Hello Ladies & Gents,

I have been chasing a ghost for sometime now and I have gone to two mechanics with no luck.

Car: 2011 Corvette ls3 4lt Grandsport 68k miles (ALL STOCK)

Problem: My car is having a stutter of about 200-300rpm and when it does it, i lose voltage as well.

Story: I bought the car used, sent it directly to the shop for a harmonic balancer, oil leak from the valve covers and they changed the sparkplugs at that time. When i got it back, i fueled her up since she was empty and put in a car of lucas injector cleaner with 93 octane. i do not know what the car ran before in regards to fuel but i always put the highest octane. I have gone through 3 tanks of gas with same effect.

Fixes: I went back to OEM plugs, checked for leaks, changed plug wires to Accel ceramic boots and still nothing has fixed it. Now the plugs made it stutter less by a little.

I plugged in my reader and i am seeing large droppage on the driver side bank 1 oxygen sensor. one mechanic told me to change the o2 sensor the other said nothing was wrong.

Could my stutter be a clogged injector because of the lucas and that causes the droppage in the voltage? Car runs fine when accelerated. Only feel it when idle in gear or out of gear...

 

Pull and spray clean the MAF sensor.

As for O2 sensor, data log them to make sure not lazy, and give either lucas or tecron enough time to clean that they can of the fuel system, make sure not getting a drop in fuel pressure on the rail, and that you have an inject semi clogged that the cleaner is not going to solve.

Next to point out, idle should be holding strong at 600'ish rpm/not dipping lower than that, and if dropping below that, then other problems going on.
Hence idle dropping down below that, alternator is not being spun fast enough to really put out any amperage/voltage.

Also, should be running oem plugs and plug wires, since alternator is controlled by ECM, and not enough resistance of the after market wires or plugs, can caused RF noise problems to the ECM, to cause the alternator to drop/lower it output voltage.

If you are having problems with the voltage at higher rpms as the engine starts to move about, then check the starter solenoid terminal nut where the battery and alternator wire connect together on that terminal on it for loose nut, the engine grounding bolt just above the starter that the battery grounds to the engine block, and even check to make sure that engine fuse block terminal nut for the battery wire is tight as well. Also, under the battery tray, is another ground that you want to check, since battery acid may have spilled down to cause a corrosion problem there as well.

 

I’d let those 2 mechanics stick to oil and brake changes…they don’t know how to diagnose cars…99.99% of them read a trouble code and will replace a part and that is not how we do it…the upstream O2 sensors are supposed to switch between 200-800 mv’s and the downstream O2’s remain fairly constant at 600-800mv’s…was it stuck below 100mv’s for a period of time ?? …was there a DTC stored ??…you may have a dirty throttle body…this would not affect your voltage…I’d use your code reader as a chock and invest in a better aftermarket factory level scan tool…can that code reader graph data PIDS ??…just looking at the numbers isn’t the best way to look at live data…if you want to bring the car to a sharp diagnostician I know someone in your area…you can try voltage dropping the injector circuit from the battery to the injectors and see if you see a drop…if you don’t have a DMM and know how to use it then forget about this test…a lot of circuits like O2 sensors, coil packs and injectors go through the Powertrain Ignition 1 Relay…that may be something to look at.

 

no it does not stick and fluctuates from negative to positive 0.800 and back only on bank 1.

No codes stored or pending either. I cleaned the throttle body which i forgot to mention and air intake sensor.

I don't think i can graph anything... it was a 50.00 tool that i bought to delete codes and ****.

You think replacing the relay or you mean looking into the harness?

Thank you for your time

 

As mentioned I don’t know if you know how to use a DMM and I’m not into just replacing parts…I’d leave this diagnosis to a professional…there is no negative and positive when referring to O2 sensors…like I mentioned upstreams oscillate between 200-800 mv’s…that is 0.2 to 0.8 volts…if you are not going beyond reading and deleting codes your scan tool is fine…if you need to see a sharp diagnostic tech see Mario Rojas at Autobahn Performance in Oakland Park.