1990 GTU N/A street port with 5k on rebuilt motor. Car runs and drives great on initial startup then after about 30 minutes of driving goes into limp mode and when trying to drive it just tries to stall and won't go above like 1500 rpm. I replaced a bad o2 sensor
which did not solve the problem and I know the ecu is still good so I don't think its the OMP. Could it be the air flow meter? I have another one I can drop in but not sure how to test if the other is bad. Thanks and sorry so long

 

I'd shoot for the OMP.since it is often the culprit of the CEL going on and putting the car into limp mode.

 

Ok thanks for the input...also I'm not getting a cel when it goes into limp mode is that normal?

 

If you keep driving the car you will burn out the ECU-if you haven't already done so.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/s5-mop-ecu-failure-diagnosis-710938/

https://www.rx7club.com/showthread.php?t=710938


Good Luck.

 

No that isnt normal. You need to run codes.

 

Can you explain how to run codes please.. Thanks sorry kind of a noob

 

http://fc3spro.com/TECH/HOWTO/ERRORC...KI/kerror.html

Keep us posted.

 

OK...ran codes and got nothing...car went into limp mode again today and still no cel...i pulled ecu and saw no burn marks...what are the possibilities? How long does it take the ecu to burn? Thanks in advance

 

Does the check engine light come on once its in limp mode?

The most common cel is the damn electric OMP going to ****. Might want to change that and see if it goes away.Worked for me, never had a problem or cel since.

I understand to replace parts that you arent sure are bad is the wrong way to go about it but if you know what your doing it is easy and pretty cheap part to get from the parts section of this forum. Keep us posted, could help others.

 

I dont get a CEL...

 

When you turn the key to ON does the check engine light come on at all? Should come on then go off i think. If not i'd look into swapping out the ecu and see if the light comes on then.

 

Yes it comes on when i turn the key on...just wont seem to come on when the car goes into limp mode...frustrating!!

 

it could be a bad fuel pump, filter or clogged charcoal canister too

 

Would the car still run and drive fine until it goes into limp mode? And would those things be causing it to go into limp mode? Im really confused lol

 

like Jackhild said, if you continue to drive the car you will burn out the ECU

I it was the Canister he will smell fuel in the engine bay, I would test the fuel pump and take a look at the tank, it could be full of crud. If the pump and tank check out to be fine the filter is also fine.

Turn the key to on,but DO NOT Start the car, if you hear the pump turning on then the pump is good.

My car went into limp mode ALL The time. The ECU/OMP short out will cause it to go into limp mode, thats it.

I hope that helps alittle.

 

^like said above ONLY the OMP failing will cause limp mode, and the during limp mode the front rotor shuts down fuel above 3500 rpm, and the rear rotor shut down fuel after maybe 25-30 percent thorttle. if your issue is at 1500 or varies, and you DONT have a code, its not the omp. another thing, if it's the OMP it should take about 6-8 seconds to come into the limp mode, turn the key off and back on with the engine running REALLY fast, and then stomp it. if your ecu would go into limp mode, it would allow it to run normally for 6-8 seconds, and then return to ^ conditions^

 

Ok the only thing that confuses me is why the car runs absolutely great for a given amount of time then it runs as lastphase describes, like fuel is getting cut off...does the fuel pump act different when warm or something? Thanks for all the input

 

The pump does not turn on till you start cranking the car. The pump will not be on in the on position.

If the car is fine for 30+min then starts to act funny i would assume the pump/filter is good.


I just had the OMP cel code like 2 months ago. i was getting fuel cut below 3k. It wouldnt do it all the time but 90% of the time.
I could free rev it all day but once i started to drive it would act all funky.

 

if the light does not come on and there are no codes, its NOT a limp home.

its much more likely to be a fuel delivery issue.

 

when my car was goin into limp mode from a faulty afm, i read a few threads where they had the same problem when the omp was failing they wouldnt get codes till it completely burnt itself out
maybe just check the plugs by the coolant neck make sure they are clean and have a good connectiion

 

Could be your throttle plates

 

Elaborate please... This is really starting to act like a fuel issue...

 

does it do it when hot, fully warmed up?