Ok, so i've been having this problem for a few weeks now.

Whenever I enter WOT from under 4k rpm, I usually get a stumble/misfire/hesitation/sputter (not exactly sure which exactly)

This issue occurs mainly when my vac goes from 2hg to about 3psi

above 4psi to about 8psi is relatively smooth, but there is a noticeable loss of power up there.

Vacuum/Boost
my vac has not changed for a year, which leads me to believe it isn't a vacuum leak/boost leak, not to mention I've experienced both and this feels nothing like it.



IGNITION:

I have replaced the stock wires and the older plugs with br7's, and ngk blue wires, and it even alleviated the problem for ~10 min. When it returned, I did notice an overall increase in performance, and minor alleviation of the problem. The problem still occurs as often as it did, but now it feels just a "little better".

After installing plugs/wires I went for a test drive for about 20 miles, and the same the next day. I then pulled the plugs and here they are, numbered 1-4, 1 being the closest to radiator, and 4 being closest to firewall.

#1


#2


#3


#4



Fuel Pressure:
I have recently replaced my stock pump, with a walbro 190lph hp pump (the problem existed on the stock pump, and still exists with the walbro)

The gauge, when f/p and gnd are jumpered, reads ~45psi at idle, and maxes my gauge at 100psi when pinched.

When the car is on/idling, the gauge reads

50-55psi bouncing between the two at like 10x/second


MISC
I had a CEL 3 and 16(i think, it was the o2 code, namely cuz the wire wasnt connected ^^ )
I re-soldered the wire for the o2 (after disconnecting it, which made this hesitation/stumble problem occur less often, but the shitty milage didnt warrant the unplugged-ness)
I also re-soldered the connection of my MSD ignition box to the CAS wiring harness, as the previous job was sub-par. (code 3 = g-signal, aka CAS bullshit)
This all resulted in
NO CEL after a reset of the ECU




I could fathom the following being the culpret:
Dirty/Shitty Injector
Bas CAS
Bad Coil
Bad MSD Ignition
Bad FMU (using old style Cartech)

Can anyone point me in the right direction?

 

you have a vacuum leak.

 

Is this based on the gauge?

I realize the number displayed is rediculously low, but I idle clearly at ~1k.

The gauge has displayed that vacuum reading since I bought it (used :( ) and the car operated perfectly untill recently, which didn't even result in a change in the displayed vacuum.

I'm not trying to tell you you're wrong, as I will go ahead and check my vacuum bs over again, but I'm not 100% sure my gauge is accurate.

It's resting position (car off) is 2hg vacuum

 

vacuum gauge and fuel pressure suggest it.

 

your idle pressure seems a little high. I'm only running 33-35psi at idle with a 255lphHP and 48-50 at 0 on the boost gauge

 

Well, that would go and offer some explanation as to the jumping fuel pressure. Odd that my gauge would display the same number for so long, yet behave as if it were quite healthy. Maybe an opening that only allowed air to enter under vacuum, but managed to keep boost in until recently?

I will go ahead and strip the bitch of its hoses and work my way up from scratch later this week

 

You probably have a vacuum leak. It should pull more vac. at idle. Also, do you have a wideband? I would go over ALL your vacuum hoses. Also, this sounds like shitty wiring could be the culpret. If anything is suspect, redo/test/fix it. We need more info to help you. How about more pics for starters. 1.6 or 1.8? You could put some info in your signature so we know what ya got.

 

fuel pressure at idle should be closer to 35psi and very stable. the less vaccum, the more the number reaches 48-50psi, idling at 45psi suggests loss of vaccum. vacuum gauge at 10~hg at idle suggests the same. you should be much closer to 20~hg.

hesitating into boost could be a negative effect of a bad fuel mixture, ecu fight the FMU and the AFM giving it bad readings.

 

Alright, sig updated (thought I did that a while ago, actually).

