I have a 2008 Honda Civic coupe with a 1.8L engine and automatic transmission. The problem I am experiencing doesn't happen all of the time, but it happens at least a few times per week while I drive to and from work. When I stop at a light or stop sign sometimes when I press the accelerator I feel the engine shake and hear a clunk before the engine shuts off completely. The car has about 92k miles and I have replaced the spark plugs and coils along with the mass airflow sensor and PCV. About six months before experiencing the issue I had to replace the fuel pump unit because the old one had burned out. The fuel pump connector plastic was slightly melted but I was still able to unplug it and plug in the new pump. I asked a mechanic near me to take a look at it and they could not find any issues with it aside from a service bulletin to update the ECU which I have already done. Another mechanic that I took it to said that he thinks the engine mounts are worn which might be the cause of the clunk and vibration but I'm still not sure what is cause the engine to shut off. I would appreciate any help.
Thank you Triton8484 and Doc for replying. I have scanned the ECU for codes and have gotten nothing except for one time when I had a check engine light because my lower coolant temp sensor went bad. After replacing the faulty sensor I still have no codes or check engine light. In my original post I forgot to mention that I replaced the throttle body and gasket with a new OEM unit. I have also done the idle rpm learning procedure.
Echoing what Doc has said above with the scan. You can also look into the throttle body and the throttle position sensor, as idling/stalling issues can often relate to the throttle body assembly.
Run a scan and check what codes come up.
Have you also checked for vacuum leaks and the condition of your fuel injectors?
I have checked the vacuum hoses for crack and leaks, they looked fine and I didn't find any leaks. I've added at least two cans of fuel injector cleaner to the gas tank.
Also, check your fuel pump relay make sure it’s good. $30 just get a new one and replace it. I had a similar issue with my vehicle. It ended up being a bad relay.
Thanks, just ordered a new fuel pump relay and fuel pump connector pigtail. I should have replaced those when I replaced the fuel pump since one of the pins on the pump got crispy. There is a strong possibility that the relay was damaged.
Let me know how it turns out! Hopefully its that easy!
Quick update. I replaced the fuel pump relay and changed the fuel pump connector. It seems a little better, I haven't stalled the engine on the road yet thankfully but I can still feel see the RPMs lower and feel a clunk sometimes when I press the gas a little too hard from a stop. Something else I have noticed is that when I turn the steering wheel or even roll the window up or down I feel RPMs drop slightly and then raise. I checked the voltage on the battery with the engine running and it was at about 14V so I think the alternator is fine.
Since you say you notice rpm drop when your windows roll up and down, You might have the battery and alternator load tested just in case. Free at the auto parts store, It may say 14V but if something is off a bit it can act squirrely.