resolved! new primary o2 sensor did the trick.

Hello s2ki community,

My car is an 05 ap2 with roughly 60k miles. Running 10w-30 oil if that matters. Morning weather is California is right around 50 to 60 degrees. Night time is about the same this time of year. Before heading to work, i warm up my car to about 4 bars. I'll be in 5th gear right under 3k rpm and my car will hesitate once and it drive normal. Same thing when I'm heading home from work, it will hesitate once and drive fine, which seems kind of odd. Ran some Techron fuel system cleaner to see if it would help but the problem still persist. Car still drives hard and hits vtec without a problem. No cel btw

-I changed out the map sensor
-removed the throttle body to clean out the channel leading to the map sensor,
-serviced my fuel injectors through RC Engineering as my car was smelling of gas during startup(found out they were leaking),
-did a valve adjustment,
-changed intake filter to k&n
-change out spark plugs(PFR7G-11S)
-changed out the intake arm as it was old and had a tear to OEM
-did an oil change
-clean iacv

Currently running radium dual catch can
koyo radiator
1320 testpipe
radium fuel surge tank

Could it be that my previously leaking fuel injectors fouled my o2 sensor, that's why it's running weird? Should i run a stronger fuel system cleaner like bg44k to see if it would remedy my situation?

Tried searching but it seems like my situation is a unique compared to others on the forum.

 

Those spark plugs are tight? Coil packs are good?

 

You warm engine to 4 bar before you drive the car then?

 

correct, i wait until my car hits 4 bars before driving off. i take it easy and drive like a granny. last night my catch had a little bit of oil, maybe like a tea spoon so i cleaned it. the hose connected to the pcv valve. this morning i waited 5 bars and the car drove fine. ill report back tonight.

appreciate both of your reply!!

 

Its not clear what you mean by hesitation...but it does not seem like there is anything wrong.

No CEL is usually an excellent indicator that nothing is actually wrong.

I would refrain from using fuel system cleaner or any other additive to chase a non-existent issue. The car doesn't need any of that stuff to run well.

Make sure the plugs are torqued and everything is in good general maintenance.

You're also wasting your time with warming the car up. Cars don't need to be warmed up at all unless you live in extreme winter.

If anything, the idling is hurting the engine.

Turn the car on. Give it maybe 5 seconds. Set off. Drive conservatively until the car comes up to temp. This way, you're warming up the trans and diff and engine gently. And you're not idling the engine and building up carbon and junk.

 

Agree. Warning up an engine is bad for it.

Most wear occurs when engine is cold. Idling is slowest way to warm an engine. When engine is cold, more contaminants get into the oil, causing more damage even once engine is warm.

 

1.) I'm not fond of those in-a-can fuel system cleaners. There is a lot of needed cleaner chemicals already in most top tier gas.

2.) I live in a hilly area. Much of my early morning driving is up and down hills. I let the car idle about 15-30 seconds, when it is stone cold. As it will be doing work climbing those inclines. The worst thing to do is lug the engine, especially when it is cold.

 

thank you for the reply again! much appreciated. learn something new regarding not needing to warm up the car for so long. I'll just wait couple seconds and drive off next time.

car did do it again when i left work. hesitation felt like a slight power lost for like 2 seconds. car drove fine and redlined normal after. My car did have a 25row oil cooler before. i never took off the oil cooler to perform an oil change as it's such a hassle. perhaps the residue oil in the oil cooler built up over time, causing the car to perform poorly. i just drained the oil and put in fresh oil as a precautionary measure.

 

Try cleaning out the MAP sensor.

Sometimes carbon builds up inside the hole that the MAP uses to reference pressure.

You basically unscrew the MAP sensor, take it out of the car, and clean with throttle body cleaner (not brake cleaner). You can lightly tap out the buildup by tapping the sensor until it comes out.

Look up "S2000 MAP whack"

Zip tie-ing the connector is another thing to do when it goes back together.

 

Make sure none of your injector clips are broken and the connectors are fully seated. If not, it will cause the car to hesitate if the injector connector moves around and temporarily loses connection.