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RPM Dropping = Engine Stalling

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Old 12-09-2008, 02:08 AM
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RPM Dropping = Engine Stalling

One of our local RX8 friends (Vyndictive) have been dealing with an issue that I feel should be discussed here to get everyone’s feedback and expert opinion that has me scratching my head.
This is his car’s description taken from his signature:
'04 Bril Black MT
Revi Intake w/ ram air duct - RB Cat back Exhaust - Clear Corners - Painted Fender Vents - Fog Light Rewire - Rear "Foglight" - Bose - Sirius - Interior LEDs - Painted calipers - TC Sportsline front+rear strut bars - Mazcare Gutted Cat Midpipe - RB Gauge Cluster - RB Plug Wires - RB Air Screens - VooDoo Shift ****

Here is the story:
We first met to change out his mid-pipe.
Taken the normal precautions, I disconnected the negative battery.
After getting everything together and hooking the battery back up, I did the KAM and NVRAM reset.
We started the car and let it sit idle for roughly 10 minutes while we cleaned-up, nothing abnormal was observed/heard.
As he drove it down the road, he experienced the sporadic RPM fluctuation that is commonly seen after resetting the PCM.
I told him that this will occur for a little bit but will get better once it relearns itself.
We drove it for a while and everytime he pushed in the clutch to start braking (coming up to a stop), the RPM would suddenly drop and never attempt to recover itself.
The car would just stall, to which I told him I had that occur a couple separate times, but shouldn’t be that bad next time we run the car.
He wanted me to drive it, so as I’m driving his car I find myself fighting to keep it from stalling when approaching a stop.
You have to give it a slight amount of gas to keep it from stalling (which is hard while braking and holding the clutch in).
I pulled into a parking lot and let it sit idle, but it idled just fine (around 880 rpm).
I then revved it up in 1K rpm increments and let it drop back to idle, but each time it stalled.
I restarted it and continued revving it (and stalling it) until it got better (which took a while).
So we drove back to the shop and I left, but he informed me that it stalled a few times during the day.
After a couple days it ran just fine without any stalling (until the next time we met months later).

So this past weekend we met to change out brake pads, rotors, and spark plugs.
So once again, following the proper precautions, I disconnected the negative side of the battery.
Once we got everything back together we ran it at idle for roughly 10 minutes.
As we were taking it out for a drive, we once again had continuous stalling like crazy (worse than I’ve ever seen).
We drove it around for awhile and he constantly revved it up to redline and everything sounded normal and smooth, but everytime he let the RPM drop below 800 RPM the car stalls (just continuously drops... never even attempts to stop).
Like before, we stopped in a parking lot and constantly revved it up and letting it drop to idle, but it could never recover itself.
No matter what we did, it kept stalling.
Hoping that it would be better the next day (like last time) I left and tried to search this forum for similar symptoms, but couldn't find anything like this.

It’s been a few days and he still experiences constant stalling when he lets the RPM suddenly drop.
Remember, if we start the car and let it sit idle, it runs just fine and doesn’t jump around.
Only when we rev it up and let the RPM drop does it stall.
I noticed he had several grounding cables going to the battery terminal.
I suggested that he try removing those ground cables and use different grounding points on the chassis.
I also suggested that he cleaned the MAF sensor just to rule that out (I read a thread where a guy had somewhat similar issues and cleaning the MAF helped).
What gets me is that last time we experienced this; the stalling went away after a couple days and never returned (until we disconnected the battery).
If there were any mechanical issues or vacuum leaks, this would constantly occur and not “go away” days later.
We never received a CEL.
Its almost like the PCM is VERY VERY SLOW to relearn itself.

Can anyone think of other areas to focus on?
Any reason why the car would run fine at idle, run fine revving it to redline, but not stop at the idle target while dropping RPM)?
And then possibly run fine DAYS later and never stall again (until the battery is disconnected).
He is getting upset dealing with his unpredictable RX8.
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Old 12-09-2008, 10:00 AM
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reset the e-shaft position sensor profile in the nvram

make sure all the plug boots are completely on.

if that doesn't work its a bad neutral sensor on the tranny
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Old 12-09-2008, 12:59 PM
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Plug boots are on tight...

correct me if I'm wrong, but a bad neutral sensor would mean that the car would never idle properly? Cold starts it idles fine, and after a few starts at operating temp it will idle fine... only when dropping from higher rpm under no load will it still.

