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JoeHonda
JoeHonda, Honda Technician
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99 accord ex 3.0 v6 automatic. code p0300 through p0306.

Customer Question

99 accord ex 3.0 v6 automatic. code p0300 through p0306. new plugs, wires, distributor (including cap and rotor) and coil. good fuel pressure, map, and tps. vtec solenoid screen clean. no other trouble codes, only misfires at high rpm under load, won''t do it in the shop on the scope.any ideas?
Submitted: 6 years ago.
Category: Honda
Expert:  JoeHonda replied 6 years ago.
Misfire codes can be difficult on these. I would suggest that you unplug the egr and drive the vehicle, see if the misfire goes away. It can be opening when its not suppose to and causing the misfire, also check the EGR vls it should be about 1.15 volts or less at idle. If it is higher the egr valve is stuck open, this is usually more noticeable on take off as a stumble but can cause a misfire anytime. Since you have already done the plugs, wire, cap, rotor, and the fuel pressure is good I would think that you may have some bad gas.

Let me know how you make out, please feel free to contact me if you need more help.

Thanks
Joe
JoeHonda, Honda Technician
Category: Honda
Satisfied Customers: 276
Experience: ASE Certified Master Tech. Honda Certified Master Tech. Honda Platinum Level Customer Service Award
JoeHonda and other Honda Specialists are ready to help you
Customer: replied 6 years ago.
Reply to JoeHonda's Post: I already disconnected egr and drove vehicle, problem only appears at approx 4700 rpm and it will fall "flat on its face". It will lose power, and will not shift into the next gear. It's kinda like an excessive exhaust resriction. the exhaust checks out okay.
Expert:  JoeHonda replied 6 years ago.
What is the vacuums like? Is it strong and stable? Have you tried adjusting the valves?
Have you checked the valve timing? . The other thing is the ignition control module in the distributor. It can be weak and not able to keep up at higher demand.

Let me know where you are on these items.

Thanks
Joe
Expert:  JoeHonda replied 6 years ago.
Just another quick thought, what is the fuel pressure when the misfire occurs? What is the pressure at idle?

Let me know
Joe
Customer: replied 6 years ago.
Reply to JoeHonda's Post: The manifold vacuum is good at both idle and high rpm, the problem will only show itself while driving, no symptoms under load in gear or in park while not moving. The timing belt was replaced to ensure no excess vibration in cam timing. this vehicle runs excellent under acceleration. Only at wot and transmissin downshift will the problem exsist. super smooth and quiet idle. plenty of power and pickup. The problem will only exsist so long as you at wot, not lifting. as soon as you back off of the throttle the slightest bit, the problem goes away. If you not sensed into the feel of the car, you may not even notice it. but the check engine light will begin to flash and ony the codes p0300-p0306 are there.
Expert:  JoeHonda replied 6 years ago.
See if you can check the fuel pressure under load when the misfire occurs. Let me know what you find.

Thanks
Joe
Customer: replied 6 years ago.
still dealing with the issue. fuel pressure is ok during misfire, o2 voltage stays high. is there any possibility that the transmission could be the cause? i've seen a lot of tsb's pertaining to transmission problems. also, keep in mind it runs perfect 99% of the time. just at really high rpm, and not all the time, it shutters and the check engine lamp starts flashing.
Expert:  JoeHonda replied 6 years ago.
No not likely that it i a transmission issue. The check engine light flashing is because of the misfire, it will flash when it detects a misfire that could cause damage to the converter . Can you capture the freeze data from the misfire and post it to me. I am looking mostly for the long term and short term fuel trim but it would help to see all the data.

Let me know.
Thanks
Joe
Customer: replied 6 years ago.
Joe,thanks for your time. The problem ended up being water trapped in the bottom of the air filter housing (under the filter) and water trapped in the lower section of the air intake tube. Under heavy accelleration, the water was being sucked into the engine. New air filter and cleaning out box solved problem. I will pay you for your time.
Expert:  JoeHonda replied 6 years ago.
Thanks you very much. That is a very interesting problem and a great find. Congratulations on the repair and feel free to contact me again in the future.

Thanks
Joe

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