Sputtering Troubles!!! HELP- Tried a few things...

[chrismo240sx]

So ive run into some problems unfortunately with the sr. Its an s13 blacktop for starters with basic mods, intake, turbo-back exhaust and FMIC, simple/basically stock setup.

Okay, problem is, I cannot give the car more than 1/4 throttle otherwise it breaks up BAD! Sputters and backfires like crazy. Will rev out, doesn't have a limit so I dont think its the MAF, and theres no black smoke from the exhaust, or any smoke for that matter.

So far, I have...
Cleaned out MAF
Cleaned out IACV
Replaced fuel filter (old and stock, replaced with 300zx)

What else could it be?
Heard of problems related to TPS, Knock Sensor, Fuel Pump? (stock Ka pump)

Anyones thoughts or related problems, please help me out with any advice!
Thanks in advance, as always!

[kamilp1908]

What ECU do You have? If 62, you can check ECU codes.
Do You have stock MAF from BlackTop? Mayby You have wrong MAF. What revs it starts working bad?

[PyR0NiAk]

TPS is something you should definitely check. Fuel pump should be swapped for a 255 either way. Only way you're going to know if your knock sensor is throwing any codes is if you pull the codes as kamilp suggested. Has this car ran correctly before, and just started doing this, or is it a, somewhat, fresh swap?

[zachattack_5491]

Set the TPS correctly, and pull codes as mentioned already. That's your best bet. Knock sensor is unlikely, I've driven without it for a week with a hardly noticeable effect.

[chrismo240sx]

For some reason i feel its the TPS. I ordered a Walbro 255 pump so that should be here around xmas hopefully.

Kamilp: It starts breaking up at any rpm, once i give it more than a 1/4 throttle gas, it will rev out as long as im real easy on the throttle...doesn't cut out, so i dont think its MAF.

Pyroniak: Thanks, I wish i could pull the codes...dont have a red led light hooked up to ecu yet. But the car was running fine up till yesterday. Ive been driving around a month or so with no problems, then out of nowhere this problem occured. So no, its not a fresh swap, which is why im so shocked as to what went wrong.

[zachattack_5491]

You should try unplugging the tps and driving it. When the TPS is unplugged the ECU runs solely off of the MAF reading. It won't run perfect, but you should notice a difference in the symptoms.

[rc1honda]

Yeah the TPS is suspect. Break the voltmeter out. I keep mine at .48 even though the service maual calls for .35-.45 at closed throttle and over 5.0 volts at WOT. .48 seems to idle well and have good throttle response.

A bad TPS can be hard to spot. You have to open the and close the throttle while watching the voltmeter. A good indicator is when the TPS is really jumpy. Now it will jump for to low to high throttle quickly but when held in place it should hold the voltage. And when slowly going from closed to open throttle it should climb in voltage realtivley smoothly.

EDIT: another thing i just thought off. If it happens at 1/4 throttle are you just starting to get into the boost? If it happeneing right when boost pressure is buliding it miught just be porlly gapped spark plugs. Pull a plug and check the gap. Should be around 22-35 thous. 35 at the largest. 35 might even be to big for your setup. I run NGK BKR7e's or something to that effect. A little colder plug at .28 thou gap. My motor was breaking up bad cuz the gapping was so huge once i fixed it it pulled hard all the way through redline.

[chrismo240sx]

Thanks rchonda, helpful info there.

Okay so i had a friend help me wire an LED to the ECU and heres the codes that came up..
21 Ignition Signal ????
34 Knock Sensor
43 TPS

Can all 3 really be bad, or does 1 have an effect on the other?
Im gonna check the plugs as well though tomorrow.

[kamilp1908]

You can always check Nissan Manual, how to solve ecu code problems.
As I remember, ECU codes inform You about problem in circuit (in your case Ignition, Knock Sensor and TPS).
Check all coil packs resistance, check PTU and check groundings.
Download s14 manual and there instructions how to solve ECU/electrical problems in You engine (chapter EC - engine control system)

[hboninc19]

Im having the same problem did you figure anything out?

[chrismo240sx]

well i didnt fix it yet....but i ordered a new TPS and Knock sensor, im pretty sure this will fix the problem, being thats what the ECU codes were pulling. Also, changed out the spark plugs being 2 were a little black from running rich. Also, have another set of coilpacks if all else fails, but Im pretty sure its the TPS sensor mainly!

[hboninc19]

keep us posted.