05 Honda Pilot - Starts rough, then runs fine

[2005HondaPilot]

Hello all,

I was hoping to get some suggestions on diagnosing a problem I'm having with my 2005 Honda Pilot EX-L.

Symptoms:
- Occasionally has trouble starting up. Keeping the key turned and feeding a little gas seems to get it going. Can sometimes take 2-3 rounds to get going
- Has enough power cranking it (Doesn't sound like a low battery or anything)
- Once it gets going, runs perfectly fine. I can turn it off and it starts right back up with no problem
- MIGHT be temperature related? I park it overnight (get home at 5pm and don't drive it until 7am the next morning) and it starts relatively easily (not perfect, but not bad). However, when I go to lunch and it's hotter it will start a lot rougher (even though it's only been 4 hrs vs the 14 hrs it sat overnight)

Background
- About a month ago I had an overheating issue. I've since replaced the radiator cap, thermostat, and replaced an anti-freeze reservoir elbow that had a hole it in. That seems to have fixed the overheating, but not sure if it contributed to the current problem.
- It was misfiring consistently. Cylinders 1, 2, and random codes. I replaced one of the ignition coils (number 2) and that fixed the constant misfire

Things I've tried so far
- Replaced ignition coil #2 (fixed the constant misfire)
- Replaced the Engine Coolant Temp Sensor
- Let gas get down to 1/8 tank and refilled with regular non-ethanol gas (Usually use Ethanol)
- Did a compression test on all 6 cylinders to test head gasket. All checked out around 160psi
- Tried a bottle of Lucas fuel additive

Other ideas
- Fuel pump? If it was the fuel pump, wouldn't I have issues all the time and not just when it starts up?
- ECM? How would I test this?

[94eg!]

Have you replaced your plugs? You can try some inexpensive Copper NGK v-powers. These are outstanding performance plugs, but they should be replaced regularly. Copper cannot last as long as Platinum.

Is your engine consuming motor oil? Perhaps your valve seals are leaking oil down into the cylinders. I don't know if this would cause a problem starting, but the idea popped into my head...

[xGS]

Originally Posted by 2005HondaPilot

- Occasionally has trouble starting up. Keeping the key turned and feeding a little gas seems to get it going. Can sometimes take 2-3 rounds to get going
- Has enough power cranking it (Doesn't sound like a low battery or anything)

How old is the battery?
You can have it load tested to measure the CCA in its present condition.

How many miles on the vehicle?

Second the suggestion to check (or replace) the spark plugs.

[rocky]

When you say you filled with normal non Ethanol gas, I'm puzzled. All gas uses 10% Ethanol. What were you running your car on before?
What your MPG?
Hows the air filter?
What codes is it throwing?
Whats the fuel line pressure?
What voltage is the alternator producing?
Has the timing belt been replaced?
Did these problems start after replacement or any other work?

[xGS]

Originally Posted by rocky

When you say you filled with normal non Ethanol gas, I'm puzzled.

All gas uses 10% Ethanol.

Not necessarily so.

It depends upon your location.

Ethanol-free gas stations in the U.S. and Canada

[bdac2k]

The symptoms you list (eg: hard to start when hot) is indicative of a bad coolant temp sensor. Fairly inexpensive part and easy to swap, and may cause starting issues when the engine is hot. If this sensor is broken, the ECU doesn't know if the engine is hot so it cannot properly calculate the air/fuel ratio causing the starting issues you are experiencing.

Give it a try!

[rocky]

A Bad coolant temp sensor is fairly high on my list, but there seems to be more going on than that

[2005HondaPilot]

Originally Posted by 94eg!

Have you replaced your plugs? You can try some inexpensive Copper NGK v-powers. These are outstanding performance plugs, but they should be replaced regularly. Copper cannot last as long as Platinum.

Is your engine consuming motor oil? Perhaps your valve seals are leaking oil down into the cylinders. I don't know if this would cause a problem starting, but the idea popped into my head...

All spark plugs were replaced with NGK Laser Platinum plugs 2 weeks ago
I haven't noticed any drop in oil levels, no smoke, no oil puddles, and no discoloration/foaminess in coolant

Originally Posted by xGS

How old is the battery?
You can have it load tested to measure the CCA in its present condition.

How many miles on the vehicle?

Second the suggestion to check (or replace) the spark plugs.

I will take it down to have the battery tested
There are 60,000 miles on it

Originally Posted by rocky

When you say you filled with normal non Ethanol gas, I'm puzzled. All gas uses 10% Ethanol. What were you running your car on before?
What your MPG?
Hows the air filter?
What codes is it throwing?
Whats the fuel line pressure?
What voltage is the alternator producing?
Has the timing belt been replaced?
Did these problems start after replacement or any other work?

-I usually fill up with the option that lists "10% Ethanol" above it. The other option just says regular. I'll double check the info/labels on my next fill up

-Nothing noticeably bad w/ the MPG. I'll monitor it after my fill up

-I did not throw any codes for the past 2 weeks with this problem. However, just yesterday, it did throw 4 codes: Cylinder 1 misfire, Cylinder 2 misfire, Cylinder 4 misfire, and Random Cylinder misfire

- I am not sure how to test the fuel line pressure. Does this require special equipment?

