Corvette Forum : DigitalCorvettes.com Corvette Forums banner

1 - 13 of 13 Posts

·
Registered
Joined
·
313 Posts
Discussion Starter #1
OK, i thought my opti spark was going out again, but i took the spark plugs out and 2/4/6/8 plugs are dark, and 1,3,5,7 look clean. my car is still stuttering, what could be going on??
 

·
DC Crew
Joined
·
2,988 Posts
What exactly has happened, bad idle or poor performance at low rpm?
 

·
Registered
Joined
·
257 Posts
Ohm the injectors and do a fuel pressure leak down.
 

·
Registered
Joined
·
313 Posts
Discussion Starter #5
What exactly has happened, bad idle or poor performance at low rpm?
When i am driving at 1500 rpm its starts to run pretty rough, but when i get on it runs good. Also at idle you can hear a pop. pop from the right exhaust. Thats probably why the right side spark plugs were alot darker than the left side.
 

·
Registered
Joined
·
74 Posts
Your car's a batchfire. Investigate from there.
 

·
DC Crew
Joined
·
2,988 Posts
Driveway Optispark test:

1. Start car, leave in neutral
2. Floor the gas quickly and hold for 1 second
3. If there is a obvious stumble/bog then it's your Optispark

pm me with any other questions
 

·
Registered
Joined
·
111 Posts
Ohm the injectors and do a fuel pressure leak down.
I agree!
Get yourself (or borrow) a digital volt-ohm meter and unplug each injector one by one and check the resistance value on the injector itself. Do the good side and the bad side so you'll have a reference. I forget what the exact value range is...
Then get a pressure gauge and hook it up to the schrader valve on the fuel rail start the car up and check your pressure. Then after you shut it off watch the pressure gauge closely to see how quickly it drops...if it drops fast you know you have a leaky/faulty injector.

Good luck!
 

·
Registered
Joined
·
313 Posts
Discussion Starter #10
I checked the codes and it says right bank oxygen sensor (lean exhaust indicated) Could that be causing it?
 

·
Registered
Joined
·
111 Posts
Yep.
That would be a start. Replace it and then remove the battery cable for a few minutes to clear the codes.

I'd still do the injector ohm test and fuel pressure test just to make sure.

Found this today:
Specs for the injector ohm test should be 16.5 ohms + or - .3
 

·
Registered
Joined
·
724 Posts
If it is effecting one bank only, it could be a vacuum leak on the intake on that side. Very doubtful that all the injectors on one side would go bad all of a sudden. If the O2 sensor on that side is showing lean, then that means the engine will be dumping fuel in to compensate for what the O2 sensor is reading. Which would cause what you are describing. Remember, the computer tries to compensate for what the O2 sensors are telling it. Which means there has to be a vacuum leak on that side that the O2 sensor is picking up as a lean condition, so it is dumping fuel in trying to compensate, thus the black carboned plugs, and poor idle quality. Under hard acceleration, you wouldn't be able to tell as bad because the computer goes to full rich under wide open throttle anyways. There is an old mechanic trick to finding a vacuum leak. Get a small propane torch for like brazing plumbing pipes, make a way to attach a small vacuum line to the nozzle. Open the valve on the bottle, but DON'T LIGHT IT. Using the vacuum line to direct the propane, lightly spray it around the intake, vacuum lines etc. Try to concentrate on small areas at a time. If there is a vacuum leak, it will suck in the propane(won't harm the engine) and you will hear the RPMS raise up for a second.
 

·
Registered
Joined
·
313 Posts
Discussion Starter #13
If it is effecting one bank only, it could be a vacuum leak on the intake on that side. Very doubtful that all the injectors on one side would go bad all of a sudden. If the O2 sensor on that side is showing lean, then that means the engine will be dumping fuel in to compensate for what the O2 sensor is reading. Which would cause what you are describing. Remember, the computer tries to compensate for what the O2 sensors are telling it. Which means there has to be a vacuum leak on that side that the O2 sensor is picking up as a lean condition, so it is dumping fuel in trying to compensate, thus the black carboned plugs, and poor idle quality. Under hard acceleration, you wouldn't be able to tell as bad because the computer goes to full rich under wide open throttle anyways. There is an old mechanic trick to finding a vacuum leak. Get a small propane torch for like brazing plumbing pipes, make a way to attach a small vacuum line to the nozzle. Open the valve on the bottle, but DON'T LIGHT IT. Using the vacuum line to direct the propane, lightly spray it around the intake, vacuum lines etc. Try to concentrate on small areas at a time. If there is a vacuum leak, it will suck in the propane(won't harm the engine) and you will hear the RPMS raise up for a second.
Thanks, will check it today
 
1 - 13 of 13 Posts
Top