Problems after 730 ecm swap
Thread Starter
Burning Brakes
Joined: Jun 2001
Posts: 830
Likes: 2
From: VA
Problems after 730 ecm swap
Ok, I just did an ecm swap on my '89 vette. I figured it would be worth the trouble to allow the 383 to breathe better by switching to the 730. Anyway, after the swap, I'm having trouble getting it to run. I've double checked all the wiring changes, and that's all good. Added a new map sensor, so that should be good. Checked timing and tps voltage, both good. I've tried two different 730 ecms, and also tried both a stock chip and my fresh Fastchip.
No codes come up in the computer except the expected code 12, and after starting and attempting to run it will store a code 33. So at this point, I don't have any real clues coming from the codes. I assume the code 33 is tripping because of the difficulty it has idling.
Here is what it does. It will start a couple times and idle high for a bit, then it tries to drop the idle and completely stalls out. After a couple attempts though, it will no longer start at all. If I unhook a vacuum line then reconnect it so that it has no vacuum stored when I make another attempt, it will start again. Also, while it is running, if I very slowly give it some throttle it will rev up. But if I jab the throttle at all, it just dies.
Other info of interest:
Can't connect a Snap On scanner to ALDL, will not communicate
Everything was working fine with old computer and chip
Car still has EGR system in place, but it should be disabled in new chip
Any ideas or suggestions are appreciated. I need to get this thing running because I may need to sell it soon.
Gary
No codes come up in the computer except the expected code 12, and after starting and attempting to run it will store a code 33. So at this point, I don't have any real clues coming from the codes. I assume the code 33 is tripping because of the difficulty it has idling.
Here is what it does. It will start a couple times and idle high for a bit, then it tries to drop the idle and completely stalls out. After a couple attempts though, it will no longer start at all. If I unhook a vacuum line then reconnect it so that it has no vacuum stored when I make another attempt, it will start again. Also, while it is running, if I very slowly give it some throttle it will rev up. But if I jab the throttle at all, it just dies.
Other info of interest:
Can't connect a Snap On scanner to ALDL, will not communicate
Everything was working fine with old computer and chip
Car still has EGR system in place, but it should be disabled in new chip
Any ideas or suggestions are appreciated. I need to get this thing running because I may need to sell it soon.
Gary
Thread Starter
Burning Brakes
Joined: Jun 2001
Posts: 830
Likes: 2
From: VA
Re: Problems after 730 ecm swap (Gary K)
Ok, I now know why the scanner won't communicate...need to move a pin in the connector. I'll go fix that when I get a chance and see if I can find anything by connecting the scanner.
Burning Brakes
Joined: May 1999
Posts: 760
Likes: 1
From: Greenwich, CT
Re: Problems after 730 ecm swap (Gary K)
"33 Code: MAP sensor signal voltage was too high (low vacuum) for 1 second when throttle opening was under 2%. "
Suggestion: Check the MAP wiring connections for a reversed 5v ref on the output line.
Thread Starter
Burning Brakes
Joined: Jun 2001
Posts: 830
Likes: 2
From: VA
Re: Problems after 730 ecm swap (Gary K)
Ok, its fixed...and I'm a dummy. I got in a hurry and temporarily had the MAP sensor hooked up, I teed into a vacuum line....with a check valve in it. Oh well, lesson learned. Patience is a virtue :)
