Low Compression in ALL cylinders and P0300/0303 code
11-19-2013, 01:30 PM
#1
New Member
Thread Starter
Join Date: 11-18-2013
Location: Bessemer, Alabama, USA
Posts: 18
Low Compression in ALL cylinders and P0300/0303 code
Greetings All! Long-time Ford owner, first-time Chevy owner: 2008 Charcoal Gray HHR LS, bought used with 110K, just about to turn 130K.
CEL turned on, scan showed P0303. I changed the plugs (maybe original plugs?) and the misfire remained. I swapped coils #2 & #3; scan showed P0300/0303. I swapped fuel injectors #3 & #4; scan showed P0303.
Drivability does not seem to have changed, but the idle has roughened considerably.
Went to a mechanic for a compression test yesterday. #1 was 140 psi, #2 was 125, #3 was 70, #4 was 140. The mechanic wondered about a stretched timing chain and promised to do research after putting it all back together. He called a contact with GM Fleet and was told the chain was a possibility, but the valves were more likely the issue. He wants to do a leak down test next.
Are we headed in the right direction, or does the low compression across all cylinders with a specific misfire in one cylinder lead anyone to a different conclusion?
CEL turned on, scan showed P0303. I changed the plugs (maybe original plugs?) and the misfire remained. I swapped coils #2 & #3; scan showed P0300/0303. I swapped fuel injectors #3 & #4; scan showed P0303.
Drivability does not seem to have changed, but the idle has roughened considerably.
Went to a mechanic for a compression test yesterday. #1 was 140 psi, #2 was 125, #3 was 70, #4 was 140. The mechanic wondered about a stretched timing chain and promised to do research after putting it all back together. He called a contact with GM Fleet and was told the chain was a possibility, but the valves were more likely the issue. He wants to do a leak down test next.
Are we headed in the right direction, or does the low compression across all cylinders with a specific misfire in one cylinder lead anyone to a different conclusion?
11-19-2013, 01:35 PM
#2
Senior Member
Join Date: 05-01-2013
Location: Poway So Cali
Posts: 354
You are going in the correct direction. With the low compression on just number 3, I would say the head is coming off, next for inspection. A leakdown can give you a clue, but either way, the head is coming off.
11-19-2013, 06:34 PM
#4
Technical Moderator
Join Date: 01-23-2009
Location: Fredericksburg, Virginia
Posts: 24,698
The #2 #3 thing reads head gasket likely, the book says.
When you have the the head off might as well replace the chain, sprockets, guides and oiler, (comes as a kit) they will be off anyway. Think about the water pump at the same time (sometimes comes in the chain kit).
When you have the the head off might as well replace the chain, sprockets, guides and oiler, (comes as a kit) they will be off anyway. Think about the water pump at the same time (sometimes comes in the chain kit).
11-19-2013, 07:16 PM
#5
Senior Member
Join Date: 03-22-2012
Location: Rogers City, Michigan
Posts: 1,012
Low compression usually indicates worn piston rings.
Boydie
Greetings All! Long-time Ford owner, first-time Chevy owner: 2008 Charcoal Gray HHR LS, bought used with 110K, just about to turn 130K.
CEL turned on, scan showed P0303. I changed the plugs (maybe original plugs?) and the misfire remained. I swapped coils #2 & #3; scan showed P0300/0303. I swapped fuel injectors #3 & #4; scan showed P0303.
Drivability does not seem to have changed, but the idle has roughened considerably.
Went to a mechanic for a compression test yesterday. #1 was 140 psi, #2 was 125, #3 was 70, #4 was 140. The mechanic wondered about a stretched timing chain and promised to do research after putting it all back together. He called a contact with GM Fleet and was told the chain was a possibility, but the valves were more likely the issue. He wants to do a leak down test next.
Are we headed in the right direction, or does the low compression across all cylinders with a specific misfire in one cylinder lead anyone to a different conclusion?
CEL turned on, scan showed P0303. I changed the plugs (maybe original plugs?) and the misfire remained. I swapped coils #2 & #3; scan showed P0300/0303. I swapped fuel injectors #3 & #4; scan showed P0303.
Drivability does not seem to have changed, but the idle has roughened considerably.
Went to a mechanic for a compression test yesterday. #1 was 140 psi, #2 was 125, #3 was 70, #4 was 140. The mechanic wondered about a stretched timing chain and promised to do research after putting it all back together. He called a contact with GM Fleet and was told the chain was a possibility, but the valves were more likely the issue. He wants to do a leak down test next.
Are we headed in the right direction, or does the low compression across all cylinders with a specific misfire in one cylinder lead anyone to a different conclusion?
11-20-2013, 11:48 PM
#8
Platinum Member
Join Date: 01-09-2007
Location: SE USA
Posts: 15,865
11-21-2013, 11:07 AM
#10
Administrator
Join Date: 10-13-2011
Location: Welland,Ont Canada
Posts: 36,519
I've had this issue on one of my other cars, turned out to be a cracked head near the exhaust valve, but I think we are starting to dig up any scenario, time to pull the head and do a visual check, have the head inspected, and Magnafluxed if possible, while you're at it change out all the timing chain water pump, tensioners gaskets and such, check the piston movement from the top, if they're sloppy, make a decision then to change the motor or pull it for a full rebuild.