Honda Car Forum

Few days ago i replaced complete DPFI throttle body (the one with two
injectors) with "new" junkyard part. The old one had worn throttle
plate shaft that was sticking like hell and making my life miserable
in stop and go traffic.

Well the sticking is now gone but there are new problems that make the
previous one a joke :-(

1. After car is warmed up there's throttle response delay so if I
don't apply throttle really really gently the engine will first stalls
for about 0,7sec before revving up.

2. After engine breaking and pressing the clutch engine almost stalls,
most of the time it recovers by itself and idles fine however idle is
a little bit too high or low.

3. When cold, engine starts a little too fast. With old throttle body
it always took about 1 sec for engine to fire up. Now it starts almost
immediately after turning the key. Should it be like that?


As far as I checked there seems to be some vacuum issues. The upper
tandem throttle plate is not opening under throttle and I can't feel
any vacuum on it's diaphragm hose, not even on air intake chamber
which it is connected to.

After disconnecting EACV engine RPM drops to around 400 rpm and I can
still feel a little bit of vacuum. Not much but it's there.

As I understand there's a coolant line that goes into throttle body
(not sure), should the system be bleed after TB replacement?

I also checked throttle angle sensor and it seems fine.

Thanks for any help!

Kerozin wrote:
> Few days ago i replaced complete DPFI throttle body (the one with two
> injectors) with "new" junkyard part. The old one had worn throttle
> plate shaft that was sticking like hell and making my life miserable
> in stop and go traffic.
>
> Well the sticking is now gone but there are new problems that make the
> previous one a joke :-(
>
> 1. After car is warmed up there's throttle response delay so if I
> don't apply throttle really really gently the engine will first stalls
> for about 0,7sec before revving up.

check tandem valve and tps.

>
> 2. After engine breaking

braking, not breaking. unless you mean your engine broke. [sorry, but
you're getting the flak someone else started - please get the right one.]

> and pressing the clutch engine almost stalls,
> most of the time it recovers by itself and idles fine however idle is
> a little bit too high or low.

set the base idle correctly - if it's too far out, the eacv takes too
long to kick in.

>
> 3. When cold, engine starts a little too fast. With old throttle body
> it always took about 1 sec for engine to fire up. Now it starts almost
> immediately after turning the key. Should it be like that?

instant start is unusual - could be an injector leak. run injector
cleaner through it.

>
>
> As far as I checked there seems to be some vacuum issues. The upper
> tandem throttle plate is not opening under throttle and I can't feel
> any vacuum on it's diaphragm hose, not even on air intake chamber
> which it is connected to.

it's switched by a solenoid - so no vacuum all the time. check hoses
and diaphragm for leaks. run motor with air cleaner off - you can see
if the valve is operating at higher revs.

also, some dpfi's have a restricted tandem valve - check to see if it
opens all the way and whether that matches your old one.

>
> After disconnecting EACV engine RPM drops to around 400 rpm and I can
> still feel a little bit of vacuum. Not much but it's there.
>
> As I understand there's a coolant line that goes into throttle body
> (not sure), should the system be bleed after TB replacement?

self bleeding.

>
> I also checked throttle angle sensor and it seems fine.

how'd you check?

>
> Thanks for any help!
>
any codes? and are you in the usa? dpfi was only on the 88-91 civics
over here.

> check tandem valve and tps.

Tandem is not working that's for sure.

> braking, not breaking. unless you mean your engine broke. [sorry, but
> you're getting the flak someone else started - please get the right one.]

Sorry for my English, haven't used it for a while, you can expect more
nonsense to follow :-)

> set the base idle correctly - if it's too far out, the eacv takes too
> long to kick in.

Is this the procedure?
http://media.honda.co.uk/car/owner/m...k301/6-133.pdf

> instant start is unusual - could be an injector leak. run injector
> cleaner through it.

I have two good injectors on old TB that I can salvage. Can injectors
be removed without damaging the seals since there's no way I can get
new ones?

> it's switched by a solenoid - so no vacuum all the time. check hoses
> and diaphragm for leaks. run motor with air cleaner off - you can see
> if the valve is operating at higher revs.

Diaphragm is ok, I have checked it with small vacuum pump, it doesn't
leak. Solenoid is open when engine is off so I guess it's also ok.
Bloody thing just won't move.

