cliffkemp

My car recently started acting up. It will start sometimes and stay on for about 2 seconds and die. If it starts again, it will stay on and rev around 2500 rpms constantly, even when it warms up.

It had an O2 sensor issue several weeks ago but, according to readings in here, it should not have affected its ability to start or drive but, just should start getting bad mpg and may not want to idle all that well.

These sensors are expensive and before I replace them, I want to be sure there is not something else that is the main issue.

When the car does start and stay on, it will idle at around 2500 reguardless of engine temperature. If you floor the car, it will speed up to about 3k rpms at best.

I have read that the fuel pumps on these cars are not that good...I have tried replacing relays that have to do with the ignition and fuel with known working ones and to no avail. I have run out of options on this car and, I cannot afford for the dealer to look at it and tell me it is going to be a 1000 dollar job. The coils and plugs are new with less than 1000 miles on them and check out fine...no burn marks and plugs are not wet or anything.

On another note, sometimes, although rare, it will start up and run as if there is no issue at all. Is there any one that can help me diagnose what is going on or suggest new things to look for to fix the problems? Please help.

RIWWP

iTrader: (2)

Sounds like an airflow problem and the ECU can't figure out how much air is being used.

Do you have an ODB2 reader?


Edit: And no, it's not limp mode. Typical limp mode is a 4k rev limit but should act somewhat normally below that, though pretty down on power. I say "typical", because there are a few different limp modes, for example there is a "limp mode" for an accelerator pedal position sensor failure that pegs the RPM at 3,000rpm regardless of the temp of the car and what you are doing with the pedal. It's enough to give you 7 possible speeds, zero and whatever speed 3k rpm is at for each gear. Drop the clutch and get it moving, up to 60mph in 6th with unpleasant gear changes between. "Typical" limp mode from the ECU not being able to figure out what is going on or seeing an active problem that needs immediate attention (like the OMP failing), is what I previously described.

No, your O2 sensor will not cause limp mode in any way.

cliffkemp

I do not have a reader...My new motor has less than 25k miles on it as well. I may try to limp it to autozone again. The last time I took it there, it did not do the 3k rpm thing. It ran fine but, would just randomly shut off but, not often....like it would only before it warmed up on the way to work.

It would not start back up right away then, it would start and drive normal and that is when it gave a CEL. Autozone reader said upstream O2 sensor for both banks were not heating as they should. That cel went away after a couple of days and then it died on my daughter at target.

It did the 3k thing in the parking lot but, did not know what the issue was cause I just drove it home as I have a couple other cars and post on here to see if anyone can help figure it out. I have some knowledge of cars as I rebuild my laser engine from the block up but, this is not a piston engine. The electronics on the 8 are far more sophisticated and not used to where everything is on it. Since it has a drive by wire throttle, not sure what all is going on since most of it does not make sense.

The tube in front of the MAF came off and caused it not to idle when stopping and would go dead but, fixed that and ran fine til the O2 thing and now the 3k rpm thing.

What do you recommend doing to it to check for any issues? I can try to limp it back to autozone so they can put a reader to it. It is just a pain to try to drive but, was hoping someone has experience with this and knows exactly where to look and test motor voltage and such to pin down the problem. I am sure the O2 issue is not the main problem.

dannobre

iTrader: (3)

Sounds like limp mode.....might want to give the MOP position switch a bit of a jog

If you do a reset and start the car does it rev OK for about 5 seconds and then stop responding normally?

RIWWP

iTrader: (2)

Autozone isn't going to get you what I was going to suggest. If you could actually pull up live ODB2 data on various sensors (specific ones like the MAF, TPS, STFT etc...), and watch what is going on when the issue is occurring it would help point to what is causing this.

My first guess with your added information is that it's MAF related. Either your MAF got damaged or fouled when it had unfiltered air from the "tube before the MAF coming off" I assume you mean the accordion? Check to see if both screens are still in place in the intake, one before and one after I believe. If they are skewed or fluttering this could cause all sorts of random issues. The MAF depends on smooth and consistent air flow that is a solid sample of the air flow going by. If a screen is out of place it adds turbulence, and if this is putting the MAF sensor tip in an 'eddy' in the air flow it could read REALLY low and not be adding fuel, or other issues. I don't think it would cause your whole problem though.

You have some really good local members down in GA, and they may become your best resource to get this solved. I'm going to send a note to olddragger and slvrstreak to see if there are any immediate locals that could check out your car in person.

dannobre

iTrader: (3)

Car will run without the MAF and not go into limp mode. The MOP and the ECT are the only things that usually will set it into limp mode.

cliffkemp

Thank you for the insight and the help and everything. I will check the screens and a few other things as well and will let you all know. I normally take the car to a friend's shop in Atlanta but, was not sure if I could get it there as it is about 60 miles away and traffic is not that good in the Atlanta area.

Thanks again. I will report back in a couple of days as I have to work the next 2 and do not get off til 7pm.

Sounds like limp mode.....might want to give the MOP position switch a bit of a jog

If you do a reset and start the car does it rev OK for about 5 seconds and then stop responding normally?

