WOO-HOO! Grounding mod works! (02 WRX)

[BD]

Hey, all...

So - for the longest time my car would hesitate slightly as I
accelerated between 3000 and 4000 rpm. Just felt a bit shaky in that
range, regardless of gear.

I read on the NASIOC forums about the 'Grounding Mod', which many
people seem to have tried, and decided to give it a go.

I got some heavy-gauge speaker wire, and ran two leads from the
negative battery terminal: one went to the grounding bolt on the intake
manifold (passenger side) and the other went to one of the bolts on top
of the passenger side strut.

When I started the car, it felt quieter, seemed smoother, even at idle.


I went for a spin and wound it up, and though I felt _slight_
hesitation right at 3000rpm, the rest of the power band was consistent.

My dealer said that the reason for the hesitation was that I was
running 91 gas and that I should be running 94. I wonder if I should
tell the dealer that they REALLLY need to pay more attention to these
solutions that the driver populace comes up with. It makes them seem
like they don't even know the limitations/issues with their product.

Anyhoo. It was an easy change, took me an hour and cost about 5 bucks.
The speaker wire I had laying around anyway, so I only had to buy the
ring clips.

Anyone who finds acceleration choppy between 3000 and 4000, I expect
this little fix might well help!!

Oh - I'd LOVE to understand how something like this could have such
pronounced effects. If anyone knows of any discussions on the topic,
I'd love to hear about them.

Cheers,

BD

 

[Clifford Heath]

I got some heavy-gauge speaker wire, and ran two leads from the
negative battery terminal: one went to the grounding bolt on the intake
manifold (passenger side) and the other went to one of the bolts on top
of the passenger side strut.

Great that you got it fixed! As an electronics person however,
I'd warn that if grounding the engine made a difference, there
might not be a suitable path to ground while cranking, and you
don't want the cranking current running through your speaker
wire. It could start a fire and wreck your car. That said, if
you didn't have a good ground before... how did it start?

Every car should have a fat ground - as thick as your finger -
taken direct from the battery to the chassis (some Suby ones
are too long), and from the chassis to the engine.

If the grounds aren't solid, the ECU cannot do its job - neither
sensors nor spark&injectors can work properly.

 

[BD]

Great that you got it fixed! As an electronics person however,
I'd warn that if grounding the engine made a difference, there
might not be a suitable path to ground while cranking, and you
don't want the cranking current running through your speaker
wire. It could start a fire and wreck your car. That said, if
you didn't have a good ground before... how did it start?

This could happen with the *negative* battery terminal connected to the
strut and the manifold??

'cranking current' - that's a new term for me.... ??

The car always started fine; it just hesitated slightly at certain
revs.

 

[BD]

Great that you got it fixed! As an electronics person however,
I'd warn that if grounding the engine made a difference, there
might not be a suitable path to ground while cranking, and you
don't want the cranking current running through your speaker
wire. It could start a fire and wreck your car. That said, if
you didn't have a good ground before... how did it start?

Clifford - here is the thread on the forum regarding this fix. Issues
discussed concern sensors being very sensitive to EM interference, and
this fix addressing that *somehow*.

http://forums.nasioc.com/forums/archive/index.php/t-156303.html

I am very curious about your concerns of a fire hazard. If you'd be
willing to review a bit of that thread, perhaps gleaning a clearer
sense of what has been done, and confirm that you are still concerned,
I'd like to hear it. Not that I'm asking for a primer in electronics
theory, but just that I don't see how connecting 'inert' engine
components to a negative terminal could constitute a hazard.

Thanks!!

 

[mulder]

Hey, all...

So - for the longest time my car would hesitate slightly as I
accelerated between 3000 and 4000 rpm. Just felt a bit shaky in that
range, regardless of gear.

I read on the NASIOC forums about the 'Grounding Mod', which many
people seem to have tried, and decided to give it a go.

I got some heavy-gauge speaker wire, and ran two leads from the
negative battery terminal: one went to the grounding bolt on the intake
manifold (passenger side) and the other went to one of the bolts on top
of the passenger side strut.

When I started the car, it felt quieter, seemed smoother, even at idle.


I went for a spin and wound it up, and though I felt _slight_
hesitation right at 3000rpm, the rest of the power band was consistent.

My dealer said that the reason for the hesitation was that I was
running 91 gas and that I should be running 94. I wonder if I should
tell the dealer that they REALLLY need to pay more attention to these
solutions that the driver populace comes up with. It makes them seem
like they don't even know the limitations/issues with their product.

