Vince's TBI woes, progressive revelations, and tbi mods.

[Vbb199]

Alrighty gents, i stabbed the dizzy in 180° out from where i had it, unplugged the est bypass, and it fired right up

Not even a 1 second crank and it fired off. Set the timing, locked it down, killed the battery, plugged the bypass back in...

Now later i'll see if the stumble/misfire is gone

 

[Vbb199]

I should say it was running and driving in the yard and idling, so thats already a good sign

 

[Catbox]

Gently....

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[Vbb199]

Gently....

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I like the added "gently" detail haha

 

[Vbb199]

Back again!
That didnt fix jack ****

 

[Vbb199]

I guess before i take my intake off, im going to swap my ICM out, as a final ditch effort

Everyone including me believes if thats bad, it just dies, but some reading on the gmt400 forums seems to suggest otherwise.

Im seeing the tach bouncing and spiking around, and its in sequence with the misfiring and bad behaviour.

 

[AuroraGirl]

Update 69.2:
That did nothing in terms of the weird idle jumping around lol

I then proceeded to spray carb cleaner around the blocked off egr, tbi, intake and vacuum lines and saw no change.

So whats next

the screens are for production purposes in case anything upstream was introduced unintentionally and can be discarded but dont hurt nothing

also, dont know if you are having IAC issues still but
If you turn the key ON, then ground the A-B connectors of the ALDL under the dash, the ecm will drive the IAC valve all the way closed. This is ZERO "counts". The engine should be able to RUN in this condition albeit possibly lopey and may take a couple tries to start if its cold.

you can also peform a throttle snap test to determine if its over or under traveling, in that it would deliver inconsistent results and behavior that may not be apparent when viewing the live data in a given situation

THe throtle counts , to me, seem high but not too high.
basically while viewing the data at a stable idle, fully blip the throttle like 7 times quickly and quick release, then when done your final value should be within 5 counts of the beginning

If its beyond or below that, your IAC is not responsive enough or its mechanically wearing and its unable to know that itself

 

[AuroraGirl]

I guess before i take my intake off, im going to swap my ICM out, as a final ditch effort

Everyone including me believes if thats bad, it just dies, but some reading on the gmt400 forums seems to suggest otherwise.

Im seeing the tach bouncing and spiking around, and its in sequence with the misfiring and bad behaviour.

Your tach is jumping around? timing light time. sounds like it could be a weak pole piece in the distributor. when you have the distributor out, rotating the shaft can you feel the magnetic poles as you rotate? the magnetic feel will resist turning and it should happen when they get aligned (so twice in a 360 rotation i think? maybe once idk)

There is a way to see this on a timing light if you want to see the procedure i can show you a video