stingray454

Help! First mechanical problem I've had with my Z in 6 years and 40k miles of ownership. Here's what happened:

- Left the house for work, drove 10 block to gas station, took about 14 gallons of premium. Car ran fine the way to the gas station.

- Within 2 blocks of leaving the gas station, I noticed while accelerating the car seemed to be down on power and running rough. Went a couple of more stop lights, and definitely noticed it wasn't running right. Felt like at least 1, maybe 2 cylinders weren't firing. If I revved past 2,500, it felt like the dead cylinder came back to life a little, and it smoothed out a little, but still not right. Felt like it might stall, but it never did. It idled rough, but wouldn't stall. Some additional backfiring on decel too.

- No check engine light

- As soon as this happened, I noticed a horrible exhaust smell, like very strong sulfur / rotten egg smell. Didn't smell like unburned fuel, just a really foul sulfur smell. No visible smoke from exhaust.

I drove back home, parked the Vette and took the Suburban to work.

My questions are:

- Could bad gas enter the system so quickly? It was only 2 blocks from the station that it started to act up.

- What else would cause this? I'm fearing broken valve spring, but there were no unusual noises from the engine. I thought maybe a bad coil or plug wire, but there was no check engine light, meaning no codes. Maybe I didn't drive it enough to set the check engine light?? If there is a misfire, does the CEL come on right away?

Thanks in advance for any assistance.

Bigstik

i would think that if it was a misfire, or a cylinder wasn't firing, the CEL would come on and tell you. I can't remember, but you would definitely know if that was the case. Plus I don't think that would account for the smell......Maybe you put diesel in by accident

Z06_BluByU

take it to a qualified repair facility.. if it is bad gas approach the station manager/owner for a refund of the fuel and repair bill.. (that is if you didnt put 87 or diesel in to it).

stingray454

I definitely didn't put diesel in it - the diesel pump nozzle is too wide to fit in the filler neck. My Suburban is a diesel so I know. I don't think it would run at all if I had diesel in there - I had 2 gallons remaining before I filled it. I don't think I would get far if I had 14 gallons of diesel in there.

Now whether the station mixed the tanks up between the fuels, I suppose that's possible. I'm gonna check all the plug wires tonight when I get home and start with that, then start pulling plug wires one at a time to check the coils. If that doesn't reveal anything, then I guess a compression test is in order.

Crowder13

could be clogged cats

KenHorse

You said you put in 14 gallons. As the Z has 18 gallon capacity (thereabouts), is it possible you stirred the pot so to speak?

I'd have the fuel pressure checked AND the fuel filter

AU N EGL

High surfer fuel? or blown out cat

stingray454

I thought the Z had a 16 gallon tank? I don't think I stirred the pot as I always run it to near empty before fillup, so there shouldn't be any residual gunk in the tank. I haven't changed the fuel filter yet on the car, and its got almost 40k. I actually have the new filter sitting in a box in my garage, just haven't gotten around to installing it. This event may expedite replacement.

BlackZ06

The C5 Corvette (all models) has a two tank fuel system .... unlike most cars that have a single tank.

The left tank fills first, and is also the tank that is drained first, so YES, bad fuel (especially fuel with water in it) could easily cause the problems you describe.

I'd recommend you see what, if any, DTC have been set. Go here if you need instructions on how to display the DTC set in your car ...

https://www.corvetteforum.com/techti...D=26&TopicID=1

Post the DTC that are set and someone will help you diagnose/fix the problem.

tech43

Plugged Cat-converters.

Milan

Plugged cats or maybe you put diesel in it. Although that's almost impossible because the nozzle is twice the size.

stingray454

What would cause plugged cat converters? Is that a known problem on these cars? I don't recall reading anything about that.

I had a '96 Ford Contour that had defective pre-cats (common defect with those cars) which disintigrated and plugged up, and it had different symptoms. The engine ran smoothly, but had a major loss of power and knocking, along with a check engine light, no unusual odors.

heavymetals

Dump the gas (YEOWWW!) and start over.

You could have burned out a cat with contaminated fuel.

Your wiring didn't go bad after a fill-up.

BlackZ06

First ... go back to my post #9 above ... are there any DTC set ??????

Second ... why does a guy in NY have an avatar picture of a Corvette in turn 4 at Willow Springs in California ??

Finally ... most engine DTC require 2 ignition cycles before they turn on the CHECK ENGINE LIGHT .... if you display the DTC data the PCM will help point to the source of the problem ......

stingray454

OK, got home and started with checking all the plug wires. Sure enough, one of them was off, hanging on the plug by the metal heat shield. Pushed it back on, and runs good as new again. Duh. How it got loose I have no idea, but it did. Just a weird coincidence that it fell off right after I got gas. But, I got lucky, so I'll take it!

I'm surprised that the unburned fuel from just 1 cylinder not firing would make such a foul sulfur smell from the exhaust, but that went away too with the plug wire back on.

Thanks to everyone who replied - appreciate the assistance and suggestions.

You know your tracks! I used to live in Newport Beach, CA, but I had to move back to NY for job reasons unfortunately. That shot was taken in 2003.

ZeeOSix

It actually has an 18.5 gallon fuel capacity.

ZeeOSix

It doesn't take much unburned fuel to get the cats stinking.

So apparently if a plug wire comes off there is not DTC set?

cobrakraiger

Glad to hear it was such a simple fix!

wingman0330

it was probably bad gas that fouled out you're spark plugs. Check you're spark plugs if they are fouled they will look very black. I had a similar problem with one of my cars I changed the spark plugs and it seemed to fix the problem.

heavymetals

Guess wiring can go bad after a fill up.

Glad it was easy.