Hello!

I just purchased a 91 RX-7 FC and I'm having a problem with acceleration. I bought the car and drove it for about 3 hours on cruise at around 75 and then the car suddenly threw a check engine light and started decelerating. I pulled over and checked the obvious things (fluids and such) but nothing seemed out of the ordinary. I managed to limp the car the rest of the way home by forcing 3rd gear in order to accelerate a little at a time. Now that I've had more time to diagnose, the car accelerates ok at lower RPM up to about 30 or 40 mph, but if I try to accelerate quickly (with the secondaries open) or go faster than about 50 the car just can't produce the power to accelerate. the valve for the secondaries is moving freely and seems to be working ok as I can rev up to 5 or 6k rpm fine, but there's no acceleration when I do. At this point my best guess is the fuel filter? or maybe the TPS or MAP sensor? Any input would be great!

Thanks,
Connor

 

welcome to the board, Connor.

sounds like you are probably in limp mode and the first thing that comes to mind, to me, is you probably have an issue with your MOP.

 

Thanks for the suggestion! Is there a good way to check this for sure? or have I hit the point of take it to a shop?

 

As I checked more things I found that my air filter's seal (K&N) was partially molten (like actually liquid). Thankfully none of it got on the engine side of the intake but is there a chance that the intake temperature was legitimately outside the intake temp sensors range? This would theoretically put the car into limp mode and would explain most of the problems I've had. I'm fairly certain it's an issue with the fuel delivery in some way (pump rails etc) but it could potentially just be a sensor as well. I reset the codes/ECU earlier and will update this post as I troubleshoot more.

 

well, it would have been more useful to try and retrieve them instead, but i guess that's spilled milk ...

as i understand it, there are only a handful of codes that will trigger limp mode on the S5 cars. i can't tell you what they are (without searching), but i can tell you the MOP appears to be the most common.

if the car does it again, then retrieve the codes and see what you're dealing with.

 

When trying to retrieve them I get a solid check engine light that doesn't go out. Comes one when the key hits "on" goes out as expected and then turns back on and doesn't flash any codes, just solid.

 

Update after trying things and stuff -

Shop didn't have a filter, I'll have to order one. Just running without one for diagnostics. I've cleaned up the seal goop from the melted filter and reassembled the empty airbox for now.

Things I've tested so far -
Throttle Body including air valves for boost - seem to work ok, checked by having a roommate press the pedal and all the valves seem to operate as they should
Sensors - I've checked all the electrical connections I can, a little of the filter melted onto an electrical connection by the front right headlight, doesn't look like anything problematic, just on the outside of the connector.
Engine Codes - see earlier reply regarding no codes displaying

At this point I'm thinking maybe the fuel filter got some gunk in it or something else in the fuel delivery got mucked up. Other than that I'm at a loss on this one.

Thanks for the continued great suggestions!