How long after you get the problem to start do you have to wait before it starts working ok again? Sounds like vaporlock to me. The gas in one of the lines or in the tank is getting hot and turning to vapor causing the severe power loss. I have seen bad running fuel pumps cause vapor lock before but they usually arent in tank pumps but rather inline electric pumps and mostly Ford trucks. An exhaust leak near the fuel system can cause it as well. I have seen cars with mufflers that have fallen off do this and it is just hot exhaust blowing on the fuel line or fuel tank. I suppose the return line could be clogged causing the fuel to not circulate and causing it to heat up and vaporlock. A clogged return line could screw with pressure too.

 

[QUOTE]Originally posted by Freakaccident
[B]How long after you get the problem to start do you have to wait before it starts working ok again?

 

I would definitely vote for a fuel problem though. I still lean towards vapor lock or a pressure problem. You wont know until the dealer decides to troubleshoot it instead of standing in a dark closet.

 

CHAPTER 2

Well, after getting my car back from Freeman Honda they checked and reset everything and didn't find a problem, so they said. What did they check and reset? No one seems to know. They said it was my heat shroud running over the radiator top restricting the airflow - never mind that it still had the prob with the top of the air box off.

B U T . . . it is running better.

Not great, mind you, but better. It strains to rev from 4000-7500 then BAM in no time it's 9000 rpm. Driving it home I felt almost like a surging in the power. The more I drove it the smoother it got. Not completely smooth and not all the power came back, but a lot better. Power at 70 mph in 6th was non existant.

I decided to get the car dyno'd to have something to prove to Honda the power was off.

Stopped at Intercrew, which is not far from my house. I dyno'd from 193 to 198 hp. On his machine he says they normally dyno at 202-205. (You can't really compare dyno charts from machine to machine except generally.) So that means I am down 9-12 hp

AND there is a noticeable dip in power from 4000-4500 EXACTLY THE RANGE YOU ARE IN CRUISING AT 70 IN 6TH GEAR!

I came home and pulled the plugs. #1 plug was pretty loose. I figured they must have pulled it and didn't torque it all the way down.

#1 & #2 plugs looked just fine and were gapped at .40 (spec is .39-.43)

Plugs 3 & 4 were paper white which means they were running lean! #3 had blown the gap to .45. #4 was up to .43.

Is there a known fuel rail fuel delivery problem?

Some of the Miatas on the returnless fuel system (99+) have seen significant hp increases and smoother fuel delivery from larger, better designed fuel rails. They also have a #4 problem that seems to stem from a lean #4 cylinder.

I don't know where to go from here.

 

Dave,

if you really think it is a fuel delivery issue, which seems reasonable, why dont you check the fuel pressure...and change the fuel filter. They are not that much of a pain as far as I know

bassem

 

The fuel filter is in the gas tank and is part of the fuel pump so I would rather Honda did that.

The fuel pressure regulator has supposedly been checked. I do intend to check the volume of the fuel pump this weekend.