4k RPM wall under load
 

2004 Rx8 Automatic with 52k miles on it. The issues is when under load (say 50-100% throttle while driving, not idle) the car feels like it cuts out and hits a wall and then very slowly begins to accelerate smoothly. No idle or hesitation issues.

Just had diagnostic done for $120 to pull codes 441, 442, 446, and 2401 and stopped right there as the technician was not familiar with Rotaries. He confirmed coils and catalytic converter was operating normally.

I had a bunch of U codes like U0073, U0101 and U0155 but after searching it turns out those do not affect modules or vehicle operations and could be caused by my recent battery swap and loose cables

So according to my search, these codes 441, 442, 446, and 2401 deal with EVAP system

P0441 Evap System Incorrect Purge Flow
P0442 EVAP system lead detection (small leak)
P0446 EVAP system vent control circuit problem
P2401 EVAP system leak detection pump control circuit low

I printed a list of checks for these issues as well and will hand them to the dealer but I just wanted to see if someone had this 4k brick wall issue before and what their fix was.

Thanks

I hit it
 

I got the 4k wall the other day no codes except misfire on cyl 2 and a few weeks ago poped a code for cat i do believe the ignition coils and plugs need replacing the place i bought it changed these but i know for a fact they dont really know anything about mazdas let alone a rotory so i do believe they dont kbow what they were doing so idk if this is going to help you but i do believe that im having issues stemming from the issue of what they did.

Also cleared codes when they came up but no return until i hit that wall then everytime i hit it got misfire

Learn to troubleshoot.

http://foxed.ca/rx7manual/2003mazdar..._S01_0016.html

Awbrigham,

Please use periods. It makes it easier to read and lets everyone know you paid attention in 1st grade when you first learned to use periods.

Your issue is clearly different then mine. Pay for a diagnostic. My mechanic wanted 3 hours because of the time involved but you shouldn't have issues troubleshooting common ignition/coil/cat codes

Thanks, I'm sure others will find that useful but I'm on a short vacation so I don't have the time or tools to troubleshoot. Just seeing if someone ran into the same codes that I have. A search revealed that someone had the same code pattern but unfortunately he never reported back with the fix.

The manual didn't get down to fixing specific codes like the DTC manual did. I just don't know if the EVAP codes have anything to do with the 4k hesitation which is why I'm asking if anyone has experience. The checks for this turn out to be extensive and involve pulling the carpet and checking pins on the ECU and other sensors. I'll report back with what the Mazda dealer says

Results are in. I need a new engine. They said the low compression is causing the 4k RPM power issue. The drop in compression was contributed by the car sitting for 4 months and was told that the apex seals still move and wear out. I called bullshit on both accounts and the compression is 6.3 6.5 7 - 7 7 7

Correct me if I'm wrong, but low compression doesn't cause significant changes in power right at 4k RPMs or does it?

Anyways I'm not going to label the shop since I haggled the bill away and even got a free car wash. I just feel cheated and lied to

I have cash for anyone willing to troubleshoot this.

WOW...that's one I've never heard before

You could have so many issues....the compression isn't likely the problem..

Start at the basics.....fuel, ignition and go from there.

Get an OBD2 bluetooth adapter, pair it to your smartphone, download an OBD2 app, and then watch your AFRs when you trigger the problem.

It almost sounds like you are having one or more intake valves open prematurely, going way lean, massive power loss, and then slowly the airflow is stabilized and accounted for properly and the power begins to pick back up again.


And no, the apex seals don't move when the engine is off. Silly tech.

Thanks I actually have a Nexus A/F meter so I'll look at that in a moment and report back. Otherwise, I'll have to buy a smartphone ;(

I had another shop test the coils and cat so I know there are no issues there.

:lol: no, don't go buy a smartphone. I'm sure you can borrow someones temporarily if needed. Anything that gets you OBD2 data will be useful, but if you have a separate AFR gauge, that works for this particular test too.

I think your ssv isn't opening due to a vacuum leak. There is a vacuum chamber underneath your intake manifold and it should still have vacuum for at least 10 mins after the car is shut off.

Pop one of the lines off and see if you hear a hiss shortly after shut off. If you don't, there is your issue.

If you still have vacuum, I'd clean your ssv - the diy should be easy to locate.

Check your ssv for free movement as well.

Well I unplugged the vacuum while idling and feel and hear no vacuum or hiss after turning off the vehicle (although I'm in the car when I do this so I might not hear it anyways). Also, oil soaked the connectors and everything when the oil filler neck hose was not installed for the last thousand miles.

I read the ssv DIY and I'll just be ordering the full upgraded assembly and pay a shop to install. I'm betting that's the issue. I'll report back

uhhm...stinksause meant you should 1st shut off the car ... and then disconnect the vacuumhose to the VFAD chamber...not while idling. If you disconnect it while idling the vacuum in the chamber cant build up.

If you really want to figure out whats wrong post an OBD log while idling with fully warmed up engine. Dont throw random suspect parts on it ... troubleshoot! like 9krpmrx8 said...

Greetings and good luck
Thomas

Vfad has a dedicated vac chamber and line - seperate from the vacuum chamber that controls ssv vdi and air pump.

You need to disconnect it on the back either where it is hooked up to the intake manifold or where you have the 3 solenoids.

It could be anything between vacuum to solenoid to sticky ssv. All have to function properly. I'd recommend against blindly throwing money at it.

Try this: we you hit the wall take you foot off the gas and a split second later go back on. Does this get rid of the wall? If so you just generated enough vac for a split second to full get ur ssv open ...

I checked both and got no hiss or anything after turning the vehicle off and unplugging the line to the VFAD from the VFAD side, not the solenoid side (can't reach in) Both actuators freely rotate by hand though.

So would the lack of vacuum be considered an issue with the solenoid? The line goes under the lower manifold and feel no pressure from it at idle either although might be too small to detect without load. It also took me just under 10 seconds to get from car to hood to pull the hose. Would pressure drop in this time giving me a false negative?

If you are on the wrong side of the one way check valve when you pull the hose, this test is pointless

Oh ok I just saw a smooth hose. I thought check valves had the green/white ball on it. I'll see if I can pull from the other side. Thanks again, you guys are very helpful.

Stinksause, question, if the actuator moves freely in and out, does that mean the SSV is good? I've put in an order for an SSV because it comes with the impact switch and solenoid but if a freely moving actuator is is indicative of a good SSV then I can save a couple bucks

I went ahead and played with the accelerator around the hesitation point at ~4200RPMs and was not able to stop the blip in power however; after playing with the throttle in 3rd gear, I got the car to slow down while WOT. Felt like I dropped a couple gears. I probably tricked a valve into staying close be it VFAD, SSV, VDI or something.

What are your AFRs doing during this?

I'm not sure. My sister has an iPhone not an Android. The iPhone equivalent is $100 bucks + software fees so I was thinking about taking it to a Dyno and asking for a discount.

Where are you located? Lots of people on the forums have them, and could probably help you out for free.

Good point. I'm in downtown San Diego. I'll search around

Here is the hose that I am talking about and where you want to disconnect it behind the upper intake manifold- disconnect at the white end of the 1 way check valve. I heard a hiss 30 mins after shutoff

I do get a hiss. Thanks for the details shots I was able to find it right away. I guess that means I have vacuum and actuation. I'll find a dyno and see if it actually activates under load and a/f ratio at 4k.