Is my ECU retarded?
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Old 12-09-2008, 02:54 PM
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Originally Posted by zoom44 View Post
reset the e-shaft position sensor profile in the nvram
We both reset the NVRAM and the KAM

Originally Posted by zoom44 View Post
make sure all the plug boots are completely on.
After he installed the plugs and wires, I went back through and verified they were secured.

Originally Posted by zoom44 View Post
if that doesn't work its a bad neutral sensor on the tranny
This is what I thought too, but was confused when the car started running fine days later (and up until we disconnected the battery again).
Any idea why that would be?

I found this TSB, another thing worth looking at Vyn.
http://www.finishlineperformance.com...17-05-1487.pdf
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Old 12-09-2008, 03:10 PM
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Thinking along the lines of what Zoom suggested with the e-shaft sensor, might also be worth looking over the sensor and positioning plate to verify nothing is obstructing the sensor from reading the correct number of pulses (ex: debris in the plate teeth of a warped plate).

The attached pic shows the location of the sensor.
You'll notice the e-shaft pulley (which is the lowest pulley) in the upper-left corner of the pic and the positioning plate right behind it (with the teeth).
Maybe even verify that the sensor is secured to the bracket.

Once you start it, run the engine and observe the pulley.
See if it wobbles or if the plate looks warped.
Didn't you have an aftermarket pulley too?
Attached Thumbnails RPM Dropping = Engine Stalling-e-shaft.jpg  
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Old 12-09-2008, 03:20 PM
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Check for vacuum leaks - the computer can adjust for a really weak idle mixture, but it takes a long time to build up to the +20 or +30 trim level.

A vacuum leak would only affect the idle, and only after the trim is lost.......

Check that the nipple below/behind the throttle body is capped from your Revi install.

S
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Old 12-09-2008, 03:27 PM
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Originally Posted by StealthTL View Post
A vacuum leak would only affect the idle, and only after the trim is lost.......
But whats weird is that when you start the engine and let it sit idle, it runs just fine.
Only when you rev it up and let the RPM fall below 880rpm does it stall (without hesitation).
Still think it could be a vacuum leak?

Originally Posted by StealthTL View Post
Check that the nipple below/behind the throttle body is capped from your Revi install.
I clearly do recall seeing the VFAD nipple in place behind the throttle body.
Might be worth taking out to verify its not torn anywhere.
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Old 12-09-2008, 06:13 PM
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Originally Posted by StealthTL View Post
Check that the nipple below/behind the throttle body is capped from your Revi install.

S
Definitely not that. I pointed it out referring to my post-REVi install vacuum leak when I screwed up and left off the bright red cap (put it on my stock intake so I wouldn't lose it then promptly forgot about it). It's enough of a leak that it would throw a CEL after a couple drive cycles anyway.

Behavior seems identical to normal reset but the computer appears to not be relearning.

I have an uninstalled AP. Anyone know if that could be used to help troubleshoot? He wouldn't be able to use it permanently (MINE! ) but if we can pull diagnostics from it we might be able to pinpoint why the Computer seems to be acting like it's been inhaling exhaust fumes.

Last edited by RK; 12-09-2008 at 06:18 PM.
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Old 12-09-2008, 06:44 PM
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Ok... just got back from Mazda of Wooster... I'll tell you the total price at the end. No peaking, just read...

Threw Codes:
P0506 (Throttle body control system)
P2070 (Intake manifold control system)
(no surprise) P0420 for the cat malfunctioning... becauses its in a box in my office.

They're stating that the aftermarket intake (racing beat) cause the carbon build-up in the intake manifold, and there is a possibility of internal engine damage.
Also, because of the RB intake, that it voids the engine warrenty. . . So, my thoughts are to take the car to Midas. Tell them to install the old Cat.
Perhaps, pending your advice, I have the stock airbox and perhaps I should do that also before taking into Cascade Mazda with the engine TSB and requesting a compression check because my motor be bad.

My problems sound the exact same to Rotary Rasp in the following thread:
https://www.rx8club.com/showthread.p...ighlight=P0506

TSB for loss of engine power:
http://www.finishlineperformance.com...14-08-1924.pdf

Guys - this seems to fit (sort of) the power loss I thought was plugs could be do to bad seals... sure it improved, but not enough. I cannot afford 6 grand and I wouldn't mind a new engine.

