Low rpm stutter

[ajinvista]

Drove to work, car ran fine. Leave work, drive to the freeway, go to try and merge and the car starts
stuttering real bad. Idles like crap and stutters off idle all the way up the rpm's. Sitting with no load and
revving the motor, the stutter goes away after about 2500rpm or so. Put a load on and it won't stop stuttering at all. Cruising on freeway with no load it goes in and out of stutter mode, put any kind of throttle
on and it comes back.
Timing good.
Plugs good.
Fuel pump good. Haven't checked pressure yet to see if the FPR may have crapped out.
No boost leaks.
May change computer back to stock one.
The problem just came out of nowhere, WTF!
Any hints??

 

[kqodprez]

Check that the spark plugs are getting the proper voltage, it could be your alt.

 

[ajinvista]

That was going to be my next check was the alt. For some reason that is what may be causing some of my tuning issues. The belt has been squeeling at startup off and on, especially when it gets real cold. I've tried to tighten it a few times, but it seems as though I may need to check into a new belt and alt.
I'm glad someone else had the same thought.
Thanks

 

[ajinvista]

Okay,
Found that #3 and #4 cylinders aren't firing.
If my coilpack is bad, how does #1 and #2 fire.
I thought 1-3 and 2-4 were together?
Can my transistor be bad and cause this?
Now it won't start at all.

 

[ajinvista]

Okay,
Replaced coil, fpr, ecu, TPS, pump and plugs.
Parked the car stutters off idle till about 2k then clears out, most of the time.
My fuel trims are
Low; 86%
Mid; 100%
High; 100%
O2 feedback trim is where I having some issues. Most of the time it's
reading somewhere around 35% at idle, then stutters off idle till about 2K. Then the
o2 trim comes back to 100% + and seems to run good and above 2k tapping
the throttle I get good resonse and no stutter.
It will also not stutter sometimes after coming down from 2k or above, but
eventually the stumble comes back if you let it idle. And the o2 trim goes whacky
and settles at 36%?
O2 voltage at idle sits around .87, fluctuates down to 0 and back when I let off
the throttle.
When the car is in motion the stutter is so bad just trying to get the car moving
it's scary.
No boost leaks, this car has run fine with the connection to the TB blown off, just can't get out
of it's own way, but runs fine.
Injector test, all working. Plugs are all firing. NGK BPR7ES. .028 gap
Running a VPC w/GCC and chipped ecu.
Changed back to stock FP and ECU, nothing. VPC seems to be doing it's job fine.
Could it be as simple as an O2 sensor????? It's a new 4 wire. Thought the old one was bad
for another problem I had a while ago.
I have a logger so ask away. No CEL codes at all.
2 weeks and counting. HELP!