Chevy Cobalt Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
47 Posts
Discussion Starter #1 (Edited)
Very Rough Idle Codes P0300 & P0106

Two days ago the car developed a very rough idle. Up to that point I had no problems. I had replaced the front wheel bearings two weeks earlier and noticed a dramatic improvement in gas mileage. Now it idles roughly and stalls whenever I come to a stop. Once I get moving the car runs smoothly. I removed the throttle body and cleaned it thoroughly. No improvement. After doing that the check engine light came on. The codes it threw are:

P0300. Misfire

P0106 Manifold abs pressure. Barometric pressure sensor.

Taken together what do these codes suggest?

Thanks for your interest

Al
 

·
Registered
Joined
·
47 Posts
Discussion Starter #2
Rough idle P0300 & P0106 addendum

A couple of weeks prior to the rough idle problem, I noticed that there was brief roughness when stopped at a light. Not really bad. Could these problems be caused be a clogged fuel filter?

Need some help here

Al
 

·
Registered
Joined
·
47 Posts
Discussion Starter #4
Update:

I put in a new map sensor and that did not change things. I then removed the ecu sitting on top of the coil pack and cleaned the connections, put it back in and now the car won’t start! When I turn the key the starer motor runs. Also when I turn the key to on I do not hear the fuel pump start up.

It would be nice to at least get back to a rough idle.

Al
 

·
Registered
Joined
·
47 Posts
Discussion Starter #5
Thanks sc3b. I don’t think I have the tools to flash the ecu (ecm). Any other things I may try? I just checked the fuses and they seem ok.

Al
 

·
Registered
Joined
·
47 Posts
Discussion Starter #6
Connector voltage


As a follow up, I tested the voltages at the input to the ignition control module with the ignition key in the on position. Looking at the connector with the release mechanism at the top, there are 5 positions along the top row and 4 along the bottom. Numbering from left to right 1) to 5) and 1) to 4)

Top row: 1) black wire 0 volts, 4)white wire 4.7 v, 5)red wire 11.3 v.

Bottom row: 1) brown with white stripe wire .08 v, 2) orange wire 4.7v.

When I clipped on a battery pack the voltages rose from 4.7 to 5v and from 11.3 to 12v respectively. The car battery is no doubt run down.
 

·
Registered
Joined
·
47 Posts
Discussion Starter #8
Fully charged the battery from 38% to 100% still no start. I don’t hear the fuel pump but the engine turns over. Probably no spark since I had someone spray starter fluid into the throttle body when I turned the key. The battery got run down from my multiple attempts to start the car.
 

·
Registered
Joined
·
47 Posts
Discussion Starter #9 (Edited)
Partial progress?

I replaced the ignition coil module with a Delphi brand unit even though it was sold as an ac delco. But then the one I took out was a Delphi (probably original).

So now I can hear the fuel pump rev up and get a strong spray at the schrader valve. Still turns over but doesn’t start.

Just to test things I disconnected the external connector to the ignition control module, I then turned the key to the on position and I could hear the fuel pump rev up. So here the fuel pump was working even though the new coil module and icm were out of the system.

The only thing that I can deduce from this is that the the new coil module reset something somewhere to allow the fuel pump to engage.

Now I only need a spark.

Any insight would be appreciated.

Al
 
1 - 9 of 9 Posts
Top