from 810 to 560 in one night. bad idle
first off, i have a 92 sc300. mostly stock.
a few nights ago I was working on my ac system. changing out the receiver drier and expansion valve to fix my a/c. I also removed my heater core. well after I got done and put everything back to how it was before, I turned my car on. instead of getting that long deep-ish rumble I used to get, I got a short and quick deep rumble, then drop to a low almost nothing note from the exhaust.
now a couple weeks ago, I checked the idle with a timing light since my cluster is not accurate. the timing light showed that on idle, each cylinder was 810. which is normal.
side note, after fixing everything I drove my car for about 3 or 4 days and I haven't gotten a single check engine light.
today, I checked the idle and it was at 560 on all cylinders according to the timing light.
next, I removed one end of number 1 spark plug wire with the engine running to see if the engine harmonics changed. then put the wire back. then number 2, then 3 etc. I did this to see if one cylinder was not contributing as much as the others, and I found number six reacted slightly less than the rest. it still reacted, just not as much. i'm about to do a compression check and see if all the cylinders are within specs. i'm also planning on buying spark plugs since I haven't changed them ever. they look pretty bad and rusted so i'm hoping that this fixes the issue. but if it doesn't, what else should I check for?
when I removed the heater core, the whole steering column had to be removed. basically everything from the seats forward. I left the ecu intact. the only wires I really had to disconnect are the power steering ecu, and the climate control. other than those, no wires had been messed with inside. is there anything inside besides the engine ecu that can cause this?