor. I can do this in 10-15 minutes. You should also check all your clamps associated with the turbo system.
I have an 09 GXP with the GMPP turbo upgrade, automatic and my maximum boost is in the 18-22 PSI range.
grandpop07

 

[kgschlosser]

Thank you @The_Ghost....

The 2 round things that stick up in top of the engine right at the front of the engine. right in front of the coil packs..

When you change them the wiring harnesses are keyed and will only plug into the solenoid they are supposed to. remove and install one at a time making sure the wiring harness plugs into the new one before you put it in. you will need to use several flat head screwdrivers to get the old ones out. typically the thinner the blade on the screwdriver the narrower it is so you need to have 3-4 different sizes.
After you take the single 10mm bolt out that holds the part, take the thinnest screwdriver and put it where the part meets the engine and only where the bolt flange is, that last part is extremely important. You may need to tap the back of the screwdriver with a hammer in order to get it to start going under.

Once it is under give the screwdriver a twist. Take that screwdriver out and put in the next size up and give a twist. each time you twist it is going to raise the solenoid up.

After you have done that with all of the screwdrivers it should be high enough where you can take an 8mm 1/4" drive socket and lay it on it's side next to the bolt flange. You are going to use the socket as the fulcrum for a lever. Use a flat head screwdriver and get the tip under the flange and the socket under the screwdriver about 1/2" away from the flange and then push down on the screwdriver slowly! DO NOT pop the solenoid all the way out. once you have it so it's lose remove the 8mm socket, you do not want it to roll down and fall into the hole. Doing the lever thing insures the old part lifts straight up.

before you put the new one in use a little oil from the old solenoid on the o-ring of the new one. then push the new one down into the hole. put the bolt back in and reattach the wires. and that's all there is to it.

It's a 10-15 minute job to change them at most. Probably take longer to get the tools together together.. You have to remove the engine cover to see the solenoids.

The process above is how it should be done, it ensures the solenoid lifts straight up. you do not want to have the thing tilt at all or pry up on it in a manner that will cause any kind of a sideways pressure on it. They can snap leaving a piece in the top of the engine. Follow the steps above and it would be next to impossible too have that happen.

 

[sirwm]

...The 2 round things that stick up in top of the engine right at the front of the engine. right in front of the coil packs..
...
It's a 10-15 minute job to change them at most. Probably take longer to get the tools together together.. You have to remove the engine cover to see the solenoids.
...

If I can change them, anybody can change them !
my story here -> got a P0013 today...

 

[coolfog]

If you have never checked the O-rings on the MAP sensors and the EVAP solenoid, you should. You seem to be experiencing some of the symptoms that arise from pressure by-passing them and giving bad information to the ECM, etc., and there may not be a code thrown (you may or may not get a P0106 code). I speak from experience. There has been quite a discussion over the the past 2 years on the board. My "fix" for this is removing the items above to inspect the O-rings for deterioration (replace them if they are doing so) - if they appear to be OK, apply a bit of silicone grease to them and reinstall the units. I did this twice over a year and half and had excellent running. A third removal (after the same symptoms occurred again) I again removed the parts, re-greased the O-rings and added a small amount of Teflon tape to the underside of the units (do not let any tape extend down to the O-ring area) and re-installed. The car has been starting/running exceptionally well ever since for about 10 months or so inspite of the cold weather we've had here in Georgia in the past couple of months. While this may not fix your problem, it will insure that the O-rings are not contributing to it - and it costs practically nothing to do it, primarily some labor. I can do this in 10-15 minutes. You should also check all your clamps associated with the turbo system.
I have an 09 GXP with the GMPP turbo upgrade, automatic and my maximum boost is in the 18-22 PSI range.
grandpop07

Thanks @grandpop07!
I hadn't considered the possibility of the MAP and EVAP solenoid o-rings being an issue! I will definitely pull them for inspection and service them as you describe.

As for the int/exh actuators... those were both recently replaced with new units due to a CEL code.

Also... Not sure whether or not my current code reader reads the TCM??? I will have to check it and see.

One other on condition the car is exhibiting is an odd chirpy kind of noise when it's cold (it pretty much goes away completely when the engine is at full operating temperature), but exhibits at times on moderate acceleration from stop (doesn't seem to affect boost). I was thinking it might be timing chain noise due to the oil and things not being up to temp - only thing is, the "speed" of the noise doesn't increase or decrease with engine speed as I would expect. Any ideas what that might be caused by?

Regards,
John

 

[kgschlosser]

That sound is your power steering pump. It is going to eventually start leaking out of the pulley shaft. Mine did the same thing. I cut the belt to the pump so it wouldn't coat the bottom of my car in power steering fluid. That was 6 years, I still haven't replaced the pump and have no intention of doing it either. The car feels better without the power steering.

 

[kgschlosser]

OK so I have a couple of questions.

70mph at 3600 RPM. did you have the car in "D" or did you have it pulled down to "4"???
How much throttle were you giving the car? best guess in percentage.
What was the boost pressure doing while you were accelerating? numbers please.
Did the transmission down shift when you were attempting to accelerate.

One of the things you need to be aware of is turbo lag. When you are at a cruising speed and the car is not boosting and you press on the accelerator pedal to accelerate you have about 140 HP, this is because there is no boost. If you do not press on the accelerator hard enough to get the car to downshift it is going to be a long while for the turbo to start developing boost. the turbo is powered by the exhaust from the engine. so the more exhaust the faster the car is going to develop boost. higher RPM's = more exhaust.

If you didn't have the car in "D" and had it in "4" instead the transmission is going to behave completely different. The shift points are going to be raised and you are also going to have to lay into the accelerator harder to get it to downshift.

If you leave the car in "D" and take off from a dead stop does the car accelerate properly? does it develop proper boost through the gears?.. For all tests going forward keep the car in "D" There needs to be consistency because of the change in behavior of the car when the gear shift selector is in different positions we need to test one thing at a time.

Because you have changed the solenoids the chances of that being an issue and the transmission going into "limp" mode are unlikely. based on your description of the event, 3600 RPM is to high an rpm for having the car in "D" and driving at 70MPH, you probably had it in "4" and this is going to change the behavior and you didn't press down hard enough on the accelerator to get the car to downshift so it could develop boost quickly.