Just bought a 1982 Collectors Edition from a guy that couldn't fix the mis-firing engine. He changed the plugs, plug wires, distributor cap, rotor arm, oxygen sensor, EGR but never solved the problem. The diagnostic port on this car gives no reading. The engine starts, the injector is spraying a lot of gas. The engine sounds like it is running on 5 or 6 cylinders and after a few minutes of running the engine manifold closest to cylinders 2 and 7 is cold to the touch. Removed the CAM covers and valves are going up and down like they should.

Any help or pointers would be greatly appreciated.

 

Are the plug wires completely attached? I know it sounds silly, but when the plugs and wires were changed on my car, one of the wires wasn't assembled correctly and the wire didn't continue all of the way into the spark plug boot. I noticed this after my car went from having 1 dead cylinder to 2 of them and one of the wires fell off of the plug when the car was running. I replaced that specific wire and I then went back to only one dead cylinder which I am still trying to find the reason why.

Also, are all of the plug wires in the correct order?
Is it possible those 2 cylinders are switched?
Kael

 

KaelFarmer is correct on checking that first. I would take an unused plug and plug it into each wire, ground it out on something and roll the motor over. You want good strong blue spark. Also possible wires are switched. 1 8 4 3 6 5 7 2 is the firing order and the dizzy spins clockwise.

 

I cannot tell you how many times I have hoped for the simple solution of it being a cap wire loose or mis-placed. If nothing else I will buy another set of plug wires and make absolutely sure that everything is connected and attached in the right order. I am beginning to doubt my own assembly process. Thanks for the input.

 

Many thanks for backing up KaelFarmer's input and for the diagram. We all seem to be leaning towards this being an electrical distribution problem. Maybe it is time to rip everything off and start over with new leads.

 

Hopefully it's something simple. I have a followup post getting into alittle more detail if all seems AOK on the plug wiring and such.

 

If your spark plug wires and your firing order have been confirmed you gotta step up the game alittle. Keep in mind the basics. It's gonna have fuel, spark, and compression to run. Well, you've confirmed it's got fuel and you confirmed spark to all the right places. A big question to me would be left is "what is the compression on this motor"? At that point I would do a basic compression test. If you have never done one before here is the basics of how it go.

1. A well charged battery. You're gonna be rolling the motor over a bit without starting it. Plus you want it as strong at the beginning as you do the end to keep the engine speed consistent.
2. Procure a good old fashioned compression gauge. You don't need anything fancy. If you have a friend that has a decent tool and garage setup there is a fair chance they have one. If you need to purchase one they aren't that bad. About $20 to purchase at your local Autozone/Advanced/Napa etc. They might even have one in their loaner program.
3. Pull all the plugs on the motor. You want all the plugs out so that if you have a blown head gasket between cylinders it will more readily show up on the gauge. NOTE: INSPECT THE PLUGS WELL WHEN YOU PULL THEM. If you see water or coolant in the plugs then you have your problem right there. Water/coolant in the plugs would be an indication of a likely cracked head or blown head gasket. While a blown gasket will show up in a compression test a cracked head likely will not.
4. Disable your fuel pump (Not familiar with that particular animal but I would suspect there is a fuse/relay driving it. Pull that relay/fuse and it will stop running)
5. Have a notepad and writing utensil handy and thread the hose from the compression tester into the number 1 spark plug hole and hook the gauge up.
6. Put the throttle to the floor on the car and turn the motor over 3-4 times (you'll hear it labor against the compression gauge) and write down the number recorded on the gauge
7. Release the pressure in the gauge with the release button, remove the hose from the number 1 spark plug hole AGAIN INSPECT THE HOSE END THAT WAS THREADED IN FOR WATER/COOLANT. Repeat for all 8 cylinders.

Every cylinder SHOULD be within 10% of each other compression wise. We aren't gonna get too picky about that 10% thing right now. As long as your readings are within 20% of each other and above 100 PSI we're good with it for now. Any variation beyond that is a for sure problem and is most likely your root issue. If all your cylinders are making good compression and are within 10% that would rule out anything mechanical. It would have to be either you missed something on the ignition or somehow it's fuel related.

 

I would check the rotor / cap, firing relationship. I say this because my dad had a mechanic stab his disty in incorrectly and he "fixed it" by moving the wires to the new correct rotor position which is NOT a match for looking down on the cap. (make sense). If someone were to put the plug wires on based solely on the position on the cap, they'd all be off.

 

Hi, thanks for following up. Although I don't have the actual pressure test figures the previous owner told me he had a compression test done on it and it was healthy, along with the fact that he had changed the plugs/wires, cap/rotor, alternator and a few other things, and that the fuel pressure was fine. He had obviously spent a long time fault-finding and replacing the obvious in his quest to resolve the problem and pointed me towards a bad O2 sensor which I replaced first thing. I think the only thing to do now is to follow your logical steps and validate all myself. I can then return to the forum with actual figures. More later.

 

Good point, thanks. I will certainly have to check that one out.

 

Put a vacuum gauge on it. Just because the valves are going up and down doesn't mean you don't have a burned valve, damaged valve seat, whatever.

 

I guess that comes back to the compression test that I need to organize next. Thanks. I will post results.

 

Hi, Also check the coil or simply replace it with OEM or better. Delco OEM will be the correct specs, Delco Professional parts may be off a little as the Pro line is the universal fit.

 

Seriously???? What kinda sadist would do this??? Not that I'm doubting that this happened but wow.

 

Seems like I'll be replacing already replaced items, starting with the plug wires and working my way through. Thanks for the suggestion.

 

Go cheap first. Check the things that are free. I'm betting the fix is an easy one...also possibly free.

 

I do hope so. I started thinking that but was losing hope - hence the call out to the forum. I appreciate all the suggestions and encouraging support!

 

https://www.corvetteforum.com/forums...-question.html

 

It is kinda convenient that the 2 and 7 were to the two cylinders that were cold and those two just so happen to be right next to each other on the dizzy. Hoping a wire a swapped!!!!!!

 

Pull 2 and 7. It could be that they are fouled and are not firing. If you have a timing light, you can clip the pickup on any wire to determine if it is getting fire. Check them all.
Crossfire injection systems are very complex. There is a Sticky at the top of the page. Good Luck