Car vibrates at idle, RPMs fluctuate.

[Dbeck002]

When I start the car up i feel a weird vibration coming from, well, I dont know where. it just feels like a really profound vibration every second, lasts for about a second and then stops, then comes back.

like vvvvmmmmmmm stop vvvvmmmmmmmm.. not really loud, but i can feel it. its starting to get on my nerves, i feel like something is wrong with my baby and i dont know what. could it be the tranny going?

Also, RPMs at idle are a litle bouncy, and i can tell the RPMs have something to do with the vibrations, because the RPMs will drop from 700 to 600 when i feel a vibration and then back to 700 to smooth out, then vibrates and drops again. So im not sure what it could be.

TPS shows .9 volts too BTW. could it be the IAC?


BTW its a 91 LX 5.0 with T-5 and lots of mods.


thanks all

 

[90mustangGT]

Sounds like a vaccume leak, that would be the first thing I would check. If it isn't a vaccume line obvously, try spraying some solvent on different parts, if the car smoothes out right there, then that is where the leak is located.

 

[9250stang]

Or you've got a big dirty cam in there you don't now about.

Check TB connections, all Vacuum lines on back on intake. Most likely find problem there.

 

[Dbeck002]

Thanks for the replies, I checked everything 10 times and I could and couldnt find the vacuum leak. I dont know where it could be coming from

 

[jrichker]

See the Sticky at the top of the forum "Help me create the Surging Idle Checklist" for help with idle problems.