7mgte stumble HELP

[ccguy]

i installed a fuel pressure gauge. with just the walbro running the fuel pressure before the dampener is crazy bouncy like 32-36. with both of the pumps running (walbro and in-tank pump) the constant pressure is 38 psi. and it goes up to 42 ish with higher rpms.
with just the intank pump running the pressure is constant 34 psi and up to 40 when revved.

yes, i have swapped out the afm for another and it acts the same. i wish i could swap it out for a tacoma inline afm (since i have one and they are a lot less touchy.
it sucks because i have not seen even 1 mk3 supra in my town of 30,000 people. would be nice if i did so i could invite them over for dinner and swap some parts out.....shit

[cre]

Ok, so not the pump(s). The irregular pressure with one of the pumps off isn't surprising... I wouldn't leave them both in place.

Personally, I'd get a wideband and a MAFT Pro, install a GM IAT and MAP sensor, delete the KVAFM and HAC altogether and then see how well you can tune it.

I'll re-read the thread later to see what we've missed or what is still suspect.

[ccguy]

thanks. i turned off the walbro and am just running the intank pump for the steady psi.

i just got done at checking the voltage at each ecu terminal at idle and when the problem starts. the only thing that changes drastically is the egr output to the vsv. it goes from 1.11v to 14v at 2200 rpm when the hesitation starts.

i am going to try and read a bunch on the egr system and see what i can find.

i am going to try and get this done SOON. i need this truck for my elk hunt that starts in a week. otherwise i have to do a ton of work on my ford (replace ball joints, starter, and flywheel) by then.

[ccguy]

would a coil pack with a small crack from the edge of the metal underneath cause a problem like this? would the coil test ok if it were cracked?

the hac is working again. it reads 3.05 today and read 3.8 yesterday.

[cre]

I told you how to eliminate the HAC as a suspect. The HAC is quite low on my list of suspects.

If the crack in the coil pack could either allow for an arc to ground OR allow moisture inside then yes, it could cause a stumble. If it's on the low voltage side it's unlikely to cause a significant problem but I suppose it's still possible. A picture might help. Filling in the crack with enamel may patch it long enough for you to go for a drive and see if that is the problem.

[ccguy]

i did what you said and bought the resistors at radio shack and now the hac is giving me the correct volts to the ecu.
the cracks start at the edge of the metal on the bottom so i think even if i epoxied it, it would still be able to arch deeper in where the epoxy could not reach so i ordered some new coil packs to try....if they ever come in, they were to be here today so i dont know.
here r some videos of drive by's. when it bucks in the first video i am holding the petal steady. when it hesitates it does that with the petal steady and if i push down it is just like n the video of reving it by hand and it not going above the hesitation.
http://www.youtube.com/watch?v=RAVWI...ature=youtu.be
http://www.youtube.com/watch?v=XaZRQyf-lpQ&feature=plcp
when it is stumbling the petal is steady and on the drive back by the petal is steady and it just comes out of the stumble and accells fine.

it feels like when a carb has the float set wrong and it is starving the jets of fuel.

[ccguy]

the cracks under 2 of the coils

[cre]

Well, it seems minor but I've never cut up a coil pack to see how they're built.

I have had issues similar to what is in your video from just a hairline crack in the plastic stem of a spark plug boot, toward the top no less... So I wouldn't dismiss it as a possibility. I wasn't affected to the same degree but keep in mind that if it's the coil pack then there are two cylinders firing erratically, not just one.

[ccguy]

coil packs made it a little better but still heavy stumble.
if the ground going from the metal coil pack bracket is not hooked up it runs just the same. then if i ground it, it still acts the same. i think i remember reading if it does not have a good ground it will not run right. so what am i missing????
i am testing the plug wires for a grounding crack issue now.

[cre]

There's an internal ground in the igniter which is known to corrode and can cause these symptoms. There may be a writeup in the MKIII FAQ section which I think was written by Suprra_girl.