DID I #@%#@ UP HELP
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Junior Member
Joined: Oct 2000
Posts: 5
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DID I #@%#@ UP HELP
Tody SUCKED!! I was driving down the road and my check eng light came on. The car ran but lost power. I got home checked the code MAF sensor poped up. OK I put a new sensor on, took it for a ride. Not bad at first then bam the light came back on same truble. Got home put the jummper wire back in the light flashed a few times then stayed lit. I took the jumper out tried to start BAM no spark. Did I short something out???
changed the coil still no spark?? HELP! oh yea 305 eng.
changed the coil still no spark?? HELP! oh yea 305 eng.
Member
Joined: Jul 2000
Posts: 163
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From: Ft. Worth,Tx.
88, Anytime that you do the ECM diagnosis procedure you must be sure to have the ignition off each time you plug into the diag. connector and when you unplug this connector to keep from damaging the ECM.
I would try disconnecting the battery ground for a few minutes to reset the ECM. Sorry, I am not sure if the light staying on is an indicator of a fried ECM or just a temporary glitch. Check the fuse/fusable link for the ECM also.
Next time you get a code do not go right out and purchase a new part. There are certain procedures to try and identify the exact problem because a bad sensor may affect other parts of the system thus confusing the ECM which in turn will spit out a code which may or may not be the ultimate problem. Also, always disconnect the battery when you work on anything electrical to prevent accidentally spiking the ECM.
Our ECM's are not very sophisticated when it comes to engine management/monitoring compared to OBD II, just check out a service manual for a new vehicle, these new computers can tell you a whole lot more than ours. Maybe thats a good thing and maybe it can get more confusing I'm not sure.........
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"84Z28/'91 305TPI comp cam flowmaster TB coolant bypass/shutoff valve to heater core MAT relocated Ram-Air(home-made) gutted air-box IROC ground effects/wheels GY245/50's 700R4 superior shift kit/ corvette servo(excellent shift kit BTW) Rebuilt engine and transplanted it myself. Love this engine!
LOW performance people should drive low performance vehicles!
I would try disconnecting the battery ground for a few minutes to reset the ECM. Sorry, I am not sure if the light staying on is an indicator of a fried ECM or just a temporary glitch. Check the fuse/fusable link for the ECM also.
Next time you get a code do not go right out and purchase a new part. There are certain procedures to try and identify the exact problem because a bad sensor may affect other parts of the system thus confusing the ECM which in turn will spit out a code which may or may not be the ultimate problem. Also, always disconnect the battery when you work on anything electrical to prevent accidentally spiking the ECM.
Our ECM's are not very sophisticated when it comes to engine management/monitoring compared to OBD II, just check out a service manual for a new vehicle, these new computers can tell you a whole lot more than ours. Maybe thats a good thing and maybe it can get more confusing I'm not sure.........
------------------
"84Z28/'91 305TPI comp cam flowmaster TB coolant bypass/shutoff valve to heater core MAT relocated Ram-Air(home-made) gutted air-box IROC ground effects/wheels GY245/50's 700R4 superior shift kit/ corvette servo(excellent shift kit BTW) Rebuilt engine and transplanted it myself. Love this engine!
LOW performance people should drive low performance vehicles!
Member
Joined: Oct 2000
Posts: 223
Likes: 0
From: way over there
Car: 87 IROC
Engine: LB9 for the moment
Transmission: T5
do you have power to the coil??? what is the condition of the cap and rotor??? especially the carbon button??? check these and anything else you can think of...
Moderator
Joined: Jan 2000
Posts: 19,651
Likes: 309
88,
It's O.K. to "#@%#@" up once in a while. Personally, I get tired of "#@%#@"ing down and sideways all the time.
As IROC suggested, the ignition should be off whenever the ECM is scanned for codes using the jumper. You can insert a jumper while the engine is running to enter Field Service Mode, but it does not display diagnostic codes at the MIL lamp.
As long as you didn't crank or start the engine while the jumper was inserted, you should not have caused damage.
Of course, the jumper must be inserted between terminals 'B' and 'A', or 'B' and a ground. Those are the upper right terminals on a domestic ThirdGen.
At the very least, you should always get a code '12'. If you suspect an ECM problem, disconnect the battery for about ten minutes to clear the ECM active RAM. It's possible to have stored some "junk" data there from transients or static discharge. Make sure all ground connections are clean and tight.
Reconnect the battery and scan for codes before even trying to start the engine. If you get a '12', the ECM may be undamaged.
Once you've established that, start the engine and let it run until warm (if it will). Turn off the engine and scan again. If you get a similar response, clear the ECM again, then reconnect, scan, and start the engine. Immediately check the alternator output on an AC voltage scale directly at the alternator output stud. If the meter registers more than 1 - 1.5 VAC, you have a problem with the alternator applying AC to the system. This will "#@%#@" things up faster than you ever could. Replace the rectifiers in the alternator (or the entire alternator) and try again.
If the voltage reads less than 1.0 VAC, start checking grounds and connections at the ECM.
Waiting for results...
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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0
It's O.K. to "#@%#@" up once in a while. Personally, I get tired of "#@%#@"ing down and sideways all the time.
As IROC suggested, the ignition should be off whenever the ECM is scanned for codes using the jumper. You can insert a jumper while the engine is running to enter Field Service Mode, but it does not display diagnostic codes at the MIL lamp.
As long as you didn't crank or start the engine while the jumper was inserted, you should not have caused damage.
Of course, the jumper must be inserted between terminals 'B' and 'A', or 'B' and a ground. Those are the upper right terminals on a domestic ThirdGen.
At the very least, you should always get a code '12'. If you suspect an ECM problem, disconnect the battery for about ten minutes to clear the ECM active RAM. It's possible to have stored some "junk" data there from transients or static discharge. Make sure all ground connections are clean and tight.
Reconnect the battery and scan for codes before even trying to start the engine. If you get a '12', the ECM may be undamaged.
Once you've established that, start the engine and let it run until warm (if it will). Turn off the engine and scan again. If you get a similar response, clear the ECM again, then reconnect, scan, and start the engine. Immediately check the alternator output on an AC voltage scale directly at the alternator output stud. If the meter registers more than 1 - 1.5 VAC, you have a problem with the alternator applying AC to the system. This will "#@%#@" things up faster than you ever could. Replace the rectifiers in the alternator (or the entire alternator) and try again.
If the voltage reads less than 1.0 VAC, start checking grounds and connections at the ECM.
Waiting for results...
------------------
Later,
Vader
------------------
"Make Me Bad"
Adobe Acrobat Reader 4.0