Kevin in Atlanta

Here's how to build what you need to pressurize the intake.

Dwayne's Intake Refresh Write-up

Start at post # 4

Paddcomp

I changed the accelerator and throttle cables today, pedal cable had some wear on the inner sleeve but no fraying.
Adjusted and test driven, high idle returned after 5 minutes. I could see there was slack in the throttle cable and there was no clicking from the TPS. Diagnosed the throttle plate sticking open, independent of the cable position. Snapping that quadrant open to closed wasn't enough to overcome the stuck valve, until cooled down.

The intake is now off again and the throttle valve is free. Any suggestions on a way forward?
I'd like to test the throttle body and simulate the heat causing something to move and stick. This way I can test the throttle before putting it back on the car. I'm thinking on putting it in the oven at say 85C then try to realign the plate or whatever's causing the problem.

Brian

Mrmerlin

if you removed the throttle plate from the shaft then you have it installed incorrectly,
best guess is to loosen the 2 screws that hold it in the shaft,
then snap the throttle closed a few times ,
and then tighten the screws this should recenter the plate.

Paddcomp

Hi Merlin,
That's how I did it when I put it back together. I'll try it again if there isn't a procedure to set it. Do you see any problems testing it in an oven at 85C?

Brian

Mrmerlin

no that shouldnt hurt anything.

BUT before you oven test ,it could also be possible that you have the plate turned around and the edges are binding.
IE the part of the plate that was facing to the rear of the car when the plate is closed might now be facing forward

Bertrand Daoust

+1.

From Dwayne's site.

Paddcomp

Thanks for the feedback, it might be easier if I show some pictures of the installation.

This is the installation now with the throttle body upside down.


And the springs




How it was before the intake refresh


The arc on the plate is in the same place, and the plate moves smoothly with the TB cold. I assuming that the alignments not 100% and somethings moving when warm, I could either oven the whole thing or use my heat gun on the plate only to see if I can reproduce the problem on the bench.

Thanks.
Brian

the flyin' scotsman

the springs are not installed correctly; there should be a plate under the outer nut.........suggest taking apart fully clean and rebuild.

Also the arm where the cable attaches is bent.

From Dwaynes epic:

Paddcomp

I presume these parts aren't available separately? Well spotted.

Thanks
Brian

the flyin' scotsman

Hopefully all parts are there but misassembled.........take apart and review against the pic.

good luck.

Paddcomp

Made some progress today, firstly I purchased another plenum and complete throttle body from a breakers for spares / reference.
Then I tested the throttle plate with my heat gun on my original TB, and in less than a minute the throttle plate was sticking and wouldn't close. I loosened the screws and allowed the plate to reseat, but this had no effect. I took the plate out and heated again and the shaft itself doesn't stick.
With the plate removed I noticed some end float in the shaft, about 2-3mm, is this correct? I refitted the plate and heated again, but couldn't free it by moving the shaft on the end float (which isn't there with the plate installed as the plate stops it moving).
Also tried my TB with the plate from the other TB, no difference.

Any ideas on what to try next? Do I just rebuild the replacement TB with new bearings, not sure how this can be different to mine as it's cast.

Paddcomp

Replacing the throttle body cured the high idle. I'd like to have found the problem with the original TB but it wasn't to be.

FredR

Did you replace the bearings/seal? This is a known common aging problem with the TB. Whether it would explain your issue I do not know but if you have a square peg in a round hole..?

Rgds

Fred