I looked around a little bit, but couldn't find any definite answer. I have a 92 Civic with a 97 B18c1 GSR swap that's had this low idle problem for the past a couple months. The low idle only occurs when the car has been warmed up for about 10 minutes, when cold the car runs brilliant.

What happens after the car gets warmed up, is that it idles at around 800 normally, then drops to about 300-400rpm and repeats idling from 800 to 300 for several minutes. It seems like after those several minutes are up, it fixes itself and stays at 800 the rest of the time. Also when this all happens I can feel the car lose power as a whole, kind of boggy when accelerating, and having a slightly jerky or hesitation feeling when cruising around holding the exact same throttle percentage.

I've replaced the IACV which didn't fix anything, I've looked and tested both the TPS and MAP sensors which they came out looking fine, and there's no check engine light nor can I get any codes.. After hours of recording everything on Hondata, everything looks to be perfect. To me I've always thought it was a bad TPS seeing the symptoms I have, but all tests come back looking great. Now I'm to the point where I have no clue of what to do other than throw parts at it. Thank you any answers.

 

What condition are the plugs, wires, cap, and rotor?

Have you cleaned and adjusted the FITV, if you have one?

Does the CEL work? =CEL turns on and then off after 2 seconds when key is turned to ON(II)

 

The plugs, wires, cap and rotor all seem to be in good condition but were thinking about replacing them just to see if it did anything, but haven't yet. It doesn't have a FITV and the CEL does work correctly.


And for general knowledge, the car has been together for at least 5 years after the swap.. So the problem has only been recently.