Need help! Problem with P300 codes. P301-6 and Random Misfire occasionally.

Completed the following: Over the past 18 months.

P1456 Code: Changed EVAP Purge Control Valve and Canister
P 091 Code: Changed Fuel Pressure Regulator w/Kit
Changed PCM
P1491 Code: completed EGR Port Clogging
Cleaned Intake Manifold
Cleaned Throttle Body

The vehicle has 300k on it and runs GREAT! I have completed most all scheduled maintenances over the life of the vehicle and only use Mobil one synthetic oils and filter.

My research show that I have a fuel boiling point issue with type of gas we have in our region. Ethanol Mixture.

I have the Old fuel injection systems with the lower fuel pressures.

Is there a fuel additive I can use to get the fuel boiling point up so that I won’t have this issue when starting after "Hot Soak"

Other suggestions?

 

For the hard start after is it hot, may indicate a problem with the main relay, refer to this link:

techauto.awardspace.com/mainrelay.html

For the P1491 code, although you did the EGR port cleaning, was the EGR valve changed? An EGR valve stuck in the open position can cause the random misfires you are experiencing. The EGR valve may be intermittently getting stuck in the open position. Usually, P0401 would be for the EGR ports, although Honda does recommend port cleaning for certain models with the P1491.

 

Redbull-1

Thank you for your response.

P1491 code: Yes I completed the entire maintenance as required on to include changing the EGR Valve. I have completed the following maintenances in this order based on the codes and research at that time of the problem. This has all happened over about a 12 – 18 month time period.
Service Bulletin 00-024
Service Bulletin 99-074
Service Bulletin 99-075
Service Bulletin 99-085
Service Bulletin 01-004

Again, my research suggest that I have a Fuel Boiling Point issue as the fuel is retained on the fuel rail and boils. The residuals from this ratians in the intake and floods the car after HOT SOAK. If the car is cold or if the car sits for over 30 – 45 mins after HOT SOAK, I do not experience this problem.
The problem can also be reproduced if the vehicle sit at Idle for over 30 mins. (My assumption is the engine reaches fuel boiling point temps at that point.)

This is why I was concentrating on a retail fuel additive solution to potentially increase the fuel boiling point temps that can be used during the winter season when the industry ethanol fuel mixtures change to more light components with light combustion and lower fuel boiling points.

Thoughts?

 

What region are you in? An area where a "boutique blend" fuel is mandated? Simply winter-blend with a higher Reid vapor pressure? Are you in the southern hemisphere where it's summer now?

Also, what do you mean by the "old fuel injection system" with lower pressures?

I'm not sure I understand "hot soak" in this context. Your Accord has a recirculating fuel system where fuel is constantly pumped & returned to the tank at pressure controlled by the FPR. The pump is in the tank, not in the hot engine compartment. Once the fuel pump runs for a second or less, cooler fuel is delivered to the rail under pressure.

I think temperature influences vapor-pressure more strongly than the fuel blend anyway. In wintertime it seems more likely that too LOW a vapor pressure would cause problems like this.

So...
Parts of your description sound a bit like an injector is leaking down after you turn off the engine. When you start, that puddle of fuel in the intake port results in a too-rich mixture. After 30-45 minutes it's evaporated & you're OK.

 

If it helps at all. I used odyssey parts to fix the hot soak problem on my wife's 2000 v6. I swapped the rails fpr, mounting block and fuel lines to the block from the van. since the van's rails are set up as a "pass through" the fuel doesn't sit in the rails and boil. I got my parts from the local u-pull junkyard for less than $100. and the dealer wanted $2500 for a new ecu. Also I have heard that some people have had success just updating the fpr to the new honda replacement. I wasn't that lucky but it might be worth a try.

van set up http://www.hondaautomotiveparts.com/...28+00%2F+01%29

accord set up http://www.hondaautomotiveparts.com/...8V6%29+%283%29

I used a 2000 van as a donor. Hope it helps