DIAGNOSIS HELP (Running Rich) - CAS, CPS, Coilpack, TB, or worse? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 05-14-2014, 10:37 PM   #1
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Default DIAGNOSIS HELP (Running Rich) - CAS, CPS, Coilpack, TB, or worse?

Hi everyone,

My 97í NA has been running extremely rich ever since going to Mid-Ohio Race Course last weekend. When I pulled into the garage after my second session and popped the hood to let the engine cool, I noticed motor oil was dripping from my K&N intake filter and onto the chassis in my engine bay, where it was beginning to make a small pool of oil. I figured it was a bad issue of blow-by/elevation changes that caused the oil to reflux out of the crankcase and into the intake piping, so I simply dried the filter and intake tubing as much as I could and took the car out for a brief spin. Here is what I got:

-Rough start, but fires up every time, it immediately revs extremely high (2200-2800) for the first rev then rapidly drops down to 800-900, where it usually dies out.
-After setting the idle adjustment screw to idle at 1800, it idles pretty rough but sounds better. A small backfire can be heard occasionally.
-Under light throttle/acceleration the car runs fine. In fact, I was able to drive the car 400 miles from Mid-Ohio to my apartment in Indianapolis, then from Indianapolis back to my parentsí house in Chicago where the car stays.
-However, anything more than that (moderate/heavy throttle) and the car misfires/bucks pretty bad and doesnít accelerate.
-Gas mileage has gone down severely. It got 34mpg highway on the way to the track, and 22mpg on the way back.
-Spark plugs were dry, but completely black upon pulling them at the track. Replaced them with new ones, and were black by the time I got to Indy. Replaced them again and Iím assuming they were black again by the time I got back to Chicago.

-Before installing the MSPNP, running speed density, and getting the car tuned, the car was throwing the following codes on the stock ECU:
PO335 - Crankshaft Position Sensor / Circuitry Malfunction
PO443 - EVAP system control purge control valve circuit failure
PO140 - O2 (No activity detected bank 1 sensor 2)
P1170 - Heated oxygen sensor
-Iím assuming that since these codes were not addressed, my CPS or CAS was going bad, and simply got worse once I was on the track? However, the only thing that makes me weary about that is the car was able to get its base timing set to 10 degrees and made good power prior to the incident (34mpg, 130whp), so Iím wondering what else it could possibly be?


-99-00 NB motor, 47k miles, 180 psi dry across all four cylinders
-EUDM squaretop intake manifold
-MSM BP5A camshaft
-K&N 69-6000TP Intake
-Racing Beat header, wrapped
-RS*R Exmag GTII catback exhaust
-Exedy Stage 1 - 1.6 clutch
-XTD Prolite 9.5lb 1.6 flywheel
-MSPNP v1.1
-MAF delete, IAT sensor
-Hondata Intake Manifold Gasket
-93 octane
-Charcoal Canister Delete


Iím not sure what the differentiating symptoms would be between a bad CAS, CPS, coilpack, slipped TB, or worse, a bent valve would be. If anyone knows what they are, or simply have advice on where to proceed from here, Iíd greatly appreciate it. I have a time attack on June 1st so Iím in a rush to get this issue sorted out!

Thanks in advance everyone,
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DIAGNOSIS HELP (Running Rich) - CAS, CPS, Coilpack, TB, or worse?-photo11_zpsfbfa3b56.jpg   DIAGNOSIS HELP (Running Rich) - CAS, CPS, Coilpack, TB, or worse?-photo31_zpsc57d02d3.jpg   DIAGNOSIS HELP (Running Rich) - CAS, CPS, Coilpack, TB, or worse?-photo4_zpse77b7366.jpg  
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Old 05-14-2014, 11:15 PM   #2
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The evap code is probably from removing the charcoal canister. I'd focus on having both upstream and downstream o2s faults. If you have access to a decent scan tool that can show streaming data, look at the b1s1 o2s pattern and see if it looks funky. It should oscillate evenly between like 100mA and 800mA in cruise. If its stuck at one value regardless of rpm you probably need a new one. The downstream one is less important to drivability.

I know the nb's have a ckp off of the pulley but don't the na's just use the cmp for both signals? I'm not sure how you have your 99 engine wiring up to the 97?

Last, check to see if your pcv is still free and not stuck.
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Old 05-15-2014, 06:30 AM   #3
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Right now the 99 motor has all 97 sensors and is running off the 97 wiring harness and ECU. The 96-97' NAs use both a Crank position sensor by the pulley as well as a Cam angle sensor. Any way I can check those?

Ill check the PCV when I get home this weekend, im assuming thats by shaking it and hearing for an audible rattle. Unfortunately, I don't have access to an OBDII tool that can read streaming O2 values. Either way, i don't think the OBDII port will work anyways with my MSPNP. Any alternative?
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Old 05-15-2014, 08:23 PM   #4
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Bump for other suggestions
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