Hard Shake/Shutter on launch

[bpaultra]

I have a 1998 Buick Park Avenue Ultra 3.8L Supercharged. I am getting this really hard shake/shutter from the front end when I take off from a stop light. So when the car is at idle from a dead stop, if you give her significant throttle, it wants to pause for a second and then hard drop almost like the engine is slamming against the frame. Then shakes violently to tapering off the shake fairly quickly and starts to accelerate. I have been disabled for the last 5 years and I can't get as immersed into a problem like I used to. But I just cant figure this one out. This had to have happened to someone else I am hoping.

 

[MelsRegal]

Do you have a check engine light on?

 

[bpaultra]

Do you have a check engine light on?

No check engine light is NOT and does NOT come on. Which is driving me nuts. I believe the check engine light does work, because I just had issues with coils and it worked for them.

 

[MelsRegal]

Did this problem start after you resolved the coil problem?

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[bpaultra]

Did this problem start after you resolved the coil problem?

It was happening before coil issue and after.

 

[Alan 55]

It was happening before coil issue and after.

What is the status of your motor mounts? It sounds like you could have one or more defective mounts. They are easy to test, I will describe the procedure if you like.

 

[bpaultra]

What is the status of your motor mounts? It sounds like you could have one or more defective mounts. They are easy to test, I will describe the procedure if you like.

yes, that would be great. I need to get up close and inspect. Just difficult right now.

 

[Alan 55]

yes, that would be great. I need to get up close and inspect. Just difficult right now.

To inspect the mounts, an assistant will be required. One person will be behind the wheel in the vehicle. The other person we will call the observer will be over to the drivers side of the car. Hood is open, assistant starts the engine and holds the brake petal. Observer never gets in front of vehicle but remains alongside looking at the engine. Driver holds brake and puts the gear selector first in drive then reverse with engine at idle. Observer looks for the amount of “pitch” or movement of the engine. There will be some movement but not excessive. The mount that gives the most problems is the front mount on the drivers side. In most cases this is the easiest mount to observe as the others are much more hidden. The driver should repeat this test multiple times by shift from drive to reverse as the observer views the front mount as well as the overall amount of movement of the engine. Please follow safety measures by never getting in front of the vehicle during this test.

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[bpaultra]

To inspect the mounts, an assistant will be required. One person will be behind the wheel in the vehicle. The other person we will call the observer will be over to the drivers side of the car. Hood is open, assistant starts the engine and holds the brake petal. Observer never gets in front of vehicle but remains alongside looking at the engine. Driver holds brake and puts the gear selector first in drive then reverse with engine at idle. Observer looks for the amount of “pitch” or movement of the engine. There will be some movement but not excessive. The mount that gives the most problems is the front mount on the drivers side. In most cases this is the easiest mount to observe as the others are much more hidden. The driver should repeat this test multiple times by shift from drive to reverse as the observer views the front mount as well as the overall amount of movement of the engine. Please follow safety measures by never getting in front of the vehicle during this test.

Yeah I had somebody comment on how he thought there was excessive vertical movement of the engine on reving. But do you think that would cause the radical shaking on launch?

 

[BuickGirlFromMars]

I would put money on your left trans mount(front of car, on the craddle, is on the right side near ABS unit.) or your Torque Axis Mount (TAM) which is on the front of the engine(serpentine drive, mounts through the belt drive and is right by the water pump). The TAM Is now produced aftermarket and also its possible, but spendy, to convert to the 2000+ design which uses a hydraulic mount like the 2000+ park avenues

The forward one did a shutter at speed for me when it was bad, and my torque axis mount caused shaking proportional to load because a stud was broken and it pivoted on the remaining stud rather than be solid

 

[bpaultra]

I would put money on your left trans mount(front of car, on the craddle, is on the right side near ABS unit.) or your Torque Axis Mount (TAM) which is on the front of the engine(serpentine drive, mounts through the belt drive and is right by the water pump). The TAM Is now produced aftermarket and also its possible, but spendy, to convert to the 2000+ design which uses a hydraulic mount like the 2000+ park avenues

The forward one did a shutter at speed for me when it was bad, and my torque axis mount caused shaking proportional to load because a stud was broken and it pivoted on the remaining stud rather than be solid

are we talking this, which is 1998, vs This? And do I have to change out the bracket mounted to the engine or the tranny? Then if yes the next question would be does the new arm/bracket bolt up the same?

 

[BuickGirlFromMars]

For 1997 1998 1999 Buick Park Avenue 3.8L 5237 Front Right Engine Motor Mount | eBay THIS IS YOURtorque axis mount in a 98. 2000+ use the bottom photo mount just like on the driver side wheel well. The driver side wheel well in a 98...should? Have the bottom one? I think it does. The front of the engine, technically trans bay, is the top mount you posted

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[bpaultra]

First of all I want to say thank you to everyone who posted a reply. I believe I have it fixed. Time will tell. I may in the future change out the TAM from 1998 model to 2000+. Problem is I already ordered part before I learned of new mount. Also looked into it had hard time finding alternate bracket. But anyway, has been replaced with stock and I will just have to keep my eye on it. The hard shake on launch now I believe to be contributed to the triple ignition coil pack. Many months ago I had a feeling they might be the issue and I traded them out with another 3800/3.8L. And this is why you should never use used parts to diagnose an issue. They were both bad. I had a friend hit me in the back of the head with a ball peen hammer and swapped out one coil pack with another. Because I refused to believe that was the issue. And it did something different. Epiphany moment..... and I broke down and bought all new 3 coils and TADAH!!!! it works like new. Hopefully this is permanent fix. Again thank you everyone. Without insight I would be lost. I think the take-away here is when you do a light tune up, change out coils, (with new ones...lol). Rock auto has descent enough prices not to include the coils. Will make diagnosing much easier. -BPAUltra

 

[BuickGirlFromMars]

First of all I want to say thank you to everyone who posted a reply. I believe I have it fixed. Time will tell. I may in the future change out the TAM from 1998 model to 2000+. Problem is I already ordered part before I learned of new mount. Also looked into it had hard time finding alternate bracket. But anyway, has been replaced with stock and I will just have to keep my eye on it. The hard shake on launch now I believe to be contributed to the triple ignition coil pack. Many months ago I had a feeling they might be the issue and I traded them out with another 3800/3.8L. And this is why you should never use used parts to diagnose an issue. They were both bad. I had a friend hit me in the back of the head with a ball peen hammer and swapped out one coil pack with another. Because I refused to believe that was the issue. And it did something different. Epiphany moment..... and I broke down and bought all new 3 coils and TADAH!!!! it works like new. Hopefully this is permanent fix. Again thank you everyone. Without insight I would be lost. I think the take-away here is when you do a light tune up, change out coils, (with new ones...lol). Rock auto has descent enough prices not to include the coils. Will make diagnosing much easier. -BPAUltra

I had a coil pack with a rusted contacts and it would only misfire under load/boost. Glad you fixed it. Im changing my TAM today, the old style. The newer style requires an aluminum pan that the bracket connects to I believe. Then the bracket on the engine side, the car-side bracket, then the mount itself. Then of course, bolts to go with them.