shawns

Hi

I got the fuel pump changed today of my 8 , the car was working fine before changing the pump and after changing it. Then the mechanic changed the battery terminals , after that the idle was unstable but the car didnt stall while idling. I took it for a drive the power is fine but when i press the clutch and try to stop , the rpm goes to 0 and it stalls.

I have tried the 20 times pressing brake pedal to reset the memory but no luck .
There is no CEL or anything. The car idles just fine , only when im driving and going to a stop it stalls. Starts back up fine too.

Anyone know what could be wrong?

Battery is new , there is no cat , coils are new , plugs are new.

shawns

Specailly when i press the brake pedal with the clutch pressed it seems to stall quicker

shawns

Guys no help at all? Ill provide you with whatever info that is necessary. What are the main reasons that would make the car stall when letting off the gas?

This has only happened once before and that was when the battery terminals were loose. This time ive checked the terminals and they are tight

RIWWP

iTrader: (2)

Short Answer: Stalling after a battery disconnect is normal.

Short Solution: Start the car and let it idle itself warm, and then idle for another 5-10 minutes. It should solve the problem


Long Answer:
Disconnecting the battery clears the fuel trims, and the point of greatest impact is at idle. If your MAF (and other sensors) calibration is a bit too far off in one direction, then the fuel trimming is needed to produce a correct and stable idle. Without the fuel trims the ECU has more trouble 'catching' the revs as they fall back to idle, like on clutch in. Rebuilding the idle fuel trims will almost always solve the problem, and just letting the car idle for a while while hot will usually build enough trimming to solve the immediate problem.

Magnaflowrx8

I am also having The exact same issue! Put on new coils wires plus MAF sensor, E sensor etc but still no luck dies when I am driving and put in the clutch and sometimes while idling when she gets warmed up she will shut off. I will try to rebuild the trims better when good weather comes.. I have low compression but not super low and I recently updated starter but still won't start on warm start... 05 Mt 83,000kms borderline low compression

Budman,

Magnaflowrx8

Coils wires plugs*

Budman,

RIWWP

iTrader: (2)

They are not the same issue.

Shawns' issue is lost fuel trims due to the battery disconnect. It is most clearly indicated that this is his issue and not compression because of zero problems before and noticeable problems after the disconnect.

Magnaflow, your problem is compression, not fuel trims. Feel free to reset them and re-learn them, but it won't solve your problems. You know you have low compression, and that will indeed produce the behavior you are seeing.

They are very subtly different problems.

Magnaflowrx8

Ok thank you for the information I had been told that my car should not shut off unless compression was super low but I have the numbers somewhere it was like 90s on one rotor and low 100's on the second.. Mazda tech said she is borderline low compression for there numbers and recommended engine replacement, do you think this will for sure solve my problem? Not starting on warm start with new starter indicates for the engine swap I guess.. Going to cost me 3k for motor and 1500 installation.. Or I could send away to Adam at rx7 specialties and get rx7 seals

Budman,

RIWWP

iTrader: (2)

100psi on a single face will fail the engine if the starter speed is about 265rpm or higher. If you recently got a new starter, you are almost certainly over that. Even a 95psi on a single face fails around 245rpm. You are probably around 280-290, which means that "90s" and "low 100s" will fail every single face of your rotor, badly.

That's the reason for your starting troubles.


I highly recommend against "RX-7 seals". Lots of evidence is mounting that they were out faster than the stock RX-8 seals when used in an RX-8 motor. They are heavier and have more inertia that increases the amount of friction between them and the housings. Unless you are trying to save them from bad tuning, there is no advantage to them and a lot of disadvantage. And if you are trying to save them from bad tuning, well, that has a different solution.

Magnaflowrx8

Thanks for the info once again I appreciate this insight so much, I will tell u the actual numbers when I get home and find the sheet, I got the compression tested before the new starter and it was borderline low so I had figured if I got the updated one she should start while warm but she still does not, and shuts off when idling for too long and when slowing down/putting in the clutch just like Shawn's problem

Budman,

Magnaflowrx8

Rotor 1 is, 103 100 94 rotor 2 is 93,92, 94 and rpm was 266 this was with old original starter... These numbers are low enough to cause the car to do this?? I am going to get the car analyzed before motor swap just in case its not the motor but most likely it's from the previous owners neglect of mantenience but I now have done enough research to know how to take care of the Renesis and get it to last longer, fir example premixing gas, never let oil levels get down, and always let the car warm up.. These key things are essential if you want a long lasting rotary am I right? I have a 2005 4 speed auto but I'm selling because I bought the manual with magnaflow and intake.. Sounds so much nicer and so much more fun to drive... Should have stuck with the auto though because I never had a hitch with her, but like I said the manuals problems are due to previous owner I'm willing to bet. I want to get new motor and see how long it will last me if I maintain it right.. My manual has 83k Kms and auto has 88k

Budman,

Magnaflowrx8

Also use high octane fuel and red line at least once a day are good for the rotary... RIWWWP, if I do end up going with the motor swap what else should I replace? I was told the cat, maybe fuel pump etc

Budman,

RIWWP

iTrader: (2)

Have you read the new owner's thread? I'd rather not try to retype that entire set of information here, but your questions are answered there.

Specifically within the thread, it even has a compression chart so you can tell what numbers fail and what do not: New and Potential Owners Start Here: Compression Test Results

It also has the maintenance information, important failure points to address, etc...