1998 civic
So as the title says a low speeds and starting from a stop the car bogs down and almost loses all acceleration power even coming to a stop on very small hills. at high speeds its runs perfect it seems, and i have yet to find the problem as i checked/replaced everything
so i have replaced fuel pump, fuel filter, fuel injectors. Plugs and wires. just put all new timing belt and water pumps. new Map sensor and tps sensor, checked the IAV and it seemed to be working as should. smoked vacuum lines and didn't find anything. pulled the cat off and hallowed it out.
really at this point i have no clue what else to even check ive went and read tons of forums with other with almost the same issue and nothing has helped. Also ill add the car has never actually died when its bogged down. Someone also said maybe transmission and was told when driving when it bogs down stay on the gas and put it in neutral if rpms go high then maybe transmission but whenever i tried that still in neutral rpms wouldn't get past 1500.
Any suggestions on what next to test or try I'm all out of options at this point.

 

Here are potential causes and tests, prioritized based on your symptoms and what you haven't mentioned checking:

Throttle Body Issues:
A dirty or malfunctioning throttle body could restrict airflow at low RPMs, causing bogging. Since you’ve checked the TPS, focus on the throttle body itself.
Test/Action:Inspect and clean the throttle body thoroughly with throttle body cleaner. Check the throttle plate for smooth operation and ensure it opens fully.Verify the throttle cable isn’t sticking or misadjusted, limiting throttle response.Check for any carbon buildup or gunk in the throttle body passages.

Ignition System (Distributor/Coil):
A weak ignition coil or faulty distributor components (e.g., igniter, rotor, or cap) could cause poor spark at low RPMs, especially under load. You’ve replaced plugs and wires, but the distributor itself hasn’t been mentioned.
Test/Action:Inspect the distributor cap and rotor for wear, carbon tracking, or corrosion.Test the ignition coil’s primary and secondary resistance with a multimeter (refer to a service manual for specs, typically 0.6–0.8 ohms primary, 12–18k ohms secondary for a 1998 Civic).Consider swapping the distributor or coil with a known good unit to test.

Mass Airflow Sensor (MAF, if equipped):
Some 1998 Civics (depending on engine, e.g., D16Y7 or D16Y8) use a MAF sensor. A dirty or failing MAF can cause poor air measurement, leading to bogging at low speeds.
Test/Action:Confirm if your Civic has a MAF sensor (typically located between the air filter and throttle body).Clean the MAF sensor with MAF-specific cleaner.If cleaning doesn’t help, test the MAF output with a scan tool or multimeter, or swap with a known good unit.

Fuel Pressure Regulator/Delivery:
Even with a new fuel pump and filter, the fuel pressure regulator or fuel return line could be faulty, causing insufficient fuel delivery at low RPMs under load.
Test/Action:Use a fuel pressure gauge to measure fuel pressure at idle and under load (should be ~30–40 psi for most 1998 Civics, check manual for exact specs).Pinch the fuel return line briefly while idling to see if pressure increases and symptoms improve (indicating a bad regulator).Inspect fuel lines for any restrictions or kinks.

EGR System (Exhaust Gas Recirculation):
A stuck-open EGR valve can cause excessive exhaust gas recirculation at low RPMs, leading to bogging or hesitation. This is common in older Hondas and fits your symptoms.
Test/Action:Locate the EGR valve (usually near the intake manifold).Check if the EGR valve is stuck open by removing it and inspecting the valve/passage for carbon buildup or sticking.Test EGR operation by applying vacuum (with a hand pump) to see if it holds and moves properly.Clean the EGR valve and passages, or temporarily block the EGR port to test if symptoms improve.

Engine Compression/Vacuum:
Low engine compression or a minor vacuum issue (not detected by smoke test) could cause poor low-end power. A small valve timing issue (even with a new timing belt) or worn piston rings/valves could be culprits.
Test/Actionerform a compression test on all cylinders (should be ~170–200 psi, with less than 10% variation between cylinders).Conduct a vacuum test at idle (should be steady at ~17–22 inHg). A fluctuating or low reading could indicate valve issues or a timing problem.Double-check timing belt alignment (ensure cam/crank marks are perfectly aligned).

ECU or Wiring Issues:
A faulty ECU, bad ground, or wiring issue could cause incorrect sensor readings or fuel/spark delivery, especially at low RPMs. This is less likely but worth checking since other systems seem fine.
Test/Action:Scan for trouble codes using an OBD2 scanner, even if the check engine light isn’t on (pending codes may exist).Inspect ECU grounds and wiring harnesses for corrosion or loose connections, especially near the throttle body, MAP, TPS, and distributor.If possible, test with a known good ECU from a compatible Civic.

 

That's a good write up, captainblue. I'll keep these in mind if I have any similar issues with my 96 ex. I hope it fixes terrylotus's issue.

 

Check timing