03 VVT Miata- SLOW- 140k- Trying to figure out why it is slow? Power feels linear.
 

Recently bought this car. The previous owner said that the coil pack was changed. That is all I have to go by...

When I drag race my buddy in his 94 we are dead even, he may pull on my a bit. I also have a 91 with 19x,xxx miles that feels faster.

What things can I check? I don't get any additional pull in lower or higher RPM's. Is my VVT functioning? How can I tell?

Should I replace the coil packs again? Change all wires and plugs again?

I'll pull the plugs and do a compression test. Anyone know what number I am looking for?

Wish I could give more info... Thanks for any help.

The car has about 140,000 miles on it.

5 or 6 speed; what wheel/tire size are you running?

I'd like to see about 170lbs of compression.

6 speed, 15 stock wheels from a 2000. 195s. I'll test compression this afternoon.

PSI from front to back
152, 153, 153, 158

Is this a problem? I'm also getting a code from the cat.

Definitely low for a standard engine, but not on the death bed yet.

I just re-tested. This time at WOT with all the plugs out. 7 cranks on a weak battery.

Front to back 168, 171, 167, 166

Guessing this is ok?

I'll run some seafoam through and see if that helps.

My code is the cat converter. Do these things go bad? What is a sign if it has gone south?

Ignition coil packs. It has one new one and one older one. Can I test these?

Yes, cats can get plugged. That will definitely hurt power. An exhaust shop will be able to test for a plugged cat by monitoring exhaust back-pressure.

Your engine compression looks good.

How does one measure back pressure? I have an OBD-II thing, is this a reading I can get from that?

Getting codes P0103 and P2004.

What an exhaust shop usually does is find a place where they can put a pressure gauge on the exhaust upstream of the cat. They then monitor backpressure with the engine running. I've seen them use the O2 bung for this. Sometimes they drill a small hole for the test.

This is not a parameter that appears in OBD-II.

Google is your friend, but I happen to know the first code.

po103 is an unexpectedly high reading from your MAF (voltage of the input signal is above max range).

P2004 has to do with the VTCS being stuck open. Check out this service bulletin from Mazda about it.

Great link. I cleared the codes and the P2004 keeps coming back. I just started getting this code after I sprayed deep creep into the motor today. Wonder if the deep creep stuff was too stout.

Just got my hands on a high flow cat. Taking it to be installed this week.


FWIW: I've driven Hondas and such with the VTEC and this VVT motor doesn't feel at all like that. Matter of fact I don't hit any type of "Power Band" (Old 2 stroke dirt bike term)... Feels pretty linear.


Shouldn't I feel something extra as I climb in RPM's?

No, it doesn't ramp suddenly like vtec.

On some vehicles, after sitting overnight and being started, the MIL comes on and DTC P2004 sets into PCM memory. This occurs because vacuum (momentarily) does not flow into the Variable Tumble Control System (VTCS) shutter valve actuator. The contact surface between the valve and the valve body inside the check valve is smooth, causing the valve to momentarily stick before more vacuum applies, opening the valve.


Is the VTCS something that could get in the way of this motor making power?

Comparing VVT to VTEC...lol. Not nearly on the same level hahaha. Look up both acronyms and use deductive reasoning to figure it out.

If the VVT is not working (rarity), it would result in less peak HP from Mazda rated it at. Also, a timing belt off a tooth could do it. If the VTCS is broken/stuck, it would definitely cause a loss of power.

This is the VTCS system, clearly if the actuator was not working or the butterflies were sticking closed....well...you can guess..

https://www.miataturbo.net/attachmen...ine=1367846289

Have to admit that I am not fully aware of how the VVT motor functions. Working on it. I'm a Corvette guy. GM has had the same push rod design for a while. I originally bought this miata for my GF to race while I raced my C5. But then I started to like running the Miata. Now I'm hooked. I can field a Miata on street tires and no prep and still have a good time. The vette can be a handful and without blowing $1750 on slicks twice a year it's unusable.

I need to get this Miata going right. I already have a good suspension and a roll bar. If I get all the normal stuff sorted out I may be looking at a flying Miata turbo kit soon.


