2005 Honda Accord starting system issue, can not rev past 5000RPM

Question

I have two issues on my 2005 Honda Accord (2.4L 4cyl engine) that may be related:

• Sometimes the engine will not start.
  • The engine turns over a few times but eventually stops and then fast clicks.
  • Trying again sometimes will start the engine, other times will not.
  • Battery "boost" equipment I have doesn't seem to make a difference.
  • Jump-starting from another car almost always works, but I have to leave them connected for a few minutes.
• In park, if I step on the throttle the engine will not go past 5000RPM.
  • The engine RPM will start to pulse around 4800RPM
  • The harder I step on the throttle pedal the faster it will pulse
  • Battery voltage remains solid at 14.6V above 1500RPM

I have so far:

• Replaced the battery with a brand new battery
  • The old battery was 6.5 years old so probably needed replacing!
  • No battery light indicator on dash when engine is on
  • I still sometimes have to jump start from another car even after getting a new battery (see above)
• Verified the alternator is charging the battery
  • 12.6V when engine is off
  • 11.1V during cranking
  • 14.2V when engine is on
  • Ground/connectivity paths between alternator and battery seem to be OK
• Connected an OBD2 scanner
  • No DTCs
  • RPM, temp, etc. on scanner appears to match what is indicated on the dash
  • Battery voltage on scanner appears to match what is indicated on multimeter
• Tested the new battery with a battery tester
  • Tester says battery is OK
  • Tester says car charging system is OK

Next steps:

• I've been reading about the ignition system in the Honda 2.4L 4cyl system:
  • The ignition relay could be bad, but it's not clear to me how to diagnose this other than replace it and see if the problem goes away
  • The alternator could be bad, but it's not clear to me how that would explain the 5000RPM problem

I could be dealing with separate issues. I would really appreciate advice from the community on what to try as next steps. Thank you!

Update

Thank you @Paulster2. I inspected the positive terminal battery connection and it was very corroded. I disassembled the battery connector and thoroughly cleaned it with baking soda and water. The car turns over consistently now, although still a bit sluggishly, but at least it turns over every time.

I may still be dealing with a dying starter. Is there a way to test if the starter is failing?

Answer 1

I think you have one issue and one "works as designed" thing going on.

First, the "as designed" ... and obviously I'm not talking about the starting :P

I'm not sure about your specific vehicle, but a lot of vehicles will only let you rev so far when you are in neutral or park. There is just a set speed the computer will allow it to run. Yes a "rev limiter", but for when the engine is not under load. I ran into this once with a Ford Excursion, but for it the max speed was ~2500 rpm. An easy way to test my theory would be, on a safe stretch of road, put it into first gear and wind the engine out. If it will go to redline there, then this is what's causing your "issue". If it stops revving again at 5k, then something else is going on.

Your second issue is starting (obviously). For this I'm thinking it could be one of two things, neither of which is your alternator. An alternator will have absolutely ZERO to do with starting, unless it has completely died and has stopped charging the battery.

Seeing as how you've shown good voltage numbers from the battery both with and without the engine running, I'm going to say you have one of two issues. The first would be the starter is having problems. It could be the brushes are worn out or something along those lines. Personally, I think there is an issue with the main positive cable going from the battery to the starter. If there is any corrosion inside of this line or at the connection to the starter, it's going to be hard for it to pass the amount of amperage from the battery to the starter and may behave as you're suggesting. My suggestion is to inspect the positive cable and look for any bulges in the cable along the entire length. Any place where you might see something like this is corrosion and will cause issues. If so, replace the cable.