my 3100 won't run right with 3400 TB?...

[2.8/3400 1985 Camaro]

Swapped a 3400 TB onto my 3100 and for some reason it runs like ass and seems like its misfiring, put the 3100 tb back on and its fine again....anyone know what the deal is???? I mean the two TBs are identical other than size, are the sensors wired different, or maybe bad or something??

[Azrael]

Have a look at IAC passages between the 3400 TB and the 3100 intake manifold. The old 3100's had a notch for it on the throttlebody but some 3400's had it on the intake manifold instead. So your engine might be running on whatever air makes it around the throttleplate.

If that isn't the case then try swapping the TPS and idle air control valves.

[pocket-rocket]

Have a look at IAC passages between the 3400 TB and the 3100 intake manifold. The old 3100's had a notch for it on the throttlebody but some 3400's had it on the intake manifold instead. So your engine might be running on whatever air makes it around the throttleplate.

If that isn't the case then try swapping the TPS and idle air control valves.

You might have to notch either the TB or the UIM to get the IAC to do it's job to allow air to flow past the TB to control idle.

[2.8/3400 1985 Camaro]

I am reasonably certain they are of the same design, sensors are in the same spot, my UIM has the circle bore to match the throttlebody, with a big square chunk of metal above that the IAC passage goes against, from what I can tell looking at it, the IAC dumps the air behind the TB against this backplate, forcing it down and back into the main air stream if that sounds right, pretty sure the 3400 one was the same, but if anyone could post pics of this difference that would be great, I do plan to try swapping the sensors out tomorrow, wanted to today, but ran out of light..

[2.8/3400 1985 Camaro]

Sigh, stupid POS still won't run even after swapping sensors over. Really don't feel like undoing everything only to put the crappy TB back on, but seems I have no choice.....

[2.8/3400 1985 Camaro]

Well now I know what difference you guys were talking about, one manifold type has an actual port that runs through from its mouth for the IAC, whereas the other dumps it against a back plate, well apparently the 3400 TB was the former, finally something to put my new carbide dremel bit through its paces, lol. Already started hogging out that area to dump it against the plate, bout halfway done. Apparently I forgot to press enter, and now I am completely done, lol. Just letting it dry after washing out all the metal flakes, hopefully this does the job.

[2.8/3400 1985 Camaro]

Sigh WTF is it with this stupid stupid stupid car. Even after removing the material blocking the IAC air from getting back to the manifold it still does the same crap, try to start it, sputter, cough. This is ridiculous, there is not a single difference between these two TBs other than size....

[Z3500]

I would bet the TPS is giving not giving the proper reading.

[talon2swords]

I had a spare 3400 throttle body laying around, and I did the same thing, I ground out a passage on it for the idle air circuit. Then I switched out the throttle plate cable assembly shaft, and I think there is a little hole in the old 3100 throttle choke plate so I think I drilled that into the 3400 one just in case. I can't remember if I had to do anything to the gasket, but I after I was finished I bolted it onto the old 1999 upper intake and it works, no problems.

[2.8/3400 1985 Camaro]

Thanks, but I worked out the problem a while ago, lol.

[trewyn15]

Thanks, but I worked out the problem a while ago, lol.

shoulda posted as solved then lol

[2.8/3400 1985 Camaro]

I believe I did, but in a separate thread or something.

[rocklakeyachtclub]

I believe I did, but in a separate thread or something.

Over here:http://60degreev6.com/forum/showthre...ht=#post444954

[talon2swords]

What have I done?

Anyhow, I guess this thread reminded me to put a 3400 TB on my pre-2000 upper intake on my second 97 Lumina. Runs better as well. I did some rough measurements with an old caliper of the internal diameter of the 3400 TB and the older 3100 plenum opening. Seems they are very close, so I'm think this is the max upgrade for the older intakes. Btw, I installed the updated LIM gaskets w/ the older intakes, before I really knew about the newer upper intake swap, so now I'm too lazy and don't want to spend extra money on new gaskets for a complete swap. lol.

[TGP37]

The difference between Men and Boys is the price of their Toys.