Miata List Archive

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Mail From: don (Don Clark)

Hi Guys-

I have a 99 Miata with 30k miles on it. I've owned it for the last 6k miles.

Lately when I start the car up after it has been sitting for a while and
drive off it feels like one of the tires is horribly unbalanced or the
engine is acting up. This is at speeds of 0-30 MPH. After the engine warms
up the feeling goes away. It feels like it's the engine that's acting up,
but I can't really tell. For those of you that have waited too long to
replace your plug wires, that's almost what it feels like.

There are no engine modifications to speak of.

Here's what I've done to try and get rid of this:
Can of Techron
Replaced plugs
Replaced wires (1 time with Magnecore and second time with NGK's)
Replaced coil pack

Couple of other things that might be of interest.

Gas mileage is not what I expected. Looking at my log book I can tell you
that I'm getting 23.0 MPG in this thing. That's the average over the last
6,000 miles all but about 2,000 miles of that is city driving. In my old
Miata I was getting pretty close to 28 MPG. The old Miata was a 1990 model
though and I know that they get better mileage. Is this 'good' gas mileage
from this car?

There's black soot on the tailpipe!

The previous keeper of my Miata said that he thought that the thermostat was
going out because the heater wasn't as hot as it used to be.

The CEL hasn't come on during any time that I've owned it. The light shows
up when you first turn the key so I know it's still good.

I can hear a pinging sound when I accelerate under loads. I changed to 92
octane and it's still there, but I think it's not as bad as it once was.


Any ideas? If not can anyone recommend someone good in the Seattle area? I
don't mind spending a little money to figure out what's wrong, but I like to
do this stuff myself.


Thanks,

Don

This read-only message was archived from a public mail list.
Mail From: john.freas (John Freas)

Previously on Rough Running, "Don Clark" <(email redacted)> said...

> I have a 99 Miata with 30k miles on it. I've owned it for the last 6k
miles.
>
> Lately when I start the car up after it has been sitting for a while and
> drive off it feels like one of the tires is horribly unbalanced or the
> engine is acting up. This is at speeds of 0-30 MPH. After the engine warms
> up the feeling goes away. It feels like it's the engine that's acting up,
> but I can't really tell. For those of you that have waited too long to
> replace your plug wires, that's almost what it feels like.

How long ago did you change out the coil pack and why?

I won't wait for the answer to suggest that you check all the mounts and
connections to the coil pack, especially the upper two bolts. The coil pack
grounds to the engine through those mounts and needs that ground to
function. If it is getting an intermittent ground you'll get a rough
running engine, as the assembly and engine warm up it is possible that
things tighten enough to make the ground solid again.

> Gas mileage is not what I expected. Looking at my log book I can tell you
> that I'm getting 23.0 MPG in this thing. That's the average over the last
> 6,000 miles all but about 2,000 miles of that is city driving. In my old
> Miata I was getting pretty close to 28 MPG. The old Miata was a 1990 model
> though and I know that they get better mileage. Is this 'good' gas mileage
> from this car?

The newer cars don't get as good mileage as the older ones, especially the
1.6 liter cars. I've heard people with NB cars talking about mileage in the
24 mpg range, but I'll let someone who actually owns one to answer that
question.

> There's black soot on the tailpipe!

Should indicate rich running, which if you have an intermittent spark would
tend to follow.

> The previous keeper of my Miata said that he thought that the thermostat
was
> going out because the heater wasn't as hot as it used to be.

That shouldn't be related to your rough running, but if the heater isn't
working it's easy to replace the thermostat.

> The CEL hasn't come on during any time that I've owned it. The light shows
> up when you first turn the key so I know it's still good.

The CEL seems to have a threshold that has to be reached before it comes on,
maybe you haven't reached it yet. That doesn't prevent the system from
logging the malfunction. You can still download any error codes from the
computer with an OBDII reader.

> I can hear a pinging sound when I accelerate under loads. I changed to 92
> octane and it's still there, but I think it's not as bad as it once was.

