Hello,
I have a problem with my C4 LT1 from 1996.
I have driven it over 2000 km since I bought it 3 months ago.

At first, it burned from the kick, but over time it began to choke slightly when I was starting her.
Recently I had to gently add gas when igniting.

So far, I have replaced the radiator plus hoses, oils and fuel filters.
Recently I also replaced the spark plugs for Autoline 106. And then I observed disturbing symptoms.

During the second drive after replacing the spark plugs - when I was standing at the traffic lights - the engine began to wave at slow RPMs. This was more evident once I warmed up the machine. Symptoms was:
- the battery voltage needle swayed slightly
- the screen dimmed slightly
- the RPMs dropped by about 200.
On neutral gear the situation looked better than on drive gear.

Unfortunately, the day after, quickly after I started driving, it went out completely at the traffic lights once and didn't want to start for a while. I succeeded after a 2-minute break with the accelerator pressed to the maximum.

With the mechanic we replaced the ignition wires, because we noticed that there was a short circuit and sometimes the wires lost their spark.
Unfortunately, the "Walker ThunderCore PRO OE replacement wire set (WL-9241425)" had a matching 8 spark plug cables, but cable between the coil and the ignition module was no matching.
Unfortunately, it is difficult to have it available in my country, but I will do my best to change it as well.

Despite this, there are still symptoms with the battery indicator waving, screen dimming and RPM drop. Please let me know what could be the cause?
I don't want to risk stalling, because I keep the car in the underground garage, so in case of emergency, I won't have a way to tow it or burn it out if it floods.

My mechanic's hypothesis indicates that the Corvette gives too much fuel and then overflows.
Or some sensor is failing, but we are not sure.

Do you have any suggestions?
What to check?

 

Any codes? Scan it and look at the live data. Gas to the floor as you crank is "clear flood mode"-cuts off fuel.

 

Thanks.
Mechanic plugged the computer and read the data, but nothing that he had a concern about.

Then, please let me know how should I start the Corvette if it does not start by a key. Should I use gas, but only the little?

 

If you give it a shot of quick start and it starts up then that will point to problem with fuel.

 

@drive it

> If you give it a shot of quick start and it starts up then that will point to problem with fuel.
Is that an advice what to do when it does not start by a key or is that the advice to use in order to further diagnose the general symptoms? Excuse me, I am not English native speaker. I feel I didn't got it right.

- - -

general problem:

I was riding my C4 and my mechanic had connected computer and we found anomaly. So when there is a problem at live, the map sensor values are fluctuating. The correct values was 42-43 but, when engine did waving it fluctuated between 41 and 45.

We could observed:
- jerking when accelerating, the first moment when you add gas suddenly, like it was flooded
- interrupting the engine at slow speed
- unjustified changes in idle speed, the so-called waving

The question is whether the map sensor does not take this measurement from the intake manifold and does not change this value itself, e.g. under the influence of vacuum in the manifold or e.g. on the basis of some sensor?

Any hint?
Any part to be replaced? Map sensor?

 

Ok, I thought you meant that the engine will turn over when you turn the key to start it, but the engine will not start/run-yes? or no?

 

Well to clarify (chronologically):

- it was no problem 3 months ago when I bought
- it started to turn on longer week by week
- it happened that I needed to touch gas when turning on, but still it always started up to this moment
- I changed sparks for Autoline 106
- I had a ride and almost each time when I have stopped at the traffic lights the engine started waving - RPMs down, accumulator indicator goes up and down by little, lights losing a little bit bright, all at the same time
- I had a ride next day - after 2 km - at the traffic light - Corvette turned off himself - lost RPMs to 0 - and didn't wanted to turn on again, I waited 2 minutes and with max gas on it turned on, so I just went to mechanic directly
- we changed ignition wires - because we observed with the mechanic that ignition wires was losing the spark; but one wire wasn't changed because it didn't fit the coil
- still engine waving happens

I am scary to drive now, so I don't lost the power at the traffic lights And this waving is not something fine I believe.
Again - waving happens when I stop it for a moment - e.g. traffic lights, it rides more or less fine.

My last post gives some more details we found - map sensors etc.

 

Your description of needing max gas to start-that is called "clear flood mode". When you put the gas pedal to the floor when turning key and cranking engine to start it - the computer stops all flow of gas from the injectors. So that is pointing to a problem with fuel. I would check injectors if they are leaking or stuck open.