Weird A/F ratios and cutting out

[blaster17363]

I really need help with my car. It's been giving me these problems and I can't find out what it is.

So at idle my A/F will be at around 14/15. This is normal right?If I so tap the throttle the A/F will stay at 16/17. Boosting or not. At any speed. I really don't know what this can be. I've checked the MAF, the o2 sensor etc.

I am changing the fuel pump to see if that is the problem, but the fuel pressure gauge reads 40psi(My car has a stock pump, bought it that way, the fuel pressure reads 40psi)

Can it be the throttle position sensor? Are there any other sensors I should look at? Can the injectors not be getting enough current? I want to get this fixed.

Any help appreciated, thanks.

Modified by blaster17363 at 6:16 PM 12/15/2009
Modified by blaster17363 at 6:17 PM 12/15/2009

[Beems240sx]

what is the fuel pressure under boost? dont try it if you dont know it. 16-17 under boost is VERY BAD. ultra lean. where is your wideband 02 at on the exhaust?

doubt full that its the TPS. it could possibly be a clogged fuel filter or injectors.

and your injectors get a constant voltage supply, the ECU grounds them to make them fire.

[240life]

You said you are using a stock pump? By stock I assume your running USDM OEM. You need to upgrade your fuel system, get a 300zx filter, a walbro 255lph pump (or equivalent ) and an adjustable FPR (fuel pressure regulator). Adjust your FPR so it is set a t 43psi with the vacuum source unplugged.

[blaster17363]

The car is getting a pump installed monday. The fuel filter is a brand new z32 filter. I don't understand why I need a new FPR and such if the car is stock (T25 @ 7psi). My fuel pressure gauge is under the hood but when I look at it with the car at idle it reads 40psi.

The wideband is installed on the testpipe.

The reason I believe it to be the throttle position sensor is because my car displays all the symptoms of a faulty one:# Bucking and jerking of the car# Idle surging# Hesitation while the driver of the car is trying to accelerate# poor startup of the car # inefficient response of the throttle of the car

Another thing is that the car runs fine at idle after its been warmed up, A/F in the stoic range, however any little bit of throttle(just a tap) causes it to go lean.Even on the highway under vacuum it runs lean.

I'm trying to give you guys as much information about my car as I can. Thanks for the replies, keep them coming.

[240life]

Has the TPS been removed by anyone.....They have to be installed facing straight up and then rotated 90 degrees in order to set the spring, then you can test your voltage. As far as the stock FPR goes high volume pumps will eventually wear out the unit due to the increased volume and pressure

[blaster17363]

I don't know about the TPS being moved. This cutting out and ultra lean-ness has only started recently.

And the FPR and rail and injectors are all getting installed in January, along with a new turbo. However before they install my fuel/turbo/tune they want to get this problem sorted out.

They said my car is a wiring nightmare and they're going to redo the engine bay harness if the pump doesn't help.

I'm just trying to get some opinions on what you guys might think is wrong with my car.

[vocationalzero]

You might have a dead injector. I was trying to tune my car (safc2 w/ z32 maf). And I couldn't get my AFRs down and I was running numbers like you (16 etc). Do this, while the car is running unplug each injector one by one and see if the idle changes. Obviously if it doesn't you have a dead injector.

[blaster17363]

Would 1 dead injector be causing all the other problems I am having?

And I have checked the fuel pressure with the vac source disconnected and it reads about 43psi

[240trackjunkie]

What ecu/motor combo are you running?

Reason I ask, my stock redtop runs great on a 62 ecu. But it runs exactly the way you describe when a E5 ecu is hooked up.

[blaster17363]

Changed the TPS and that did the trick.

Thanks for all the replies though

[240trackjunkie]

Good job! Thanks for posting the fix.

[DuckyD]

Reason I ask, my stock redtop runs great on a 62 ecu. But it runs exactly the way you describe when a E5 ecu is hooked up.

That is because the E5 ECU is looking for a fat o2 sensor while the 62/63 uses a skinny o2 sensor.