RBodeman

I have not been on here in ages but I am returning because it always seems like someone here has the answer or points in the right direction. I hope this is no different this time. I searched the forums for a similar problem but its kind hard to describe, so its hard to find any old posts about it.

The problem is occasional low power when accelerating. The car is a 2010 HHR SS with approximately 108,000 and no aftermarket performance parts added other than just a simple K&N drop in air filter. It is a 5 speed and I have been the owner since about 11,000 miles.

The problem occurs about 50% of the time and is most noticeable in 2nd and 3rd gears. It is hard to notice in 1st but the problem will occur in that gear also at times. The car will accelerate slow and I would not call it a hesitation because there is a slow build of speed. It stays as this low power all through the RPMS and will only go away if I flick the gas pedal. At which point the low power issue is instantly gone and the car pulls like the crazy little 2.0 turbo should. It will then proceed to drive fine until I have to come to a complete stop and start up again. At which points it may or may not be a problem but could be a problem 30 seconds later if I come to a complete stop again.

Some things to note, during low power acceleration, the fuel pump PSI will typical be around 1,000 to 1,100 PSI and the boost will be around 2 or 3 pounds all through the RPM range. After the flick of the gas pedal fuel pump goes back to the 2,000 + PSI on full acceleration and turbo boost up to the typical 15+.

The car is not throwing any codes and otherwise drives fine. My suspicions are that the fuel pump is going bad or is getting some signals messed up. But I am also no expert here.

Thank you for any help you guys can give.

Rich

donbrew

My guess is the HPFP is failing.
The SS has 2 fuel pumps. The one in the fuel tank should be 55-60 psi the high pressure pump is what the RPD will read varies depending on RPM, it is cam driven.
Any strange noises?

firemangeorge

You can read both with the RPD. Key ON, engine not running will give you the in tank pump supply pressure.
Engine running the RPD will show HPFP pressure.

donbrew

However, the in tank pump only runs for a few seconds if the engine is not running.

Oldblue

And the intank pump shuts off at full pressure, just like testing at the schrader valve in the full rail, the RPD reads that pressure.

RBodeman

No strange sounds. No strange unusual odors such as gasoline. No codes yet. Car idles and runs fine otherwise.
As noted, once I flick the gas pedal when the low power situation arises, the low problem is instantly gone. This works every time so far.

Just checked the fuel pressure before start and it was a consistent 72 psi after several key on/offs. Fuel pressure immediately went up to 1,700 psi after cold start and dropped to 500 psi after warm up.
I don't know if this makes a difference but my air/fuel ratio was at about 14.5 at idle. Would air/fuel be out of whack if the HPFP is bad?

Some back story that just occurred to me...I did have a long issue with the Evap system and on occasion would have a tough time starting after fueling up. The engine would crank for about 5 or 6 seconds before firing up. Eventually I got the evap issue was corrected after a year plus. But could the long cranks have been doing damage to the HPFP? And now its showing up as this low power acceleration?

How is the HPFP tested and where is it located? Easy shade tree mechanic repair or no?

Oldblue

Here’s a how to thread

https://www.chevyhhr.net/forums/how-...el-pump-54230/

RBodeman

Thank you so much. The thread looks very detailed.

However, is the low acceleration power issue I'm having most likely caused by a faulty HPFP?
I understand you can not say for sure. But I was just guessing it was the pump when I mentioned it at the top of this thread. I'm far from any kind of expert on these things.

Oldblue

It might be at that transition from low pressure intank pump to high pressure pump.

firemangeorge

Not sure what you’re saying here. Transition ?