I'll leave this to someone more experienced than I, but I will say that you
shouldn't be hearing pinging in any healthy, normally aspirated Miata with
92 octane fuel, even mores so in an NB car since the built-in knock sensor
should be retarding the timing to stop the knock.

-John
_______________________________________________
John Freas
Red '90 Base-ish #7690
Owensboro, KY
Team LS1,2, SP, the Gap...
I love my Miata girl.
"I have no idea what those dimple things on the windshield frame are for."

This read-only message was archived from a public mail list.
Mail From: don (Don Clark)

John,


Thanks for the response. I'm using Outlook, but I'll do my best to make this
readable with my comments in line.

Here's a key:
> Don
== John

One other question:
Could the rich running contribute to the ocassional 'rotten egg' smell I
get? I assume it's the cat complaining.


-----Original Message-----
From: John Freas [mailto:(email redacted)]

Previously on Rough Running, "Don Clark" <(email redacted)> said...




> I have a 99 Miata with 30k miles on it. I've owned it for the last 6k
miles.
>
> Lately when I start the car up after it has been sitting for a while and
> drive off it feels like one of the tires is horribly unbalanced or the
> engine is acting up. This is at speeds of 0-30 MPH. After the engine warms
> up the feeling goes away. It feels like it's the engine that's acting up,
> but I can't really tell. For those of you that have waited too long to
> replace your plug wires, that's almost what it feels like.

== How long ago did you change out the coil pack and why?
==
== I won't wait for the answer to suggest that you check all the mounts and
== connections to the coil pack, especially the upper two bolts. The coil
pack
== grounds to the engine through those mounts and needs that ground to
== function. If it is getting an intermittent ground you'll get a rough
== running engine, as the assembly and engine warm up it is possible that
== things tighten enough to make the ground solid again.

1) Coilpack. I replaced the coilpack about 500 miles ago. I replaced it
because I thought that it was the source of the problems. At that time I
installed new NGK plugs and wires. I can't say that I've noticed much of a
change in the way that the car acts when first started with the new pack.
However, for a short while I thought that the problem was fixed. But I think
that has more to do about wanting the $200 I spent to have fixed the
problem.

After I got home this evening I checked the bolts. They were tight, but I
was able to tighten both of the upper bolts slightly. Maybe they need a
serrated washer to ensure conductivity?


> Gas mileage is not what I expected. Looking at my log book I can tell you
> that I'm getting 23.0 MPG in this thing. That's the average over the last
> 6,000 miles all but about 2,000 miles of that is city driving. In my old
> Miata I was getting pretty close to 28 MPG. The old Miata was a 1990 model
> though and I know that they get better mileage. Is this 'good' gas mileage
> from this car?
== The newer cars don't get as good mileage as the older ones, especially
the
== 1.6 liter cars. I've heard people with NB cars talking about mileage in
the
== 24 mpg range, but I'll let someone who actually owns one to answer that
== question.

I agree with this but am concerned about the mileage. I've kept track of all
of the gas I use at each fillup since buying it. I'm at 23.0 MPG right now,
and I'm not a leadfoot. On one 200 mile freeway run at 70-75 mph I got
25MPG. Can anyone with a 99 comment on the mileage?

I also think that the build quality on my 90 was better! But maybe that's
just wishful thinking.

> There's black soot on the tailpipe!
== Should indicate rich running, which if you have an intermittent spark
would
== tend to follow.

I agree with this.

> The previous keeper of my Miata said that he thought that the thermostat
was
> going out because the heater wasn't as hot as it used to be.

== That shouldn't be related to your rough running, but if the heater isn't
== working it's easy to replace the thermostat.
> The CEL hasn't come on during any time that I've owned it. The light shows
> up when you first turn the key so I know it's still good.

I didn't realize that an OBDII reader would read out the problems before the
CEL went on. I'm going to get one of these.

