FlyGuy2000

'90 GTU - problem is intermittent, happens maybe once a week. the check engine light will come on and i have no power when i try to accelerate, engine just kind of stumbles. after about 30 seconds the CE light goes away and i'm back to normal.

has this ever happened to anyone else? anyone know what might be wrong?

vaughnc

Yeah I had that problem too. What's happening is your O2 sensor's are being fooled and the ECU is trying to compensate for what it thinks is a ritch or lean condition (can't remember which). This is from cracks in the air intake system or a warped air intake manafold.

You can verify this by having the codes pulled. It will either be water-thermo or o2 sensor.

Mazcare basically patched up the cracks and fixed the problem. I had also replaced a wareped air intake manafold as well which can also cause that.

This is different than the 3500 rpm hesitation. That problem is related to the additional fuel injectors not firing when there suppose to due to a grounding problem with some sensor or ECU.

Another possibility is the fuel pump sucking air, dirty fuel injectors, clogged fuel filter, or clogged fuel strainer (in the gas tank).

Find a good rx-7 mechanic (if you don't work on them) and describe what I said here. You shouldn't have to replace the entire intake piping - but you might have to replace a warped intake manafold (metal).

FlyGuy2000

vaughnc - thanks for the reply, could it also be my Intake Air thermosensor?

i recently replaced the O2 sensor so i'm thinking now that the O2 sensor is working properly it's actually letting the ECU know there's something else wrong. previously i just burned rich, getting about 13 mpg. after replacing the O2 sensor i get 14.5 mpg. i'm thinking after i replace that IATS i might get the 17+ mpg everyone says they're getting.

vaughnc

I know the TII has 2 O2 sensors - but the GTU might only have 1.

I think the mazda troubleshooting books say replace the sensors giving the errors, verify the sensor wiring, and step 3 or 4 is the intake piping and/or manifold.

Is there any IATS senor errors?

FlyGuy2000

for some reason when the CE light flashes briefly like that it never stores the error codes. before i was getting the O2 sensor error code 15, after i replaced it and reset the ECU i get no codes anymore.