Won't rev when flooring. Revs fine when accelerating gently!
 

Hi guys. I have a 1993 JDM FD. Trying to figure out what the problem is.

Basically, if you step on the gas immediately, it won't rev past 2000rpm. It's like a rev limiter. If you gently accelerate, it's revs all the way to about 5000rpm, and then won't rev beyond that.

Same story when driving. Seems load dependent. When accelerating gently, it's nice and smooth until 5000rpm. Steeping on it makes the car buck at whatever rpm. Like shifting to 5th at 10mph.

I'm also getting a strong fuel smell from under the hood.

What could this be?

Sounds like something triggered “limp mode” in the ECU. It’s what the name suggests, when the ECU senses a critical system isn’t working, it will not let timing advance and will cut fuel if the boost sensor doesn’t see vacuum at the manifold.
On NADM models it generates a CEL and codes can be pulled. Not sure how it’s done on a JDM model. Someone else will have to chime in.

The JDM cars have the same/similar diagnostic port under the hood, just no check engine light.

https://www.rx7club.com/3rd-generati...jdm-fd-664425/

Check Engine Light Codes

Not all codes will cause Limp mode. And I don’t think JDMs have all of those on the NADM cars.
Probably the most common in my experience are any one of the three associated with the Metering Oil Pump (MOP)

It's either limp mode or something wrong with the secondary injectors. Had a friend with a bad secondary (it tested as open circuit) and it had similar behavior.

Dale

I thought the secondary injector codes triggered limp. ??

I agree, sounds like you are in limp mode. Any positive boost pressure will cause the car to fall flat on its face. If you can get your hands on a Power FC you can plug it in and quickly check if the sensors are in spec.

Thanks a lot for the response guys!

I thought limp mode is Rpm dependent. Not load. When I'm driving the car, if I press the accelerator pedal hard, the car bucks back and forth violently. But if I press it gently, it's nice and smooth. Can limp mode do that?

I do not have a Power FC :(

Get a power fc or chase your tail... it's very inexpensive insurance and a great diagnostics tool. Leaps and bounds better than the stock ecu

Yes, that’s exactly what limp mode does. It’s specifically load dependent because the second that vacuum isn’t seen at the intake (where the boost sensor is located) it pulls timing. And as the throttle opens the vacuum disappears. It’s also why it starts and idles normally and you can VERY gradually add rpm...up to a point but not without any power.

A PFC will certainly get you out of limp, but it doesn’t cure what caused the factory ECU to trigger it. That critical system is still not working or working properly. So it still needs to be addressed.