Code 35

Well we'll see if anyone has some ideas as I'm still
scratching my head ( and The Captain is as well) HIS, NOT
MINE. 2 years ago I went after an exhaust leak on the
inboard side of the 2.8. Though I can't remember if I had
to pull the head for(broken exhaust bolt)that must have
been the case as there is no reason to have to remove
push rods and reset valves for anything lesser that that.
After putting it back together ( yes I torqued the head)
I developed a code 35 which is a vacuum leak. The car
went away for 20 months at that point. Now its out and I
checked out all the lines and there is no leak found. So
since I wasn't totally satisfied with the setting of the
valves ( not sure if they were set right)and that the
vacuum leak could be anywhere below the plenum, I gave in
and tore it apart again. Resealed everything 150% and
reset the valves. No I did not re-torque the head as I
trusted it was correct and sometimes re-torqueing isn't a
good thing to do on heads. Now that it is running again
I am still getting a code 35. I put the scan tool on it
and the IAC starts at 70 or above and eventually drops to
zero ( which means it has attempted to shut off all extra
air ( thus vacuum leak) I checked the readings against
the other 2.8 and all is good except for the Idle Air
Control (IAC) I then rechecked and found that it was a 70
(perfect) and was holding. Great!! Checked again later
and it went back to zero. No good. I checked the vacuum
at the port off the plenum that faces the distributor and
it is the same at 18 pounds vacuum. ( compared to the
other car) All the spaghetti lines were checked and there
is no leaks. Hose into the valve cover on the inboard
side has a tight fit so it isn't leaking there, nor at
the PCV point. The 3/8 hose into the base of the throttle
body that runs to the inboard valve cover has a nice snug
fit, so its not that. Thinking about changing out the
throttle body and components, from a spare engine to see
what results I get. So at this point I am not frustrated
but rather concerned as this issue is bothering me. Any
ideas?       

Hey the problem is resolved Wow. I happened to see my
neighbor outside who is a real mechanic. So I asked Randy
can I pick your brain a bit and he came over. So looking
over it and in a few minutes pops off the air intake hose
from the air filter,takes a look of the adjustment screw
which I thought was out all away, loosens it a bit more,
pops the throttle a couple of times, puts his finger down
the
throttle body assembly and pushes the butterfly closed a
bit, and says the butterfly is not closing up on my way. It
can close more, and they do wear out. so we took another
throttle body off a spare motor that I had, and he says
this one is closing up much better and feels better than
that one so I would change it. When he pushed down on the
butterfly, the IAC numbers came up to where they should be.
Wow problem resolved. Maybe I didn't have to take it all
apart again, but I do know that motor better now because of
it, and I know my valves are set perfectly. Thanks Randy
and
to Patrick

Edited by Fieroman88

Just so very happy to have it: all running good.😀

Fieroman88 wrote: ...the throttle body butterfly is worn out.

Glenn, how many kilometres on that '88 GT?

In 15 years on Pennock's, I don't believe I've ever read a post there about a Fiero throttle body (2.5 or 2.8) with a worn out throttle body butterfly.

I suppose it's possible, but I think it would have to be an awfully high mileage car.

Edited by Patrick