== The CEL seems to have a threshold that has to be reached before it comes
on,
== maybe you haven't reached it yet. That doesn't prevent the system from
== logging the malfunction. You can still download any error codes from the
== computer with an OBDII reader.



> I can hear a pinging sound when I accelerate under loads. I changed to 92
> octane and it's still there, but I think it's not as bad as it once was.

== I'll leave this to someone more experienced than I, but I will say that
you
== shouldn't be hearing pinging in any healthy, normally aspirated Miata
with
== 92 octane fuel, even mores so in an NB car since the built-in knock
sensor
== should be retarding the timing to stop the knock.
==
== -John


Thanks!

Don Clark
Seattle, WA

This read-only message was archived from a public mail list.
Mail From: john.freas (John Freas)

Previously on Rough Running, "Don Clark" <(email redacted)> said...

> One other question:
> Could the rich running contribute to the ocassional 'rotten egg' smell I
> get? I assume it's the cat complaining.

Possibly, but the sulfur smell from the tailpipe is not necessarily
indicative of a problem. See this link:
swri.edu/10light/catalyst.htm

Basically, it requires a rich condition to create the smell, but that's not
a bug, it's a feature. If it's only occasional then it's probably normal.
With 30K miles on your car I'd say it's probably normal and will get better
with time.

> After I got home this evening I checked the [coil] bolts. They were tight,
but I
> was able to tighten both of the upper bolts slightly. Maybe they need a
> serrated washer to ensure conductivity?

It doesn't take a lot to make good contact, as long as the coil pack isn't
moving around or otherwise insulated it's probably fine.

> I agree with this but am concerned about the mileage. I've kept track of
all
> of the gas I use at each fillup since buying it. I'm at 23.0 MPG right
now,
> and I'm not a leadfoot. On one 200 mile freeway run at 70-75 mph I got
> 25MPG. Can anyone with a 99 comment on the mileage?

You also said that most of your driving was in the city. The EPA figures
for the car fueleconomy.gov/feg/noframes/14806.shtml are: 25
city, 29 highway, 27 average. Personally I think those are a little
optimistic for a NB based on the comments I remember hearing around this
list. The NA cars and especially the 1.6 liter ones generally get better
mileage, but my '90 has averaged 27 mpg from the day I bought it over 6
years ago. What I'm saying is that the Miata is not really a great economy
car.

> I also think that the build quality on my 90 was better! But maybe that's
> just wishful thinking.

No, that was my (and other's) reaction when seeing the NB for the first
time. Mostly it was little things, but it's clear that they were saving
money where they could.

> > There's black soot on the tailpipe!
> == Should indicate rich running, which if you have an intermittent spark
> would
> == tend to follow.

It should be noted that I have heard of black soot on the tail pipe of
perfectly normal running Miatæ. If it's just inside the pipe I wouldn't
worry too much about it, both my '90 and my wife's '95 have the soot in
there and at least her car is running perfectly. If you have soot all over
the outside of the lip of the pipe and/or on the bumper cover around it,
then you probably have an over rich condition that needs to be addressed,
but otherwise I wouldn't be too concerned.

> I didn't realize that an OBDII reader would read out the problems before
the
> CEL went on. I'm going to get one of these.

This is my understanding and belief, not a fact, but if you're going to get
a reader it will definitely help troubleshoot. If it's just for this
purpose you might be better off going to the auto parts store and seeing if
they'll read the code for you.

I thlnk that of all the concerns you list, the only ones that are an actual
problem are of course the rough running, and the pinging.

You didn't mention any particular time or condition under which the car ran
rough, except that it only happened when the engine was cold and had been
sitting. Does it seem worse during acceleration? Does the ping occur at
relatively low throttle settings, or only on wide open throttle on hot days?

