I am having an issue with my 2000 Civic EX (D16Y8) where it struggles on the low end especially on WOT. The issue only presents itself when it is at normal operating temperatures, but if it is cold (starting up first thing in the morning and driving off) it runs normal with no lack of power. I have done a bunch of troubleshooting already and running out of ideas on what to do next.

Things I have done recently (I know not all of these pertain to my issue, but I thought I'd list it anyway):
-Replaced fuel filter -- Fuel pump works fine
-Replaced spark plug wires
-Gapped and replaced spark plugs
-Replaced manifold absolute pressure (MAP) sensor
-Cleaned throttle body
-Cleaned idle air control (IAC) valve
-Replaced catalytic converter
-Replaced timing belt
-Set ignition timing to 12 degrees BTC
-Tested throttle position sensor (TPM -- .5 idle / 4.5 WOT)
-Unplugged primary o2 sensor to see if issue is still present -- Yes, the issue is still present
-Replaced head gasket
-Replaced distributor o-ring
-Replaced oil pan gasket
-Replaced air filter

I am not sure if it is a bad distributor, but I will pull apart the cap and rotor later this week to see if there is any corrosion present. Only thing that I have not done is replaced the ECU, both o2 sensors, and check compression.

If you have any ideas on what I should try next, it would be of great help!

TLDR;
-When engine is cold it runs fine
-When engine is warm (normal operating temp) it has hesitation all the way up until 2700 rpms
-Replaced, checked, and serviced certain things already

 

clarify low end issue.

 

I'm not sure how to explain it. When at cold engine temperature it drives normal, whereas if it is at warmwarm opera tempetemper it feels like it's chugging all up pass 2500 RPM.

 

Bump

 

 

Yes, when it hits 2700 and above it's fine! Also when the car runs cold it's fine.

 

This is almost always weak sparks. When the engine is cold it runs a richer mixture which is easier to ignite.

 

Would you suggest bad distributor? I haven't had the chance to pull it yet.

 

Bump anyone?

 

Update:
-Swapped and tested known working TPS sensor and calibrated
-Swapped and tested known working distributor and timed

Issue is still present. I've also noticed that the issue sometimes resolves itself and comes back.

Weak fuel pump maybe?