It seems they're only two possibilities. There's leak through seal
between air intake chamber and throttle body (almost impossible) or a
leak through EACV that is also unlikely since it worked just fine with
old TB

I'll try connecting old TB to a vacuum hose to see if it works any
better.

> also, some dpfi's have a restricted tandem valve - check to see if it
> opens all the way and whether that matches your old one.

That crossed my mind so I already checked that. They're the same, I
can open it manually all the way.

> > As I understand there's a coolant line that goes into throttle body
> > (not sure), should the system be bleed after TB replacement?
>
> self bleeding.

I kinda hoped that would be it.

> >
> > I also checked throttle angle sensor and it seems fine.
>
> how'd you check?

Not by the book to be honest, just measured resistance. I didn't find
any spikes, readings are linear as I move the throttle.

> any codes?

No, no codes at all.

>and are you in the usa? dpfi was only on the 88-91 civics
> over here.

I'm from Croatia and the Civic is for French market. Most of the 5th
gen. Civic's here are DPFI, 3rd world country specs :-)

Thanks a lot for your help!

Kerozin wrote:
>> check tandem valve and tps.
>
> Tandem is not working that's for sure.

did you check the electrical for the solenoid? does it click if you
apply direct voltage? is the connection good?

>
>> braking, not breaking. unless you mean your engine broke. [sorry, but
>> you're getting the flak someone else started - please get the right one.]
>
> Sorry for my English, haven't used it for a while, you can expect more
> nonsense to follow :-)
>
>> set the base idle correctly - if it's too far out, the eacv takes too
>> long to kick in.
>
> Is this the procedure?
> http://media.honda.co.uk/car/owner/m...k301/6-133.pdf

yes. check the idle rpm's for your car - they vary a little from model
to model.

>
>> instant start is unusual - could be an injector leak. run injector
>> cleaner through it.
>
> I have two good injectors on old TB that I can salvage. Can injectors
> be removed without damaging the seals since there's no way I can get
> new ones?

it's not so easy to do without damage. assume for now that the
injectors are good - honda injectors are /very/ reliable. simply put
injector cleaner in the tank when you get this thing running properly.

>
>> it's switched by a solenoid - so no vacuum all the time. check hoses
>> and diaphragm for leaks. run motor with air cleaner off - you can see
>> if the valve is operating at higher revs.
>
> Diaphragm is ok, I have checked it with small vacuum pump, it doesn't
> leak. Solenoid is open when engine is off so I guess it's also ok.
> Bloody thing just won't move.

check for damage or obstruction. if you remove the air ducting, you
should be able to operate the valve with your finger. once moving, look
for gotchas like linkages. also, the rubber hose between the solenoid
and the tandem valve diaphragm is frequently shot, so i recommend
replacing it.

>
> It seems they're only two possibilities. There's leak through seal
> between air intake chamber and throttle body (almost impossible) or a
> leak through EACV that is also unlikely since it worked just fine with
> old TB

set the idle correctly for the new tb. makes a huge difference.

>
> I'll try connecting old TB to a vacuum hose to see if it works any
> better.
>
>> also, some dpfi's have a restricted tandem valve - check to see if it
>> opens all the way and whether that matches your old one.
>
> That crossed my mind so I already checked that. They're the same, I
> can open it manually all the way.

good.

>
>>> As I understand there's a coolant line that goes into throttle body
>>> (not sure), should the system be bleed after TB replacement?
>> self bleeding.
>
> I kinda hoped that would be it.
>
>>> I also checked throttle angle sensor and it seems fine.
>> how'd you check?
>
> Not by the book to be honest, just measured resistance. I didn't find
> any spikes, readings are linear as I move the throttle.

ok, good. at high mileage, the tps can wear, but it usually sets a
code. they can be repaired, but it's a pita. easier to replace.

>
>> any codes?
>
> No, no codes at all.

good!

>
>> and are you in the usa? dpfi was only on the 88-91 civics
>> over here.
>
> I'm from Croatia and the Civic is for French market. Most of the 5th
> gen. Civic's here are DPFI, 3rd world country specs :-)
>
> Thanks a lot for your help!
>

> > Tandem is not working that's for sure.
>
> did you check the electrical for the solenoid? does it click if you
> apply direct voltage? is the connection good?

