TXC5CHICK

So I took my car to a different shop to get it looked at and see why my car is missing....they called me yesterday to say the spark plugs and wires are bad and need to be replaced as well as the fuel filter.....well he got the work all done and its still missing.....anyone have any ideas what would be causing this?

Bill Curlee

IS THAT A SELFIE???

Anyway,,,, There are several things that need to be checked:

Your engine requires the following to run:
FUEL
COMPRESSION
SPARK
AIR

AIR: We will take for granted that you have proper air to each cylinder.

Spark: New Plugs and Wires. Good Start but still misses. You have eight coils. If one or more are not working you will have a miss.


FUEL: The engine runs so, most of the cylinders are getting fuel. You have EIGHT FUEL INJECTORS. They ALL must work and work the same. One could be defective.

So,, how do we figure out what cylinder/s are not working properly? The shop SHOULD have a GM Tech 2 and can do a power balance test and figure it out in a FEW MINUTES.

You can do it your self. Disconnect ONE fuel injector connector at a time. If you disconnect one and the engine idle does not change or changes a lot less than the other cylinders, that CYLINDER is having the issue.

You can also pull one plug wire at a time and do the same test BUT, you are dealing with 50,000 volts AC and may get a little ZAP if you don't do it correctly.

Compression: One cylinder could have a ring or valve issue. You would need to do a compression test to prove that.


I would figure out what cylinder is actually missing and post up that info. We can go from there.

Bill

Not4spd

What code is being thrown for the miss? Could be a bad coil and an easy way to tell would be to pull the coil for that cylinder and move it to a different plug. If the new cylinder starts missing then you found your culprit. What shop did you take it to out of curiosity?

Fastbird

Did you check for any codes? If you have a miss bad enough to set a trouble code, pull them up on the dash:

https://www.corvetteforum.com/forums...post1565921090

If it's misfiring on one particular cylinder, you'll see a P030x where the X would be 1 up to 8 to denote which cylinder has the misfire. If it's a P0300 then it's a random misfire across multiple cylinders. Harder to troubleshoot but still a starting point.

@Bill Curlee, I'm surprised you didn't quote yourself on pulling the codes. That's one of the first things I always see you bring up when trying to troubleshoot.

Bill Curlee

Well,,,,,,,,,,,,,,,,,,,,,, When a C5 has a misfire, It "NORMALY" sets a P0300 DTC. Which is pretty useless other than letting you know something your *** DYNO already knows. . Any SECONDARY Ignition issue wont set a SPECIFIC DTC other than P0300. You also will see a FALSHING CEL (Check Engine Light).

There are some 12 VDC Coil supply issues that will show up but that usually a BANK DTC.

Should I recommended a DTCs read,,, yea,,, probably. I was DISTRACTED!

Jeff T.

I'm surprised with all our TX guys that we don't have someone in Dallas to help a young lady in need.

Bill Curlee

HELL,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,, If that is her actual picture,,,,,, She ought to have GUYS DRIPPING off her little finger.

On a more serious note,, you are correct.

LOTS of TX Vettes and talent out there to lend a hand!

BC

TXC5CHICK

The car isn't throwing any codes on the DIC or when scanned that's why the guy that's working on it is lost for words and now dealing with GM to figure out what the issue is he's checked everything on the car but the electrical which will prob be done on Monday 😩

neutron82

is the car stock?... just curious because the tune can be manipulated to where it will not throw any codes even though you definitely have a misfire

TXC5CHICK

Yes everything is stock this car had to of sat for along along time I had a lot of vacuum leaks which have all been fixed new oil sending unit new front brakes new AC belt new spark plugs and wires new fuel filter new high pressure oil hose

neutron82

what symptoms does it have?... are you sure it's misfiring and the mechanic isn't just trying to take your money?... I would check for power at each coil pack and if that checks out then check for spark at the plug end one at a time... it is tedious but that should tell you if there is a problem between the coil and plug on a given cylinder... did the mechanic gap the plugs correctly?

TXC5CHICK

I know it's misfiring the car feels like it's gasping for air or almost feels like it's going to die it's been taken to two different places so far

Bill Curlee

If it is truly misfiring, you should see the CHECK ENGINE LIGHT (CEL) flashing when the event is occurring. Usually when accelerating.

If you check the DTCs when the engine is running "BEFORE" you turn the ignition OFF, if its misfiring, the P0300 (misfire DTC) should be there.
The P-0300 DTC clears its self after each ignition OFF cycle.

Bill

formula1nut

This is kind of a long shot but cheap to fix.

You mentioned that the car sat for a long time. Maybe the gas tanks accumulated water from condensation?

That would be particularly possible if it was low on fuel when stored..

Certainly that would cause the symptoms that you describe.

Fill it with the best quality high octane fuel that you can get. Might take two tanks to cure it.

57gman

I'm in PA, but can someone from Dallas give her tried and true places to take her vette? Shops you've taken your vette.

This is the power of this forum, helping each other. Good luck.

Jeff T.

Maybe a bottle or two of Techron as well?

Not4spd

A couple I would feel comfortable taking mine to LG Motorsports(currently in Lewisville), Truestreet Motorsports (McKinney), Corvette World (Dallas)

CactusCat

If you want to have a field trip, bring it up to OKC and have XP Racing get you going. He's an LS engine guru. A long drive might also solve the above mentioned water/condensation issue if it exists.

Arodman

if the car sat for a period of time, this issue could be as simple as just needs new fuel. I so of had that issue with a car (non vette) that sat for 1 year. Finally got it started and it was running really rough. Filled the tank with premium gas, and slowly it started running better. Just a thought

vetintheblood

I had the same thing. It did need new spark plugs and wires, but ultimately I replaced the coil overs and that made it run like new. Good luck!