I have a 1999 baja h2x recently put a 415hp in it cause motor was busted when we purchased it. It has a air motive aftermarket fuel system on a mpi set up. Should I put a new stock fuel pump and start back like factory! My problem is it loads up in no wake zones and the computer messes with the timming! Next thing you know it wont start for a while!! Just looking for some good advice cause im ready to carb and intake it and be done with it!! Runs great other than the fuel preasure not cutting back at a idle!

Any help would be appreciated! Thanks in advance! !

If it is all factory stock save yourself a lot of time, headaches and money by putting a scan tool on it and find the problem without guessing. At least then you can make informed decision on whether or not to go carb. Been down the same road before and so have many others. Good luck. Ijust saw you have aftermarket fuel system, so my suggestion may not work. Sorry.

I would start by seeing what the fuel pressure is doing at idle. Perhaps it is overrunning the fuel pressure regulator? Fuel pressure is a constant with the ECM and without O2 sensors it does not know if it is injecting too much fuel and will not compensate for it.

It almost sounds like you are experiencing vapor lock. Which year mpi setup is it?

1999 genVI

About 35 psi at end of rail. Im going tobput one where fuel line first goes in and in the manual it says to not use the gm regulator thats factory on rail cap it and use bottom line in. Maybe with this pump not being factory it should go threw the regulator on the rail!

Mefi 2 is the fuel injection

So you're trying to use that Aeromotive pump with a factory regulator ?

Am I reading that correctly?

If so, thats not going to work if its not adjustable.

Why not ?

Pump doesn't create pressure - it pushes against it. Regulator is what stops or restricts flow depending on demand to keep the psi.

If the regulator orifice size, or something else in the system with too small orifice size, that flows less than what the pump can flow, will cause over pressure.

Anyway, the 502MPI ATI procharged set up used a FMU after the factory regulator to add more psi when under boost. Without boost, the factory regulator mainted the fuel psi....which it did fine. These systems had the Aeromotive 1000 fuel pump.