Sputtering and loss of power when hot...

[Mark.c0000]

Now that it is getting warmer out I have been driving my 8 to work (about an hour drive each way) after driving for about 40-45 min I have a drastic power loss a hard time getting to higher rpm's and sputtering. I have checked or changed all the normal issues and can't pin it down.

Motor is under 20k still and always premixed.
New battery.
New coils plugs and wires.
New e shaft position sensor.
Just pulled and cleaned the ssv Sunday.
Fans are both working properly.
Alternator is charging at proper voltage.
Only cel code is for o2 sensors (no catalytic converter)

Anybody know something I'm missing? I'm down to the throttle body being bad or the computer. Really don't want to spend the money on them if they are good. I already have more in to the motor than I paid for the car lol.

[~Groll69~]

have you ensured no vacuum leaks?  Maybe it heats a vacuum hose up enough to cause it to leak after engine is warmed up.  I am guessing at this point based upon what information you posted.  If someone has other suggestions please say them.

[Mark.c0000]

have you ensured no vacuum leaks?  Maybe it heats a vacuum hose up enough to cause it to leak after engine is warmed up.  I am guessing at this point based upon what information you posted.  If someone has other suggestions please say them.

I have went as far as spraying starting fluid around in my engine bay listening for an idle change and haven't found any leaks. And yes any suggestions are appreciated. If it's 35-40 degrees out I never really see the problem it only seems to happen if it's warm out and the car is warm.

[~Groll69~]

is there an air intake temp sensor?  If there is, maybe it is getting to much heat soak and causing selective failure when it gets too warm.  Mass airflow sensor not fully connected?  Another thought is secondary air ports in the throttle body not opening properly and sticking closed.  I know the second gen has the secondary air ports which many people will remove later on. 

[murz]

Do you notice the loss of power throughout the entire band? Does it want to stall when idle? When do you first notice it, after leaving a stop?

[Mark.c0000]

Do you notice the loss of power throughout the entire band? Does it want to stall when's​ idle? When do you first notice it, after leaving a stop?

It only really does it above 5-6k RPM that's why I assumed the ssv was dirty and sticking. It will stall sometimes if I let off the gas after I try bringing the rpm's up. Takes off from a stop fine as long as I don't try to bring the rpm's up high. I can drive around fine at 3-4k RPM and never notice it until I try bringing the rpm's up. Maybe a slightly rougher idle when it's​ warmed up.

[Mark.c0000]

is there an air intake temp sensor?  If there is, maybe it is getting to much heat soak and causing selective failure when it gets too warm.  Mass airflow sensor not fully connected?  Another thought is secondary air ports in the throttle body not opening properly and sticking closed.  I know the second gen has the secondary air ports which many people will remove later on.

I'm not sure on an air temp sensor. I will look into it. The mass airflow sensor I have pulled and cleaned but forgot to list. I will probably try to pull check and clean the throttle body this weekend if I have the time. I would love it if it was something that didn't cost a lot and was an easy fix.

[Mark.c0000]

I am starting to think it may be the fuel pump. Worked day shift today so it was warmer out for my drive home. As it got warmer during my drive I noticed the power loss get lower and lower in my rpm's. It ended up stalling at a stop when I tried to take off. Wouldn't bump start from a 10 mph roll so I stopped and tried to start it. First time no start turned the key off tried again no start turned it off again let it sit for about 45 seconds and fired up easy and went through all 9k rpm no problem. Ran good for about another 5 min and started acting up again. Sound like anything but the fuel pump to anybody?

[~Groll69~]

sounds like a good culprit.  The pump could be getting to warm and worn out just right that as things heat up there is a loss in fuel pressure.  could put a pressure tester on it and see where the fuel pressure is at.

[ITSWILL]

As mentioned check fuel pressure. Doubt there is any heats oak on that air temp sensor, but it could be out of whack causing the engine to pull timing. Engine coolant could be bad too. This could dump extra fuel in the engine and bog it down. Both sensors can be tested with a multimeter.

[Mark.c0000]

It was the fuel pump. Changed it out last weekend and haven't had it stall or sputtering anymore..... I am starting to hate this car now. Driving home from work about 40 minutes​ ago I lost 6th gear without even a warning. Going down mound I came to a red light and started slowing down it changed to green so I popped it in 5th and went to go back to 6th and it wouldn't go. I would have been ok loosing 5th for a little bit but loosing 6th until I get another trans is going to be terrible. I may need to admit defeat on this 8 soon and trade it for a better daily...

[~Groll69~]

keep it for a fun car and grab a different one for a daily. 

[murz]

Jeez, that sucks man. There was a 6 speed for sale on CL not too long ago. I still want an RX8!

[ITSWILL]

I hear you, my coolant seals seem to have crapped out in my 8 with barely 60k on the odo. Shit gets old.

[Mark.c0000]

The annoying part is it's something new every week or two. I only had the new fuel pump in for two days​ when the trans went out. Before that was all four struts and a new motor before that. I have more in to parts than I paid for the car now lol.