I have a 2005 Civic Si, only mod is a Injen CAI. The issue is after the car is warm it gets a hard stutter or hesitation under normal driving from 2000-3500 rpm. I originally thought the TPS was bad and replaced it thinking it had gone bad in the normal driving range. This isn't a slight stutter its pretty pronounced, usually several times in a row until out of the rpm range. No CEL. Idle also seems to be slightly erratic but not sticking or excessively high or low just seems to move around and not be consistent. Any help or input is appreciated. TIA

 

Try reseting your ECU and see if that does anything. You can reset it by pulling the ECU fuse from the fusebox under the hood and putting it back.

 

Have you tested the voltage at the TPS making sure it is in range? I would first guess that the tps is it, and since you have replaced it with another what kind? I would look at the primary o2 as well, but then again it would throw a code most times, but not always.

If it was cam or crank timing, or vtc related there would be an immediate CEL.

 

The voltages are within the correct range that I found online, 0.53 at no throttle to 4.52 at wide open to be exact. It's just a 30$ replacement from ebay, could still be the issue since I can't exactly test it when it is happening, unless there is something else I can do to test it other than the voltage range?

I was leaning towards the o2 sensor since it is happening once the car is up to temp. It started on my long drive(1100 miles) to Kansas over the weekend and progressively seemed to get worse on the way back. If I had cruise control on and rpm was about 3500 or so it would cruise fine then hesitate intermittently maybe every 10 miles or so. When I drove it this morning to work everything seemed normal until about 20 min in when it started to hesitate some and again this afternoon on my way home it hesitated about 20 min in on the way home and continued until I got home, never throwing a CEL or anything. The only other way to describe it is it feels like when you are driving at steady speed and get off the gas completely then it almost bounces once you decelerate a bit in gear, but this is happening when accelerating under normal driving conditions. Very frustrating/annoying.

 

Swapped back to the factory TPS to see if there is a change in the symptoms. Originally I swapped it due to a small hesitation in the same rpm range and with the new one it was worse once up to temp. I'll see tomorrow if it is showing the same problem on the OEM sensor.

 

Put a diagnostic tool w/live data feed on it and see what the ECM/PCM is reading from that sensor in real time.

 

How many miles are on the car? Does the engine sound like its misfiring (new spark plugs?) or is the throttle just not responding to pedal input?

 

Car has 50,000 miles, at first I thought it was a misfire but I would think that would throw a code that I could read with a scanner and there was nothing. Car responds to throttle just when its hesitating it just jerks, almost like someone who is just learning to drive a stick.

I swapped in the old factory sensor and the symptoms are back to the slight hesitation, not the heavy jerking. Ill keep this one in and see if the symptoms come back.

Thanks for the help thus far, maybe I should just stick with my DSMs