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I just got this car about a week ago, 2004 corvette 130k miles at a very decent price but it has a rough idling problem when it’s running on hwy runs smooth but once i park I can feel the engine rought idling, sometimes not often but happens where I turn it on and it’ll turn off idle down to dead also sometimes cranks 2 seconds longer than normal to turn on
any idea where I can start ? Maybe bad crankshaft pos sensor ? I got no codes related to the issue just some for the abs system and 10-PCM P0161
but honestly I’ve had many chevys with bad oxygen sensors and never had this issue
A plugged fuel filter/fuel pump check valve could cause the issue, it could be the original. From what I understand 2003-2004 had some fuel pump issues.
At that mileage I wonder if you still have original plugs and wires. The double platinum plugs originally installed often lose the platinum plug on the ground side, leading to a very large plug gap. I liked the erratic idle I had before I changed my plugs/wires, but the new ones smoothed it out.
That said, I’ve also had an erratic idle after a local shop let the engine sag on the mounts, pulling several of inlet tube joints apart just enough to futz up the idle tune. Adjusted the intake to close all gaps and got my idle back.
If the car runs rough at idle but OK under load it may be a vacuum leak…the P0161 is B2S2 O2 sensor HEATER code…may be bad sensor or wiring…if you have a scan tool you can verify that it is a vacuum leak.
When I first got my 2000 a few years ago, it also had a rough idle. Was skeptical at first when Techron was suggested but after a few tanks treated with Techron, the idle smoothed out tremendously. I run a bottle in every second or third tank now just for maintenance. Didn't do anything else that might affect the tune until later such as PCV valve, air filter and MAS cleaning with not nearly as much noticeable improvement if any but was already running great after just the Techron treatments. So pretty sure the Techron really worked. I'm a believer.
Could be as simple as water in the gas, but probably not. But it won't hurt to drain the old fuel and dump 5 gallons of fresh premium into the tank. Dump a bottle of dry gas in it BEFORE the 5 gallons of fresh gas. This will ensure a good mixing. It may, or may not, fix it. At least you'll know you have good fuel, and can go from there if it doesn't do the trick...
Last edited by grinder11; Jan 13, 2025 at 01:40 PM.
Also, there is an "idle relearn" step, at least on the earlier C5s. I have a 2000, and it's in the factory service manual. It may, or may not still apply to the '04s. Doing it on my 2000 made a noticeable improvement in my idle quality, even though I have a cammed LS7 in it...
Last edited by grinder11; Jan 13, 2025 at 01:51 PM.
Rough idle
