Poor Acceleration

Need some help here. Last night on the way home the Miata started having no acceleration. I was having trouble maintaining 60mph with the accelerator floored. There is a loud roar from the engine compartment when trying to accellerate. Motor sounds normal at idle or when revving in nuetral.

The facts: 1995 Miata

Timing belt changed 40k miles ago.
Fuel filter changed 1500 miles ago.
Seafoamed intake 1500 miles ago.
Timing advanced to 14 degrees 1500 miles ago.
Gas is at half a tank and just started experiencing it so I doubt bad fuel
Swapped plug wires to see if that was it. Nope.
Plugs look good but a bit white. (too hot?)
Two of the coil pack outputs had greenish white corrosion which I cleaned.
Also cleaned all electrical connectors to coil pack and CAS
Cat recently started rattling and is likely going bad.
10 and GND says Code 3 (Bad G Signal)

An odd thing to mention. When adjusting the timing the timing mark on the Crank was jumping around a bit. This had actually happened about three years ago when I lowered the timing done to 10 degrees due to pinging in the summer heat.

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Originally Posted by black roadster

An odd thing to mention. When adjusting the timing the timing mark on the Crank was jumping around a bit. This had actually happened about three years ago when I lowered the timing done to 10 degrees due to pinging in the summer heat.

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My first guess would be the cat beginning to get clogged. Eventually it will just stop. Too bad it was welded in and you can't just pull it and check it.

As for the jumping around timing, my harmonic balancer was causing the slip. I had never heard of this part going out, but after mine there were 3 more that I heard of.

That's was my first thought but why the Engine code? From what I read on the pointy board, a G Sensor code has to do with a bad coil pack or CAS but typically it kills the motor completely. Mine still runs. Can't be an old code either as I just had the battery disconnected a month ago.

I'm going to try and unbolt the cat/midpipe and see if I can shake out some broken catalyst.

My exhaust is custom because they are FM Duals for a NB modified to fit my NA.

My exhaust looks like this.

\\\\____I<CAT>--[glasspack]--I-{Muffler}=
Header

The I represents a bolted flange

It should have been like this.

\\\\____I<CAT>I--[glasspack]--I-{Muffler}=
Header

Probably CAS related.

I have a spare here at the house I was going to list on the classifieds... if you want to drive by and try swapping 'em.

RJ

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Originally Posted by channelmaniac

Probably CAS related.

I have a spare here at the house I was going to list on the classifieds... if you want to drive by and try swapping 'em.

RJ

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I'll send you a PM.

Crap...

Got your PM...

For some dumb reason I thought you had a 1.6... I don't have the 1.8L CAS.

Sorry to get your hopes up.

RJ

doh!

Got little girl down for a nap. Time to go jack up the car and remove the exhaust. Fingers crossed this fixes it. :(

Clogged Cat.

Tell me if my thinking is correct. I removed the exhaust completely and ran straight from the header. It was loud as hell but it kept reving past 3500 rpm to 4500 rpm before I cut it off. Last night it bogged at 3500 rpm while in gear.

Also, the cat has a large piece rattling around. Of course it's on the side that is welded. ::Censor:: I think I'll just hollow out the cat until I can afford the $250 to get a new cat and flanges put on.

I second the hollowed out cat idea. Just get a pipe, a hammer, and got to town on it.

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Originally Posted by Nexus Flux

I second the hollowed out cat idea. Just get a pipe, a hammer, and got to town on it.

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Cat is hollowed out First some lunch and then I can get it off the jack stands and test drive it.
I think this was it because there was a huge golf ball sized chunk loose in there.

Back in business. ::Banana::

Need to order a new cat between now and March when my inspection is due.

Those :cat:'s are finicky critters.

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Originally Posted by sammm

Those :cat:'s are finicky critters.

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It's always about the :cat: with you guys... ::Clown::

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Originally Posted by CraiginTX

It's always about the :cat: with you guys... ::Clown::

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Well duh, what is it about with you?????? ::Fruity::

::Clown::

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Originally Posted by CraiginTX

It's always about the :cat: with you guys... ::Clown::

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Yeah... all of us except OzCop... he thought it was a purple rabbit. Must have been the 60's.

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Originally Posted by tailchaser

Yeah... all of us except OzCop... he thought it was a purple rabbit. Must have been the 60's.

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Yup... for the longest time I thought he was a professional chef with all his talk about mushrooms.

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Originally Posted by CraiginTX

It's always about the :cat: with you guys... ::Clown::

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You say that like it's a bad thing! ;)

Hey BR,

Describe the rattling in the :cat: prior to the big power loss. Mine may be headed in that direction as well...

Thanks

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Originally Posted by CraiginTX

Hey BR,

Describe the rattling in the :cat: prior to the big power loss. Mine may be headed in that direction as well...

Thanks

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Sounded like rocks in a coffee can when revving down or at a particular RPM and the exhaust got quieter.

Couldn't here it on the road. Just when at a stop or pulling into the garage.

Does anyone have a test pipe that would bolt in to my '96? I'd like to try eliminating the cat and see if the noise goes away. It does sound a bit like "rocks in a coffee can."

If it turns out to be the cat, any suggestions? Magnaflows are cheap - FM's not so much, new OEM's $$$...

Craig