Help! Runs poorly after I get gas...

[85bim]

So I just recently finished my swap, and as the title states after I get gas it runs horrible. The idle fluctuates and it cuts out under acceleration.

Background on car:

1985 318i
- M52 with OBDI, M50 intake and TB, S52 Cams, 413 red label with TRM chip...
- zf tranny
It gets a little bit better as I drive but seems to take a while. The first time this happened (right after I got gas) I thought it was the idle air control valve so I took it out cleaned it and fixed a small vacuum leak and that seemed to do the trick.

It just happened again after I filled up the tank and I’m baffled...


Any help is much appreciated

[jim325]

When was the last time you replaced the fuel filter? What grade of gas are you putting in it? 87?

[85bim]

Fuel filter is new, though its just a small plastic one ( saw no need for a big bulky filter like the stock one was and didnt have much room). Im using 92 octane fuel.

Maybe releasing the pressure of the gas cap does something?

[MattM]

crud in the tank?

im guessing you have been to multiple gas stations with the same results?

[devon.818]

drain your gas tank and replace the fuel filter again.
chances are you have sediment in your tank that normally sits on the bottom, but when you fill up it stirs it all around and gets in the system.

just a guess

[85bim]

Thanks for the tips, sounds like a good place to start. And yes it was gas from multiple stations.

[Adrian_Visser]

So what kind of filter are you using? I really don't know why you would use a different filter than the original. If you are using a smaller filter it might not have the surface area to flow enough fuel at the required pressure.

[7pilot]

I hope that you don't set your car on fire.
Plastic fuel filter....Designed for Carbs.... less than 10 psi fuel pressure.
Fuel Injection 43psi that regulated down from a pump that can push 100+ psi

Get the correct filter ASAP.

m

[e30s50dan]

so what kind of filter are you using? I really don't know why you would use a different filter than the original. If you are using a smaller filter it might not have the surface area to flow enough fuel at the required pressure.

+1

[85bim]

Thanks for all the input, I'll pick up a new filter tomorrow and throw it in see if that makes any difference.

[Vtec?lol]

that and the plastic ones explode after so long. ask me how I know...

[AnimalE30]

Maybe releasing the pressure of the gas cap does something?

Are you saying when you open your gas cap you hear air rushing in to your tank?

IIRC that should not happen, either your charcoal canister is clogged (or you may have plugged it if you removed the system) or your gas cap is no longer letting air in. If there is a vacuum in your gas tank, you're making your fuel pump run harder and making it go bad.

[10Toes]

Make sure you evap purge valve is in the right direction, when I had the M50nv in my car the first time it would do this untill i switched the valve. I would only do it with a full tank, and once the level was down a little it would act fine.

[85bim]

Ok, so I put in the correct fuel filter and still having the same problem. I am sort of thinking vac. leak there is a small tear in the hose going from the ICV to the intake housing, I ordered a new one from pelicanparts, we shall see how if that makes any difference.

On a side note... I freaking love my car! I can't wait till all the small stuff is taken care of and get the suspension done, by far the most fun car I have ever owned!

[85bim]

Bump...

So I replaced all the hoses on the Idle Air Control Valve and still no change. I am leaning maybe toward fuel pump? Or a relay...

The idle is a bit rough and does not want to accelerate much without losing power. It seems like when I gradually accelerate it is better than just pushing down on the pedal.

Any other ideas...??