Question: 82 corvette acceleration hesitation

[allenc74]

I have had my 82 (crossfire injection) vette in the shop and we are having a hard time solving this problem.

It starts up and idles fine with no problems. When I push the gas while it is in parked the RPMs increase like normal with no hesitation. It is when I have it in drive and am accelerating from low RPMs (like from a stop) the engine bogs down as if it was going to die. If I push the gas farther it will then take off and run fine.

Not sure if anybody here has had the same problem or has any ideas for me to try.

It has been through a full tune-up including plugs, wires, cap, rotor, filters......

 

[Hib Halverson]

Ok...so the engine sags when you open the throttle with the engine under load.

Have you run or had your mechanic run the fuel pressure tests listed in the Factory Service Manual?

When was the last time the fuel filter was replaced.

Has the TPS been checked and/or adjusted to spec?

Does the check engine light come on and go off during bulb check after key-up?

Does the check engine light stay on when the engine's running?

 

[allenc74]

Ok...so the engine sags when you open the throttle with the engine under load.

Have you run or had your mechanic run the fuel pressure tests listed in the Factory Service Manual?

When was the last time the fuel filter was replaced.

Has the TPS been checked and/or adjusted to spec?

Does the check engine light come on and go off during bulb check after key-up?

Does the check engine light stay on when the engine's running?

Thanks for your reply. The fuel filter was just changed about a week ago with the tune up. The check engine light does not come on while running. I will have to look into the TPS and the fuel preasure.

 

[jdp6000]

Thanks for your reply. The fuel filter was just changed about a week ago with the tune up. The check engine light does not come on while running. I will have to look into the TPS and the fuel preasure.

Mine was doing the exact same thing. It was the fuel pump.

Jim

 

[geekinavette]

Does the check engine light come on and go off during bulb check after key-up?

This is important...if that "bulb check" does not function as Hib describes then all bets are off as far as the ECM is concerned.

When you check fuel pressure...it is not enough to just look at it while idling or under no load...you MUST know what it is doing under load (a common problem with 82 & 84 stock fuel pumps).

If everything mentioned checks out and you still have the symptom...look into the throttle bodies being out of balance and/or worn throttle shaft bores. This along with fuel pressure are the most common causes of what you describe.

Not necessarily related, but also make sure your Coolant Temp Sensor is not falling apart (the one in the front of the intake manifold). If it has not been upgraded to the 2-wire version, then plan on doing that.

 

[allenc74]

Mine was doing the exact same thing. It was the fuel pump.

Jim

I finnaly got the problem solved! It was indeed the fuel pump. Just like geekinavette said, "When you check fuel pressure...it is not enough to just look at it while idling or under no load...you MUST know what it is doing under load (a common problem with 82 & 84 stock fuel pumps).
"

Prior top reading this, the fuel preasure was checked with no load and came back with good preasure.

Thanks for everybodies help!

 

[geekinavette]

:cool

 

[Gohot]

This hesitation

I have something of the same problem on an 82. If I floor it, it bogs, rather it seems it looses fuel, recovers, or maybe bogs again and then accelerates like regular. I don't know if this is something or not, but as this happens (full throttle acceleration) it almost seems the throttle peddle cant be pushed all the way, or there is something blocking full peddle pushing. It reminds me of traction control that I had on my 94 LT1 and on my 94 Supra. It always happens so fast, I can't mentally compute fast enough lol.... But as I say, it feels like you can't push the peddle all the way, like it's being blocked, and the bogs and then acceleration like it should accelerate once past these two occurrences... Anybody want to comment on this. I have a new fuel filter that I got. I will install it and see if that cures the bogs. Mind you these 'bogs' aren't like carburetor bogs, they are like mechanical bogs, or injector hesitations/fuel loss????