eldertek

Have a Stumble on take off from a stop...
Sometimes it stalls, but it starts right back up no problem.
More times it happens on an easy gas start, doesn't happen when I take off fast.
New Fuel pump, filter, plugs, cap, rotor, IAC valve, air filter.
Whenever I Open the Gas Cap, the sound of Air sucking back into the tank is very evident.
Could that be causing the fuel pump to have a hard time getting gas?
1991 Coupe.
AT.

DUB

Hesitation, sag and stumble is defined and outlined in the Factory Service Manual in detail.

Do you have a scanner????

Do you know what the TPS is reading when you turn the key on????

How does it idle???? Did you verify fuel pressure????

Did you possible replace the Oxygen sensor and forget to write that you had????

Possible vacuum leaks.

What type of fuel cap do you have???? It should be the design that allows air to be drawn into the tank and not one that seals up the fuel tank. Maybe drive it (carefully)with the cap loose and see if that changes things...but doubtful. because you did not write if it happens when you first crank the engine...when it is still in OPEN LOOP and the engine is cold and then the problem starts to develop.

DUB

eldertek

Starts up great
Idles great
Dealer says I need a new EGR valve.
Loosened the gas cap and it has not stumbled...went out for about 30 minutes, stop and go etc...

Cliff Harris

You shouldn't have vacuum in the tank. It's much more likely to be pressure. The fuel gets hotter and hotter as you drive because it picks up heat in the fuel rails and then gets recirculated back to the tank. That causes the pressure to go up. There was a thread a while ago on this...

http://forums.corvetteforum.com/c4-t...nk-normal.html

You might have a problem with the charcoal canister and its connections.

eldertek

It's definitely Air going "Back In" the tank!
When I unscrew the gas cap.

GKK

Replace the Charcoal canister located in the rear passenger side wheel well and also, the Vapor canister Purge valve, located in the same location.

DUB

I guess you do not want help...because the questions I asked in POST #2 were not answered...which leaves me to conclude that your reply in POST #3.... is that you are taking it to a dealer and getting it repaired.

I AGREE...and I have seen charcoal material get sucked up into the hose by the valve cover.

Hopefully your local dealer actually has a tech that KNOWS the Corvette. I SERIOUSLY DOUBT that it is an EGR valve....because your idle is fine....as you stated.

AND...TRUST ME....you do not want some 'monkey' messing around with tubed runners and plenum if it NOT required. I repair so many Tuned Port engines due to the previous 'monkey' got in there and hit all the surfaces of the aluminum with a brisket pad and damaged the surfaces....then...they torqued the bolts WAY MORE than required......because the 'monkey' can not take time to read a service manual because he is in such a hurry to make BUCK.....and this action created MORE vacuum leaks than should be legally allowed.

BEST of luck to you.

DUB

eldertek

New Gas Cap. Allows air to get in. Runs Great!!
Took it to the Dealer last week for an opinion.
Thanks for the Solution!

DUB

SO it is FIXED?????

If so...enjoy the ride.

DUB

eldertek

Runs Great!!
Thank you!
New Gas Cap from NAPA, $10

DUB

awesome!

Dub