- I can try to test the alternator voltage, but I'm not sure what it currently is

- I have not checked the timing belt, but I will. I have had this vehicle for about 6 months, so not sure what the previous maintenance was

- I did change one of the ignition coils to fix the constant misfire. The car would not run smoothly, but as soon as I replaced the coil it ran fine. Now that you mentioned that, I think the rough start developed after this IIRC.

Originally Posted by xGS

Not necessarily so.

It depends upon your location.

Ethanol-free gas stations in the U.S. and Canada

I am located in Nebraska

Originally Posted by bdac2k

The symptoms you list (eg: hard to start when hot) is indicative of a bad coolant temp sensor. Fairly inexpensive part and easy to swap, and may cause starting issues when the engine is hot. If this sensor is broken, the ECU doesn't know if the engine is hot so it cannot properly calculate the air/fuel ratio causing the starting issues you are experiencing.

Give it a try!

Originally Posted by rocky

A Bad coolant temp sensor is fairly high on my list, but there seems to be more going on than that

I replaced the engine coolant temp sensor about a week ago with no improvement. (Beck/Arnley 158-0811 Coolant Temperature Sensor)

[belundy]

You didn't mention that it is missing or running rough after a hot soak start, so ignition components are probably fine. Without putting a scan tool on it to see what sensors read under hard starting, my first guess would be fuel related.

Might be marginally low fuel pressure or regulator issue, which doesn't raise the pressure high enough in hot fuel lines to prevent vapor lock. This is especially a problem with ethanol blends in the summer and right after the engine is shutoff--under hood hood temps spike for some time before dropping.

If your area has non-ethanol blends available during the summer, you might try a tank of that, first, and see if that helps.

[2005HondaPilot]

After a few weeks or running, I've found some more info that may be helpful. It's taken a while to really get a good idea of what was making changes because I would have to wait until the next day to test it again.

If I turn the ignition to stage 2 (dash lights, radio, and AC have power), then I can hear the fuel pump running for a few seconds. As long as I do this, then the car seems to start fine. I've gotten into the habit of turning the ignition to stage 2, wait a few seconds, turning it off, turning it back to stage 2, waiting a few seconds, then starting the car. This starts it every time without hesitation.

Back to the fuel pump?
Am I on the right track thinking that it could still be the fuel pump? I originally threw that idea out since the car ran fine and had no problems feeding fuel to the engine after it started. However, I've heard that it could be something to do with the fuel pump regulator?

I just borrowed a fuel pressure test kit and would like to test the fuel pressure. However, I haven't been able to find any good info on how or where to test this.

[2005HondaPilot]

Originally Posted by belundy

You didn't mention that it is missing or running rough after a hot soak start, so ignition components are probably fine. Without putting a scan tool on it to see what sensors read under hard starting, my first guess would be fuel related.

Correct on the hot soak. After it's running I can stop/start the car immediately with no issues.

Originally Posted by belundy

Might be marginally low fuel pressure or regulator issue, which doesn't raise the pressure high enough in hot fuel lines to prevent vapor lock. This is especially a problem with ethanol blends in the summer and right after the engine is shutoff--under hood hood temps spike for some time before dropping.

If the car sits over night, I still have this problem. You mentioned "in hot fuel lines", but it happens when it's completely cold. It starts up right away after the engine is shut off.

Originally Posted by belundy

If your area has non-ethanol blends available during the summer, you might try a tank of that, first, and see if that helps.

I am on my third or fourth tank of regular, non-ethanol blend of fuel. Didn't make a difference.

[94eg!]

Well, the fuel suction line and return should be submerged in fuel in the tank.

Of course that may not always be the case. It sounds to me like something is letting air up into the fuel lines as the car sits. Perhaps there is a leak somewhere. Can you ever smell raw fuel anywhere around the car?

Of course a leak on one of the components inside the fuel tank (pump or regulator) would be very difficult to diagnose. It will simply allow air from the tank up into the lines. Perhaps that is what they mean by a regulator problem...

[belundy]

Check valve in pump could be leaking, however overnight many systems depressurize,

One or more injectors could be leaking, which would depressurize and flood the affected cylinder.

I'm still not taking low pump pressure/volume off the table.

BTW, I haven't looked closely--does the Pilot really have a bypass/fuel return to the tank? I thought most manufacturers had moved to returnless regulators.

[cbp1]

To: 2005HondaPilot: Did you ever solve this problem? I'm having similar problems with my 2006

[2005HondaPilot]

Originally Posted by cbp1

To: 2005HondaPilot: Did you ever solve this problem? I'm having similar problems with my 2006

Yes, I let it sit one weekend and it started really rough and put out a lot of white smoke. This lead me to believe it was an antifreeze leak, so I took it down to a local tech to have it specifically tested for this (I'm not sure what the test was exactly, maybe a die test?). They confirmed that there was a leak.

I'll probably get flamed for this, but I ended up using the Bar's Leak product. I've been running this way for about a month and have not had a problem since. This was the exact product I used:
www.barsproducts.com/HG1.htm

It's hard to know for sure if it's the same thing as yours. In addition, I've been told multiple times that this type of leak is really rare. If yours is putting out white smoke, starting really rough (rougher when it sits longer), then it might be worth getting tested for this type of leak.