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Clayso
Clayso, Master Automobile Technician
Category: Pontiac
Satisfied Customers: 880
Experience:  ASE Master Certified Automobile Technician. 30 Years Experience.
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I have a 87 pontiac firebird when I startry it up it runs

Customer Question

I have a 87 pontiac firebird when I startry it up it runs smooth but when I give it gas it shakes more like a vibration and it does it going down the road when I give it gas
Submitted: 9 months ago.
Category: Pontiac
Expert:  Clayso replied 9 months ago.

Hi There, I'm Clayso a certified master automobile technician with 30 years of automotive repair and diagnostic experience.

From your description sounds like an ignition misfire under a load. How old are the plugs,wires, cap and rotor button?

Let me know

Thanks

Customer: replied 9 months ago.
replaced plugs, the wires, and the rotor button and distribution cap
Expert:  Clayso replied 9 months ago.

That's cool. Have you verified fuel pressure?

Fuel Pressure
Key On 40.5-47 psi
Idle 30.5-44 psi

Customer: replied 9 months ago.
I was told it might have a cracked fly wheel
Expert:  Clayso replied 9 months ago.

A cracked flywheel would definity cause a vibration. Automatic or manual?

Customer: replied 9 months ago.
automatic
Customer: replied 9 months ago.
I can start it up and runs smooth like a baby but when I give it gas it starts to vibration
Expert:  Clayso replied 9 months ago.

Cool. Unbolt the torque converter and push it back into the transmission. Start the engine and see if you still have the vibration. Also with the torque converter back you can flex the flywheel, might even be able to see up to the flywheel bolts. Flywheels usually crack around the bolts to the crankshaft.

Expert:  Clayso replied 9 months ago.

This would also eliminate the torque converter as a possible cause also.

Customer: replied 9 months ago.
ok thanks would there be anything things else that u might think can cause it so I can check
Expert:  Clayso replied 9 months ago.

There's always the vibration damper on the front of the crankshaft to consider, as long as it's coming apart or separating it should be ok.

Expert:  Clayso replied 9 months ago.

You're welcome. Let me rephrase, as long as the vibration damper is not coming apart, and I'm sure the timing has been checked and being that the timing mark is on the damper I'd say it's ok.

I hope this information has been helpful. You can reply back to me through this thread at any time.

Kindly rate my assistance in a positive manner so I may have credit for helping you.
Positive ratings are greatly appreciated.
Thanks.

Expert:  Clayso replied 9 months ago.

Hi There,

Just checking to see if you found the vibrations source. Let me know.

Thanks