red top sr20det stumbles between 2500 and 3000

[s13240sx10psi]

hey guys and gals got a problem with my budys red top sr20det it stumbles between 2500 and 3000 basically like a on a off switch. It all started when i set the timing to stock (guy had it before had it at tdc ) it didn't do it before but it was very slow go figure. We have adjusted the tps which was at .12 at idle we set it to .48 at idle. then found the ground on the z32 maf going to ?ecu? not body ground was broke in half soldered that back no change. Also found walbro fuel pump plug was burnt up replaced that still no change. she is not throwing any codes eather. Sadly he has no wide band but he will get one with in the week or 2. The guy who did the swap realy screwed the harness up. please help thanks in advance

list of mods
z32 maf
gt2871 11psi
550 injectors
walbro 255
enthalpy tune
z32 fuel filter
3 inch exhoust and test pipe

list of stuff replaced
another used tps
a good maf
new brk7 gaped to .30
checked coils
changed temp sensor for good one
new fuel pump (walbro)
check timing a billion times
checked timing chain alignment
will check for boost leaks this weekend

[s13240sx10psi]

bump for help

[compactfean]

There are 2 grounds for the z32 maf. One goes to the ecu, the other goes to chassis. What's plug gap? And what's fuel pressure?

[s13240sx10psi]

fuel pressure is 32 at idle and plugs are gaped to .28 also the maf has both grounds the body ground and ecu the ecu ground was broke so i soldered and heat shrink it still no change. im completely stumped which is rare. thanks by the way

[s13240sx10psi]

it also gets very s*** gas mileage. last night i pulled the o2 sensor out and one of the heater wires were broke fixed that to.

[compactfean]

O2 sensors don't do very well without the heater.,(single wire o2 are recommended to be replaced every 15k) 32 fuel pressure at idle is very low. Pull the vacuum line off, then adjust to 43, then put the vacuum line back on. (usually ends up 37-38) also rev the engine and watch fuel pressure. If it stays the same or drops, fuel pump is probably going bad.

[s13240sx10psi]

ok will raise the pressure up on fpr and the o2 sensor is a three wire o2 sensor is that normal for a redtop and the plug is black ,red and blue and the red wire was the one broke

[compactfean]

Yes thats normal. If your using the #62 ecu you need a skinny o2. I don't go by colors with o2 sensors. If its an outer wire it is power or ground (heater is not polarity sensitive) and the middle wire is signal.

[compactfean]

The only reason I brought up how long single wire o2 last is because if the heater hadn't been working most likely the o2 is ready to be replaced. The heater drastically extends the life of an o2 and if not working properly will destroy it'd lifespan.

[s13240sx10psi]

ok i will replace the o2 then couse it was an out side wire and its getn very bad gas mileage. how do u tell if its a #62 ecu should it sey it on the ecu it self

[compactfean]

Yes. On the front cover.

[SlidingSR20det]

Its my car this is really makimg me mad that we cant figure this out.

[s13240sx10psi]

welcome to the fourm man and yes agreed

[SlidingSR20det]

Knock Sensor maybe?

[s13240sx10psi]

disconnected and reconnected battery stopped stumble n know but she only getn 13 volts to ecu so gota check some stuff

[s13240sx10psi]

when it stumbles between 2500 3500 it leans out to 19 its like a switch the hotter it is the worse it is

[compactfean]

What tests have your performed? still thinking fuel pressure issue.

[blkvrtswp]

Does it run ok OVER 3000 rpm?

[s13240sx10psi]

It had a walbro 255 that burnt up and we replaced it and it holds 35psi idle and 43 with vacuum line unplugged we tried different pressures none made a difference between 2500-3500. We have checked the maf with a know good one replaced tps replaced plugs found a bunch of wire joints the were s*** spliced fixed those (one of the grounds for the maf was broke) asoon as the head lights get turned on the motor will hiccup then smooth out in a sec only way i know to describe that, voltage will sometimes be at like 12.5 and u have to have more than 50% throttle to get it to lean out and miss between 2500-3500 im pretty good with motors but this has me stumped before 2500 its fine after 3500 its fine asson as u hit 2500 at 50 % or mor throttle it leans right out and starts stumblen thanks for the help