[258617]

I have a 2003 Honda Accord V6 4 door and have had multiple cylinder misfires at high rpm (usually above 4500) ALWAYS starting with cylinder number 1 then followed normally by cylinder number 2 then the rest.

Before the brake warning light and the TCS light came on, we replaced all 6 ignition coils, all 6 spark plugs and the fuel injector on cylinder number 1. Engine still misfired ALWAYS cylinder number 1 then the rest under load. We did a smoke test and no vacuum leaks anywhere. We now have code 83-1 (ECM/PCM Relation Failure) and code 84-1 (Sensor Logic Failure) when we scan the ABS system (no ABS light is on). Our accelerator position pedal sensor sensor #2 only rises to 2.2 volts when the throttle is fully opened and sensor #1 rises to 4.5 volts when fully opened. Are these codes all related? Do I need a new ECU/ECM or accelerator position pedal sensor?

Bank 1 of the engine is also reading a negative short term fuel trim that reaches below -10% under load.

 

[BLCKFLSH]

I don't know what is causing your issues, crank or cam sensors maybe??? How many miles on this car? Has the timing belt been changed? Did you get OEM coils and plugs?

 

[greg1c]

The basics first, before I would replace a bunch of parts. The first thing is to check the battery connections and make sure they are clean and tight. The next thing to check is the timing belt is properly lined up. The next thing to check is compression on all cylinders. A lean condition can also cause multiple misfires and it seems you are lean at -10 fuel trim.

 

[258617]

All oem parts, 156k miles

The compression tested good and we got a new battery

 

[tin42man]

I had basically the same problem on my 03 v6 and after much investigation I replace the throttle position switch and it corrected the issue. I had about 300,000 miles at the time.

 

[258617]

Misfire in cylinder 1 at high rpm

My 2003 Honda Accord EX v6 with 150k miles has multiple misfires when driving above 4000 rpm and sitting still when revving the engine to the limit in cylinder number 1 (100 last drive cycle) and very little misfires in cylinder 4 (8 last drive cycle). We replaced the fuel injector in cylinder 1 and spark plugs and ignition coils have been replaced on all cylinders which raised the rpm at which the misfire happened from 3000 to 4000 rpm but didnt fix it. The catalytic converters tested OK in our scanner. Car has a new battery. We did a smoke test and we do have smoke coming out of the EGR valve but the only code is the misfire on number 1 and 4. What is happening??

Ps. We also have a ECM/PCM relation failure code and a Sensor logic failure code in the ABS codes with the TCS and brake warning light on.

 

[greg1c]

What is the compression on all cylinders and is 1 lower then all the rest.

 

[258617]

Compression is the same in all cylinders including 1

 

[greg1c]

What psi are all of them

 

[258617]

They are all around 210 psi

 

[sockuno]

My 98 Accord V6 had identical issue with misfires on multiple cylinders. The problem was simply an air intake leak from a crack in the intake hose. I put duct tape on the crack and it was good to go. The fact that your Accord running lean on short term fuel trim suggest that it has intake leak somewhere. Check your intake hose for cracks and holes and consider replacing your manifold gaskets if you cant find any obvious leak.

 

[enne]

My 98 Accord V6 had identical issue with misfires on multiple cylinders. The problem was simply an air intake leak from a crack in the intake hose. I put duct tape on the crack and it was good to go. The fact that your Accord running lean on short term fuel trim suggest that it has intake leak somewhere.

My '99 I4 had a big crack in the intake hose as well, but I caught it before it caused any issues. It was right where the clamp was around the end of the hose near the back of the bay. I sealed it with silicone.

 

[greg1c]

210psi? Have you modified this engine as a stock engine should be closer to 180 or 185. Or you have severe carbon buildup in the combustion chamber. That could be the issue, also have you adjusted the valves recently.