2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

1991 NA - wierd CEL issue

Old Apr 28, 2016 | 07:10 PM
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1991 NA - wierd CEL issue

Car runs great from idle up to 8k rpm until 10 mins of idling or driving. CEL comes on and car sputters but does drives. Turn car off, runs great again and CEL comes on in ten mins exactly. Strange thing is CEL code does not stay in computer, can not get code.
I have had my OMP fail before and it held a code that pointed me to the OMP. Car isn't acting like limp mode when I lost my OMP.
Just replaced the TPS and adjusted it. This seemed to fix my pulsing idle but CEL did not get fixed.
Anyone experienced anything like this before? Thanks
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Old Apr 28, 2016 | 09:14 PM
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Did you pull codes?
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Old Apr 28, 2016 | 10:31 PM
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From: https://www2.mazda.com/en/100th/
chances are that it needs a harness and or an ecu, and maybe an OMP too
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Old Apr 29, 2016 | 01:16 AM
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As I stated, the code doesn't stay in computer. I tried to pull a code but nothing is there.
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Old Apr 29, 2016 | 06:03 AM
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roTAR needz fundZ
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We've seen your story before, many times, and it usually led to a bad OMP and ECU

you said you replaced the OMP before, did you replace it with new or used? And did you replace the ECU at the same time?
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Old Apr 29, 2016 | 06:06 AM
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From: Central Massachusetts
It was replaced with a used one. Did not replace the ecu at that time as everything checked out after replacing the OMP.
Car doesn't seem to be acting the same as it did when the OMP went. It would not let me drive the car for more than a minute and I couldn't step on the gas more than 30% when it went into limp mode. I was able to read the code that time as it stayed in the computer and came on every time I started the car.

Last edited by pls91fc; Apr 29, 2016 at 06:08 AM.
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Old Apr 29, 2016 | 08:22 AM
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From: tulsa,ok.
Unplug your boost sensor and see if the ECU will show the error code. If it does not then you probably know the answer.
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Old Apr 29, 2016 | 11:24 AM
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From: Central Massachusetts
do you mean the pressure sensor? My car is an NA. Thanks If the error code doesn't stay my ecu is messed?
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Old Apr 29, 2016 | 02:14 PM
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Originally Posted by pls91fc
do you mean the pressure sensor? My car is an NA. Thanks If the error code doesn't stay my ecu is messed?
Boost/pressure means basically the same item. And yes to your last point.
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Old Apr 30, 2016 | 07:03 PM
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From: Central Massachusetts
Good call search. Unplugged sensor and code did not stay. Had a good ecu on the shelf and swapped out. Threw code 27 after driving for ten minutes.
Old ecu had a burnt resistor or two when I opened it up. Definitely should have replaced when my OMP went the first time. Now to do it all over again! Can OMP's be rebuilt or are my options still only new and used?


Backside




Inside
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Old Apr 30, 2016 | 10:02 PM
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From: https://www2.mazda.com/en/100th/
the OMP's can't really be rebuilt, but you could swap just the stepper motor, or the position sensor if needed.

my FC, has an FD engine and ECU in it, but its running an FC harness, so the OMP is an FD mechanical pump with an FC stepper motor and position sensor, so it plugs in.

since we're talking about it the 92-97 FD OMP has an identical stepper motor and position sensor, just a different harness connector
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