85 Corvette running horable
Thread Starter
3rd Gear
Joined: Jun 2016
Posts: 3
Likes: 0
85 Corvette running horable
My car all of a sudden is very hard starting and back fires a couple of times and will start but will not idle. The check engine light comes on as soon as the ignition is turned on. I disconnected the battery because the computer will drain the battery if left for a few days. Reconnecting the battery does not erase the codes the light comes on. I tried to read the codes by shorting with a wire and I can not get code 12 to display. Checked the fuse for the ECM and it is ok. Does this mean that the ECM is bad? Is there anyway to check the ECM? Need some advice.
Drifting
Joined: Mar 2013
Posts: 1,952
Likes: 239
From: Venice Cali.
My car all of a sudden is very hard starting and back fires a couple of times and will start but will not idle. The check engine light comes on as soon as the ignition is turned on. I disconnected the battery because the computer will drain the battery if left for a few days. Reconnecting the battery does not erase the codes the light comes on. I tried to read the codes by shorting with a wire and I can not get code 12 to display. Checked the fuse for the ECM and it is ok. Does this mean that the ECM is bad? Is there anyway to check the ECM? Need some advice.
Thread Starter
3rd Gear
Joined: Jun 2016
Posts: 3
Likes: 0
I just went and redid the AB short test for the 6th to 10th time to make sure I did it correctly. After shorting the AB pins I turned the key to the run position and the fan does not run and the check engine light stays on and does not flash 12. As I said in the first post the fuse for the ECM is good and also grounded pin B to the cig lighter to make sure I had a ground. Does this indicate I have a possible ECM problem. If gets a little cooler tomorrow I will try the finger tap test on the ECM.
Drifting
Joined: Mar 2013
Posts: 1,952
Likes: 239
From: Venice Cali.
I just went and redid the AB short test for the 6th to 10th time to make sure I did it correctly. After shorting the AB pins I turned the key to the run position and the fan does not run and the check engine light stays on and does not flash 12. As I said in the first post the fuse for the ECM is good and also grounded pin B to the cig lighter to make sure I had a ground. Does this indicate I have a possible ECM problem. If gets a little cooler tomorrow I will try the finger tap test on the ECM.
Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 764
My car all of a sudden is very hard starting and back fires a couple of times and will start but will not idle. The check engine light comes on as soon as the ignition is turned on. I disconnected the battery because the computer will drain the battery if left for a few days. Reconnecting the battery does not erase the codes the light comes on. I tried to read the codes by shorting with a wire and I can not get code 12 to display. Checked the fuse for the ECM and it is ok. Does this mean that the ECM is bad? Is there anyway to check the ECM? Need some advice.
your problem:
My car all of a sudden is very hard starting and back fires a couple of times and will start but will not idle.
I have had similar problems in the past - once it turned out to be a timing chain issue. so far, hard to say - could be anything.
The check engine light comes on as soon as the ignition is turned on.
I disconnected the battery because the computer will drain the battery if left for a few days
Reconnecting the battery does not erase the codes the light comes on. I tried to read the codes by shorting with a wire and I can not get code 12 to display.
Checked the fuse for the ECM and it is ok. Does this mean that the ECM is bad? Is there anyway to check the ECM?
finally, do you have a FSM? if not, get one. you need a systematic approach to troubleshooting a start problem. anything else is second guessing. good luck....
Last edited by Joe C; Jun 12, 2016 at 08:07 AM.
Oil Producer
Joined: Apr 2014
Posts: 9,371
Likes: 2,736
check to make sure your OBD one port is not upside down. Mine was upside down. And I thought I was jumping a and B when I wasn't because it was upside down. You can find a diagram on the Internet. And use the slot in the middle to orient you're up and down.
let me break down your post and give you my 2-cents - FWIW
your problem:
start with the basics. the first thing I would check is the fuel pressure. run a fuel pressure diagnostic test.
I have had similar problems in the past - once it turned out to be a timing chain issue. so far, hard to say - could be anything.
this is normal.
are you sure it's the ECM draining the battery?
can't get code 12, but you are getting some codes - ??? what codes are you getting? you say you're not getting code 12 (3X's). exactly how are you pulling codes? what pins did you short on the OBD port? are you 100% sure it's A&B? you should get, key on, code 12, pause, code 12, pause, code 12, pause, then fault codes. ??? why are you expecting the fan to come on? you lost me here...
the fuse check is good. can't say for sure if the ECM is bad, but if you are not initially getting code 12, that's not good. no way of checking the ECM that I know of - either bench or on-car. I would not go out and buy an ECM and start throwing parts at the problem
finally, do you have a FSM? if not, get one. you need a systematic approach to troubleshooting a start problem. anything else is second guessing. good luck....
your problem:
start with the basics. the first thing I would check is the fuel pressure. run a fuel pressure diagnostic test.
I have had similar problems in the past - once it turned out to be a timing chain issue. so far, hard to say - could be anything.
this is normal.
are you sure it's the ECM draining the battery?
can't get code 12, but you are getting some codes - ??? what codes are you getting? you say you're not getting code 12 (3X's). exactly how are you pulling codes? what pins did you short on the OBD port? are you 100% sure it's A&B? you should get, key on, code 12, pause, code 12, pause, code 12, pause, then fault codes. ??? why are you expecting the fan to come on? you lost me here...
the fuse check is good. can't say for sure if the ECM is bad, but if you are not initially getting code 12, that's not good. no way of checking the ECM that I know of - either bench or on-car. I would not go out and buy an ECM and start throwing parts at the problem
finally, do you have a FSM? if not, get one. you need a systematic approach to troubleshooting a start problem. anything else is second guessing. good luck....
Thread Starter
3rd Gear
Joined: Jun 2016
Posts: 3
Likes: 0
I just came back from a test drive, all is normal and runs great. The problem was with the computer. I replaced the computer and prom with a used computer and prom I bought on ebay for $85.00. Thank you all for the advice you gave me.
Chip
Chip
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