Low power and awful idle

[95opal]

Just bought this car so I know little to nothing about it. Everything is stock except for catless xpipe but still has mufflers and resinator. First thing I did was new iridium spark plugs gapped to .054 I believe. But car will jump up and down at idle between 500-1000 and then just die. But has no issues idling when in neutral and in motion. Also had decent lack of power. Any thoughts on what it could be?

So what i get from your post is that there is no CEL.
Car only fluctuates idle when its in gear with brakes applied?
What is decent lack of power?
How did the plugs you took out look?
Has the fuel filter been changed?
MAF clean?

 

[Newtosn95]

Update: I replaced all the plugs and did a base idle reset and it’s definitely doing better. But still has a somewhat lack of power. I also noticed when I turn the wheel now, it immediately drops in rpm and dies if I turn it enough when in stationary idle, did I possibly miss a step in the reset? I plan on doing the fuel filter and checking for vacuum leaks. What do y’all think?

 

[Michael Plummer]

If you don't know the health of the engine I would recommend a compression and leak down tests but you will need the proper tools to do both tests. Or you can visit a local shop and they should be able to do that for you. If the health of the engine is okay. I would move to conducting a smoke test test for vacuum leaks. Once the health of the engine is verified, you can move to other issues.

Good luck
Michael Plummer

 

[Methodical]

I agree with previous posters to do an OBDI check first to get a baseline check before diving into all that other stuff to see if there are any codes and get rid of those fancy plugs; keep it simple with these cars. You should be able to find a cheap scanner on Amazon or as someone stated to check for codes using the paper clip trick (see video below). I made a jumper cable.

Note: For idle issues, check the Idle Air Control valve. The IAC is locate on the throttle body. While the car is running (let it warm up 1st) unplug the connector, if the idle doesn't change, the IAC is at fault, but if the idle changes, then the IAC is ok.

Also, you need to give the car some time to re-adjust to the idle. Do some regular driving like you would normally do so the car can relearn.

Check throttle body for build up
Check MAF

 

[shovel]

These poor cars are 30 years old and have had every sort of dingus doing what they believed were repairs and "performance mods" so it's practically impossible to diagnose anything over the internet. Take a thousand pictures and video and maybe we can piece together what's missing or janky from a visual perspective... maybe.

 

[Methodical]

These poor cars are 30 years old and have had every sort of dingus doing what they believed were repairs and "performance mods" so it's practically impossible to diagnose anything over the internet. Take a thousand pictures and video and maybe we can piece together what's missing or janky from a visual perspective... maybe.

I agree. You don't know what the previous owner did to the car. You just have to start with a code check and start analyzing the items that affects idle (IAC, TB, MAF, TPS).