99 convertible, LS1, 80,000 miles. obtained it at 60,000, not sure if ever plugs/wires have ever been replaced.

for a few weeks now, when I start up the car. regardless of outdoor temperature (I only drive in the summer however), there is a miss that is only noticeable during acceleration. During acceleration it causes a noise like a dead cylinder, like a crackle or gargle. It usually seems fine at idol. there was once or twice that I noticed the RPMs dropping and jumping a little at a red light. this all goes away after a few minutes of driving, once engine is up to temperature. So today I put all new plugs 41-110, checked gaps on all, 0.040". and went for a test drive same thing.

the plugs were all perfectly clean which leads me to believe its not a spark problem becuase if it was it would be flooding a cylinder and that would be obvious on the plug. however that fouling may have been burnt off as soom as it gets running good. may still be a bad coil or wire.

I did a quick check over the vacuum lines, the all seem tight and in good shape.

So, I'm thinking it may be absence of fuel. ie a failing injector. Any idea how I can identify which cylinder is acting up. I know everyone is going to say change your plug wires so I'm on that right now, but any other troubleshooting ideas from the Corvette forum?


Thanks,
john

 

Clean your MAF

Also look at the plug wires at night to see if they are tossing a spark

Peace
Chip

 

Check the exhaust backpressure at the HO2 sensor in the exhaust manifold. If it is much over 2 psi, check the pressure after the cats, rear HO2 sensor. Both should be close. If your cats are getting plugged they will act that way and get progressively worse until the car won't run at all...Go for the easy stuff first.

Ask me know I know.

 

so when this happened to you, did your sluggishness go away after the vehicle warmed up? becuase I don't think a warm cat would pass more air than a cold one... I'm thinking theres other more likely possibilities to check first... but I will keep that suggestion in mind! But one thing is that if you are right, that would explain why all the plugs I pulled were identicle. Thanks

 

Spray your MAF...

Its a closed loop issue...

or a bad plug wire

Peace
Chip

 

Understand completely, when mine started it acted like a normal misfire and was somewhat intermittant. Although it happened more often under acceleration. As the problem progressed, the symptoms changed.

Now, Chip has way more experience than me, by far, so I'd take his advice. Just keep the others in mind BEFORE you go and spend too much money.

The lesson I learned though is that after about 2 1/2 month of great suggestions from members, it turned out to be the last thing we checked!!

For your problem, there is a troubleshooting procedure in the GM service manual that will get you there. Do you have the manuals?

 

I do have the GMO service program which has my 99 vette in there. I will check that out tonight thank you for reminding me.

I have another lead however, I am also battling the problem of the passenger door electrical connector causing the computers to go haywire (DIC alarms, passenger window/lock controls not functioning). I've done the liquid electric tape repair on the exposed wires but the problem is still coming back on and off.

Reading up on THAT problem, guys have experienced engine power loss. so I'm shifting gears now to resolve that problem before anything else.

 

I was getting multiple communication faults U1016 on multiple modules. So I looked into the connectors in the doors, tightened them all up by bending the tabs tighter. There was a few very loose ones, and since then, no communication OBD codes and normal power has been restored. So it was not a control device on the engine after all.