Rough running c5
Thread Starter
Drifting
Joined: Feb 2010
Posts: 1,923
Likes: 427
From: Dunedin Florida
Rough running c5
My C5 was I parked in my garage for 7 months while I was out of the country. I kept it on a battery tender. Now it’s running rough at idle and driv8ng. The exhaust smells like bad gas. It had half a tank. I added sea foam to the gas and added 5 gallons of the normal 93 octane. I then let it idle for 45 minutes. The idle sounds better but any throttle action and it goes really rough again. What else could be wrong? I should mention the check engine light is on but I haven’t pulled any codes since it was perfect when I parked it.
Burning Brakes
Joined: Feb 2019
Posts: 1,028
Likes: 377
From: SW Ohio
If it is simply bad gas, which is a prime candidate for a cause of this type of issue, it is easy to drain the system. Here is a thread to show how get the fuel pump running with the key on run.
https://www.corvetteforum.com/forums...l-pump-on.html
If you take the valve core / schrader valve out of the drivers side fuel rail, put a piece of hose on it running to a fuel c \an, and turn on the pump as above in the thread. It will empty the tanks completely.
https://www.corvetteforum.com/forums...l-pump-on.html
If you take the valve core / schrader valve out of the drivers side fuel rail, put a piece of hose on it running to a fuel c \an, and turn on the pump as above in the thread. It will empty the tanks completely.
Last edited by CinciZ06; Dec 16, 2019 at 08:02 PM.
Thread Starter
Drifting
Joined: Feb 2010
Posts: 1,923
Likes: 427
From: Dunedin Florida
If it is simply bad gas, which is a prime candidate for a cause of this type of issue, it is easy to drain the system. Here is a thread to show how get the fuel pump running with the key on run.
https://www.corvetteforum.com/forums...l-pump-on.html
If you take the valve core / schrader valve out of the drivers side fuel rail, put a piece of hose on it running to a fuel c \an, and turn on the pump as above in the thread. It will empty the tanks completely.
https://www.corvetteforum.com/forums...l-pump-on.html
If you take the valve core / schrader valve out of the drivers side fuel rail, put a piece of hose on it running to a fuel c \an, and turn on the pump as above in the thread. It will empty the tanks completely.
Thread Starter
Drifting
Joined: Feb 2010
Posts: 1,923
Likes: 427
From: Dunedin Florida
ok so my codes are:
10PCM P0161 HC
10PCM P0300 HC
28-TCS C1225 H
40-BCM No Codes
58-SDM No Codes
60-IPC No Codes
80-Radio No Codes
99-HVAC No Codes
A0-LDCM No Codes
A1-RDCM B2263 H
A1-RDCM B2265 H
A6-SCM B2860 H
B0-RFA No Codes
10PCM P0161 HC
10PCM P0300 HC
28-TCS C1225 H
40-BCM No Codes
58-SDM No Codes
60-IPC No Codes
80-Radio No Codes
99-HVAC No Codes
A0-LDCM No Codes
A1-RDCM B2263 H
A1-RDCM B2265 H
A6-SCM B2860 H
B0-RFA No Codes
Pro
Joined: Jan 2016
Posts: 524
Likes: 126
From: Sandown NH
The P0161 is a bad heater in the 02 sensor AFTER the passenger side Cat. That will not make the car run rough but the sensor needs to be inspected for damaged wiring. If none is found, replace the sensor. The rough running is being caused by the P0300--random cylinder misfires. Check for cracked or broken vacuum lines, check plug and coil wires, and remove and clean the MAF sensor. It could be caused by old gas but 7 months is really not all that old for gas.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
2027 Corvette vs The World: Every Model vs Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!
Joe Kucinski
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,319
Likes: 3,927
From: Cape Coral, Florida
Since your car sat for a long time get a long screwdriver and while the car is idling hold the tip to each injector and put your ear to the end of the screwdriver...if the injector is firing you will hear it click...as far as your 0161 measure the resistance on the heater circuit...the brown and the black are your power and ground to the heater...resistance should be 3.5 to 14 ohms...also make sure you are getting 12 volts to brown wire key ON !!..with a clogged cat you would have a loss of power !!..you really need a scan tool and a back pressure gauge to diagnose this properly
Last edited by C5 Diag; Dec 30, 2019 at 01:50 PM.