Will check out that as well.

olddragger

iTrader: (3)

hey fellow Ga rx8 owner. I was directed to your thread by another since i also live in Ga.
There is the best shop around in Marietta . Its called Mazcare. They are honest to a fault, do great work and have been in business for a long time. Allen will answer the phone and tell him Denny aka olddragger sent ya. Charlie owns the place. It is also our fast and furious home--kinda. Wait until you see the cars they have there.
This doesnt sound like a complicated fix.
Please do yourself a favor and call them. Mazcare in Marietta Ga.
if you cant get your car to him--just PM me--I will help in any way I can. A lot of us are having a tuning session aug 18th at a members house if you can wait that long and want to come over.
Go to the Ga RX8 club--sign up and look at the thread.

RIWWP

iTrader: (2)

I'm not convinced that it IS limp mode.

I'm not disagreeing with you, since I think it's going to be based on how it's actually responding when it's acting like that. His description could be interpreted a few different ways, and I don't think it rules out that it's not limp mode, or rules out that it is. Like your example there, disconnect the MAF and it "won't rev over 3k", though it's because the engine is getting flooded with fuel, not because of an ECU limp mode.

RIWWP

iTrader: (2)

Thanks OD.

dannobre

iTrader: (3)

For sure....internet diagnosis is so dependant on getting the correct info

Usually if it is a fuel/ign issue that just suddenly starts up it will stutter and stumble and then rev more fully...a limp mode problem will be more of an absolute won't rev past ? no matter what

It is easy to tell if the throttle is working if you take off the intake tube and have a look. If it is in limp mode..the throttle will open fully before the car starts after a reset...and it will work for about 4-5 sec after it starts and then it will only open a very small amout. If there is a DBW problem it will do the same basic thing..but you will get a CEL. For some reason the CEL doesn't seem to come on for the MOP problem

RIWWP

iTrader: (2)

^ good info on the throttle plate identifying limp mode. Never knew that.


I always take "won't rev past #,###" with a grain of salt, since it could be a deliberate cut of ignition, fuel, or air by the ECU, an unintended cut of the same because the ECU isn't seeing what is actually happening and retarding one or more, or more of a physical restriction due to a parts failure (like what a clogged cat or stuck throttle body would exhibit)

How it "won't rev past" (what it feels like, whether or not it's responding to inputs and how it's responding) is usually information that is critical to the pinpointing and also usually missing from the author's description.

cliffkemp

I will see if I can get it anywhere. It is acting strange, that is for sure. Also, Allen is no longer with mazcare. Another Charlie is there now, last time I was there. Clint is still there though. Love their v8 fc's. Still love my rotary though.

cliffkemp

It does not act as if it is getting too much fuel. It revs pretty good while on...as in it is not backfiring or anything like that. It just will not go above 3k and idles at 2500 when it is in this 'mode'. Just another thing, it was making an electrical noise....like the TPS was getting power but not moving. I unplugged it and plugged it back in to see if something was stuck and, when plugging it back in, no noise. It did not do any good though as it still just idled and will not respond to pressing the accelerator hardly at all except to go to about 3k.

cliffkemp

While it was running around 2500, I did pull the fuel relay, went dead. Pulled the fuel pump fuse, went dead. Pulled the ignition relay, went dead. Pulled a few other relays and swapped with the ones that were working and no change. Short of putting a voltmeter to various things, the fuse box is good (was replaced years ago when a wire was grounding to the intake and blew the original one)

I will try a few things until I can get it to someone that knows more about it. If I or we have not figured it out by then, will try to get it to a shop and see what is going on.

RIWWP

iTrader: (2)

You are proving my point to dan

You are still being quite vague with your description, leaving lots of room for different interpretations. I'm trying not to hassle you about it either, because it's common for people to have trouble explaining exactly what's going on.

Consider:
"It revs pretty good while on...as in it is not backfiring or anything like that."
Does this mean that it responds to the accelerator pedal normally? Or just that it revs freely? Does it only rev good under the 3k limit you are seeing? or do you mean that it revs good outside of the 3k limit when you aren't having the issue?

"It just will not go above 3k"
HOW does it not go above 3? Does it rev freely to 3k and then act like you are hitting the 9k fuel cut? Does it struggle to get higher and higher and it just doesn't have the omph to get above 3k? Does it jump around and just never make it over 3k?

" and idles at 2500 when it is in this 'mode'."
Does it idle there in neutral as well as in gear? does it rev there regardless of clutch in or out? If you are driving and let off the gas, does it just drop to 2,500 and stay there? Is it rock steady at 2,500 or does it waver around a bit?

"and will not respond to pressing the accelerator hardly at all except to go to about 3k.
Either the engine is responding to the pedal or it isn't. It can't do it partially. If it's not responding then you wouldn't be able to get it to move at all. If it is responding, but "hardly", then I would guess that it's acting like you aren't moving it as much as you actually are, or the issue means that opening the throttle plate simple "doesn't change the air flow much"



Every single point of clarity I asked you about will help rule in or out various possible issues.


The more detailed you get, of what exactly is happening and what it feels like, as well as when it doesn't happen, and what THAT feels like, the closer we can get to pinpointing the problem.