Anyhoo. It was an easy change, took me an hour and cost about 5 bucks.
The speaker wire I had laying around anyway, so I only had to buy the
ring clips.

Anyone who finds acceleration choppy between 3000 and 4000, I expect
this little fix might well help!!

Oh - I'd LOVE to understand how something like this could have such
pronounced effects. If anyone knows of any discussions on the topic,
I'd love to hear about them.

Cheers,

BD

While adding additonal grounds may in fact have some benefit, you
should also bear in mind that if you disconnected the battery in the
process of doing this mod you also reset the ECU. This will often make
the car run better for a while because it returns the timing cells to
their default values and clears all the "learned" values. You may find
after some driving over the next few days or weeks that as the ECU
re-learns, some of the hesitation may return.
Also, note that the strut tower bolts are a poor place for a ground
connection because the strut mounts which those bolts go into are
rubber-isolated from the frame. There may be some ground contact
between the bolt and tower but there is paint underneath. The most
important grounding point is from the engine manifold to the battery.

 

[BD]

While adding additonal grounds may in fact have some benefit, you
should also bear in mind that if you disconnected the battery in the
process of doing this mod you also reset the ECU. This will often make
the car run better for a while because it returns the timing cells to
their default values and clears all the "learned" values. You may find
after some driving over the next few days or weeks that as the ECU
re-learns, some of the hesitation may return.
Also, note that the strut tower bolts are a poor place for a ground
connection because the strut mounts which those bolts go into are
rubber-isolated from the frame. There may be some ground contact
between the bolt and tower but there is paint underneath. The most
important grounding point is from the engine manifold to the battery.

I'd read that resetting the ECU is also a 'pursued strategy' for
clearing the hesitation problem, and that a recommended next step would
be to drive normally for 30 minutes or so, so that the ECU resets to
typical values.

Interesting point about the ground. That makes sense... I wonder if
these folks removed some of that paint? Or perhaps the bold does make
contact with raw body metal in the hole.

Arguably I should have ensured that the negative lead did not come off
the battery at all, and that I only did one wire at a time. That would
have told me considerably more.

 

[mulder]

I'd read that resetting the ECU is also a 'pursued strategy' for
clearing the hesitation problem, and that a recommended next step would
be to drive normally for 30 minutes or so, so that the ECU resets to
typical values.

Interesting point about the ground. That makes sense... I wonder if
these folks removed some of that paint? Or perhaps the bold does make
contact with raw body metal in the hole.

Arguably I should have ensured that the negative lead did not come off
the battery at all, and that I only did one wire at a time. That would
have told me considerably more.

Another reason the strut tower bolts make a poor ground is that they
do not actually screw into the frame but just pass through it. The
ground bolts on the inner fenders and firewall DO thread directly into
the frame, and are a more suitable place to attach additional ground
wires. For better contact, even with the factory ground wires, you can
remove the existing bolts and make sure that enough paint is removed
underneath them to ensure a good metal-to-metal contact for the bolt
and lockwasher. Don't overdo it though, you do not want a lot of
exposed metal beyond the area covered by the bolt and washer. After
you're done you can apply touchup paint or heavy grease over the
connection to protect it.

 

[BD]

Another reason the strut tower bolts make a poor ground is that they
do not actually screw into the frame but just pass through it.

Good advice. I'll see how this pans out before reassessing additional
grounding.

Kind of took the wind out of my sails, however, realizing that it may
have been the ECU reset that fixed it, not the ground.

Is this a chronic problem with these cars? Seems to me that no system
should settle into timings that have this kind of hesitation... How
much of this owes to how the driver drives as the timings are being
established? And how much owes to a 'problem' in the ECU? I've read
about models that have over-sensitive knock sensors, and that a TSB has
been issued in some cases.

You'd THINK the dealers would know more about this stuff than anyone
else. I described the issue, and they told me I should switch to 94
gas. I'm all but convinced that the octane was _not_ the issue here...
;(

 

[Clifford Heath]

Clifford - here is the thread on the forum regarding this fix.

I scanned it about halfway. Lots of opinions there, mixed with a
little bit of science... here's my take (not being a WRX owner).

* The radio ham mentioned that the car generates *lots* of EMI.
Cars normally do, but I assume he meant much more than expected.
Thing is, if there's a way for EMI to get out, there's a way for
it to get in, including the car's own RF emissions mucking up
other parts of the circuitry.

* The fix that seems to work is the wire to the intake manifold.
This manifold is where the MAF sensor and air temp sensor reside,
so if there's "ground bounce" in the grounding there, these analog
signals will also bounce around. If the ECU doesn't smooth out the
noise *very* carefully, it could see semi-continuous false readings
either above or below the actuals. That seems the most likely
cause of surging and hesitation.