Melting Slicks
Joined: Mar 2018
Posts: 2,502
Likes: 187
From: California
I would go pick up a fuel octane booster 104 stuff and see what that does with some fresh gas! Ethanol collects water I wouldn’t be surprised in today’s gasoline with all those added detergents if they also collect moisture! Best is to use a fuel stabilization additive when letting the car sit extended periods of time!
Thread Starter
Drifting
Joined: Feb 2010
Posts: 1,923
Likes: 427
From: Dunedin Florida
So I am here draining my fuel tank as suggested above and am using a clear hose on the schrader valve. The first 7 to 8 gallons came out in a nice steady stream. Then at half a tank as showing on dash gauge I start seeing air mixed into 5he fuel stream. This increases until I see the fuel is no longer a steady stream but now coming in burst of fuel followed by no fuel. It would appear as if the tank was almost empty but the gauge shows over quarter tank. Is this normal? Do I keep going or am I at a risk of damaging the fuel pump?
i can’t seem to add the video of what it’s doing.
i can’t seem to add the video of what it’s doing.
Last edited by Crosis; Jan 10, 2020 at 02:14 PM.
Drifting
Joined: May 2007
Posts: 1,544
Likes: 208
From: Huntersville, NC
when you ran the fuel pump so long you didn’ t leave enough returning fuel to run the educator pump in the other tank. excess fuel at the rail return to the side with the educator, so now you have one tank with some fuel in it you can’t get out. Pour back about a gallon or two, the run the pump for a while, then bleed some off the schader fitting on the rail
Thread Starter
Drifting
Joined: Feb 2010
Posts: 1,923
Likes: 427
From: Dunedin Florida
So tank got emptied and I put 5 gallons of 93 octane in. Started the engine and check engine light turned off. Went for a drive and as soon as I got into the throttle with some zest, the check engine light came back on and it ran like crap. So I guess the next step is the vacuum hoses although I think they are not the problem.
Thread Starter
Drifting
Joined: Feb 2010
Posts: 1,923
Likes: 427
From: Dunedin Florida
I have never changed the coils. Plug wires are 10 years old. I considered them but since it ran fine when it was stored, I tend to think it can’t be something that can’t just fail when the car isn’t running. I have found no signs of mice. Still getting p0300 and p0161.
Last edited by Crosis; Jan 15, 2020 at 05:43 PM.
Burning Brakes
Joined: Feb 2019
Posts: 1,028
Likes: 377
From: SW Ohio
If you can get your hands on a Tech2 it will let you see misfire data, stored codes, etc and it will possibly keep you from igniting the parts cannon. I bought the ebay tech2 emulator deal and it works great for diagnostic work.
https://www.ebay.com/itm/USA-Shippin...oAAOSwkeddxm-I
https://www.ebay.com/itm/USA-Shippin...oAAOSwkeddxm-I
Last edited by CinciZ06; Jan 15, 2020 at 08:02 PM.
Advanced
Joined: May 2011
Posts: 58
Likes: 13
Like has been mentioned above. If you don’t want to bring this to someone to diagnose then you are going to need some tools. First you’ll need a scanner that can read data stream. You have a random misfire so that means we are effecting both banks. So we either have a fuel issue, spark issue or mechanical issue.
The most likely culprit here here is a fuel issue. So let’s start there. Let’s get our new scanner and look at fuel trims. What are fuel trims both long and short term? What is your MAF reading in g/s at idle? Next let’s get out our fuel pressure gauge and see what the fuel pressure is with key on engine off, let’s start the cAr and see what fuel pressure does, next let’s tape the fuel gauge to the wind shield and see what fuel pressure does while driving. Report back your findings and we will go from there. You won’t fix this car yourself without some tools.
The most likely culprit here here is a fuel issue. So let’s start there. Let’s get our new scanner and look at fuel trims. What are fuel trims both long and short term? What is your MAF reading in g/s at idle? Next let’s get out our fuel pressure gauge and see what the fuel pressure is with key on engine off, let’s start the cAr and see what fuel pressure does, next let’s tape the fuel gauge to the wind shield and see what fuel pressure does while driving. Report back your findings and we will go from there. You won’t fix this car yourself without some tools.
Last edited by hondaracer2oo4; Jan 15, 2020 at 08:38 PM.