84 - won't idle, no codes - HELP
Thread Starter
3rd Gear
Joined: Jan 2004
Posts: 3
Likes: 0
From: Auckland
84 - won't idle, no codes - HELP
H-E-L-P from New Zealand!!! My stock standard 84 vette suddenly stopped idling, a few miles after I changed the battery. Starts and runs fine, just dies with foot off gas. Two other things - the 'Check Engine' light stays on, and the gas mileage guage is stuck on 0mpg. When I short out terminals A & B on the ACLC to get the code (engine off), zip happens, no flashing, the check engine light just stays on. :confused:
Racer
Joined: Jan 2002
Posts: 469
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From: Clifton NJ
Re: 84 - won't idle, no codes - HELP (dhutch)
I HAVE AN 85 TPI AND DONT KNOW MUCH ABOUT CROSSFIRE BUT CHECK THE OBVIOUS. PERHAPS WHEN YOU THE BATTERY YOU KINKED,BROKE OR ACCIDENTALLY KNOCKED OUT A VACUUM LINE. IT COULD BE A VACUUM LEAK. AND DID YOU CHECK ALTERNATOR OUTPUT? JUST LOOK AT THE BATTERY LEVEL ON THE DASH. IT COULD BE ALOT OF THINGS. BUT IF IT HAPPENED AFTER YOU CHANGED THE BATTERY, I WOULD REMOVE IT AND CHECK WHAT MIGHT HAVE HAPPENED WHEN YOU PUT IT IN. LET ME KNOW WHAT HAPPENS.GOOD LUCK! :confused:
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: 84 - won't idle, no codes - HELP (dhutch)
Two other things - the 'Check Engine' light stays on, When I short out terminals A & B on the ACLC to get the code (engine off), zip happens, no flashing, the check engine light just stays on. :confused:
RACE ON!!!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: 84 - won't idle, no codes - HELP (dhutch)
Was my interpertation of your first post correct? With the engine running, the check engine light stays on? With the engine not running, the ignition on, and terminals A&B shorted, the check engine light stays on and doesn't flash any codes, not even code "12"? If so, this pretty well narrows it down to the ECM or prom. I'd bet on the ECM. Did you connect or disconnect the battery, with the ignition on? If so, that could be the cause. If you REALLY want to know all the possibilities, you NEED a service manual. The checks aren't ALL that difficult or lengthy, but it's more than this old, hunt and peck, typer, can transcribe. The diagnostic chart has you checking for an "open in one circuit and a short (ground) in another. Then, there is a proceedure for isolating the problem between the ECM and the prom.
ECMs should be available at an auto parts store. They are sold as, "rebuilt, exchange". I am not familiar with their cost. You can do a "Wanted to Buy" in the C4 parts section. I have seen them for sale, from time to time. You should also try the "Crossfire Vault" www.crossfire.homeip.net/. A lot of those guys have converted over to later, faster ECMs. Some may have their old ECMs, for cheap. Good luck, and...
RACE ON!!!
ECMs should be available at an auto parts store. They are sold as, "rebuilt, exchange". I am not familiar with their cost. You can do a "Wanted to Buy" in the C4 parts section. I have seen them for sale, from time to time. You should also try the "Crossfire Vault" www.crossfire.homeip.net/. A lot of those guys have converted over to later, faster ECMs. Some may have their old ECMs, for cheap. Good luck, and...
RACE ON!!!
Pro
Joined: Dec 2002
Posts: 603
Likes: 0
From: 84 383 XFire Chandler, AZ
Re: 84 - won't idle, no codes - HELP (CFI-EFI)
I have an 84. I would try resetting the ECM by removing the battery cable for about 30 secs and connect and restart the motor. When you short A-B on the ALDL can you hear the IACs moving back and forth? You may need to remove the air filter cover to take a look. If they are not then check your fuses just to make sure. I have disconnected by battery a zillion times and never fried the ECM.
If you do need a new ECM and you decide to convert over to the 7747 then you will need to be prepared to make a prom. I have a 7747 and a Prominator and I am in the process of tuning my setup now. Unfortunately there are not any 7747 prom's for stock 84s. I am just running a ported crossfire manifold and 1.6 rockers which required a new prom to get it to run right.
Checkout the Crossfire Vault - the folks there are quite knowledgable and may be able to help you better than I can. It is worth registration and a post or two.
If you do need a new ECM and you decide to convert over to the 7747 then you will need to be prepared to make a prom. I have a 7747 and a Prominator and I am in the process of tuning my setup now. Unfortunately there are not any 7747 prom's for stock 84s. I am just running a ported crossfire manifold and 1.6 rockers which required a new prom to get it to run right.
Checkout the Crossfire Vault - the folks there are quite knowledgable and may be able to help you better than I can. It is worth registration and a post or two.
