carb engine misfire at 4000

[FrankD]

I get a misfire when aproaching 4000 rpm. Its worse when accellerator is floored. I've put in platinum 4+ plugs, new dist cap, rotor, fuel filters,air cleaner. Timing belt is good. Distributor shaft has no play that I can feel. Doesn't burn a drop of oil. 270,000km. How can I narrow it down to fuel supply or ignition problems?. How many lbs pressure should I have after the fuel filter. I've owned this car since new and accelleration has never been 100% smooth.

[A20A1]

hmm... clean the carb out... maybe get new vaccum lines and gaskets for the carb...

I think new vaccum line size should be 5/32... hmm that sounds wrong but I'll double check.
I think the PSI is close to 3.0 - 3.5

It sounds like your spring on the accelerator pump it losing it's tension... but it would only affect the acceleration... and also the power valve may be geting stuck so the vaccum can't pull in open.



check the vaccum advance vaccum line...
check you timing... make sure you hook the pick-up to the #1 plug wire... the one closest the the timing belt.

[FrankD]

Do you mean I need to dismantle the complete carb to clean it by hand or use a fuel system cleaning product(of which I have STP in the tank now) Also is there anything I can spray on the gasket temporarily to check if theres a leak there?

[A20A1]

get carb/throttle body cleaner with the red plastic tube to make a direct spray of the cleaner around the base of the carb... if the rpm's raise then you have a leak.

[njpeter]

my money is always on the ignition coil, cheapest to replace , never hurts to have the "spare" in the trunk in the event I'm wrong and avoids the expense and humilation of using carb cleaner. If that doesn't pan out, check the fuel inlet screen at the tank pump ( and beware the black goo-you will be assimilated if any part of your body touches it-gas only makes it hungry)

[ACCORD EX]

i'll start with carb cleaner ! but don't spray it while th engine is hot ! because its flammable stuff !

MIKE

[Don87LX]

Originally posted by njpeter
[B]the expense and humilation of using carb cleaner.

Expense?!? Carb cleaner is what 1.29 a can?

Humilation??? Dont know about you but the guys at the store have never giggled at me when I brought some gumout to the counter...

[POS carb]

fuel pressure will never reach 3.0 psi, the carb can't handle it, the reading should be about 2

[rocky2]

Is the misfire in exhaust or intake? exhaust would be a emmissions malfunction,intake would be a distribter inarded malfuntion.

[FrankD]

Its more like the fuel is being cut off in a pulsating manner or the timing is being totally thrown off. If you put your foot to the floor and turned the ignition key off/on rapidly this would feel pretty close to whats happening. The other thing is when I start car first thing in the morning it dies during fast idle after about 5 seconds. It never dies for rest of day. The misfire is intermittant also. Sometimes I'll reach 5000rpm ok, then shortly after I won't get to 4000rpm. I'm going to try all the ideas so far. I'm leaning towards fuel starvation. Its been raining for 3 days so I havn't done a whole lot of troubleshooting.

[rocky2]

Next time it does it. Keep a small hammer nearby. And gentlly tap on carb,then see if it helps. Your needle/valve seat in carb maybe hanging up. Run a little 2-cycle oil or Marvel Mystery oil in gasoline in an effort to clear it up if indeed tapping carb corrects it.