1996 corvette random misfire at highway speeds 1996 corve...

Q: 1996 corvette random misfire at highway speeds

asked by on November 08, 2017

1996 corvette LT1 138k miles auto trans. P0300 random misfire code. Check engine only comes on at speeds 60 mph and above and stays on/ blinks. Have replaced optispark with MSD distrubtor and wires, plugs also replaced. New fuel filter, replaced vacuum lines. Compression tests all 120+. Replaced PCV and EGR and Purge. P0300 continues to pop back up on the dash after about 3 days of driving. Car is straightpiped but not sure if that would have anything to do with it. Misfire counter showed zeros across board when at idle or parked with throttle at high rpm. Just when it gets on road at consistently 60 mph the check engine comes on.

A possibility is vacuum leaks around the intake. If the lobes on the camshaft are worn, that can cause a misfire and other inefficiencies as well. I would first check for a vacuum leak. If no leak, secondary firing patterns on all the cylinders should be examined on an oscilloscope. The waveform will help narrow the potential causes to fuel versus ignition. Another possibility is the random misfire is due to intermittent faults in the injector and/or ignition components so although these components appear to be in spec during static testing, in fact they are not reliable and are later, in service, operating intermittently. Finally, the ignition and fuel driver circuits in the PCM for the misfiring cylinder(s) could be faulty; that is the absolute last thing to test though unless you happen to have handy a known good PCM that you can substitute. If none of these possibilities pan out, you can request a misfiring diagnostic and the responding certified mechanic will get this resolved. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

How do I extend the sun visor?

Extending the sun visor allows you to block sunlight and brightness that is coming in through the center of the windshield. To extend one of the sun visors, first unfold it. Then, detach the end of the visor that is...

My brake pedals squeaks when I release the brake and then press the accelerator.

Hello. A squeaky brake pedal can be caused by a few different things. The most common reason for a squeaky brake pedal is a brake pedal mechanism that needs to be lubricated. The brake pedal has moving parts which can...

Truck running rough

Hello. If this only occurs when the engine is cold then you may have a sensor reading incorrectly or you may have a vacuum leak. Most of the time if the Check Engine Light is on I start by scanning...

Related articles

The Best Used Cars to Buy If You’re a Wedding Planner
As As a wedding planner, the demands placed on your time are going to be significant, even if you’re only dealing with one or two couples. You need to be a master juggler when it comes to your time and...
2012 Chevrolet Cruze vs. 2012 Hyundai Elantra: Which One Should I Buy?
When you’re looking for a four-door sedan, you’re likely interested in a smaller family car that still offers decent styling and looks, great gas mileage, and a comfortable interior that will keep your family safe as you’re driving. While not...
A Buyer’s Guide to the 2012 Chevrolet Corvette
The The Chevrolet Corvette is an American original that has stood the test of time. With the 2012 version, you’ll discover improved handling and horsepower that delivers the superior performance you’ve come to expect from this icon. With options as...