Lack of performance after half throttle

[my81c3]

My 81 is my first experience with a computer-controlled system (and, as luck would have it, the first year in Vettes too). Original engine has 81K on it, and runs decently up to half-throttle. After that, I feel the secondaries open, I HEAR the secondaries open, but the car won't accelerate any faster and just sounds like it's dumping gas thru the carb and not going anywhere. Is this the result of computer control (as someone has told me), or something else??? I was going to change the plugs and wires, but nothing seems amiss and it idles and runs smooth otherwise. Any hints, or do I just wait till it expires eventually and then go get myself a crate motor to get some power?????

 

[Yoda]

First.. Welcome my81c3 to the Corvette Action Center Community ..

Second.. NICE photo in your avatar

Third.. Isn't Retirement GREAT

I don't know what is causing your condition, but I can tell you that when my Quad Opens it's like someone gave her a boot in the butt 1st or 2nd (4-speed) I can mash the go pedal and break the rear tires a bit, enough to bark'em

Hopefully someone that knows engines will chime in, I'm not an engine person by any means..

Welcome aboard enjoy the

Bud

 

[my81c3]

Thanks. Pic was done by my son, who works at KSC (took my car out of the garage while I was out of town and posed it by the launch pad). Retirement's especially good, when mixed with a Vette and sunny days. Good to know it's not everybody's problem, just mine. Guess I'll see if any engine techs chime in with some easy diagnostics. At least half the fun is still there with a 4-spd, so I can at least wind up 1/2 way in each gear!

Len

 

[Yoda]

Len,

Yea, even out on the highway, when I kick Rare down, she acts like she steps into a passing gear, there's even a noticable "jump" ... My ole pal BlackDog can vouch for this :dance

Hopefully you'll experience the same "Thrill" once you get this all worked out..

I'll move this up into the L81VetteRegistry Forums, for a bit and see if any of the guys up there chime in... Between GerryLP, Big2Bird, Sensei , Bill, 6880 Mike, SIXFOOTER, Peer81 and MANY others that escape me now, should be able to help you

Bud

 

[Fast Freddie]

reminds me of a fuel delivery issue. unless you have access to diagnostic equipment, i would start out cheap and replace the fuel filter. then possibly look into restricted exhaust.

 

[my81c3]

Thanks for the assistance, Bud. Once I get it running like it should, it'll be like having a new toy instead of playing with a worn out one.:J
Freddie, I know the filter hasn't been changed in some time so that's a possibility, though it doesn't feel like fuel starvation -- feels and smells like it's taking it all in, just bogging down and not going anywhere. We'll check that out, though. Guess checking the timing won't hurt, either.

 

[Barry08]

Could be a lot of things.Timing,partially plugged cat,fuel filter,air filter,worn out camshaft,check for trouble codes.The 81 is no big performer from 4000 to 5000 rpm anyhow,power seems to drop off after 3500.

Good luck

 

[spikebot 81]

My first thought was the cat starting to plug up.

 

[my81c3]

Thanks, all, for the tips and advice. Unfortunately, the car is stored about 15 miles away right now while we do some major house renovations, so I can't get to try anything for a few months or so. However, I did buy an NOS converter shell (no beads, etc.) to swap in, as well as a "test pipe" to try to see if the problem is a plugged converter. Should be a no-brainer swap out. I'll report back in few months when it gets done and we'll see if that was the problem.

 

[Peer81]

Sorry for my late reply.
I think the carb issues are more in the corner of Sensei and Sixfooter but I'll try to give it a go.
The primaries are computer controlled. The secondaries kick in around 70% to 80% of full power and the secondaries aren't controlled by the computer!
Sorry I can't give you a direction to look for the problem,
Good luck and enjoy your 81!

Groeten Peter