Very rough idle, stalls, on hot starts

[beachtech]

My 2000 Accord V6 EX auto sedan just turned 150K. It has been a very reliable vehicle. Other than routine maintenance, it hasn’t needed anything.

However, something odd happens on a hot start. For example, I drive the car for 15 minutes or more. I turn it off, go inside for about 15 minutes (not long enough for the car to cool off completely), come out, start the car, and it runs like it is only firing on 3 cylinders. It runs REALLY BAD to the point I am worried something seriously wrong is going on. The idle bounces up to about 700, then drops to 200, then stalls. I can try to start it a few more times, but unless I give it significant throttle, it will continue to stall every time I start it.

No CEL light. I have a code reader, but from what I understand, no CEL means no codes in memory, so I haven’t tried to read the codes.

It tends to happen on cool nights (40-50F). It doesn’t happen all the time, but seems to be happening more and more. Since I can usually start it by giving it significant throttle, I haven’t really worried about it, but yesterday I had my 4 year old daughter in the car and I don’t want to be stranded somewhere with her in the car.

Any ideas? I am pretty skilled at working on my vehicles. I had a 1986 Bronco with a 5.0L V8 EFI. I did everything to that engine except rebuild it. It ran for 250,000 before I sold it.

Thanks for the help!

BTW-I replaced the battery a few months ago. I think the alternator is going bad since I only see max 12.5V on hard idle, and it dips to 10.7V at night (with lights on, stopped at a traffic light).

 

[001Stunna]

From the voltage you mentioned...i would look at your ground/positive wires first to make sure everything is tight in place and in good condition and recheck the voltage. On high rpms i get about 13.8-14.5 last time i checked.

 

[TheSilverBullet]

there's also been a documented problem with these engines because the fuel rails don't have a return line the fuel will vaporize in the rail and as such will run rough as hell for a while.

this happens to my car every once and a while and i usually just keep it over revved until it settles down.

This is a bit over the top but I saw a solution where one guy swapped the fuel lines from the Odyssey of the same generation and that seemed to solve his problem. Just putting it out there.

 

[beachtech]

Thanks SilverBullet. No return rail, that's odd. Well, I'm not going to switch it out. I am just wondering why until recently I never had that problem. It's probably due for a fuel filter, but I don't know if that would cause this issue.

BTW-It did it again tonight. Drove about 15 minutes. Parked it in the driveway. Went for a 20 minute bike ride with the daughter. Came back, went to move the car into the garage. It's dark and 56F outside right now. Stalled three times before I could get it in the garage.

there's also been a documented problem with these engines because the fuel rails don't have a return line the fuel will vaporize in the rail and as such will run rough as hell for a while.
.

 

[jwong512]

Could also be a main relay issue. Search it up, I believe there is a fix already for the V6's on the forums. The 4 cylinders don't have this problem since the main relay doesn't generate enough heat to fry something.

 

[beachtech]

Jwong, I searched and read-up on the main relay issue. From what I read, I would bet my money the main relay is the issue. Fortunately, I am very skilled at soldering, so I will pop it out and resolder it. THANKS!

Could also be a main relay issue. Search it up, I believe there is a fix already for the V6's on the forums. The 4 cylinders don't have this problem since the main relay doesn't generate enough heat to fry something.

 

[CDsDontBurn]

From my understanding of this problem - because it happens exactly as you described to my car also, but mainly during the summer - is that the Fuel Pressure Regulator and the PCM are the problem. Somebody else here has fixed their heat soak problem and here's how they did it.

http://www.6thgenaccord.com/forums/showthread.php?t=32974&highlight=heat+soak

 

[LeBirdNest]

check your alternator connectivity. the terminals can become corroded and break in half. the wire is still in place under the rubber but no true connection is made. making for a faulty idle and very unreliable electric connection. check the alternator.

 

[cl206]

I posted that heat soak thing and it has been over a year and I haven't had the issue since. There has been a couple of times when it *almost* sounded like the problem might come back but it hasn't died like it did before. So for me I would say so far so good. Since I posted that I had 126XXX and now have about 132XXX. But read my post and see if the issues are indeed the same.

BTW I did change the main relay myself and for me that didn't solve it.

 

[beachtech]

check your alternator connectivity. the terminals can become corroded and break in half. the wire is still in place under the rubber but no true connection is made. making for a faulty idle and very unreliable electric connection. check the alternator.

Thanks, I will do that first. Your post could explain why the Accord I have suffers from low voltage as well. Thank you.