Hi everyone. I'm new to this forum. I own a civic si 98(canadian model: 127 hp VTEC) with automatic trans and the car has 149 000 km. The only mod on the car is the CAI. The problem that i have with the car is intermittent: somes days the car works perfectly (i have plenty of power) and some other days (especially when it's hot and humid) there is NO power. Let's say you're cruisin at 50 km/h and you wanna accelerate, you hear the intake get noisy the more you push the gas pedal but the car doesn't move (the RPM doesn't move either). But if you push more and more the gas, eventually the tranny is gonna downshift and then you feel the car accelerate. I also noticed that the car idles close to 1000 rpm instead of around 700, and that the tranny shift points change when the problem occurs(shifts too early). So far i changed the wires / plugs/ distrib. cap and rotor (original honda parts). I got the injectors cleaned by the dealer. I tried 87, 89, 91 and 94 octane gas = no difference. Compression is perfect. Any help would be appreciated.

 

That's normal. Generally speaking your car will behave better when it's cooler, like at night. When it's cooler the air is denser and has a higher 02 concentration. When it's hot the air tends to be thinner and there is lower concentration of 02 in the air. Yup. Same reason N/A cars suck at like 3000 feet above sea level.

 

I drove the car tonight and it was very cold. I went to put gas : i filled my tank with 94 octane fuel. I noticed that it was running a bit better after that. The combination of cold air and good gas makes it run better....but there is still a problem, the car was running much smoother and faster before. Could it be the map sensor??

 

Try checking your 02 sensors.

 

how do you check the o2 sensors? What happens if i disconnect it?