Stalling, Idle Hunt, No power, I am stumped
 

Hey guys, long time rotorhead but new to the Rx8. I have a car that has stumped me.

Stats:
2004
110K
Compression = 90PSI on all 3 hits per rotor


Symptom: Car has no pull under 5K RPM. Horrendous to drive from starts. Revs fine when not under load. Idle hunts from 500 to 1000 RPM. likes to stall. When coming of idle sometimes the motor does not seem to respond to the throttle pedal. Literally feels like a shot of nitrous when it hits 5K.

Front pulley set was wobbling by 1/4". (further inspection showed the motor had .025" end float)

CELs: P0301 (cyl 1 mis-fire), P0172 (System rich bank 1)

Action: Removed front cover and replaced all thrust washers and bearings with new Mazda parts. Replaced both front pulleys, trigger wheel and the hub with new Mazda parts. Put the motor back in.
Same running issues. Mis-fire CEL gone.

Action: Replaced the gutted Cat/midpipe with a used functioning unit.
Results: Same

Action: Replaced coils and plugs with new Mazda and NGK. Cleaned MAF.
Results: Same

Action: Replaced MAF with used Item (from Tom @ the Parts Group <- Seems like a great guy)
Results: Same.


Possible Next Actions?:

Neutral switch
Drop rear muffler section to check for blockage.

Any ideas?

-billy

I would check intake system. Since you were running rich and a new set of ports, aux ports if I remember right, opens around 5K I would guess you might have starved it for air.

You didn't leave a paper towel in your primary runners, did you Billy?

Currently I am leaning towards a stuck SSV or primary injectors.


Your funny.


-billy

Well.................if/when you need it.

https://www.rx8club.com/series-i-do-yourself-forum-73/diy-remove-ssv-beta-teaser-video-184663/

SSV is at 3500 and does throw a CEL for being stuck open or closed.

Hey, do SSV, VDI and APV all have little limit switches to confirm when they're full-open and full-closed? If you alternate +/- 12V across the APV by unplugging the harness at the ECU and just driving it with some gator clips, are there other pins you could sample to know that it's going full-open and full-closed?

APV does a self test...and will set a CEL..same with SSV...and the VDI doesn't open at any RPM that would affect the driveability....

Primary injectors .....unlikely as well...

Throttle body is a possibility..it controls the idle....but if it is really fubarred it should throw a code..

Clutch switch can cause a hunting idle..but not the other symptoms..

Hows the compression?..that would be nice to know...poor compression can cause low speed problems...and get better because the compression ( sealing) gets a lot better with engine speed

Compression is good. 90PSI using a standard tester with the schraeder valve removed. Actual compression would be a tad bit higher.

-billy

get your a/f's yet? and if possible your fuel trims.
OD

Apparently the ODBII scanner I have does not show A/F. I need a USB to COM adapter in order to hook up my wideband.

I have found the car runs great when in open loop. Once it goes to closed loop it has no power.

-billy

as I suspected when I posted on the Ga forum---now ? is "why".:)
Just have to drive WOT all the time:)

Reset your ecentric profile shaft.

hope that you did not damage it or eas damage before you replaced the pully.

Hunting idle has been a neutral switch. I think I have read oone other solution.

In other cars/bikes a hunting idle can be a vaccum leak so check all the air conncetions just for fun.

Have reset the E profile a few times. Not the issue.
Neutral switch does not see to be the issue since it is more related to fuel system open lop verses closed loop.


Been a while so here is an update. Been busy and not had time to work on it.

While the issues were still there I drove it a bit by pulling hard in first and it would trigger the car to stay in open loop1 or open loop2. Worked for a while but each redlight it would try to go back into closed loop and had no power. Had to pull over and let the cat cool off one day so I decided to let the car sit while I was busy.

This morning I swapped in a front 02 sensor (29K mile used unit I picked up from Tom @ the Parts Group). It has been running like a champ. I have not driven it to much or to far in fear I would get it stuck on the side of the road with a glowing cat again.

Next step will be to build a cat midpipe . I will toss in an extra bung for the wideband. Then we will see if stays running well or if the running issues fouled the front O2 in the first place. Hopefully I can get it to stop throwing codes long enough to get it to pass emission.

-billy

If you have a glowing cat that is an indication of the cat being restricted. Another possibility is a bad fuel tank purge system. If the purge system has failed (solenoid) it could be drawing extra fuel into the intake from the charcoal canister/evap. Causing a flooding issue at low rpm's.