Edit: Title should say FC not FX...
Calling all rotary buffs...
I have not replaced the fuel pulsation damper on my recently acquired 1988 FC RX-7 yet because I did not see or smell any signs of a fuel leak. However, I am not sure that the fuel pulsation damper is functioning properly because I can not really feel it pulsing. How much is the damper supposed to pulsate at idle? Are you supposed to be able to visually see the plastic case of the damper deflect? Can you really feel the pulse if you place your fingers on the damper? Do I need to check for the pulsation at midrange or high rpm's?
The 13B is stock. The cold idle fluctuates from approximately 800 to 1200 rpm. The idle at normal operating temperature is smooth but high; 1700 rpm. Is this a symptom of a malfunctioning fuel pulsation damper? My plan was to check the ground connections, throttle position sensor, and jump "the initial set connector" so I could attempt to set the normal operating temperature idle at approximately 750 rpm with the adjustment screw on the top of the throttle body. But, I am worried that if the pulsation damper is not functioning properly I will just make things worse. On the other hand it looks like a real PITA to change the fuel pulsation damper and I would rather not rip the intake maifold and plumbing apart unless I am sure that the fuel pulsation damper is shot.
Thanks for your advice.
-Ray
Unplug your BAC valve first and see if the idle changes. I ran one without a pulsation damper at all and it didn't run any different.
Another victim of the 'don't touch it' screw. The throttle plate stop screw is not the idle speed screw but many people mistakenly think it is. The screw is there to keep the throttle plate from digging into the throttle body. If it's been tweaked, it will do like you describe. To rough adjust: loosen the locknut, turn the screw back out until it no longer touches the lever. Work the throttle a couple of times, recheck, the screw should still not touch the lever. Now turn the screw in until it touches the lever, then turn about 1/2 turn further. Work the throttle, let it 'pop' closed on its own and then work it again. if it seems to stick when you first move the throttle, give the screw another 1/2 turn.
When you start the engine, it will idle like crap until the ECM relearns adaptive idle. It should idle around 800 or so and not drop when the lights etc are turned on. Then you should be OK. If not, start hunting vacuum leaks. Some throttle bodies have an idle speed bypass screw, this can be used to adjust the idle as well.
Jensenman,
I am a bit confused. The throttle body on my 13B has 3 sets of throttle plates. On the face of the throttle body closest to the front of the car I see a set screw with a locknut as you described. It contacts a lever on the top shaft of what I think is the secondary throttle plates. I could swear that the secondaries are closed at idle with the way that screw is set now. At least that is what it looks like when I pull off the intake plumbing and look into the throttle body. On the top of the throttle body under a rubber cap is what I thought was the idle air screw. It does not have a locknut. This is what I was thinking I should tweak. Am I all mixed up? Thanks.
-Ray
The setscrew with locknut is the one I'm talking about. Pull the intake boot and work the throttle to see for sure whether the one you are looking at is for the primary or secondary throttle valve. The last one I had to fiddle with was an '87 and the primary valve setscrew was on the rear side of the TB (the side closest to the firewall). BTW: if either has been tweaked the same symptom will occur but check the primary side first.
If the stop screw is too far in, the top adjusting screw without locknut (that's the idle bypass) you are talking about won't work because all the air for the engine is going through the throttle body instead of the bypass.
Make sure you check carefully for vacuum leaks before doing any adjustments. Any vacuum leak on the engine side of the throttle valves will have the same effect as if the throttle were partway open. A stuck EGR valve can cause idle problems, but that's usually stalling.
The factory service manual shows the position of the various bits n' pieces and describes the adjustment procedure. Somewhere out there is a FSM online, you might go to rx7club.com and do a search. You have to register but it's worth it.
