car is stuttering at certain rpms...
 

ok im driving along and when it hits a certain rpm (either 3500 4k or 5k) its starts stuttereing. also when i start my car when its cold it sounds like its struggling to stay started at first...

any ideas?

secondary fuel injectors...?

either spark plugs or fuel system. My first thought would be fuel filter. I could be way off though.

I installed a Walboro fuel pump in my 86na. I don't know how it ran before I did this because I bought it with a bad pump. But, now when I put a load on the engine, such as trying to accelerate quickly or driveing at hi speeds, it has a huge flat spot.
I'm thinking it's getting to much fuel, and I plan to replace the ECU. Is there something else that might be causeing the problem? If not is there a way I can equil out the air fuel ratio manually?

loose ecu contact

simple possibility: bad wires and plugs?

complex possibilities: could there be some reason that the computer may be thinking there is more air than there actually is or maybe something wrong with the temperature signal? just guessing ...

s4's are notorius for the 3800 RPM stumble whitch is cuased by bad ecu soldering

Thanks I'll check it out.

The ECU is black, inside the driver side kick panel, and the PCM is on the passenger side. Which one needs to be checked or replaced, and what is the difference between the two if they go bad (or soldering)?

Still no luck.
 

I replaced the ECU with no luck. Any other thoughts?

3500rpm hesitation probably. You can search the 2nd gen section for "3500 hesitation" or "3800 hesitation" (not accurate, but it'll give the right results).

It's caused by bad grounds.

The Walbro is WAAAAAAY overkill for an N/A that's anything under bridgeported. You need to replace that beast with a regular N/A pump.

So my fears Have been realized. Thanks.

What about adding a JDM Fuel Pressure Regulator? Will this allow me to drop the pressure back to normal?

Fuel PD!!!

Fuel PD search