I recently bought a 1984 Corvette knowing it would be a project car from the start. It has a little over 72,000 miles on it, and it won't be getting many more until I figure this problem out.

Since buying it, I have removed and cleaned most of the top end of the engine and then reassembled everything. Before I started working on it, it barely ran well enough to get home.

While working on it, I replaced most of the ignition components, including:

• Distributor cap
• Rotor
• Spark plug wires
• Spark plugs

Unfortunately, it still doesn't run the way it should.

The main problem is that it won't idle properly. The RPM slowly drops until the engine dies. If I blip the throttle, I can keep it running, but if I hold the throttle open for too long, the RPM rises, then falls, starts misfiring, and eventually dies unless I blip the throttle again.

Things I have checked so far:

• Base timing is around 6-8 degrees BTDC.
• Both injectors appear to be working and are spraying a steady, cone-shaped pattern.
• I have searched for vacuum leaks using brake cleaner around the intake and top of the engine, but I haven't found anything obvious.

I have attached a video of the problem, along with photos of the distributor with and without the cap installed.

If anyone has any ideas, suggestions, or things I should check next, I would greatly appreciate it. I'm open to any suggestions, no matter how simple they may seem.

Thanks in advance to anyone willing to spend some time helping me figure this out.

The engine will occasionally backfire through the throttle body, and moving the distributor slightly seemed to improve how long it would run.

Without and with Cap on

Also a link to a youtube video on how the car runs right now

Crossfire Injection

 

Make sure you set the throttle position sensor voltage and install an upgraded coolant temp sensor if that hasn't been done yet.

 

Oh thanks for the info i did not know you needed to set the voltage for it, and i will look into the coolent temp sensor thx

 

Fuel pump/filter

 

Each throttle body has an Idle Air Control valve that has a pintle that moves in and out via a stepper motor. If the pintle or the seat of the TB that it mates up to gets clogged up with gunk/carbon give them a good cleaning, or just replace them. Either way clean the TB valve seat as well. I put these on my '84 two years ago and it helped fix surging idle, stalling when lifting off the gas pedal and hesitation when accelerating from a stop, along with replacing the EGR valve and finding all the vacuum leaks.

Edit: There is a proper relearning procedure to follow if you replace the IAC's. Google has the specifics.

 

I did these steps as well along with replacing ALL the vacuum hoses even if they looked ok. Been running great for over 20k miles now.