Been having this problem lately. As rpms get to 7000 there is hesitation from there up regardless of boost level. Its feeling somewhat like if there is some restriction in exhaust or too small of turbo. I was able to take it to 8200 in the past with no problems and i have not changed anything since. The logs show it richening up at that stage to low10's. I have since leaned it to low 12's which improved it, but it there is still a bit of hesitation and a slow climb from 7000 to 8000. WHAT COULD BE CAUSING THIS? I have a large street port with a GT4094R (106a/r) with 3" exhaust and I see no reason for it to feel so lame up top. I am now leaning towards some fault with ignition the ignition sys.

Things I have done to troubleshoot. (Troubleshooting done at low boost 7-8psi)

-changed plugs
-changed plug leads (to magecor 2.5mm)
-added Twin Power
-Ignition coils tested (per FSM manual) and swapped for known good set
-leaned the afr in that area to low 12's.--- this helped alot
-adjusted ignition timing in that area between 12* & 15* (no split used)
-ignitor removed and grounding areas cleaned
-added additional ground between engine and chassis
-checked that all plugs firing

Do you think my ignition timing may be too low for that boost level? Can low ignition timing cause this type of thing?

Is there anything else I may have overlooked?

 

Do you have a CAT installed in the exhaust, this could have colapsed, or the baffles in your exhaust have broken up partially blocking the exhaust flow

 

Which plugs? Did you have to gap them? did the problem happen with ngk wires as well? I'm not a fan of magnecores at all.

Also, are you premixing? how much?

 

Sorry forgot to mention, no cat. I mentioned exhaust restriction just to describe how the car feelson high rpm, but I hardly think thats the case.

 

Plugs= NGK 5671A-9 gapped presently to .018"( have tried gaps .015 - .025)

Premix, interesting, this has crossed my mind but never followed up on it. Can to much cause a problem like this? I use 11oz per fill up on the Fd.

 

Just came across this old thread I started a couple years ago. I did find the cause, and thought i would let everyone know in case someone should have this same problem. I was the vac source to the map sensor. I had it connected to one of them under the UIM pointing to the fire wall. I think it was the same port used by the factory sensor (REW). During trouble shooting I decided to tru another port and months of headaches were instantly gone.
However, I never figured the exact reason.

 

I am having the same problem. Could you explain where you got the vacum source from to correct it. I drill and taped mine just after the TB on the bottom side of the upper manifold. I use 1/4 quick connect plastic air lines for all my lines. I shaved all my factory nipples off and welded them in. I have one line going from the manifold then to a 5 way manifold to all my stuff.

 

fuel pressure?!?!?!?

 

edit: just realized thread is from 2010 LOL

thewird

 

not enough timing...too much fuel...try using a different wideband. its trial and error