on_alert

My car is STILL stumbling.
So far I have:
1) replaced spark plugs with ac delco plugs
2) replaced TPS
3) cleaned Throttle body
4) replaced PCV valve
5) replaced spark plugs again with NGK's
6) replaced fuel pressure regulator

between 2k-3k rpm, watching my SAFC (still untuned...) if i let my throttle go to 0% and i punch it it hesitates and stumbles (almost like its running lean). If I let it go down to 1% throttle, it doesnt stumble.

Sounds like the WOT sensor or TPS right? Its not. I changed it. I also put in new plugs (NGK coppers STOCK heat range), cleaned throttle body, new PCV valve and fuel filter. No change.

I did notice one thing. If i watch my fuel pressure, when i mash it, it imediately goes up from 38 psi to say... 8 psi, stumbles, then jumps another 7 or so and stops doing it. That made me thing stock FPR.

The only other thought i had was maybe the aftermarket FMU has a vaccuum leak and is responding slow. But my blow off valve is T'd into the same line and seems to work just fine. Whatever it is it is slowly getting worse. Car starts kinda hard now and is stumbles longer.

Any thoughts?

-ctn


Any thoufghts would be terrific.

-newman

MaxEffect414

iTrader: (2)

Do a Compression check and a vacume check and you should find the problem, It sounds like you have a bad coil pack, You might also want to check that.

bobjohnson

iTrader: (2)

wow. for starters and a personal opinion i would just remove the sc pulley and run without it to see what the actuall prob is. that may help save life on the sc as well. just a thought.

See all those things you replaced i did all too.
including ks, ects, plugs , tps
Yet I still Too idle Rough as all Hell. Check my sig. Shift_ "what"

on_alert

OK. Thanks for the advice guys.
(BTW: its a turbo not a SC)
I have 12 extra coil packs, i will try to swap them out today.
Compression is a little low at about 160 on each cylinder, but i dont think that is too low.
What exactly am i looking for in the vaccuum check. I was thinking that too but I get about 10psi of vaccuum and it will go to zero pretty quickely when i mash the gas. I am going to check the vaccuum at the FMU today, but it is t'd into the same line as the stock fpr, and that seems to work well????

ejj

iTrader: (5)

160psi compression is low, but acceptable.

Stock vaccum at idle is about 17-19in-hg. 10in-hg is low (to little vaccum). However, maybe that's typical for a turbo?

I think the easy solution is just swapping engines.

on_alert

10psi=20.3in-hg
so thats ok.
i cant put in the new engine until i get an e-manage unit and the new pistons and rods... its not in the near future... :tdown:


-ctn

ejj

iTrader: (5)

Doh! I should read a little more closely!

What disc in the FMU?

If you want to try an aftermarket FPR or different FMU, you could try either of mine (plus from 7/12-7/19 the car will be sitting engine-less at my dad's).

Have your tried putting a fuel rail/injectors/fpr from another engine on?

Confused

iTrader: (4)

fuel filter (last change?)
fuel lines (check for kinks and connections)
fuel pump (check the voltage, walbro's seem to love to crap out)

on_alert

fuel filter is brand new
fuel pump is new, and goes to >80 psi under boost

question: How does the fuel pump work, is it always running at a constant pressure, or does it vary pressure and flow rates?

The car runs fine (1382 EGT) under boost and anytime not jumping right off zero throttle.

Taxvictim

Maybe you should check the fuse or other electrical connections for the fuel pump. When I pulled mine out to depressurize the system, the car ran like you describe. I could still rev the engine (to my surprise), but it would putter out at low RPM's.