Finally,
Total Cost (out of warrenty) from Park Mazda Wooster. $6,500 bucks. I almost threw up. 2 grand just for a cat.... wow.
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Old 12-09-2008, 07:06 PM
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have they verified carbon in the intake manifold? if so this is an issue that can be verified as an issue not connected to the intake as it occurs to people with the OEM one. If this is actually the case hold on tight and fight them to prove the issue is from the intake- because they cant. 500 members on here with the RB intake can send affidavits affirming the RB intake does not cause carbon build up and another 500 can affidavit the fact that their engines carbon locked and died stock.

the engine recall paperwork with the de-carbon procedure showing the problem on stock motors would be enough for any judge to apply the Magnussen Moss act in your favor.
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Old 12-09-2008, 07:07 PM
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do not switch dealers- escalate this up the chain at this dealer and then on to mazda etc. they need to man up
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Old 12-09-2008, 07:13 PM
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same thing happens to my motor when i do a flash with my accessport (fuel trims get reset). If its hot and gets flashed I need to hold the throttle at a steady 5% and wait for the idle to settle, then 4% and wait, then 3 and wait, then 2 and wait, then 1, and about 10 minutes later it will finally idle by itself.

The fuel trims never wonder more then +/- 4%. Then ignition timing is all f'd up though for some reason while its "learning". My engine just tested to be weak but not replaceable yet.

Not sure if its a trend, but after an engine cleaning - it acted normally when getting flashed.
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Old 12-09-2008, 07:23 PM
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6500 dollars is ridiculous.....2000 for the cat that is just crazy...mazda what ********
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Old 12-09-2008, 08:37 PM
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Originally Posted by zoom44 View Post
do not switch dealers- escalate this up the chain at this dealer and then on to mazda etc. they need to man up
I'd really like to pursue that also... but I really don't think that is the best way to go for me. They know the car is catless - they have seen all the mods done to the car, which is why, without question, they said, warranty is void.

I emailed racing beat to see if they have lab tests to prove their Revi intake performs at, or better than OEM. Protects me under the Magnuson-Moss Act.

I have a stock airbox accessible also and I will probably install that also before taking it into a different dealer.
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Old 12-09-2008, 09:10 PM
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not a single one of your mods has done anything to cause carbon build up in your engine. your warranty is not void unless the mod causes a problem.

Clear Corners - Painted Fender Vents - Fog Light Rewire - Rear "Foglight" - Bose - Sirius - Interior LEDs - Painted calipers - TC Sportsline front+rear strut bars - Mazcare Gutted Cat Midpipe - RB Gauge Cluster - RB Plug Wires - RB Air Screens - VooDoo Shift ****
not a one has anything to do with engine performance.


Revi Intake w/ ram air duct - RB Cat back Exhaust
Neither can causes carbon build up. If your Intake was causing any issue AT ALL you'd have a CEL for the MAF sensor. even then it would have no effect on carbon build up.

wait check that- it does have the effect of making you want to redline more WHICH BURNS CARBON OFF. so the problem is LESS because of your intake

and thats IF they have even confirmed carbon build up in the manifold.

gawd i wish i was in ohio. seriously don't switch make them prove the problem and honor the warranty
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Old 12-10-2008, 12:12 AM
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Originally Posted by zoom44 View Post
and thats IF they have even confirmed carbon build up in the manifold.

gawd i wish i was in ohio. seriously don't switch make them prove the problem and honor the warranty
I'm trying to calm him down and convince him to let me look at it before taking it into the dealer.
I've had many times where I just wanted to give up and let someone else deal with the problem... but the easy way out isn't always the best way.
I'll take all your comments/suggestions into consideration and go through everything I can with him.
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Old 12-10-2008, 12:20 AM
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Easy folks. Concentrate on the problem. We'll worry About fighting the man at some later date. For now if someone can figure out what would cause his computer to not relearn proper trim... Is it possible that carbon build up would affect the engine Management? If so a sea foam or other carbon build up fixes should help. Keep in mind his car has been running fine before the battery reset.
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Old 12-10-2008, 11:26 AM
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Check the charging system. You may have an alternator going bad.

A bad battery can do the samething, run at idle but when you drive you use more amps, then let off the throttle and Bam she dies.

Last edited by Razz1; 12-10-2008 at 04:31 PM.
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Old 12-10-2008, 01:11 PM
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Originally Posted by Razz1 View Post
Check the charging system. You may have an alternator going bad.

