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Hey i never used this before so if im posting this in the wrong spot or its just bad im sorry.'

So i have a 2000 honda civic LX and the idle is at 1500 but flucuates a little. and when i press the gas it revs up but then goes down to 1000 ish rpms then jumps back up to 1500. ive already replaced the intake gasket cause a mechanic told me there was a small leak in that but no difference. also when your going into first no matter what rpms ur at they drop down to like 1000 and lug the engine (i can get it going by reving to about 4k rpms and feathering the gas but man its kinda hard and cant be good for the clutch). My car also is back firing more which is weird. Also if your in first and get to about 4.5-5.5k rpms it makes a weird noise kinda like its redlining but not as harsh. and overall the car just dosent "feel" right like i can deal with a high idle but this is just weird.
If anything in this dosent make since just ask for more clarification. anything you can tell me proboly help. it is my daily so im in a bit of a hurry to get it running good again.
Thank you to whoever reads this.

 
Rep Power: 211

Backfiring symptoms: https://www.midas.com.au/what-causes...-your-exhaust/
Pull the plugs and inspect them visually to look for signs of fouling. Spark plug fouling chart: https://www.aa1car.com/library/spark_plug_fouling.htm
Rich running condition: https://cartreatments.com/engine-running-rich-symptoms/

Free things you can check and do that may help:
* check mechanical timing (crank + cam). The timing may have jumped a tooth.
* do a valves adjustment
* remove and clean the IAVC + it's gasket screen with brake cleaner spray
* clean the throttle body with throttle body spray and a toothbrush OR remove it and clean it more thoroughly.
* adjust the throttle body cable and ensure the cable is not getting hung up (sticking) anywhere along it's path. you may need someone to press and release the gas pedal while you watch the cable. Spray the cable, TB butterfly (flap) return spring, and the butterfly's shaft pivot points (small holes inside TB) with silicone spray (don't over-spray).
* ensure the air filter is clean
* while the sparks are removed check the gap on them
* a dry and wet compression test (if you have a compression tester). This one's cheap and decent enough: https://www.harborfreight.com/compre...-pc-62638.html

Clogged catalytic convertor could be a possibility: https://www.goldeagle.com/tips-tools...tic-converter/
Other possibilities as well but start with the free and/or cheap stuff first that may help and then update us please.

 
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Hey so first of all thank you that helped a lot. i replaced spark plugs (there were carbon deposits all over them they were pretty much pure black), cleaned throttle body/iacv, checked throttle cable and i got a new air filter(K&N). now it dosent drop rpms when going into first and just shifts normally but the idle is still 1500 and sometimes 2000 (fluctuates a bit) and after you drive it for like 15-20 mins it will go down to 700 ish . but if you rev it up when its at 700 when going back down it like stops for a second at 2000rpms and again at 1500 ish rpms but then eventually goes down. (takes a few seconds to go down once it gets to 2000, its like its taking steps). also idk could just be cause its been a bit since i drove it but it seems like when i put the clutch in to change gears the rpms drop pretty slowly. like it makes shifting easier but idk if thats normal or not so thought id just say something. i think its a sensor or something but im not positive.

 
Rep Power: 211

​​​​​Okay, those things are good general maintenance and will serve the engine well. So, now you have to figure out why the plugs are fouling? Read this: https://e3sparkplugs.com/blog/are-yo...20plug%20wires.

Watch the video (spark diagnosis) in my signature at the bottom of my reply. You can do the same test with a grounded long-handled flat head screwdriver. Known as a spark quality or arc test.
If the coil in your distributor is weak this test will most likely kill off the coil, but in this case it's a good thing because a strong coil should survive this test.

​​​​​Did you spray silicone spray on the TB flap and spring?
There's a possibility the TB flap is intermittently sticking and isn't returning to a full closed position...which would cause a high idle.

If you don't know when the valves were last adjusted it's good maintanence to check and adjust them if need be. It seems like a difficult job if you've never done it before but it's actually pretty easy, somewhat time intensive the first time around. Plenty of write-ups, youtube's on it.

This may help: https://www.ericthecarguy.com/honda-...-hunting-idle/