Thottle surge/drop at speed

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Old 30 May 2006, 09:42 am   #1 (permalink)
rkj1974
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Default Thottle surge/drop at speed

Hello, I have a '96 Camry(4 cylinder, 5spd) that has a slight throttle
surge/drop at a constant speed. It only happens when you just holding a speed
(not during acceleration) and it's not that bad(just slightly annoying). It
runs perfect in all other aspects. The Haynes manual says that it could be an
intake air leak, fuel pump, or engine sensor. I just thought I'd ask here in
case there's a "common" problem that can cause this. Thanks in advance.
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Old 30 May 2006, 10:42 am   #2 (permalink)
Daniel
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Default Re: Thottle surge/drop at speed

It's not common, but I'd check the vacuum ports on the throttle body
that control the vacuum modulator for the EGR valve.
Should be three.
The recommended method is to clean them when the throttle body is
removed - solvent and compressed air, but you might try removing the
vacuum lines and using solvent and compressed air from the outside. Do
not use any type of wire that could mar the openings.
When I cleaned mine with the TB off, a little glop of residue was
cleared from the smallest of those three orifices. Afterwrd a slight
part throttle hesitation seemed to have improved.
EGR is off at idle and full throttle, but on during part throttle -
modulated by those vacuum ports.

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Old 30 May 2006, 10:50 am   #3 (permalink)
rkj1974
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Default Re: Thottle surge/drop at speed

Thanks for the reply. That sounds like an easy place to start. Can I use
heavy carb cleaner on the throttle body? I just purchased some a month ago
when I rebuilt the carbs on an outboard motor. The "dunk can" heavy duty
stuff. It worked great. Will I damage anything on the throttle body if I do
the same deep clean on it? Thanks

Daniel wrote:
>It's not common, but I'd check the vacuum ports on the throttle body
>that control the vacuum modulator for the EGR valve.
>Should be three.
>The recommended method is to clean them when the throttle body is
>removed - solvent and compressed air, but you might try removing the
>vacuum lines and using solvent and compressed air from the outside. Do
>not use any type of wire that could mar the openings.
>When I cleaned mine with the TB off, a little glop of residue was
>cleared from the smallest of those three orifices. Afterwrd a slight
>part throttle hesitation seemed to have improved.
>EGR is off at idle and full throttle, but on during part throttle -
>modulated by those vacuum ports.

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Old 30 May 2006, 01:15 pm   #4 (permalink)
Daniel
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Default Re: Thottle surge/drop at speed

I like the Berryman B-12 Chemtool, and it's only around $2 or so.
The main consideration is that it must be emissions control safe.
If by "dunk" you mean "gunk" - I recently bought a can of that just to
clean the exterior of my old Toyota truck water pump from (oil leak)
residue prior to removal. The Berryman seems to instantly liquefy oil
and varnish, but the gunk didn't work anywhere near as well from what I
saw.

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Old 30 May 2006, 01:33 pm   #5 (permalink)
rkj1974
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Default Re: Thottle surge/drop at speed

By "dunk can" I mean the heavy duty carb cleaner(from napa) in a 1 gallon can
that has a basket to submerge your carbs completely in the solution. It works
really well. Anything foreign seems to just go away.

Daniel wrote:
>I like the Berryman B-12 Chemtool, and it's only around $2 or so.
>The main consideration is that it must be emissions control safe.
>If by "dunk" you mean "gunk" - I recently bought a can of that just to
>clean the exterior of my old Toyota truck water pump from (oil leak)
>residue prior to removal. The Berryman seems to instantly liquefy oil
>and varnish, but the gunk didn't work anywhere near as well from what I
>saw.

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Old 30 May 2006, 03:40 pm   #6 (permalink)
Daniel
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Default Re: Thottle surge/drop at speed

How would you use that with the throttle body still on the car?
My idea was an aerosol spray.
I've got a gallon of that type of carburetor cleaner, but I haven't
used it since I last disassembled and cleaned a carburetor.
>From what I remember, the instructions tell you to rinse parts with

water afterward. Perhaps there's some newer version now.
If you're going to take the throttle body off the car, then check the
manual and follow all the steps for adjustment.
http://www.turboninjas.com/camry/
Still don't think you're going to want to "dunk" it though, because the
throttle position sensor is still attached on the one side with a
flexible cover for the throttle stop on the other which shouldn't be
immersed in solvent either.
That's why I mentioned the low price on the Berryman's - but of
course, you're free to do as you like.

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Old 30 May 2006, 05:43 pm   #7 (permalink)
rkj1974 via CarKB.com
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Default Re: Thottle surge/drop at speed

OK, I misunderstood I guess. I'm used to pulling parts off the car, but hey,
easier is better. I'll try the aerosol spray first and see what happens.
Thanks

Daniel wrote:
>How would you use that with the throttle body still on the car?
>My idea was an aerosol spray.
>I've got a gallon of that type of carburetor cleaner, but I haven't
>used it since I last disassembled and cleaned a carburetor.
>>From what I remember, the instructions tell you to rinse parts with

>water afterward. Perhaps there's some newer version now.
>If you're going to take the throttle body off the car, then check the
>manual and follow all the steps for adjustment.
>http://www.turboninjas.com/camry/
>Still don't think you're going to want to "dunk" it though, because the
>throttle position sensor is still attached on the one side with a
>flexible cover for the throttle stop on the other which shouldn't be
>immersed in solvent either.
>That's why I mentioned the low price on the Berryman's - but of
>course, you're free to do as you like.


--
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http://www.carkb.com/Uwe/Forums.aspx...camry/200605/1
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Old 31 May 2006, 07:56 am   #8 (permalink)
Daniel
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Default Re: Thottle surge/drop at speed

rkj1974 via CarKB.com wrote:
> OK, I misunderstood I guess. I'm used to pulling parts off the car, but hey,
> easier is better. I'll try the aerosol spray first and see what happens.
> Thanks
>

==============================
That would be aerosol and compressed air.
When I saw that bit of goop fly out, it was after being soaked with
solvent, but then also hit with a blast of compressed air - and that is
the method given in the factory manual also.

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Old 31 May 2006, 08:00 am   #9 (permalink)
Daniel
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Default Re: Thottle surge/drop at speed

rkj1974 via CarKB.com wrote:
> OK, I misunderstood I guess. I'm used to pulling parts off the car,

==========
That would be much better.
That's the way it is supposed to be done.
Plus, then you can clean the back side of the throttle body that tends
to get fouled with PCV blowby and also check adjustment on the TPS more
easily.
Read the section in the manual about throttle body cleaning and they'll
give you all the steps and adjustments - there were a number of items,
and on mine, they were all in need of adjustment.

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Old 31 May 2006, 08:00 am   #10 (permalink)
Daniel
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Default Re: Thottle surge/drop at speed

rkj1974 via CarKB.com wrote:
> OK, I misunderstood I guess. I'm used to pulling parts off the car,

==========
That would be much better.
That's the way it is supposed to be done.
Plus, then you can clean the back side of the throttle body that tends
to get fouled with PCV blowby and also check adjustment on the TPS more
easily.
Read the section in the manual about throttle body cleaning and they'll
give you all the steps and adjustments - there were a number of items,
and on mine, they were all in need of some adjustment.

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