twospeed

I Need help with this one!!!
I have a 2002 C-5 Corvette. I has been sitting in my garage without being started since May 2008. That’s 2 years 4 months.
Besides the battery going bad , which I replaced since charging didn’t seem to help.
The car starts right up, oil pressure 40PSI @ idle. But the idle is very rough. Have to keep foot on gas to keep running until temp is at least 100 degrees. Put fresh gallon of high test with a can of Techron. Idle improved somewhat.
Car is occasionally back firing through the exhaust. Took it out for test ride and to burn through the bad gas from sitting too long.
And back firing got worse. While sitting in my garage car backfired through exhaust again and blew ceramic honey comb out the exhaust from one of the cats. Exhaust smells bad now. Blown out ceramic pieces and what looks like very small pieces of a cotton shop towel laying on the ground under the right side exhaust pipe. But those pieces of what looks like a shop towel are very white not burnt. I don’t remember if I put a rag in the intake so nothing got in there and forgot to remove it before I put the air intake back on. Additional info, Kooks headers and Borla XR-1 exhaust. The resonator has an X pipe inside of it no mufflers.
Could the gas have gone bad sitting for 2 years and 4 months causing the back firing through the exhaust? Only codes, show misfire decteted.

ysb02

I'd drain the gas and refill. Check the plugs also. 2+ years is a long time for gas to sit. I think there's some additive you use if you want to let it sit that long.

Red99TA

iTrader: (11)

That is a long time for gas and for water to condense in the top of the tank. I would drain it and try again with fresh gas. Not sure what to tell you about the rag question. Seems like it would be pretty difficult for the motor to ingest a rag through the intake, spit pieces out the exhaust, have them go through the cat and make it out of the exhaust tips. I guess you did say it blew out part of the cat so maybe it is possible.

DarkC5

iTrader: (2)

Here is what I would check aside from what you've already done....1) Plugs and Wires, 2) Clean out the MAF, 3) Check any codes thru a scanner or the DIC and see what it is telling you.

RedHotG8

iTrader: (1)

The fuel injectors could be corroded since it sat for so long. Try running some good quality fuel injector cleaner in the gas tank, and if that doesn't clean them you'll need to replace them.

SStheBest

iTrader: (2)

he did......Techron. As others have stated water has formed in your gas tank and your plugs could stand changing along with the wires. Depending how much gas you have in the tank you may need to go to a local hardware store and pick up a bottle of "HEET". A spray of MAF cleaner wouldnt hurt either. As far as the peices....you may have peices of the cat blown out. Try those and report back.

twospeed

Thanks for the replys,
Already used MAF cleaner, New wires also. Will try Heet or Dry-gas, and will add fuel injection cleaner. have just a little less than 1/2 tank. I tried to suction pump gas out of the gas opening but couldn't get the small hose to into the area of the gas level. Felt something blocking the hose.
I hope I don't have to jack the car up and drain the tanks that way. I'm getting too old for that stuff.
I will report progress

Buckwheat

iTrader: (13)

Pull the plugs and see if any are sooty or otherwise bad. If you have **** getting blown out of your exhaust, you need to check for blockage in your cats or muffler. Keep running it this way and you will need new O2 sensors very soon if not already. Good luck.

LS1powered09

iTrader: (13)

bad gas, empty and refill with new high octane fuel, put a can of seafoam on the tank to clean up injectors and valves. might need to replace plugs.

SCM_Crash

iTrader: (2)

Drain gas, fill with new gas, do full tune up, pull negative battery cable for 10 seconds and put it back on.

Start the car and let it idle for 10 minutes.

Then enjoy.

twospeed

Thanks for the replys guys
I added one can of Heet and one can Fuel Injection cleaner. Let it sit overnight.
Started car and ran it for about 20-25 minutes letting it idle. Not one backfire?
Idle has really smoothed out. Idleing at steady 800 RPM. Holding the shift hardly any vibration. ( Car was always rock steady)
oil pressure 40PSI
Every once in a while the engine slightly stumbles or sputters ( Water or moisture going through the individual injector ) but the RPM doesn't drop unless the sputtering is close together then the RPM moves very slightly then remains steady at 800.
Exhaust stinks, so I know that at least one cat is now gutted. Wish I could gut the other one with out the use of explosions
Have just a tad over a half tank of gas, all but a gallon and a half is old gas.
Would love to drain and start over. But I have never jacked the car up before on stands. I'm getting old for this.
Is there an eaiser way to drain the gas? Remember it's an 2002 so ther is no return line from the injectors.
I'm going to keep running it every day to try and lower the level of the gas in the tank .

