98 3.8 Vibration in park and drive with foot on brake

[Ratchet]

Firebird 98 3.8 v6 auto Car vibrates the dash apart when at a stop light with my foot on the brake. Shift into neutral, foot on brake, still vibrates. Foot on brake and rev up to 1000rpms and the vibration disappears. The rpms dont bounce when its vibrating. Sometimes the vibration feels like a pulsating. Still you would think the RPMS would pulse but they dont. Theres no vibration during driving, just while stopped. When I shift into different gears, the vibration lets up while it shifts and then starts again.

Coil packs and ECM plugs and wires are all brand new.
Motormounts and trans mount are new.

ideas?

[ssms5411]

Re: 98 3.8 Vibration in park and drive with foot on brake

Vacuum leak maybe.

[ACiFiC]

Can you take a video or anything?

[Ratchet]

Re: 98 3.8 Vibration in park and drive with foot on brake

I dunno that a video would show vibration. The RPMS dont move unless I shift the trans or rev on the gas so that makes me think its not an idle problem. Im not throwing any codes. its just wildly annoying. It vibrates the seats and change in my ashtray.
What kind of vacuum leak? EGR?

[techsan23]

Re: 98 3.8 Vibration in park and drive with foot on brake

Might check the condition of the rubber on the harmonic balancer.

[FIREBIRDV6RAGE]

Re: 98 3.8 Vibration in park and drive with foot on brake

i have the same prob . idk what it is so i just drive like that i do throw a code tho for mr my bank 2 sensor isnt operating righ for some reason.

[ssms5411]

Re: 98 3.8 Vibration in park and drive with foot on brake

Might check the condition of the rubber on the harmonic balancer.

X2 I forgot about that, mine was pretty bad when it went out.

[FIREBIRDV6RAGE]

Re: 98 3.8 Vibration in park and drive with foot on brake

i just got done cleaning my throtle body like 2 hours ago. and it some what stoped , also it only starts when i drive alot and the engine starts to operate at 210 temp.

[Ratchet]

Re: 98 3.8 Vibration in park and drive with foot on brake

i just got done cleaning my throtle body like 2 hours ago. and it some what stoped , also it only starts when i drive alot and the engine starts to operate at 210 temp.

Mines different. It will vibrate with the engine cold or hot. Doesn't change w engine temp or length of operation. I forgot to say I did an L26 swap n left the L26 balancer on. Could that be the source?

[ssms5411]

Re: 98 3.8 Vibration in park and drive with foot on brake

Mines different. It will vibrate with the engine cold or hot. Doesn't change w engine temp or length of operation. I forgot to say I did an L26 swap n left the L26 balancer on. Could that be the source?

Did you do a case relearn with the L26 balancer?

[Ratchet]

Re: 98 3.8 Vibration in park and drive with foot on brake

Did you do a case relearn with the L26 balancer?

No didnt do a case relearn Ill call and see how much that costs at the dealer.. Could it be the torque converter? Maybe i need to rotate it on the flexplate? I didnt mark them when I took them apart, so maybe they are off balance?

[thebeewantsboost]

Re: 98 3.8 Vibration in park and drive with foot on brake

maybe its your tires. JK
I dont think the flexplate and TC can be installed incorrectly. does the harmonic balancer shake\wobble when the motor is running? did this start immediately after your l26 swap. i dont believe the CASE learn will be beneficial. in my experience, when a case learn is needed. it will either give you a legitimate misfire. that would leave a code. or not physically effect the way it runs but still give you a code. p0300 multiple cylinder misfire.... my experience with case learns is only with s10's though.

[Ratchet]

Re: 98 3.8 Vibration in park and drive with foot on brake

maybe its your tires. JK
I dont think the flexplate and TC can be installed incorrectly. does the harmonic balancer shake\wobble when the motor is running? did this start immediately after your l26 swap. i dont believe the CASE learn will be beneficial. in my experience, when a case learn is needed. it will either give you a legitimate misfire. that would leave a code. or not physically effect the way it runs but still give you a code. p0300 multiple cylinder misfire.... my experience with case learns is only with s10's though.

its not my tires. it smoothes out at 1000rpms. If I sit in park and put my foot on the gas and get the rpms past 1000 it stops vibrating. It started right after the swap and has gotten worse. Ive noticed when sitting on an incline its worse. The balancer shows no movement when looking at it while running.

[Ratchet]

Re: 98 3.8 Vibration in park and drive with foot on brake

My car is still vibrating like crazy. Here is everything i have fixed since this thread was started.
New Harmonic balancer (98-02 balancer)
New Transmission mount
New Plugs and wires
New Fuel filter
Rotated the flexplate to see if that changed the vibration didnt help.
Also inspected the flexplate for stretched bolt holes. They are fine.
Took the serpentine belt off and it didnt change the vibration.
Checked the exhaust and its not touching the body.
Car has new motor mounts, motor doesnt move under acceleration. Mounts have been double checked to be tight and bolted down correctly.
Car vibrates no matter what gear its in.
Car does NOT vibrate while going down the road.
Only vibrates at a stop with the foot on the brake or at a stop in park. If i rev the engine in park/Drive at a stop over 1000k the vibration goes away.
Im at wits end with this thing. I drive it 100miles daily to work so it isnt hurting the reliability, its just annoying and embarassing to be vibrating at every light and stop sign.
I jacked it up lastnight and started it and when i put my hand on the transmission pan you can feel the vibration, but its stronger on the engine oil pan. I even took the dust cover off the flexplate and watched it spin and its not wobbling.
Im not getting codes or and SES light. This has me stumped.

Next things to check are fuel injectors and cat converter. Any other ideas guys??

[ssms5411]

Re: 98 3.8 Vibration in park and drive with foot on brake

Again, did you do a case relearn on it?