Mechanics

WHAT IS CAUSING MY CAR TO FLUCTUATE IDOL AND TRY TO STALL OUT WHILE WARMING UP?

1992 Mazda MX3 • 178 miles

SO here is my problem. I have a 1992 Mazda Mx-3 with a 1.6L inline SOHC Engine 98ci. It has 178400+ miles on the odo. For a while now (I'd say over a year) the check engine light comes on and goes back off when the engine reached full temperature. Recently, it will start and then try to stall out mid-way warm up and indeed it would stall if I don't give it an 1/8th of a throttle, any more and it WILL stall. First I changed the starter (it was going to need one), then under my father's suggestion I changed the fuel pump (old one seemed all right). It continued / continues to have the same problem of idol fluctuation and falling on it's face so. I had smartened up and checked the Chilton manual for error codes. I did an OBD1 diagnostics test and got the coolant temperature sensor as the culprit. The sensor was shot, it came out of the block in two pieces (the plastic wiring housing failed from the sensor itself). I have since changed the sensor and all seemed well after I had recently reset the computer (disconnected negative terminal on the battery and held brake for 5 seconds as recommended by the Chilton manual). I think it's semi-important to mention that I was having problems with the dual cooling fans what with the secondary fan not kicking on even while using the AC unit while the primamry fan would usually come on upon turning the ignition to the "on" position. Since I changed the temperature coolant sensor and inspected the relays, the fans operate as they should as of now. I have since driven the car 67 miles since the last computer reset. It is still refusing to start sometime even now while cold, still trying to fall on it's face mid-way warm up and the idol still fluctuates on it's own as if the car was staring for a remake of the movie Christine. (Fluctuations from est. 450RPMs to- 1800 RPMs. Usually idols at 1500RPMs until up to a safe running temperature when all is normal.)

So here is the questionnaire. Someone has suggested that I have low fuel pressure due to a failing line. Also I have been told that the computer is not going to reset until I drive it over 100 miles. And I have also been told that air in the fuel line could be the culprit. I DID change the fuel pump and the filter without attempting to fill the units with fuel first so there could be air in the lines. As far as the sensor goes, the OBD1 is currently still giving me an error code on the sensor but I think it is going to take the computer to fully reset before that is ruled out, HOWEVER, I assume the computer is controlling the sensor because the fans work when they should and it seems to run excellent when fully up to temperature (with the occasional refusal to idol down to 750 from around 1100 rpm).

I am so confused with this problem and am tired of dumping money into this car however I don't have the money for a newer vehicle soooo, LONG story short. I need help! Any explanations or suggestions would be so greatly appreciated!

Thank You,
Pete


Avatar
Petergerow
August 31, 2012.



Once you disconnect the power supply, the computer resets. If a problem is there triggering the MIL, no amount of driving would reset it.

What you need to do now is to recheck if the ECT is faulty, you have a break in the wiring, a loose connction or a bad PCM.

What is the code you are getting?


KHLow2008
Aug 31, 2012.
It is an obd1 so when I connect the jumper wires I am receiving 9 flashes from the indicator lamp indicating the coolant temperature sensor is faulty. How would I know if the computer was faulty? I will check the temp sensor with an ohms meter soon.


Tiny
Petergerow
Aug 31, 2012.
I just went to start it again and after quite a few cranks (perhaps too many but regardless) I can overwhelming smell gasoline. I am starting to think that in conjunction with the electrical problems I have a hole in the fuel line somewhere. How would you suggest I find a leak? I suppose we'll leave it at that? Thank you so much though for your help!


Tiny
Petergerow
Aug 31, 2012.
If you cranked the engine for proglonged period without the engine starting, fuel smell is expeced as the engine is flooded with fuel.

Code 9 is the ECT and attached are the diagnostic procedures. Let me know if you need anything else.


KHLow2008
Aug 31, 2012.