* Since the main battery ground strap isn't taken to bare metal,
there's a distinct possibility of poor grounding. The battery in
our RX died a couple of months ago and the mobile tech that
replaced it also replaced the whole grounding strap, commenting
that both the strap and the fixture to the chassis were the cause
of endless troubles in Subies, and he always replaced the original
fittings. Even the battery terminals are crap.

* If the main battery ground to chassis is weak and you fit
alternate earth wires, then when you crank the engine, at least
some of that 200A cranking current will take the new route home.
If the wire's not rated for 200A, it'll get very hot, hence my
concern about a fire hazard. Don't do this fix unless you also
ensure that the battery has a really good connection to the
chassis, and the chassis has a really good connection to the
engine - preferably near the starter. I don't know how this
engine grounding is done in Subies, but my Alfa has a 3mmx25mm
strap of braided copper bolted from the rail to the bellhousing.
I found this out after an engine swap when the bozo welded the
exhaust before fitting the strap, with the welder earth lead
on the chassis. The weld current found its way out through the
alternator, cooking it totally, all internal wiring and the
diodes.

Don't forget that engine parts are fitted between insulating
gaskets, and the bolts that pass through are subject to surface
oxidation. Aluminium alloy protects itself with a surface layer
of *very* non-conductive aluminium oxide. Don't assume that just
because two things are bolted together, you have a good path for
high currents or RF.

Clifford Heath.

 

[strchild]

Why not put in a tank of the 94 octane as the dealer recommended, give it a
spin, and see if your hesitation is better?

What octane is recommended in your manual?

~Brian

 

[BD]

Why not put in a tank of the 94 octane as the dealer recommended, give it a
spin, and see if your hesitation is better?

What octane is recommended in your manual?

Manual recommends 91, I've been running 94 on the recommendation of the
dealer. The 94 seemed to make a difference, but the issue is still
there.

 

[strchild]

Sounds like the dealer may have been going for a bit of a longshot then. If
the book calls for the 91, then you're probably fine putting it in, barring
anything about the condition of the motor that could possibly raise the
octane rating such as carbon deposits.

I changed plug wires on my Impreza to MSG, low impedance wires, and after
about 3,000+ miles I started getting aweful hesitation between 2 - 4k RPM
until I changed out the plugs to an irridium resistance style. Were grossly
expensive for spark plugs, but the did the trick immediately. Next time I
will just use normal plug wires and not have to worry, but these silly wires
better last for the life of the car. (-;

~Brian

 

[BD]

Why not put in a tank of the 94 octane as the dealer recommended, give it a

spin, and see if your hesitation is better?

I did. The hesitation seemed to improve, but never went away. Over
time, I kind of 'got used to it', and ignored it. I'm mainly getting in
a twist about it now because it is a leased vehicle, the lease is up in
a month, and I am weighing whether it makes sense to keep the vehicle
or let it go. So every little niggly imperfection is bothering me now.

What octane is recommended in your manual?

91.

 

[k. ote]

Sounds like the dealer may have been going for a bit of a longshot then.
If the book calls for the 91, then you're probably fine putting it in,
barring anything about the condition of the motor that could possibly
raise the octane rating such as carbon deposits.

[...]

'02 WRX manual "recommends" 91, with a minimum of 89 *where 91 isn't
available.* It is silent on the benefits of 94. The '02 WRX does NOT
require 94, and if yours does, then the gas you're buying sucks hind tit.

To the O.P.: please continue to apprise us of your situation.

 

[BD]

'02 WRX manual "recommends" 91, with a minimum of 89 *where 91 isn't
available.* It is silent on the benefits of 94. The '02 WRX does NOT
require 94, and if yours does, then the gas you're buying sucks hind tit.

To the O.P.: please continue to apprise us of your situation.

Yes, I will do... the hesitation still appears to be absent, but I do
feel a *slight* difference right at 3000 rpm. Sometimes. That's about
where the turbo kicks in, so I don't expect things to be liquid smooth
at that point in the power band.

What I'm not clear on, and maybe someone can help here, is - some have
said that the effects of this mod will be transient, and that the
hesitation will come back. What I'm not clear on is how quickly. The
jury is still out, but will there be a certain number of miles before
I'll know for sure? Presumably this will also depend on how I drive...

Regardless - if it _does_ come back, the mod comes out, the car goes
into the shop, and I'll be saying to the dealer something to the effect
of '94 my @$$'.

BD