I'm thinking you may have a fuel delivery problem. It's possible that the
car got some bad gas sometime back and the fuel filter and/or injectors are
partially blocked. The fuel filter is a relatively easy thing to eliminate
from the equation, the injectors are not as easy, but are less likely to be
the culprit IMHO. Checking the actual fuel pressure is beyond my expertise,
but is probably not hard to do. I'll leave it to others to describe the
procedure, but in the meantime you might consider changing out the fuel
filter and then running some fuel injector cleaner through the system.
Carbon deposits can also cause pinging, but I'd be surprised to find serious
carbon in a 30K mile engine.

-John
_______________________________________________
John Freas
Red '90 Base-ish #7690
Owensboro, KY
Team LS1,2, SP, the Gap...
I love my Miata girl.
"I have no idea what those dimple things on the windshield frame are for."

This read-only message was archived from a public mail list.
Mail From: ian (Ian McCloghrie)

On May 21, 2003 "John Freas" wrote:
> You also said that most of your driving was in the city. The EPA figures
> for the car fueleconomy.gov/feg/noframes/14806.shtml are: 25
> city, 29 highway, 27 average. Personally I think those are a little
> optimistic for a NB based on the comments I remember hearing around this

I got about 21mpg in my 99 before I put the turbo on, but I rev it to
refline just about every chance I get. The other big factor here is
that reportedly the NB ECU runs in open loop mode any time the revs
are higher than 4000 RPM. In fifth, that happens at about 70-75 mph,
meaning that there's a huge (like 4-5 mpg) drop in fuel efficiency if
you cruise at 75 vs cruising at 65.

With the turbo on the car, I get between 18 and 19. :)

--Ian

This read-only message was archived from a public mail list.
Mail From: Moniata (Andymon Miata Email)

Is a '99 coil pack interchangeable with a '91? If so, I'd be interested in
your used '99 coil pack. What would you let it go for?
This is, of course, assuming that it is in fact a working part that you
replaced with a new part...
-----Andymon

----- Original Message -----
From: "Don Clark" <(email redacted)>
To: <(email redacted)>
Sent: Monday, May 19, 2003 10:06 PM
Subject: [Miata] Rough Running on Startup - 99 Miata


> Hi Guys-
>
> I have a 99 Miata with 30k miles on it. I've owned it for the last 6k
miles.
>
> Lately when I start the car up after it has been sitting for a while and
> drive off it feels like one of the tires is horribly unbalanced or the
> engine is acting up. This is at speeds of 0-30 MPH. After the engine warms
> up the feeling goes away. It feels like it's the engine that's acting up,
> but I can't really tell. For those of you that have waited too long to
> replace your plug wires, that's almost what it feels like.
>
> There are no engine modifications to speak of.
>
> Here's what I've done to try and get rid of this:
> Can of Techron
> Replaced plugs
> Replaced wires (1 time with Magnecore and second time with NGK's)
> Replaced coil pack
>
> Couple of other things that might be of interest.
>
> Gas mileage is not what I expected. Looking at my log book I can tell you
> that I'm getting 23.0 MPG in this thing. That's the average over the last
> 6,000 miles all but about 2,000 miles of that is city driving. In my old
> Miata I was getting pretty close to 28 MPG. The old Miata was a 1990 model
> though and I know that they get better mileage. Is this 'good' gas mileage
> from this car?
>
> There's black soot on the tailpipe!
>
> The previous keeper of my Miata said that he thought that the thermostat
was
> going out because the heater wasn't as hot as it used to be.
>
> The CEL hasn't come on during any time that I've owned it. The light shows
> up when you first turn the key so I know it's still good.
>
> I can hear a pinging sound when I accelerate under loads. I changed to 92
> octane and it's still there, but I think it's not as bad as it once was.
>
>
> Any ideas? If not can anyone recommend someone good in the Seattle area? I
> don't mind spending a little money to figure out what's wrong, but I like
to
> do this stuff myself.
>
>
> Thanks,
>
> Don
>
>
>
>
>
>
>
>
>
>
>
> _______________________________________________
> Miata mailing list
> (email redacted)
> realbig.com/mailman/listinfo/miata
>