A bad battery can go the samething, run at idle but when you drive you use more amps, then let off the throttle and Bam she dies.
I think battery/alternator are definitely on the list of possible culprits but wouldn't that be a problem that comes up on its own? I wouldn't think that disabling the battery temporarily would trigger the symptoms. Or does the NVRAM/KAM require more juice when relearning behavior then it requires during normal operating conditions?

FWIW we are discussing this in the MW forum Akron/Cleveland thread and Jon is leaning towards a bad SSV solenoid. Anyone else think of possible causes based on those codes?
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Old 12-10-2008, 02:48 PM
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Originally Posted by Vyndictive View Post
I'd really like to pursue that also... but I really don't think that is the best way to go for me. They know the car is catless - they have seen all the mods done to the car, which is why, without question, they said, warranty is void.

I emailed racing beat to see if they have lab tests to prove their Revi intake performs at, or better than OEM. Protects me under the Magnuson-Moss Act.

I have a stock airbox accessible also and I will probably install that also before taking it into a different dealer.
You will not get anything from Racingbeat, Because they're selling it as is.

But seriously, this dealership is full of ****. the Intake Carbon problem happens to even bone STOCK cars. and it has NOTHING to do with the intake itself. it was cause by backfire and all kinds of other crap. jesus ****** fooking christ. 6300 to fix it? You might as well just drive your 8 to a wall to get insurance money. shitz.

Dont switch dealership. keep bitching until u get some results. at the end. bring a lawyer into the matter. Then they will know its actually cheaper to fix it then going it into the court, why ? because you WILL WIN. They have NOTHING to proof.
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Old 12-10-2008, 04:35 PM
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Its winter time so... is it possible you have some water in the fuel line?

Heat fixes that.
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Old 12-10-2008, 06:24 PM
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If this helps any I was having stalling problems because my battery had a small crack at the bottom of the positive term, which was causing tons of corrosion. Got a new battery and my problems stopped. I have I think one or two threads about this in more detail.
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Old 12-10-2008, 06:51 PM
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Originally Posted by syntheticdarkness View Post
If this helps any I was having stalling problems because my battery had a small crack at the bottom of the positive term, which was causing tons of corrosion. Got a new battery and my problems stopped. I have I think one or two threads about this in more detail.
I have an Optima battery I can throw in there to rule that out.
Thanks for the suggestion.
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Old 12-10-2008, 07:01 PM
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Originally Posted by Razz1 View Post
Check the charging system. You may have an alternator going bad.
I thought this too when it started stalling.
I observed the internal lights (dash, LCD, etc) and didn't notice anything dimming as the RPM dropped.
But this along with the battery is worth looking at.

Originally Posted by RK View Post
FWIW we are discussing this in the MW forum Akron/Cleveland thread and Jon is leaning towards a bad SSV solenoid. Anyone else think of possible causes based on those codes?
Going off of his codes, I reviewed the Mazda shop manual.
The P2070 fails for SSV stuck open and a P0506 failure is when the idle air control system RPM is lower than expected.
I'm thinking maybe something is going on with the SSV (either the solenoid or the actuator) and this is also causing the P0506 code.

Last edited by Jon316G; 12-10-2008 at 07:06 PM.
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Old 12-11-2008, 09:18 AM
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Thank you for all the input guys... I'm just working on a list of problems that the car is having.

The lights do dim when rpms drop... perhaps it is charging system... but I've only had to jump the car once. Battery appears to be doing just fine. I put 100 miles on the car yesterday without any signs that the battery was bad.

Stalling problem still remains, and I'm getting some hesitation and loss of power in the top end (4.5k rpm and over) But the car still pulls and feels strong. If it were a compression problem, wouldn't this be worse?

But that problem of stalling at idle remains. No flashing CEL to indicate misfires or anything. (which did occur once before we changes the plugs last saturday (12/6)

On the highway, car runs and cruises just fine. That slight power loss in the top end does make me worried, but I need to ride in another 8 to confirm that they're all not like that. I had bad plugs for awhile so I've sort of forgotten what "normal" feels like.

As for the dealer and warranty information. I haven't contacted the dealer at all since I left after they tried to bend me over. I obviously don't want to get into a legal battle over this.

The real wildcard with this problem is that the car ran fine (other than the signs of bad plugs) until we disconnected the battery, which means this is a programming problem and there is nothing seriously mechanically wrong with the car.
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