Recently bought a 2009 Honda civic that needed some work! Previous owner threw some parts at it to no avail.. the car will start first thing in the morning or (cold) and run but the idle is rough and very low. If you rev the car it runs great over 1000 rpm’s.. but eventually the car will idle and die. Once that happens the car won’t start back unless you let it sit for 30+ mins then it will fire back up and do the same… I’m stumped and considering it could be the TPS has gone bad…. Any ideas?

 

When it dies and will not start again. Maybe its vapor locked, and has a bad gas cap. Try opening the gas cap, and letting air into the tank. Then try restarting the car.

 

I’ll give that a try! Also what would cause it to idle so low and rough at the exhaust I hear a slight misfire sound. But once you give it some gas it clears up until you let it idle back down then it acts like it’s gonna stall.

 

I was thinking a bug made a nest in a vent tube, making the fuel tank vapor lock. Or maybe you need a new fuel filter. Where once it uses the fuel that is available, it creates a vacuum and can't get any more fuel. Once it sits, shut off for awhile, maybe the fuel seeps back in, and gives you another 5 minutes of run time. Its a complete guess at this point.

As to the low idle: You may need to do a idle relearn procedure.

 

Do you have a link to the idle relearn? I’ve not done one on a Honda before!

 

I have found there are different procedures for different Hondas. Mine was simple. But other models are more involved. Mine was:
Drive car to operating temperature. stop car on level ground and block tires. turn off all electronics, A/C, Lights, Radio, Dome light, Take off your negative battery cable for 3 minutes. Reconnect battery. Get in car and do not touch brake pedal or move the steering wheel. Turn key on but do not start car for two seconds. Then start car, and let it idle for 10 minutes. You want no electric load or mechanical load on the engine. Meaning don't turn on lights, don't turn on the air conditioning, don't turn on the fan, don't turn on the radio, don't move the steering wheel, don't push on the brake pedal. Turn off the car after 10 minutes and the idle relearn is complete.
I don't know what the procedure is for you car. Some involve raising the RPMs to 3000 and after a period of time, turn on the A/C. You should probably look it up for your specific car.

 

This is the Computer Idle Learn steps for a 2006 Pilot, they are still just a bit different than the above videos:
(You probably don't have access to HDS, so disconnecting the battery for 5 minutes or pulling the ECM/ECU/PCM Fuse and backup fuse will suffice)

 

Awesome! I’ll give it a try! Also check out the other thread I just posted if you can! I’m not sure what to do about the key issue?

 

I'm not sure what to do on that one. I do not have experience with keys and immobilizers. My local Honda dealership charges $190 to program a key to the car. So maybe a local locksmith might have a better rate. My stab in the dark guess, is that something went wrong in pairing the key to the car, and it needs to be deleted and reattached to the system. But honestly, you should get an answer from someone who has experience with this, as I have zero knowledge on keys.

 

This may be a fuel pressure regulator problem. Do you have a way to view live engine data (like a scan tool) while the car is running ?

 

Yes I do! What do I need to look at?

 

Short and Long term fuel trim... at idle and very low throttle angle, the values will get really big and maybe even max out... but at moderate to full throttle, the trim values will reduce significantly and appear normal.