94 trans am. Has had new plugs recently,new air filter,fuel filter, fuel pump tests good under load. Replaced torn up intake bellows,cleaned maf.

Car has super bad idle it can be fine one minute than go way up and way down not stalling the car though. Car can bog on launch and just feels slow compared to other lt1 cars.

Some theories ..egr? well disconnected line didn't seem to make any difference. Is disconnecting the line off the intake to the egr a simple way to check/bypass it?
Bad o2 sensor..no codes being thrown for nothing..
bad opti or wires. He just changed plugs but not opti or wires.he is on a tight budget.
Clogged cat converter?? This one seems like a good possibilty to me. It would for sure take away power but would it make the idle go way up and down. The idle thing only started once shop changed out plugs. Not sure if that was coincidence. The car was down on power and bogging pre plugs.
Checked for any vacuum line off but found none. Intake manifold leak maybe

So lets here the suggestions. I can't scan the car as my scanner only plugs into obd2.
As said its not throwing any codes so far.

 

You obviously don't know that there are codes that do NOT light the SES. Since you can't scan it, you can't say there are no codes.

Do you notice if the engine runs good when started from dead cold until it warms up? If so, try unplugging one of the O2's and see if it then runs better when warm.

Also, when it does run crappy, you need to check for dead cylinders.

It would also be a good idea to remove the plugs and see what they show.

 

Plugs were just changed out by local shop. Car was not doing the idle up and down thing till the new plugs went in. Car was doing some boggin,down on power stuff pre plug change. I personally found his ripped to pieces on the bottom air intake bellows and he ordered a new 1le bellows for that problem. And I cleaned his maf for him properly took it apart and cleaned it right.
I realize there might be pending codes maybe?
I have scanmaster and laptop tuning but it only works on obd2 cars.
I would have to cut my scanmaster connector off to wire it to his car and not doing that.
He scanned it at local shop and they said nothing about any codes pending or otherwise.

Also I unplugged his egr hose to intake so would think that would show if he had egr problem?
I woudl think its one of the following.
Clogged cat converter this would maybe explain the low power but not sure about the idle going up and down and why didn't it do that pre plug change.
Intake manifold leak..think that could give the idle up and down but not sure about the low power.
EGR valve don't think this is problem since as said no change when remove vacuum from hose to egr valve.
Opti ..possibly we all know these go bad.
Spark plug wires..he should have changed out wires when he did the plugs..
Coil or coil wire..maybe

O2 sensor..he should change out 02 just because it might be original. But it does seem to be down on power wide open and drive not bad part throttle except for the idle going up and down. 02s of course dont' do much wot.

Maybe its a couple of the above.
Fuel pump was checked driving around and at rest. Fuel filter was changed out. Don't thnk he has checked out his injectors.

I checked for obvious things,broken wire to sensors or injectors and for vacuum line problems. Found nothing.

 

Last chance, I'll ask it again.

Do you notice if the engine runs good when started from dead cold until it warms up? If so, try unplugging one of the O2's and see if it then runs better when warm.

 

I think he said it runs better. Can maybe try this. Would of course have to get the car up in the air I assume to get to the o2 plug.

He was supposed to be taking out the cat converter over next week or so.

 

If the cat is clogged it will be well down on power,run it at night for a few miles and then look under the hood.If the cat is clogged the exhaust manifolds will be glowing red.A clogged cat would not cause your idle issues in my opinion.
Listen to "speedy",he knows his stuff.

 

This SCREAMS bad wires and/or Opti... try the wires first...

It's very easy to FUBAR the wires when changing the plugs...