jbely

I recently purchased a c5 that had been sitting for a few months and started to have a problem under hard acceleration and high rpm. I have already replaced the spark plugs/wires. Also on separate occasions i had check engine lights for oil pressure sensor and misfire. I replaced the oil pressure sensor as well as the knock sensor. The misfire was for cylinder 3 so i bought a coil and the problem did not go away. I put a new injector in cylinder 3 and the misfire has seemed to go away, idle is much smoother and the engine seems smoother all around. However, the stalling and backfiring problem is still happening. I am stuck and do not know where to go from here.

neutron82

does the car have any mods?... when you changed the plugs what kind did you use and what gap?... what octane gas?... assuming that nothing else is mechanically wrong, a few months sitting isn't very long but if the car spent most of it's life being driven gingerly then it's possible there may be some carbon buildup on the pistons and valves that create problems under heavy acceleration... you might try running a can of seafoam through the intake to burn off any residual carbon then take it out for a spirited drive to blow the excess out

jbely

Already ran a can of seafoam through it, using 93 ethanol free. Gapped per factory recommendation .060.. That is possible the man i bought it from was an older gentlemen that had cancer who was/is a cop. stock as far as i know except for a shitty cat back, also this may be unrelated once when it was running rough there was a slight rattle coming from the cats it seemed.

neutron82

what plugs?... try gapping them to about .040 and see what happens

jbely

AC Delco Double plats, will try that

runner140*

I'm thinking after three months, condensation in the gas tank....bet its the gas.

vettenuts

No sure you can regap the iridium plugs, don't think it is recommended. I would just get a set of NGK TR5 plugs.

If you hear rattling in the cats, they may be broken up inside and blocking exhaust. Doubtful but possible.

New Era Performance can clean and calibrate your injectors. I had them do a set and they came back great.

Three months is not long, mine sits for six months every year due to weather in the northeast. It is likely something simple.

mmartinez

Just a thought, could be you are hitting the rev limiter?

jbely

No it normally cuts out right around 45-5K, and stalls out completely

mmartinez

You had stated high revs, but did not give a number, so I thought maybe it was the rev limiter. I know that forum members are usually trying to obtain advise and help repairing their cars themselves, but have you thought about taking the car in to a reputable corvette repair shop or tuner shop.

mike venth

Just a thought but, could be that the fuel filter is never been replaced or is a little clogged from sitting..
mike v

Bill Curlee

ABSOFRIGGENLOOTLY! Change the fuel filter. You can also CLEAN your own injectors. Its easy and can restore their performance if they are just dirty:

There is an entire You Tube world on cleaning injectors:


YES, regap the plugs to 0.040

What wires did you install??

jbely

Fuel filter has already been replaced, taking it somewhere is the next step. I am just not sure how much that will help since it is not throwing any codes/ check engine lights. I feel like it is something electrical that is loose or something of that nature. Wires are napa belvins.

neutron82

check the plug gap before you take it somewhere, .020 may not seem like a lot but can make a ton of difference in how the car runs