Chevy406

iTrader: (12)

You could try using the fuel pump to pump out the tank into a jug. Disconnect the fuel line at the rail (need a quick disconnect tool from any auto parts store). Then use a jumper wire to put 12v on the fuel pump relay. Do a search to see if anyone has tried this already. It should work.

twospeed

I jumped the fuel pump relay according to directions that I found. I was able to pump out 1.6 gallons before gas stopped commimg out. I could also hear the fuel pump making a totally different sound. But my gas gauge was reading a little over half tank last night. Now my gauge reads empty.
And the car will not start? makes slight attempt then slight backfire?
Could the remaining gas be in the passengers side tank?
Or does the fuel system ballance itself out automatically, transferring gas from one tank to the other automatically?
If so, how do I get the remaining fuel to the other side?
Maybe my gas gauge was reading wrong in the first place. I do have that problem at times thas why I use techron.
If the gas is all out then I would like to refill and add sea foam.

SStheBest

iTrader: (2)

yes sounds like gas is in the transfer tank....however i dont know how to get that out. Somone with more knowledge than me can chime in.

twospeed

I Drained all the gas that that would pump out of the tank, then and then I added 5 fresh gallons of Chevron and a can of Sea Foam. Car started right up. Gave it gas after it warmed up and car backfired again real loud and large pieces keep coming out of the right side cat!
Next day,
I pulled all the plugs and checked all of them. 1,3,5,7, all look great.
2,4,6,8 not so good! They were all sooted up, and wet with gas (Still wet from last night),
So at this time I don't think it's the Gas being bad.
Wrong call on my part from the beginning.

It appears that either the injectors for 2,4,6, and 8 are dumping huge amounts of fuel With each cycle and foul the plugs. ( Could be, but I doubt it)
Or
Cylinders 2,4,6, & 8 are intermittently firing. Fowling the plugs and allowing a huge amount of unburnt gas to accumulate on the right side Catalytic converter honeycomb, then, after the cylinder does fire, the explosion causes the gas in the cat to go boom and shoot pieces out the exhaust.
What do you think?
Car will idle smoothly now.
But giving it gas starts the backfiring through the right side exhaust again.
The only thing that was changed was that both coil pack harness was retaped after the old tape was removed. Last year some time. ( Now’s not the time for anger and harsh words)
I removed new tubing and tape, all the way back down to wires. One wire had a small skinned area but that was taped over before the harness was retaped. Other than that I can’t see any skinned areas. Coils don’t go suddenly bad in packs of 4, all on one side? New MSD wire set.
How do you check the coil harness for shorts ?
I’m open

twospeed

I put a timing light on #2. It would only flash intermittently. Same for #4 Car backfired againg and I just can't stand that sound of my motor doing that so I just shut it down at that point. Pulled #4 plug, and it was sooted up from running less than a coupple of minutes at most. I cleaned them all after the last time I ran it.
So now I believe it is not the fuel system, or the gas.
The whole bank is not firing correctly?? Cyl 2,4,6, and 8 are firing intermittintly or firing out of the correct order??
Let me ask a stupid question at this point.
Does anybody know what would happen if you connected the coil harness in reverse ? In other words, If #2 cyl was being fired by #8 in the harness instead of #2 ?

Chevy406

iTrader: (12)

You totaly don't want to fire spark plugs are the wrong time. If you spark plug fires with the either the intake or exhaust valve open, where do you think the expanding gases will go? Why do you suspect your coil is reversed? There is only one way to plug the coil harness together. Are you getting any SES codes?

One way to check individual cylinders is to spray WD-40 on the exhaust manifold close to the cylinder. It will evaporate quickly if the cylinder is firing. May be difficult to do if you still have factory manifolds.

twospeed

Found the trouble. When I took the old tape off the passengers side coil harness and re-taped it. I must have gotten distracted and before I could re-tape the harness, I mismarked the connectors. I must have mismarked #8 connector as #2connector.
When I reversed and reconnected the harness the car fired, and runs perfectly.

RedHotG8

iTrader: (1)

Yep crossing wires will do it everytime.

NoTractionLS1

So true!