My 2009 HHR SS 5-speed has been at a friend's collision shop for a few weeks getting fixed from a minor rear-ending earlier this year.

The friend is good with collision/mechanical work but not electrical.

The car is finished. He said it has been driving fine whenever he had to move it. Then he noticed the CEL light on. He called a friend who is supposedly a good mechanic. The guy came over and ERASED the code by disconnecting the battery. I know, stupid thing-what person erases a code without knowing what it was!!!

After re-connecting the battery, the car won't idle. He says it starts and will run if you give it some gas, but stalls as soon as you let off the gas.

I have not checked the car out yet myself, he is a 45 minute drive away.

Any ideas what would cause it to not idle?

Could the timing chain have jumped a tooth? Maybe the erased code was related to that?

I am really mad about them erasing the code and they know it.

Steve

 

Lots of things are possible. You need the code.

 

Timing chain is a remote possibility, sitting for a long period has it has , did he work on the front hood or bumper? Could he have disturbed a ground wire ?
is the fuel stale? Did it ingest body shop dust , clogging the air filter?
was it sitting outside during its stay at the body shop?

 

See if you can drive it for awhile.
Good chance the check engine light will come on.

 

Drive it gently at first and see if you can hear any unusual noises.
Hopefully you will get the code again.

Silverfox

 

It was running then a "good mechanic" touched it then is won't run. Sounds like the "good mechanic" is working for free until your car is running as good as it was before he touched it. It was in a shop that invited somebody in to work on it; making it their problem not yours.

Most common cause of bad idle is somebody "forgot" the MAF plug.

 

The collision guy took it to a good repair shop and they say the fuel pressure is low (high pressure side). The pressure from the in-tank pump is good according to him.

He says his troubleshooting chart says to replace the high-pressure fuel pump, then if that doesn't fix it, replace the ECM.

He recommends taking it to the dealer because he doesn't want to replace a bunch of expensive parts until the culprit is finally replaced. According to him, the dealer has better diagnostic equipment, and if it's the ECM the dealer would have to program it anyway.

How does the car regulate the fuel pressure out of the high-pressure pump? I looked at the pump and it's basically a mechanical pump with a sensor on it. Since all this started when the battery was disconnected and connected it would seem to be more likely an electrical device got damaged rather than a mechanical device.

Also, does anyone have a schematic of the direct-injection fuel system (electrical controls/sensors)?

Thanks
Steve

 

He is right about the ECM needing dealer programming, but there are things that can be done first. How about checking those fuel pressures? There are no new codes? I would think a vacuum or intake leak (past the MAF sensor) could make it do the same things. They should throw codes, though.

Trying to help, but without codes, it's guess work. One tech I worked with recently called it veterinary work, "because the animal doesn't talk to you, and you have to do what you think is best".

 

Replacing the HPFP is pretty simple bolt on. Don't be ridiculous; ECM?????alternate spelling: L A Z Y.

The pump itself is a cam driven mechanical thing, but it is electronically controlled. The pressure is variable. There is a pressure sensor on the rail.

Did anybody bother checking the MAF?

What did the collision shop do under the hood? Did they try to disconnect the "battery"? Touching the ECM with a hot lead will screw the pooch totally, not just bad idle.

Properly disconnecting then connecting the battery shouldn't harm anything. If they caused an arc somewhere, they did damage.

A rear end collision can cause damage to some things under the hood, like the heating element in the MAF or the connections in the intercooler ducts. If the CEL was on there would have been a freeze frame stored (until the battery gets disconnected).

 

I would want to know the pressure numbers before just throwing a HPFP at it. I guess your's doesn't have the RPD unit ? If so, you could easily read the pressure there.
FWIW. About 2200 psi at cold start up. Then drops to around 400-500 at warm idle. The numbers bounce around a lot at warm idle, so anywhere close to that 400-500 range would be good.

My opinion. Doubt it's the HPFP or ECM. I would look elsewhere.