acceleration hesitation

[piper]

i've tried any and everything i can think of so far so im here hoping to find an ultimate solution. i have tried to find information for days on end, read the tsrm front to back then back to front, tested every sensor and circut to no avail.

spec:
1990 supra, 7mgte, auto, 90k mi, owned 6 years since since 50k.

mods:
tubular exhaust manifold w/ t3 flange
turbonetics evoultion wastegate
dual stage boost controller
garrett gt-35r creamic coated and water cooled
3" full back
hollowed factory cat
apexi n1 muffler
replica fmic
2.5" hand made ic piping
walboro 255
fuel pressure surge delete
12v fuel pump mod
schnider custom ground cams
ported and polished exhaust ports
spal electric fan
hks ssqv
hks 1.2 mhg
arp studs
iac(isc) delete
vsv delete
egr delete
deleted every vac line i could afford to live without.


i was getting a consistent 17 psi on my gauge before i started having issues

now

first off the problem started one day as a subtle miss while driving in the low rpm range (around 2k) so i planned on swapping out the fuel pump, one day i drove it to work, went to start it up and pull it in to change fuel pump and it wouldnt fire up. i figured to pump just failed so i replaced it with a new one. had some trouble starting up and the miss was still there while driving. next day it would not start at all, ran a 12v mod on the fuel system and still no start. started testing every sensor on the motor and changed the cps, ecu engine temp, tps, cold start time switch, cold start injector, coils, wires, ecu, circut opening relay, starter relay, maf, igniter, igniter resistor, iac check valve, and various others. the only way i could get it to start was unplug the ecu temp sensor and o2 sensor. somewhere in the time of replacing parts it lost the ability to keep its idle up, i realized my iac (isc) motor was bad. so i capped it and set the idle with the stop screw and reset the tps to its proper setting, completely fixed my idle and hard starting issue that came from no where but still did nothing for the missing. the miss has now developed to acting like a fuel cut through the entire rpm range. im out of ideas and open to anything, i probably overlooked something simple but i cant think of anything else to check i did check all the boost lines, everything between the afm and intake, air filter is also new.

any suggestions?

sorry about the spelling errors

[89ST]

Unless I'm missing something, entirely possible. I would be inclined to say its spark. Clearly you're getting fuel. and if one or more cylinder's has speratic spark you'll get a miss. Unless an injector is bad, generally speaking misses are almost always caused my not getting spark. So I would test your spark plug wires, and if they're all good and your spark plugs aren't twenty years old then I would think your coil pack is starting to die out. Hope this helps

[piper]

Originally Posted by 89ST

Unless I'm missing something, entirely possible. I would be inclined to say its spark. Clearly you're getting fuel. and if one or more cylinder's has speratic spark you'll get a miss. Unless an injector is bad, generally speaking misses are almost always caused my not getting spark. So I would test your spark plug wires, and if they're all good and your spark plugs aren't twenty years old then I would think your coil pack is starting to die out. Hope this helps

Wires all spec out, plugs are ngk iridium about 6 months old.
I tried another set of 7m coils and just did a coil on plug conversion using is300 coils and wires, its worth mentioning that my af gauge reads lean while it's missing but will boost fast and hard after 2k, it almost seems to be related to the trans throttle valve/kickdown, also after driving it for a few days I've noticed to only way to start it in the mornings is to unplug the ecu temp sender until it reaches operating tempature, after that it will start fine the rest of the day. Then I plug it back in and it runs with the miss there. If i leave the ecu temp unplugged and also unplug the o2 sensor it runs without a miss but will occasionally die at low speeds like pulling into a parking lot. I'm beginning to think I overlooked something as stupid as a fuel filter or something.

[Busted Knuckles]

I've read on-line that this is a problem with a questionable fuel dampener. I don't know the mechanics of it, but it seems that replacing it fixes this problem in a lot of Toyota/Lexus cars. I've been having a similar problem, but drive the car so seldomly right now (transmission noise) that I haven't tried it yet.

The fuel dampener is a little device on the inlet side of the fuel rail. It's purpose is to dampen the pulses from the fuel pump as the fuel enters the rail. It looks like a small vacuum motor with no lines running to it. You can feel the set screw vibrate (under the dust cap on top) when the car is running, smoothing out the pulses. I'm guessing that it gets weak and begins to allow fuel pressure variations that muck with the low-speed smoothness.

[piper]

Originally Posted by Busted Knuckles

I've read on-line that this is a problem with a questionable fuel dampener. I don't know the mechanics of it, but it seems that replacing it fixes this problem in a lot of Toyota/Lexus cars. I've been having a similar problem, but drive the car so seldomly right now (transmission noise) that I haven't tried it yet.

The fuel dampener is a little device on the inlet side of the fuel rail. It's purpose is to dampen the pulses from the fuel pump as the fuel enters the rail. It looks like a small vacuum motor with no lines running to it. You can feel the set screw vibrate (under the dust cap on top) when the car is running, smoothing out the pulses. I'm guessing that it gets weak and begins to allow fuel pressure variations that muck with the low-speed smoothness.

I actually got rid of the dampner a while back when I did my head work. It ran fine with the banjo bolt i replaced it with. Could it be the pressure regulator on the other end of the fuel rail letting out fuel at a lower pressure causing a lean supply?

[Busted Knuckles]

I'd test that theory with a fuel pressure gauge before replacing the regulator. However, if the fuel filter is more than 5 years old, or has over 60,000 miles on it, I'd replace that.