So I have a 93 Honda Accord completely stock.

Symptom:
When cruising at 15mph then accelerating to 30. Going from 1500 rpm to 3000 rpm. The car will hesitate for 3-4 sec. Then react to the demand to go faster.

1.The car's engine rpm will remain the same and so will the speed, so I know its not a tranny issue.

2. The code that seems to come on is code 43: 02 heater sensor circuit/ fuel supply system.

3. I scoped the 02 pattern at the sensor and it seems to be switching fine. I did not have a propane enrichment tool at hand so I couldn't see if it was a lazy 02.

4. I moved on to the fuel supply system. I ran the car on the dyno and the 02 and CO readings seem to point to a lean mixture.

02- 7.5%
CO-0.0

But no misfire codes!!!!

5. I had someone run the car and recreate the problem several times and while it was happening I disconnected each fuel injector one by one to see if the an injector was not working. Each injector i pulled off seemed to make the stumble the engine even more so I know that the injectors are working.

6. I havent had time to run the car with a fuel pressure gauge when this problem happens.

7. I know i should not assume but the fuel filter looks to be new.

8. I also eliminated the problem of being an EGR issue because I previously tested the EGR.

EGR does indeed work but the signal to it is not working.

Usually the EGR on hondas tend to weaken and upon accel. the EGR would open to wide and allowing more gases in than intended therfore leaning the mixture a little, causing hesitation.

9. i still need to test the TPS and MAP sensor to see if they are bad but no codes on them.

IATN members all point to 02 sensor replacement and told to make sure it was HONDA.

I scoped the pattern and seemed to be good so I am skeptical about changing it, i want to verify before throwing parts on it.

ANYBODY have any ideas??????

 

I suspect sensor feedback.

I would confirm the MAP value when you increase throttle angle during the event. I would also confirm TP value when you increase throttle angle during the even.

The primary oxygen sensor has one purpose, to control the catalytic converter. The secondary oxygen sensor is used to confirm catalyst operation and help control fuel trims for the operation of the catalyst. Without a switching lean/rich mixture the catalyst would become saturated and fail to operate.

I do not suspect a problem with either oxygen sensor in this case.