Hi, I have an 82 that suddenly started back firing and running terrible. I replaced the HEI coil, cap, plug wires and spark plugs. It's not backfiring anymore but still running terrible, gallops at idle and missing under load. Any suggestions?

 

Have you checked the computer for error codes?

 

Replace the ignition module......also check your fuel pressure (with adapter port) and CEL codes by jumping the ALDL connector.
Ignition module has come up a lot lately and a couple of members fixed their problems with them......make SURE you follow procedure and use heat sink compound. What happens a lot now is the 40 year old heat sink compound dries up...and can't conduct heat to the distributor base.....and a hot old module doesn't last long.
Here is a Genuine GM.....
https://www.rockauto.com/en/moreinfo...t=7172&jsn=963

Jebby

 

Have you bought the 82 Corvette Service manual? How about the 82 AIM?
These will help TREMENDOUSLY.

You might want to look at the spray patterns of the injectors with a timing/strobe light. As well as 'pinning-out' and checking the Voltage value on the TPS sensor.

One often overlooked reason for misfires is the labyrinthine and difficult wire routing of the spark plug wires, which actually run THROUGH the motor mounts.
Having your ignition wires tickety-boo is REQUIRED.

Running manifold vacuum as seeing if the MAP sensor is getting a proper signal.

Buccy is going to say..."what is your fuel pressure'.

Start there.

"buy the book(s) BEFORE you buy the car".

Unkahal

 

It takes a special GM Code Reader. I burnt my OBD2 out using an OBD1 adapter. Are the 82's as sophisticated as the current models?
Fuel injectors are working. I know what you mean regarding the plug wires, it seems like they could have come up with something better than that. They put heat shields to protect the wires but run channels along the side of the engine block.

 

No you don't need a code reader...YOU NEED THE SERVICE MANUAL.

Under the ashtray is the ADL (advanced data link) data-port service link. I believe you create a jumper from a piece of wire, ground between two SPECIFIC terminals and the CHECK ENGINE LIGHT flashes in sequences, giving you the codes.

This is not an OBD 1 or 2 Vehicle, this is called CCC, computer command control.

Unkahal

 

hi tech code reader. bent paper clip...

 

Mines really Hi tech...There's a switch in the middle so I don't have to remove it!

Cheers Derek!

 

Did you connect a vacuum gauge to determined if the valve train is working properly?
FYI, my Accutron scanner that can read both OBD 1&2 will also read a 82 CFI ECM

 

You're a bent paper clip!

 

OBD 1 didn't exist until OBD 2. then everything nefore got called obd 1. no standardization. european CIS is OBD 1 just like GM TBI. with no similarities besides not using an OBD 2 port.

 

Don't knock it until you tried it! Hell, Road Kill Garage hold pistons to connecting rods with zip-ties! (I'm amazed they're not dead yet!).

Unkahal

 

Just to fill out the begats....First was 1980 Corvette CA. units with rudimentary CCC (C3!!!) then came 81 version (C3.2) Us federalized. Then Came C-3.3 in the 82........

Don't mess up the computer by plugging in the wrong thing....the replacement is close to $1000.

unk

 

Thanks guys, I appreciate the responses. I think I'll pass on the paperclip. I'm sure that GM gave every owner a new paperclip when they bought their new Vette. It wouldn't surprise me though. The original owner must have kept it as a reminder to buy a Dodge. I installed a new ECM no change.

 

Did you try the EGR ? 1982 was a year they either ran well or were a hand full. When new just a first year computer controlled. Find a Corvette garage in your area and ask questions, and get a written quote or do not proceed, find another garage.

 

Sorry guys I owe everyone an apology. I got a Shop Manual and it does show using something, paper clip or piece of wire in the code plug.
After a complete tuneup and new catalytic converter we found 2 stuck valves.. The cam was shot and engine a mess. We're doing a complete rebuild. The block is in the shop. New pistons 40 over, comp cam, hp heads and while the engine is out a few other things, steering box, water pump and ac hoses. And computer chip.

 

 

Glad you found the problem! Next time you are at a GM dealership, ask for one of their paperclips.

Since you are rebuilding the engine anyway, are you keeping the Crossfire, or perhaps reverting to a carb/HEI system, or updating to a modern, tunable, EFI system?

 

If you plan on owning the car a while and want to do some OBD maintenance in the future, you might consider getting something like an old-school snap-on scanner (MT2500). You basically only need the oldest and least expensive (red) cartridges as they go back to 80 1/2. and the GM-2 connector. Not that much money. Probably the least expensive and best scanner. There are about dozen or so pressure/temp, etc readings you get via the computer that you don't get with a paperclip.Helpful if issues come up. Or if you have a buddy with just about any snap-on scanner.

Quick side-note: In the outside chance you were thinking of spending money for a scanner, it's worth noting that about all Snap-on scanners, even new ones read legacy systems going back to 80 1/2 (GM). Which means you could drop $1,500 for a Solus or Versus scanner which scans 'current' vehicles (per the scanner's software version) as well as your 82. Note: newer S-O scanners you'll need to buy the special cable for legacy OBD1 interface connectors. But it gives you versitility of working on any new OBDII vehicle ...and using bi-directional controls as well as any older vehicle. Snap on is really good that way.

Older GM OBD1 systems can be completely serviced & de-bugged using common shop tools like a VOM, Vacuum gauge/pump, Ground wire and test light. But it's nice to be able to see via a scanner what the computer is seeing (if that kind of thing interests you).

MT2500
https://www.ebay.com/itm/164973936251

 

For now I'm keeping the Cross Fire. I still want to maintain as much originality as I can. Converting to a 4 barrel would require hood modifications.