I tried following for today:

Connecting old throttle body tandem diaphragm directly to air intake
chamber (using new hose) of running engine. Almost no movement
regardless RPM.

Connected current tandem diaphragm directly to air intake chamber
bypassing solenoid. Same results as above.

Checked air intake chamber rubber seal - undamaged.

Checked voltage on solenoid - it's there

Disconnected EACV from intake chamber (thought it's stuck open) and
plugging the hole on it - still no movement of tandem diaphragm.
Interesting thing is that I still feel some vacuum on EACV even with
engine above 3krpm. Shouldn't EACV be fully closed when engine is not
idling?

I also set base idle. The manual states that when you turn lights,
defroster etc. idle should stay the same. Mine does not but drops down
with everything turned on for almost 200 rpm.

So any ideas what's happening with tandem? Is it possible that
diaphragm membranes on both became too hard? They're holding vacuum
and I can quite easily move diaphragm shaft. Or there's simply no
vacuum in air intake chamber. I just can't see where it could escape?

Kerozin wrote:
>>> Tandem is not working that's for sure.
>> did you check the electrical for the solenoid? does it click if you
>> apply direct voltage? is the connection good?
>
> I tried following for today:
>
> Connecting old throttle body tandem diaphragm directly to air intake
> chamber (using new hose) of running engine. Almost no movement
> regardless RPM.
>
> Connected current tandem diaphragm directly to air intake chamber
> bypassing solenoid. Same results as above.

that's the high pressure side, so no dice. the low pressure side, where
the solenoid venturi is, is internal. the second pipe you see is just
venting for when the diaphragm is released.

>
> Checked air intake chamber rubber seal - undamaged.
>
> Checked voltage on solenoid - it's there
>
> Disconnected EACV from intake chamber (thought it's stuck open) and
> plugging the hole on it - still no movement of tandem diaphragm.
> Interesting thing is that I still feel some vacuum on EACV even with
> engine above 3krpm. Shouldn't EACV be fully closed when engine is not
> idling?
>
> I also set base idle. The manual states that when you turn lights,
> defroster etc. idle should stay the same. Mine does not but drops down
> with everything turned on for almost 200 rpm.
>
> So any ideas what's happening with tandem? Is it possible that
> diaphragm membranes on both became too hard? They're holding vacuum
> and I can quite easily move diaphragm shaft. Or there's simply no
> vacuum in air intake chamber. I just can't see where it could escape?
>
ok, let's ignore the eacv for the time being.

if the tandem valve is not moving, it can only be the following:

1. the linkage/mechanism is jammed. but you say it's free to move.
2. the diaphragm is leaking. re-test by removing the hose, wetting a
finger, then with the throttle plate in the open position, put your
finger over the diaphragm pipe hole. if the plate stays open, the
diaphragm's good. remove finger, the plate should snap shut.
3. the diaphragm hose is leaking.
4. the solenoid's not working. you tested the electrical, but do you
hear it clicking if you apply current to it? if you attach hose and
blow, can you feel it open when you apply current?
5. there's a blockage on the solenoid venturi in the throttle body.

> > Connected current tandem diaphragm directly to air intake chamber
> > bypassing solenoid. Same results as above.
>
> that's the high pressure side, so no dice. the low pressure side, where
> the solenoid venturi is, is internal. the second pipe you see is just
> venting for when the diaphragm is released.

How could I be so stupid... sorry for wasting your time.

When I took off solenoid I thought that it's connected to fuel line
and that this port is only used for lubrication since it had little
fuel in it. I guess it came in there during disassembly of TB. A
friend of mine which is professional mechanic for heavy equipment
confirmed that... but he was wrong.

> 1. the linkage/mechanism is jammed. but you say it's free to move.
> 2. the diaphragm is leaking. re-test by removing the hose, wetting a
> finger, then with the throttle plate in the open position, put your
> finger over the diaphragm pipe hole. if the plate stays open, the
> diaphragm's good. remove finger, the plate should snap shut.
> 3. the diaphragm hose is leaking.
> 4. the solenoid's not working. you tested the electrical, but do you
> hear it clicking if you apply current to it? if you attach hose and
> blow, can you feel it open when you apply current?
> 5. there's a blockage on the solenoid venturi in the throttle body.

