possible bad ECM need help...?? - Team Camaro Tech
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post #1 of 5 (permalink) Old Jul 31st, 10, 05:15 PM Thread Starter
eyal
 
Join Date: Feb 2009
Location: portland or
Posts: 23
possible bad ECM need help...??

so it all started when i had to take the car(88 iroc-z 305) to emmision test
and fail the first time...high HC
then i got the G2P stuff to put in the fuel and that almost helped reduced the HC but still not enaugh to pass
third time i put primium gas and ran hard for 30 min and then went for the inspection...failed again this time HC even higher then second time
then i went and change the oil and replace the spark plugs to E3 hoping it would help...day after i took the test again and failed HC higher then the 1st time even....so i went to a mechanic to run the scanner and it showd that the ecm had bad tem reading meaning it change the temp to cold and hot every sec wich affecting the engine to run rich....he then said that i have to replace the ECM......any ideas for alternatives??... what can caused that to happen???.....
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post #2 of 5 (permalink) Old Jul 31st, 10, 06:42 PM
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Steiner
 
Join Date: Mar 2009
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Re: possible bad ECM need help...??

The ECM gets the temperature reading from the coolant temperature sensor mounted on the front of the intake manifold. It's much more likely that there is a problem with the sensor or wiring than with the ECM.

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post #3 of 5 (permalink) Old Jul 31st, 10, 06:47 PM
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george
 
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Re: possible bad ECM need help...??

Quote:
Originally Posted by e87camaro View Post
so it all started when i had to take the car(88 iroc-z 305) to emmision test
and fail the first time...high HC
then i got the G2P stuff to put in the fuel and that almost helped reduced the HC but still not enaugh to pass
third time i put primium gas and ran hard for 30 min and then went for the inspection...failed again this time HC even higher then second time
then i went and change the oil and replace the spark plugs to E3 hoping it would help...day after i took the test again and failed HC higher then the 1st time even....so i went to a mechanic to run the scanner and it showd that the ecm had bad tem reading meaning it change the temp to cold and hot every sec wich affecting the engine to run rich....he then said that i have to replace the ECM......any ideas for alternatives??... what can caused that to happen???.....
Imo..your mechanic should have been manipulating the ect sensor connector while viewing the bi-directional scan tool before writing off the ecm.Look for coolant in the sensor..spread contacts/no pin tension..broken wire strands inside the insulation at the sensor.
Or simply disconnect it running and then jumper it and see if the ecm sees this on the scan tool.

George
68 Camaro
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post #4 of 5 (permalink) Old Aug 1st, 10, 03:31 AM Thread Starter
eyal
 
Join Date: Feb 2009
Location: portland or
Posts: 23
Re: possible bad ECM need help...??

well...i figured that if the temp sensor was bad the fan wouldnt come on at all
but it does when it should be
so im lost on this one
also i saw the readings in my own eyes it was wierd...one sec it would be 45 deg other se it would be 165 and so on....
i was wondering if i change the ecm chip maybe it would help
or just get a used ecm from another camaro but the question is if i have to have the same year make and model or i can get it from a diffren year as well
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post #5 of 5 (permalink) Old Aug 1st, 10, 03:22 PM
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Art
 
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Re: possible bad ECM need help...??

Fan could be coming on from the high temp sensor instead of computer control. 2 things I'd check first are grounds and verify no ripple voltage in the system (AC voltage leak through rectifier bridge in alternator). Grounds are easy to check, as is the ripple voltage with a good DVOM. An quick check to see if the rectifier bridge is on its way, is to unplug the alternator field connector and see if the driveability/running gets better. Don't drive too far like that as it won't be charging the battery. Unfortunately, this check can also mask a bad ground so verify proper grounds to the body, engine, and ECM first. You can plug a 1k ohm resistor into the coolant temp sensor connector and see if the computer reads a steady temp to verify the sensor itself is ok.

Artie

67 Camaro
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