Turbodan

Ok so here is the deal.
stock motor, stock chips, all recent and very good condition vacuum lines no leaks. car sat for a month and battery died (while I waited for caliper pistons and seals back order). after charging battery with a very high end battery trickle maintainer, car has a miss or hesitation only between 3000 and 4000 rpms and dumps fuel at this speed and black smoke out the back.
changed distributer cap, rotor and spark plugs, and changed out dme relay and dme computer and put in fresh fuel. when we changed out computer it seemed to be fine for my drive home from the mechanics but the next morning same thing occurred.
does anything come to mind what could be my problem? I am taking it to the mechanic tomorrow and he wants to check a bunch of things with a voltage meter. because it is only between 3000 and 4000 rpm it makes me think it it is computer related but we changed out the whole computer with one we know is(was) good.
thank you in advance for any help/ suggestions

pontifex4

PM sent. Yours is similar enough to my (still unsolved) problem that they may share a root cause.

minho78

You seem to have a Bad TPS symptom. Someone mentioned today that if you disconnect the TPS you should be able to check if it's the problem or not, but don't take my words. Clarks also has a troubleshooting guide for the TPS. Good luck.

Ronin-951

Strange things happen as the engine transforms from vacuum to pressure, AOS seals come to mind.

Lex_GTX

likely a TPS or VAF (airflow meter) issue. My TPS was not calibrated after a lot of work was done on the car and I had to reset it. Night and day difference.

michael2e

Does it occur most of the time or only under boost?

Turbodan

most of the time between 3000 and 4000 rpm
thanks so far for the input guys I will definitely post what my mechanic finds out. I will tell him to check the tps and VAF. do any of you think it could be a bad coil?

Turbodan

car is at mechanic. will report his findings.

Lex_GTX

I adjusted my TPS as well as moved the VAF sweeper to a fresh track. My problem persists.

The car revs freely in neutral with no hesitation. However, as it transitions into boost (at the boost threshold) it hesitates. Once full boost is reached it and RPMs rise beyond 4k everything is fine.

The condition is worse when the car is cold in the mornings and seems to get much better after it warms up.

Another thing that might be worth looking into are battery cables and grounds.

Please keep us posted on what you find. I plan on playing around with some extra grounding - my voltage gauge reads below 12v while the voltage at the battery is 13.5V

jc in rb

Check bypass valve also, could be a torn diaphram

Lex_GTX

Mine was torn and it was replaced without a change. Also in my case all vacuum lines were changed under the manifold, venturi removed, the manifold gaskets, and the engine was smoked on the intake side with no evidence of leaks.

pontifex4

Dan, I'm going to swap out my coil, cap, rotor and wires next weekend. If nothing else, I'll have some spares around if you're stuck and need to try different parts...

Lex_GTX

Has anyone considered the coolant temp sensor? My hesitation is a lot worse in the mornings and it sounds like this is similar.

Black51

What did you gap your spark plugs to?

Turbodan

plugs came already set...got them from Marcus Blazak while at Mosport.
mechanic can't find anything yet will work on it tonight but it doesn't look good for tomorrow's track day (especiallly with rain forecast)