rpm will not go above 4500 and is rough
11-24-2005, 03:08 PM
#2
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Join Date: Oct 2005
Posts: 248
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.
11-24-2005, 04:40 PM
#3
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Join Date: Nov 2005
Posts: 14
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.
11-25-2005, 10:47 AM
#5
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Join Date: May 2002
Location: California
Posts: 22,465
Originally Posted by 1990vert' post='781331' date='Nov 25 2005, 05:02 AM
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
11-25-2005, 11:35 AM
#6
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Join Date: Oct 2005
Posts: 248
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
11-25-2005, 12:40 PM
#7
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Join Date: Nov 2005
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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?
11-25-2005, 01:02 PM
#8
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Join Date: May 2002
Location: California
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Originally Posted by 1990vert' post='781377' date='Nov 25 2005, 10:40 AM
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....
11-26-2005, 02:52 PM
#9
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Join Date: Nov 2005
Posts: 1
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! 
11-28-2005, 07:41 AM
#10
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Join Date: Mar 2005
Location: Central, VA
Posts: 51
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.