1990 NA and when I accellerate it hesitates and will not go above 4500-5000 rpm? New plugs and air filter make no difference. Bonez Hiflow cat a few years ago. Cat? fuel pump/filter? Any ideas? Thanks!

was the cat specifically for a rotary? rotarys require a different cat than normal pison engines becuase of heat they produce. a clogged cat will defenatly prevent it from reving normally. also it could be the damn 3800 rpm problem that everyone has and since rx7 tach's are not as accurate as they should be... it could possibly be that. when you hit 4000 rpm does the motor change sounds? i.e. when your pulling up to 4000 rpm it sounds like it should sound, then all the sudden the motor just kinda buzzes and the power drops? it just quits pulling sounds and feels kinda like it just slipped into nuetral? if thats what it is doing then its the 3800 problem. my car has this and im fixing it right now.

Mine seems to be dependant on how much gas pedal I apply. I can get it up to about 5500 rpm but it wheezes and sputters. When I let off on the pedal, it acts normally again. I pulled the plugs and there is a good bit of carbon on them for them being only a week old. Oh, and yes the cat was an rx7 cat but it could still be the culprit I guess. Hate to do it but I think I'm off to the Mazda Mechanic.

IF this helps solve the puzzle, my line from the airpump to the cat became seperated (no air to cat) and I was forced to drive it for about 40 miles. Would that cook the cat?

nah, that line hardly does anything. is the check engine light on? if not i like the cat

yeah, sounds like the cat. all that line does is supply air to the cat to burn off all the rest of the unburnt emissions, i doubt driving 40 miles with it off would do that. uh-oh, not the mazda mechanic. they dont even know what theyre doing. well, most of em dont

So you guys are saying it's the cat? really no way to check the cat is there? I was thinking of getting a RB cat-back. I guess I'll have to add the downpipe and presilencer. I sure hope it's not loud and ricey or I'll be bummed. I prefer to have a close to stock sound. Will I still use the air pump with this configuration?

you can pull the cat off and look in it....

I had the same problem, for more or less a year! nobody around here knows how to work on a rotory. n-e-wayz reading a thread one day, to check the injector harness ground, found it it was corroded, cleaned her up, put her back on, and that cured the problem, btw, i tried every other grounding solution people have said on the net, and none of them worked for me, but this one did! GOOD LUCK! https://www.nopistons.com/forums/pub...1047683329.gif

Besides a clogged cat, 4000rpm sag can be caused by faulty grounds. Check the voltage of all the ECU ground pins... There are probably 3 or 4 of them. They should show -0- volts. If they register a positive voltage then you will probably benefit from running a splice ground to a frame point near the ECU. The secondary injectors kick in at about 4000 too, so you need to check for clogged or leaky injectors and for properly functioning secondary actuators.