99 Gt Auto Shutter
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wmburns
SN Certified Technician
Sounds like lock up torque converter shudder.
Have you checked the transmission fluid level and condition?
Sometimes replacing all of the transmission fluid will fix this problem. Use Mecron V or better.
Have you checked the transmission fluid level and condition?
Sometimes replacing all of the transmission fluid will fix this problem. Use Mecron V or better.
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If a tech at a trans shop told you it's not the trans then it probably isn't. It's an easy trans to re-build and for them to make $ on. It's not likely they would turn the work away if they thought that was the problem.
Have you tried changing the plugs? That would be step one for a possible misfire and isn't expensive.
Have you tried changing the plugs? That would be step one for a possible misfire and isn't expensive.
wmburns
SN Certified Technician
Some cars don't set misfire codes easy, some set them when the wind blows in the right direction.
How did the tech know it was a misfire without a code? Did he tell you? You might be able to get a code to set if you get on the highway and just keep making the shake happen for as long as possible. If it happens long enough a PCM will usually throw a code for what it sees wrong.
How did the tech know it was a misfire without a code? Did he tell you? You might be able to get a code to set if you get on the highway and just keep making the shake happen for as long as possible. If it happens long enough a PCM will usually throw a code for what it sees wrong.
squeak93
15 Year Member
Check the coil pack boots for signs of water and the springs inside of them as well. Odds are they are deteriorating. You can buy "rebuild kits" from parts stores. They are easy to do. Basically a boot and the "spring" inside of it. Change those and the plugs and I bet your car smooths out. Worst case it's just good maintenance.
You still have no answered if there are any codes present. Just because there isn't a check engine light, doesn't mean there are not codes present. Any parts store has a code scanner you can use in their parking lot.
You still have no answered if there are any codes present. Just because there isn't a check engine light, doesn't mean there are not codes present. Any parts store has a code scanner you can use in their parking lot.
88CougarMan
Founding Member
Did you ever figure this out? I'm having the same issue, and it feels like a miss to me as well. The reason I say that is, I had MSD packs on the car and one went bad. Found the problem pack and replaced it with my stock one. Started having the vibration issue at highways speeds. Tested it by leaving it in park, and revving to about 2100-2600 and the whole car shimmied. I replaced all my MSD ones with my stock ones and the vibration moved up the rpm range to about 2400-2800 rpms.
Parts I've replaced:
I have Prothane motor mounts that were installed like 15K miles ago.
TQ Converter was sent off and inspected by PI, nothing was wrong
Transmission was rebuilt with new bands/clutches/valve body and drum
Rear end was completely rebuilt, (seals/gears/axels everything)
Transmission mount (Originally thought this was the issue)
Parts I've replaced:
I have Prothane motor mounts that were installed like 15K miles ago.
TQ Converter was sent off and inspected by PI, nothing was wrong
Transmission was rebuilt with new bands/clutches/valve body and drum
Rear end was completely rebuilt, (seals/gears/axels everything)
Transmission mount (Originally thought this was the issue)
88CougarMan
Founding Member
Yeah, its a vibration in the engine definitely. The next step for me is to take off the serpentine belt and rev it to eliminate any accessory pulleys.
88CougarMan
Founding Member
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