Tbi Q's ..... Throttle Response

[bitemedoughboy.com]

ok my used jap import vg30i idles like a top and has ok low end torque and power for a stock vg30i.... i just replaced the o2 sensor and it seemed to help a bit with the trottle response, but the power seems to start dropping off around 3k and up, and it will not rev under load past 5k. the timing is at factory specs, and i also checked the fuel pressure and while reving the engine.... it stays steady around 34psi, i have not checked fuel pressure under load conditions. the ECU is not throwing any codes out. it also falls flat on its face if you accelerate at anything but a snails pace. it will go blah for a second or two then it picks back up. any ideas?? could my fuel pump be on its last leg? or could my pick-up screen be clogged?

[88pathoffroad]

It could be quite a few things. The only way to find out is to start taking things off or apart to find out what's doing it. Tried cleaning off your MAF sensor lately? Sometimes a dirty MAF will give you poor throttle response, etc. Fuel pressure after the pressure regulator should be 36.3 psi at idle, the pump alone puts out 45-50 psi at all times IIRC, which is then reduced by the pressure regulator.

[bitemedoughboy.com]

It could be quite a few things. The only way to find out is to start taking things off or apart to find out what's doing it. Tried cleaning off your MAF sensor lately? Sometimes a dirty MAF will give you poor throttle response, etc. Fuel pressure after the pressure regulator should be 36.3 psi at idle, the pump alone puts out 45-50 psi at all times IIRC, which is then reduced by the pressure regulator.

I cleaned the MAF sensor earlier this year, i will have to give it another shot of sensor cleaner..... i will double check my fuel pressure, and try crimping the return line to see what the pump will max out at....

 

 

... if my timing belt was off by one tooth on 1 or both cams could that cause the stumbling and lake of top end?

[88pathoffroad]

Definitely. I did that once. The crank gear was off by one tooth. It stumbled, lost major power at higher RPM's and idled funny until I took the t-belt back off and got it right.