I do not have a WB02, and I have recently gone through any and all wiring I have ever modified/spliced, and I cleaned them up and re spliced with rosin core lead solder, making sure to wick to all wires, and re-wrapping them.

I've got my multimeter handy, but I'm trying to save that bullshit for when I have narrowed the problem down to a sensor.

What do you want pics of?

*i've got an olderguy o2, and a test pipe ready to be installed, which I figured would help alleviate some of these issues further.

Forgot to add bov to my sig list ;p

 

Doesn't that 2nd sparkplug pic bother anybody else? Looks like that cyl isn't even firing. It would take more than a vac leak to cause that.

 

Your idle should be around -20

 

correct, #2 is not firing.

 

I see number two as being too clean. Perhaps washed down via a bad Head gasket? Coolant in cyl, cleaning plug. Gets worse under pressure as he is noticing under boost.

Just my 2 C..

Goodluck

 

And the rest of the plugs are showing too much carbon to be in there 20 miles. That also indicates running rich.

Why anyone would spend all of the time and money putting a turbo on a car and not buy a wideband is beyond me. I want to know everything that is going on in a modified engine. If I had room to mount them I'd have more gauges than an F-16. I want EGTs for each cylinder, wideband, fuel pressure, boost/vac, oil pressure, oil temp, coolant temp, and whatever else I can find. That's the wish list. My $.02

 

#2 isnt getting fuel, Swap you injector from 2 - 4 put a new set of plugs in and see what they look like.

 

Yeah, number 2 does not look like its getting any fuel at all (hence why its white) I agree with the injector

 

will try this before work. I noticed the near white color, and that is what brought me to upload the pics.

I figured it was lean, but not LEAN lol


Makes me think inj 2 is clogged, forcing the fuel out of the other three.



and a wideband is soon on the way, in fact, if it weren't for this issue i'de have the cash to drop on it now
like all things DIY, budget rules all ;p

 

Its probably clogged but will have no effect on the other 3.

the regulator controls pressure no matter the # of injectors.

Ever heard of a JAW, its a diy Wideband.

 

I am glad someone brought up the #2 plug. I thought maybe I was the only one actually looking at the pictures.

 

Alright, I put another couple miles on the same setup, and checked the plugs, and they were all roughly evenly sooty.

I even went ahead and checked my fuel rail. There was a faint hissing sound, coming from the injectors and as I re-tightened the fuel rail bolts, the hissing became a whistle, and then silent.
One injector has s tiny bit of wiggle room, even with the rail tightened down.


After retightening/reseating the injectors, and running massive ammounts of fuel injector cleaner through the car (and soaking the injectors in the cleaner themselves) the hesitation/bogging is maybe 1/2 as intense, I do not "hear" it, but I still feel it in power loss and hesitation/stumbling, although not nearly as bad as it was.

I can drive the bitch much better right now, as every accidental push into boost used to make the car sputter and groan, but now its more of a hickup stumble and then smooths out to reduced power.

After cleaning the injectors, and reseating them, I notice more noise at the rail/injectors than before, in terms of a hissing sound.
I am not leaking any fuel at the injectors, or at least I cant smell/see it. At least at idle, I'm not.
However, I can stand verticle, not leaning over my motor with the car idling, and I can hear the injectors HISSSSSS over the motor.

My fuel pressure, after all this bs, has managed to fall to about 45 - 50, versus 50- 55.

So would this be indicitave of injector failure/seating issues (I no doubt should replace the injector o rings/spacers, any place recommended for green top 315cc seal kits? ^^) or fuel rail issues, or both?

Its odd that the stumble now lacks "sound" after I re-tightened the fuel rail, but that connection is at the injectors, and I wasn't seeing any fuel anywhere, nor smelling it ;p


EDIT:::


Forgot to mention, I got a CEL last night (came on for 5 seconds and is currently off), reading code 17, or o2 sensor output not changing. Dead o2? (its connected!)