no accelaration

[krazyme]

i need help with a problem that i have when i push the accelarater on take off if i push to hard the engine bogs down but if i bearly press it and take off slow it goes fine. i have been told by 3 diff machanics that it was my M.A.S. (mass airflow senser) well i replaced that @ 300 bucks and still doing the same thing no engine lights are coming on so i dont think a obd 2 code reader would do much help i am stuck and any help that you guys can give me please and thank you oh my car is a 1990 infinity Q 45 with the v8 (no mods yeat)

[Infinitiguy19]

i need help with a problem that i have when i push the accelarater on take off if i push to hard the engine bogs down but if i bearly press it and take off slow it goes fine. i have been told by 3 diff machanics that it was my M.A.S. (mass airflow senser) well i replaced that @ 300 bucks and still doing the same thing no engine lights are coming on so i dont think a obd 2 code reader would do much help i am stuck and any help that you guys can give me please and thank you oh my car is a 1990 infinity Q 45 with the v8 (no mods yeat)

Its called a MAF for short or Mass Air Flow meter/sensor.

How old is the fuel filter and fuel pump?

Not that it might matter in this case but was the MAF OEM or aftermarket?

The 1990-1995 Q45's are OBD1, 1996+ and up is OBD2.

Do you the the service history which any Infiniti dealer that your car was service at can give you with proof of ownership?

The Q45 never came with with anything less than a V8. Unless you count the Infiniti Essence Concept which has a Bi-turbo V6. I know I will hear people challenge me, But look at the interior and compare that to a 1990 Q45 interior then post.

Lastly I sugest you stop going to any "mechanics" and find a good one or post more info here so we can help you.
Modified by Paul Wall at 5:17 PM 10/28/2009

[qship96]

Its called a MAF for short or Mass Air Flow meter/sensor.

How old is the fuel filter and fuel pump?

Not that it might matter in this case but was the MAF OEM or aftermarket?

The 1994-1995 Q45's are OBD2.

Do you the the service history which any Infiniti dealer that your car was service at can give you with proof of ownership?

The Q45 never came with with anything less than a V8. Unless you count the Infiniti Essence Concept which has a Bi-turbo V6. I know I will hear people challenge me, But look at the interior and compare that to a 1990 Q45 interior then post.

Lastly I sugest you stop going to any "mechanics" and find a good one or post more info here so we can help you.

"1994 & 1995 q45 are OBD2".........No, they are not......1996 was first year for OBD2 on Q45 models.

[Q45tech]

Probably fuel pump and filter since they fail 10 times more frequently than MAF.

[lino]

Probably fuel pump and filter since they fail 10 times more frequently than MAF.

I'm so glad all three of those are replaced on my car.

[krazyme]

yea i know about the any mechanics but i do work at a parts house so i know the good ones in town and with that being said i replaced the fuel filter just not even a week ago still same thing i have the tps on order i was told it could be that witch it fits. the fuel pump is fine!! i can pump the gas pedal like you are airing up a bike tire and it will eventully kick in and GO

[Infinitiguy19]

From what I could BARELY understand I think you need to make sure there is sufficent fuel getting to the engine with a fuel pressure test. There are two ways of testing fuel pressure; one is grounding the fuel pump and see what happens. Or you can buy a fuel pressure gauge from harborfreigh.com and tee it in the input line and measure the fuel pressure that way.

The Thottle Postion Sensor (TPS) would cause slow accleration but would also throw a check engine light (Code). But you make it sound like the transmission is the problems...so how is the car shifting?

[goody90q45]

......and still doing the same thing no engine lights are coming on......oh my car is a 1990 infinity Q 45 with the v8....

No CEL? It's either the fuel pump or Fuel Pump Control Unit (FPCU).

......the fuel pump is fine!! I can pump the gas pedal like you are airing up a bike tire and it will eventully kick in and GO

If you've replaced the fuel pump and not the FPCU then you've probably burned up your replacement fuel pump. Pull out the FPCU (in the background in the pic) and take off the cover. Any melted solder joints? Follow the ground pin path to the circuit board and you'll probably find some melting.

You can also jumper the fuel pump from the pin shown in the pic to ground which will make the FP run in high speed only. If this fixes the problem the FPCU is bad. If it doesn't, check your fuel pressure under load.

[Q45tech]

Remember the FPCU can fail entirely or just 1 of 3 or 2 of 3 circuits can fail.

The ecu commands which circuit in FPCU operates creating the 3 speeds.

The TPS/RPM sets the function based on load.

Why idle and light load maybe ok but problems above a certain throttle pedal position!

Measure current by substituting Ammeter for fuel pump fuse............see 3 different amp flows depending on TPS position/load/rpm all discussed in FSM!