Is there a way that I can check and see if the VVT part is functioning?

And this VTSC actuator code, the message states it needs a new adapter. Is this a factory recall or something I need to go buy?


Basically I am stating that yes, I am a newbie. :noob: And I appreciate any help you guys are offering to help me get this car in shape.

Hey Mike (Doppleganger) is there a vacuum tube that goes to the bottom of your intake? Told that this may be the cause of the 2004 code.

Found a vacuum hose off the car. It runs a lot better now. But still not up to par with where I think it should be. I'm going to have a high flow cat installed and see if that helps.

It's all good :)
If the VVT is out of whack, it should throw a code. I have not seen it fail for the most part, other than when people pull it apart by accident. I'd also throw a timing light on it just to make sure the timing is correct. It would almost seem more likely that the timing would be off or something of that nature than the converter being clogged. It would help you greatly if you could throw a WB02 on there and watch your AFRs.

If you're going to do any playing with the exhaust, you might as well just get a newer, better system. I'd highly recommend looking at Enthuza exhausts.

Funny what a little vacuum leak can do.

I've been told about a VVT tuber per se'. It's where the actuator valve that called for replacement via the service bullitin. I'm going to blow it out with carb cleaner.

The only reason that I am leaning towards the CAT being clogged is that
others that have had ignition problems have had to replace their CAT converters shortly afterwards. Trust me, I'm not excited about throwing money at a problem and seeing if it will fix it.


Next up, Changeing out the coil pack. By this point I would think that teh car will have a littel bit more umph...

IMHO/IIRC, The majority of the problems of the ignition/converter you speak of were with the NB1 (99/00) cars and their coilpacks going bad (pretty common), which would cause raw fuel to get into the cat and superheat the element and eventually blow it out. I have not really heard of any problems with the NB2 ignition and this issue.

Yeah the 01+ coilpacks are much better. Cats fail when the car runs too rich for too long, which is why a failing coilpack kills the cat.

I'm changing the cat next week. If this car doesn't get any more power or torque than I will be saying goodbye to miatas forever.:sad2:

Wow, you're easily discouraged. Maybe making a slow car fast isn't for you.

He's not even boosted or considering boost. He just has a stock Miata.

That was my point, if he gets discouraged this much diagnosing his stock miata then he should not even consider adding the complexity of a turbo setup and standalone EMS to the equation. Stock cars are easy to diagnose.

You may very well be right. Some guys LOVE to build. Some guys love to polish. Some love to brag about what beats what compared to the latest car and driver mag... I like to race. My car set up skills suck. You would think that after racing for the past 35 years I would have learned a thing or two about car set up and such. :facepalm:

Some people say that this car runs perfectly fine. I disagree. It has more power hidden inside and I need to unlock this power before I even think about going FI.

Once I figure this out then I'll start working towards either a Winter build or a good person to take it to for a turbo install.

The only way I'll go FI is if it's plug and play. I'm not teh guy for remapping fuel curves at teh start line. And I hate it when a car leaves me stranded.

I've owned two supercharged Corvettes. Both L98 C-4's and both were a nightmare. Tubes comming off all the time. Limp home mode. Incorrect air fuel- blown motors. Swore off of boost a long time ago. But I've heard that you guys have the turbo kits for a miata down to a science.:brain:

I hope that this new CAT will open the car up a bit. I currently own two miatas, a 91 stock with 198k and an 03 vvt, guess which one is currently faster?

I need to change this.:skid:

Well, yes. But it is a science. Are you actually interested in learning? Your post makes is sound like you may not be.

And guess which one is lighter. With the exception of the Mazdaspeed, Miatas did not get appreciably faster through the years. They got heavier and a bit more power was added to compensate. I would not change the cat unless a backpressure check or visual inspection showed that it was bad. Could easily be a waste of money.

Maybe try finding someone local who knows Miatas very well and have them take it for a spin?

Definitely. Perhaps you could temporarily wire the VCTS arm open and test drive it to see if the car feels better. If it's staying shut the car will definitely not build any power.

(I ditched it completely on my car, removed the butterflies, pulled the shaft out and epoxied the shaft bores.)