Need help!!!
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.

 

So what is your question?

 

Caused enough pressure to blow the honeycomb mat'l out.......hmmmm could surely be your shop rag

 

bad O2 sensor maybe or wiring to it, flooding the cats with gas, that will blow out the catalyst

did it look like this? http://www.youtube.com/watch?v=tDvmjk6LHYU

 

The likelyhood of a shop rag going from the intake through the engine and coming out the tailpipe seems pretty remote-I would think it would really jazz things up trying to get through the intake valves. Maybe a compression test is in order to see if all the cylinders are up to snuff. If one cat did this, my guess is the other is on it's way out too.

 

Maybe rodents were making a "white shop towel" nest in the exhaust?

 

Sticky fuel injectors. Had this problem with a Miata I bought years back. Car had been sitting for years since the owner died. A fellow club member had spare injectors from upgraded to a super charger. Popped the OEM ones in and I was good to go. You can get the injectors serviced but in my case free was cheaper.

 

Thats my guess. If so, your lucky that the motor didn't hydraulic lock and can even break off you starter from the block. Right BC

 

Hey feeder82,
The video link you posted, was right on, That's exactly what happened. Only just one bang everything else the same!
Have added one can of Heet and one can of fuel injection cleaner to fuel tank.
Let it sit overnight.
The idle has really smoothed out, no backfireing on startup.
Hand on shifter when idling, still vibration but less than half of what it was.
Engine was always rock solid.
The reason I said it may have swallowed a rag was because of the crap on the ground mixed with the ceramic pieces from the cat. Now I'm not so sure, maybe what looks like white cotton is part of the blown out cat?
Been idling for 25 minutes a day, car gets smoother each time.
Still blowing some crap out of right exhaust on ground. So more pieces of cat still in exhause I can hear then rattling aroung inside of the pipe.
I think I am going to bite the bullet and jump the fuel pump and drain the gas that way.
Trying to drain the gas by idling is not working, I still have just a tad over a half tank.

 

get some Red Line total fuel system cleaner and also Red Line injector cleaner, put a bottle thru and give it a chance to free up the injectors. You might consider changing out the injectors at some point but I'd start with the red line.Good luck

 

I jumped the fuel pump relay according to directions that I found on this site. 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. Now the gauge reads empty.
But my gas gauge was reading a little over half tank last night.
Now the car will not start? It makes slight attemptto start then slight backfire? Acts like its out of Gas! But like I said I got 1.6 gallons out and the gauge read a little over 1/2 tank last night??
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.

 

If you still had some bad gas in it chances are you gumed up the injectors a bit. ( did you change the fuel filter? didnt see that above). I'd check out the undercar wiring and look for rodent damage and pull the whole fuel rail and have the injectors serviced. There are cleaning services out there for decent money.

 

I think these cars have two pumps, one for each side.

I have had my hands on several cars that sat for years and although the gas is not much good, if you add some octane booster and drive the crap outta it on the highway it will "eventually" smooth things out.

Letting an engine sit is not the greatest thing one can do.

I dont know exactly how it sounds or whats going on, but if it were me I'd bolt it all back together, replace, disconnect, or remove the cats, and drive it in 4th or 5th gear on the highway for a good bit (or D if its and auto), with occasional full throttle accels.

Oh, idling is not great for it either, just drive it. If something breaks you'll know what was wrong so you can fix it

 

Sounds like u may have a fuel pump problem,do u have a gauge on the car ? When u give it gas will it take it ?anytime u let a car sit for a long period of time its not good for it,I just had a similar issue,the car had another motor put in it & the car has not been running in over 1yr, come to find out it would idle fine but when u gave it gas it wasn't keeping the 58 psi like its suppose to,put another 255 ltr pump in it & problem solved

 

Geeze, if it's got lots of room in the tank then FILL IT UP FULL with some new good gas. It should begin to run better once the new gas gets pumped up to the engine and if it doesn't then you can start troubleshooting the problem. I also agree with the get out and drive it comment.

Peter

 

Like I already posted 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! I got dark and did not want to simulate gun shots at night. These things can freak the neighbors out at times!
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

 

Check engine light?
Codes?

Sounds like time to get a scanner on it and read the O2 signal and PWM duty cycle of the injectors to get some hint. Also, get a test light to check if there is a consistant spark or not on those cylinders (you can clip a timing light to each wire and see if it flashes consistantly or not). You can also pull the injector rail set and then cycle the pump on and see if any leak fuel. It's not likely that 4 on one side are leaking and the other 4 are good though. to me, sounds like Feeder is correct and the main O2 on that side is bad and giving a false lean signal.

since you did mes with that wiring harness then check the connectors over to see if there is a problem you caused there, such as pulling a wire or pin out of the connector.

Peter

 

I put a timing light on #2. It would only flash intermittently. Same for #4Car 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.
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 ?

 

it would foul the plugs and backfire.

 

No offence intended but, could you elaborate a little on that.
I 'm trying to take your reply as serious, but I'm looking at your avatar of a dog whith a human face on it. Work with me here.
Do you have actual experience with these motors or are you guessing.
Like I stated I do not want to offend you, just confirming the information as accurate before I have to take the harness apart, to test, I know you can understand that.