acceleration hesitation

[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.