Thanks a lot! I'm now almost sure solenoid is stuck closed. I'll
replace it with one from old TB first thing in a morning and let you
know if this fixed the problem.

> 1. the linkage/mechanism is jammed. but you say it's free to move.
> 2. the diaphragm is leaking. re-test by removing the hose, wetting a
> finger, then with the throttle plate in the open position, put your
> finger over the diaphragm pipe hole. if the plate stays open, the
> diaphragm's good. remove finger, the plate should snap shut.
> 3. the diaphragm hose is leaking.
> 4. the solenoid's not working. you tested the electrical, but do you
> hear it clicking if you apply current to it? if you attach hose and
> blow, can you feel it open when you apply current?
> 5. there's a blockage on the solenoid venturi in the throttle body.

I tried replacing solenoid today. Of course one of the screws is
seized and I had to take whole throttle body down but still didn't
managed to do it. This will have to wait for tomorrow.

On port on the lower side of the TB was totally blocked by liquid
gasket. I know it's not tandem vacuum port but is it used for anything
else?

This was the plugged port:
http://kerozin.dyndns.org/tb.jpg

Also is it possible to fry solenoid by reversing polarity? Tried to
check old one first on one side and since nothing happened reversed
polarity - still nothing. I had voltage passing through it but it
didn't click and current was something hardly measurable (50mA?).
Someone mentioned some kind of diode in it. I totally dismantled it
but can't find any. Now when I apply current directly to electromagnet
it works just fine.

Kerozin wrote:
>> 1. the linkage/mechanism is jammed. but you say it's free to move.
>> 2. the diaphragm is leaking. re-test by removing the hose, wetting a
>> finger, then with the throttle plate in the open position, put your
>> finger over the diaphragm pipe hole. if the plate stays open, the
>> diaphragm's good. remove finger, the plate should snap shut.
>> 3. the diaphragm hose is leaking.
>> 4. the solenoid's not working. you tested the electrical, but do you
>> hear it clicking if you apply current to it? if you attach hose and
>> blow, can you feel it open when you apply current?
>> 5. there's a blockage on the solenoid venturi in the throttle body.
>
> I tried replacing solenoid today. Of course one of the screws is
> seized and I had to take whole throttle body down but still didn't
> managed to do it. This will have to wait for tomorrow.
>
> On port on the lower side of the TB was totally blocked by liquid
> gasket. I know it's not tandem vacuum port but is it used for anything
> else?
>
> This was the plugged port:
> http://kerozin.dyndns.org/tb.jpg

bingo! never use liquid gasket dude - this a textbook example of why!
either make a new gasket out of an old envelope [if you're desperate] or
buy the real deal.

>
> Also is it possible to fry solenoid by reversing polarity? Tried to
> check old one first on one side and since nothing happened reversed
> polarity - still nothing. I had voltage passing through it but it
> didn't click and current was something hardly measurable (50mA?).
> Someone mentioned some kind of diode in it. I totally dismantled it
> but can't find any. Now when I apply current directly to electromagnet
> it works just fine.
>
probably diode protected, but don't worry about that - just worry about
whether it clicks and opens when the correct polarity is applied. and
don't worry any more about taking it off - you've found your problem.
unplug the ports and everything will now work.

> bingo! never use liquid gasket dude - this a textbook example of why!
> either make a new gasket out of an old envelope [if you're desperate] or
> buy the real deal.

Actually that was a work of professional. It's quite hard to obtain
parts for older Hondas here in Croatia so improvisation is quite
common even for dealership workshops. By the manual there should go O-
ring which is of course not there so I'll have to use liquid gasket
again.

> probably diode protected, but don't worry about that - just worry about
> whether it clicks and opens when the correct polarity is applied. and
> don't worry any more about taking it off - you've found your problem.
> unplug the ports and everything will now work.

I've just checked and plugged port is actually used by MAP sensor.
Unless ECU won't open tandem without high vacuum reading from MAP
sensor I would still presume dead solenoid. i just hope it's working
since I butchered old one really really bad. It's made from one piece
of injected plastic, had to use dremel tool to take it apart.

I'll put tomorrow everything back together and let you know if problem
is fixed. Thanks again, without your help I couldn't do a thing.