allright.. thx for coming


a few weeks back... my '95 Trans Am started stumbling at low rpms and... when the engine turns at low rpms, the whole car shakes

anyway... just taking a guess... i figured it was the optispark... so i replaced that.....

but the low rpm stumble-and-shake is still going on


do any of you guys have an idea what this might be?

maybe i should replace the coil as well?

thx for any help

 

Possible the EGR valve is stuck open?

 

IF your car is a 6spd you might want to check the pilot bearing, that was what my problem was I replaced the opti and the plugs and wires. Pilot bearing fixed it, it bounces around or sumthing at low rpm, our cars come with brass pilot bearings, get a roller bearing. Does your shifter shake at the low rpms as well?

 

Have you checked out your plug wires?

 

That could be anything from electrical to chassis related, start eliminating possibles. good luck...

 

thx for the help so far guys


plugs and wires were changed about 2k miles ago


excuse my ignorance.. but i don't know what a pilot bearing is... please enlighten me



and an update to the problem.... it would seem that at around 1500 rpms, at WOT in any gear.. the engine will backfire... the backfire sounds like it's happening inside the drivers side manifold


please keep the help coming

 

A pilot bearing is what is in the middle of the flywheel, its a tiny spacer the holds your transmission shaft to the fly wheel. You may want to check for an exhaust leak, If your car is an OBD1 you may want to block the egr and remove the AIR system(pipes coming out of the factory or after market headers) youll be amazed by the difference. i just put headers on my car and i block the egr and caped all the hoses and removed the AIR system pump and all and capped everything off and wow it idles sooo much better and feels a little better throttle response, no rumbling or anything. also it starts right up every key turn. If you wish to block the egr and the AIR system (part of it is the small metal flex pipe coming out of the passenger side of the manifold) you can find the blocking plates at tpis.com and the instructions at zmydust.com or projecttransam.com. also they have a help section that may be able to help u more than camaroz28.com can. also make sure your spark plugs are gapped right and they are the corret length, also you may want to get in the engine and tighten the drivers side exhaust manifold, it takes a 14mm open ended wrench for some and a ratchet for the others, mine were all 14mm im pretty sure yours will be the same. what ever you do if you dont know what your doing DO NOT LOSEN THE EXHAUST MANIFOLD, ITS VERY VERY EASY TO MESS IT UP AND YOU CAN MAKE THE GASKET COME OUT OF PLACE AND THEN IF YOU DONT PUT IT BACK RIGHT YOULL BLOW THE GASKET AND COST YOU ABOUT 300 IN REPAIRS, only tighten it. OH and one more thing, if you have cheap wires make sure they dont touch too much because the spark can jump for wire to wire and cause back fire and extremely bad gas mileage, if they are touching go to discount auto or pep boys and get some spacers and stick them on where they touch or come unbelieveably close. I have MSD 8.5mm wires and all of them are on top of my valve covers and wrapped in insulation (very neatly so it looks good) you can get that kit a Thunderracing.com. Try some fuel injector cleaner too. Also make sure there is nothing stuck in your exhaust, if you have a muffler welded on in place of the factory that some times causes backfire.

 

Technically, the pilot bearing is in the rear, center of the crankshaft.

 

thx guys