Mrdjc

Hi. I have a 2008 2.2l ecotech hhr that threw a p0171 code and the engine started shaking. Didn't notice it at low speed. After turning it off it takes about 5 tries to start the vehicle. I attached a fuel pressure gauge.

I'm not sure if it's working right though. I attach it and turn the key to the on position and nothing comes up. While cranking it eventually gets up to 20psi. When it manages to start it stay at 32psi. As soon as I turn off the engine the psi goes to 0. Is this how it should be or should it keep pressure after the engine is off?

Thank you,
Joe C

donbrew

Why start at the most unlikely diagnostic point? p0171 indicates a vac leak or a MAF problem or a bad flex pipe way more often than bad fuel pump.

Mrdjc

I'm not familiar with the vacuum points of an hhr. Is it the same concept of spraying carb cleaner and seeing if the rpms rise? I deleted the code, inspected the boots and MAFS and saw nothing alarming. Code hasn't returned although the car has only been run for 5 minutes due to not starting.

donbrew

Start by typing p0171 into google. That will lead you to several links to diagnosis.
Most common is forgot to plug MAF back in after filter chg. Next is flex pipe. Next is dirty MAF.
You dont have a carb, throw that stuff away, get some throttle body cleaner.
P0171 means too much air between the MAF and the #1 O2 sensor, or a malfunctioning MAF. Very rarely it means too much fuel or too little fuel. It's a computer thing, if you just said "huh!".
You will also find a lot of info by using our search tool.

I forgot, it could also be the EVAP solenoid (tho one under the hood), that counts as a vac leak. Also forgot exhaust flange gasket and exhaust manifold gasket.

When you cleared the codes you also reset the OBDII test monitors, so the EVAP test will not be running for some time, meaning a "not ready for emissions test" error, and soome of the related codes will NOT reappear.


Anyway, fuel supply is the very last place to look.

Mrdjc

https://www.chevyhhr.net/forums/showthread.php?t=45271&styleid=8

I searched before I posted and read the post above as well as another that they claimed to be a fuel pump problem which is why I started there as well as it not holding pressure once the car was turned off. I'll try spraying with injector cleaner see if the rpms shoot up

Mrdjc

I will also take a look at the EVAP as you mentioned

donbrew

Must have missed post #3 in that thread?

donbrew

You might look at this thread that I found by searching p0171 on this forum.

https://www.chevyhhr.net/forums/how-...n-p0496-48626/

Jarred767

I know it's old, but for those reading this in the future, the diagnosis in the first post was dead on. My car had the same issue, after trying a lot of other things (MAF, EVAP, vacuum leaks, flex pipe, etc), I had it hooked up to a pressure reader and it acted almost exactly as was described in post #1. Unfortunately, that correlated to a new fuel pump for me (not sure on this original poster as he never updated this thread).

Just thought it might help a future member down the road.

donbrew

I always try to make the most expensive last on the list.

Great that you figured it out.