This read-only message was archived from a public mail list.
Mail From: bonni (Bonni Weatherwax)

I don't think that it is, Andy, but I now have a spare off of a '91 ( I just
got my replacement engine for Zippy) that I'll let ya have for 50 bucks if
ya want it. At the recyclers in Rancho you can get one for between 100-150
bucks, usually. BTW, I have other spare parts off that engine as well,
should anyone need something. =-)

BW

> Is a '99 coil pack interchangeable with a '91? If so, I'd be interested in
> your used '99 coil pack. What would you let it go for?
> This is, of course, assuming that it is in fact a working part that you
> replaced with a new part...

This read-only message was archived from a public mail list.
Mail From: john.freas (John Freas)

Previously on Rough Running, "Andymon Miata Email" <(email redacted)>
said...

> Is a '99 coil pack interchangeable with a '91? If so, I'd be interested in
> your used '99 coil pack. What would you let it go for?

The 1.8 and 1.6 liter cars use different coil packs, I'd go with BW's spare.

-John
_______________________________________________
John Freas
Red '90 Base-ish #7690
Owensboro, KY
Team LS1,2, SP, the Gap...
I love my Miata girl.
"I have no idea what those dimple things on the windshield frame are for."

This read-only message was archived from a public mail list.
Mail From: RESOMMER ((email redacted))

[this was a MIME-encoded message - it has been]
[filtered of non-plaintext attachments by ALF ]


Over the last 35475 miles Genghis Kart (Black & Tan 2000) has provided me
with 25.42 mpg.

The highest was 28.00 at 35273 miles (gas purchased at Mattawan, Michigan-not
city gas, I live near Chicago, IL). Lowest was 21.58 at 23895 miles.

What these numbers tell me is that I need to get out to empty country roads
more often.

Your MPG may vary!

Hope this helps.

Rick

In a message dated 5/20/03 1:51:44 PM Central Daylight Time,
(email redacted) writes:

> Gas mileage is not what I expected. Looking at my log book I can tell you
> >that I'm getting 23.0 MPG in this thing. That's the average over the last
> >6,000 miles all but about 2,000 miles of that is city driving. In my old
> >Miata I was getting pretty close to 28 MPG. The old Miata was a 1990 model
> >though and I know that they get better mileage. Is this 'good' gas mileage
> >from this car?
>
> The newer cars don't get as good mileage as the older ones, especially the
> 1.6 liter cars. I've heard people with NB cars talking about mileage in the
> 24 mpg range, but I'll let someone who actually owns one to answer that
> question.
>




[ALF: attachment (type="text/html") removed from message]

This read-only message was archived from a public mail list.
Mail From: Moniata (Andymon Miata Email)

I'll keep that in mind, Bonnie.
BTW, I just got several copies of install instructions off the net from the
company that bought Dana for installing cruise control.
Between these three, I'm hoping to find out what additional parts I'll need
to install the cruise.
I haven't forgotten you, and I'll be kicking out a check as soon as I get
this figured out.
Thanks,
----Andy

----- Original Message -----
From: "Bonni Weatherwax" <(email redacted)>
To: "Andymon Miata Email" <(email redacted)>; <(email redacted)>
Sent: Thursday, May 22, 2003 4:06 AM
Subject: Re: [Miata] Rough Running on Startup - 99 Miata


>
> I don't think that it is, Andy, but I now have a spare off of a '91 ( I
just
> got my replacement engine for Zippy) that I'll let ya have for 50 bucks if
> ya want it. At the recyclers in Rancho you can get one for between
100-150
> bucks, usually. BTW, I have other spare parts off that engine as well,
> should anyone need something. =-)
>
> BW
>
> > Is a '99 coil pack interchangeable with a '91? If so, I'd be interested
in
> > your used '99 coil pack. What would you let it go for?
> > This is, of course, assuming that it is in fact a working part that you
> > replaced with a new part...
>
>
>