I highly suspect that it's something really simple that is just confusing the hell out of the ECU.

slvrstreak

iTrader: (3)

+1 for Mazcare!
Call Charlie and see what he says about it

1.3_LittersOfFurry

iTrader: (4)

Sorry didn't have time to read all the replies but I experienced te exact same thing the op is describing and it was a loose connection on the throttle body. HTH.

cliffkemp

To clarify

When it is running, it sounds normal. I am not sure of the AFR as I do not have a WB on it but, it sounds normal when it is running around 2500 when it does crank and is in some sort of 'limp' mode. It does not sputter or anything like that, no. It sounds like just a high idle as said rpms.

When it is idling at 2500, it does not respond to the accelerator pedal normally. If you push on the pedal, it will rise to around 3k tops. It is a semi slow rise and not responsive as it normally is. If you tap on the pedal, it will rise like the car is drunk, so to speak. If you floor the car suddenly, it will just rise the same rate as lightly pressing the pedal and stop at about 3k.

The car is a stick shift so not sure what to say about that as I have not tried to drive it when it is in this state but, it does stay steady and does not waver like it has a bad idle control motor or anything like that.

The car does partly respond to the gas pedal being pressed as in the above said. You can lightly press the pedal....say 1/4 way and will go from 2500 to about 3k in a slower than usual rate...only way to say that... or you can just stomp it and you get the same engine accel rate no matter which you do....slowly push down the pedal will equal stomping the pedal.... either way it goes up to about 3k the same way/rate.

I hope this helps. Anything else you want me to clarify, feel free to ask and thank you!

RIWWP

iTrader: (2)

Ok, yes, that certainly helps.

More reason for me to think that it's not an ECU mandated limp mode. Real ECU mandated limp modes usually act like a hard restricter as I've mentioned before, very clearly and deliberately not letting you exceed certain threshholds based on what it sees wrong. Having the RPM react to the throttle but WAY too sluggishly sounds like an airflow problem, but maybe not an airflow issue itself, but perhaps as noted above by 1.3 litters that your throttle body may not be opening correctly. Remove the intake accordion so you can see the throttle plate inside the throttle body, and (with the car off but the key in the on position, it won't run like this) have someone watch the throttle plate while you manipulate the pedal, or vise versa. See if you are getting the full expected range of motion on it. Give it a few minutes of testing too, to see if it changes it's behavior over time.

Before you put everything back together though, disconnect the negative cable on the battery and leave it for 5 minutes, then reconnect and reset the throttle plate reaction to the gas pedal. See if there is any difference from before.

dannobre

iTrader: (3)

LOL...remember if it is limp mode the throttle will work correctly with engine off after a reset...but will quit reacting when it is started. I had this problem intermittently and it was a real bitch to figure out.

cliffkemp

I had a friend to come over and hook up a reader to the car. It had 14 codes that varied from 02 sensor error/failure to emission issues to throttle and pedal sensor error.

We decided to clear all the codes and see what all codes come back after the reset. To our surprise, no codes came back and, after resetting the codes, it started right up and ran like normal. The 3k rpm deal was some sort of limp mode having to do with a few codes that we saw on the reader but, they did no make sense in it having that many failures all at the same time.

The car is running good for now. We figured that one of 2 issues are present. Either the battery connection came loose a little as I had to put a cap on top of the positive terminal due to the bolt being tightened all the way down would not yield a tight connection and it may have some corrosion on the battery terminal that I did not get off all the way (cleaned good this time), or there is a loose wire somewhere that may have caused a grounding that disrupted the whole system and it threw random codes during this grounding, if that is what it was. If it does something of this nature again, will take it to a shop to have the wiring evaluated to see if something is loose or something like that.

We did check all the wiring that we could see from the top of the car and seemed ok.

cliffkemp

To bring this back to life, after we reset the codes, none came back til the next day...all of them did for no reason.

We reset them again and car drove fine for a couple of days. It went dead again and would not start.

I stumbled upon a "fix" and has worked every time it has happened without having to use a reader. I just unplug all the fuses that have anything to do with the cpu/ fuel/ ignition and the main fuse. I unplug the throttle position sensor, and the room fuse and count to 10. I put everything back in as it was and then, the car starts up and runs like nothing is wrong for a while (days, weeks, even months) and every now and then, it does it again.

Any ideas on what is causing this? Doing the above 'fixes' it til it does it again. It has gone 4000k miles before doing it and has been a little as 1 day. Any ideas?

RIWWP

iTrader: (2)

I went back and read up... perhaps an e-shaft sensor failure? The only thing I can think of that you are doing is clearing the ECU's learned data, and the only piece that I can think of off hand is the e-shaft sensor profile. If it keeps learning it wrong, maybe the e-shaft sensor itself is failing.

dannobre

iTrader: (3)

You are doing an ECU reset the hard way when you do that...much easier to just remove the neg battery cable

Reset the ES sensor profile and then watch the codes as they come up. Chase them down one at a time and see what happens.

There are a few limp mode causes with no CEL...so it can be a bit annoying sometimes to find intermittent electrical issues

Can't hurt to have a look at connections and grounding points....