V1x0r

Lets just get to the nitty gritty, I am hopeful that someone out there can either confirm my beliefs or give me better support than my poor google searches.

I have an 02 Honda Civic Si 3dr. 2.0 liter i-Vtec motor (rsx if I remember correctly ?)

I receive error codes on the daily every time I drive. I believe that I am missing 2 error codes and will try to explain them the best i can below but will try to get them tomorrow if I can. (they are not regular error codes and are resolved by turning off and on the car about 3+ times).


Vehicle Calibration ID: NFA030..........
P1121 [Honda] Throttle Position Lower Than Expected.
P0301 Cylinder 1 Misfire Detected
P0302 Cylinder 2 Misfire Detected
P0303 Cylinder 3 Misfire Detected
P0304 Cylinder 4 Misfire Detected
P0300 Random/Multiple Cylinder Misfire Detected

The cylinder misfires happen when it's just idling, but most common is when I go to accelerate the car won't react and then finally it will go after about 2-3 seconds and the check engine light will blink, I do an error code check and sure enough, I misfire.

I have replaced the coils, replaced the spark plugs with iridium spark plugs and the same reaction.


I don't have these right now, but when I clear the error codes I get a random code that stalls out my car at times and will also cause the through to be non-reactive unless beyond 50%
P1259 [Honda] VTEC System Malfunction
P1122 [Honda] Throttle Position Higher Than Expected.
P1128 [Honda] Throttle Position Higher Than Expected.
P1298 [Honda] Electrical Load Detector Circuit High Input

and I don't have the code on hand, but I at times get a MAP sensor error also.


My thoughts are the TPS needs to be replaced or cleaned, the throttle body needs to be cleaned, the MAP sensor needs to be cleaned, and the air filter needs to be cleaned. It's a cold air intake and the guy had the cone down towards the ground, I have since elevated it to be up higher and this seems to have resolved some performance issues I was having earlier.

I purchased a new ecu which seems to have resolved my vtec related errors. the car will still chug when it's raining outside. (when I enable cruise control the car will accelerate, then stop, accelerate, then stop even when the throttle position doesn't change). I've verified this by physically having my foot on the gas pedal and manually reproducing this issue as well as monitored via Torque on my tablet.

when I clear the current error codes I believe I get the MAP sensor error code and/or one other code that I may not have listed (it is too late right now to try this as I have work early in the morning) which causes the car to react very poorly (the no throttle response unless beyond 50%). During this time the exhaust sounds a lot deeper and my fuel economy drops substantially.

I have been looking at different options, to include a MAP Bypass Valve in hopes to alleviate the MAP sensor error.

for the most part the car is stock. Minus the Cold Air Intake, the headlights, and the muffler. (I did none of these modifications as they came like this with the car). I have always had a check engine and was told "that's normal when you modify the car"...at a performance loss I do not find this normal. I hope I gave enough details here and thank you all for your support in this. I love my Si and I want to give it the best treatment. Have an awesome day!

V1x0r

so, I cleared the error codes and the "P1121 [Honda] Throttle Position Lower Than Expected." came back right away and caused the car to have the very little throttle response. nothing before 50%. So, would this be the TPS? It was not set as an active error code at first, it was a Pending Error code. after killing the car twice it became an active error code and the problem went away. This clearly isn't good/normal behavior. I'm certain that on my way to work I will get the cylinder misfires. Any suggestions beyond my thoughts? I don't want to jump into something and be working on the wrong thing. thanks again guys.

V1x0r

So, monitoring my ecu I found that my intake while idle is displaying as 4.5 psi and when I accelerate it displays at 14.7 psi.

the Boost at idle says about -10.2 psi and when accelerating gets to about -0.2 psi.

I am not certain what "Timing Adv" is, however that sits about 14deg-15deg.

if there are any other details that would help more on this please let me know and I will get those numbers.

Also, I feel like a fool, it's not a cold air intake, it's a short ram intake.

after doing some reading I think a Map Bypass Valve by Blox or synapse may be helpful as common suggestion is at 10psi or above I should use that to avoid going into limp mode/ throwing MAP sensor errors.