84 crossfire help needed!!!!
Thread Starter
Intermediate
Joined: Jan 2014
Posts: 48
Likes: 0
84 crossfire help needed!!!!
Just bought my first vette an 84 crossfire automatic and it has started missing and stalling sometimes backfiring heck the timing plugs cap rotor all seem good it keeps throwing code 51 a prom error I have tried two different ECMs and two different proms I found in the car when I bought it one hypertech street runner chip and one superchip still code 51 and running horrible is it possible that my chips have just gone bad and would that explain the problems I'm havin also does anyone have a known working ecm or known good prom their not using I could by or atleast use to see if that's the problem
Thread Starter
Intermediate
Joined: Jan 2014
Posts: 48
Likes: 0
That's is if these ECMs and proms r any good like I said I found them in the car does anyone have a good working ecm and prom or can burn me a prom chip as I buy the ecm of anyone has one Layin around let me know hoping this fixs the car
Le Mans Master
Joined: Sep 2009
Posts: 6,311
Likes: 1,125
From: Vermilion OH
Where are you located? I do have a spare ecm with a hypertech chip that I would let you try. I'm not interested in selling it currently, but you are welcome to try it.
Have you checked the timing? the timing chain is an item that is a wear item and can stretch causing power loss and missing.
Starting with the basics is always the first place to start. Cap, wires, plugs, rotor, air and fuel filter, intake and vacuum leaks. Check the the fuel pressure and ensure both injectors are operating properly. The injectors do clog up and need cleaned. Check the connections on the distributor and check the plastic vacuum barb that threads into the intake plenum on the left side near the firewall. Its prone to cracking and causing a vacuum leak.
Another area to check is the fuel pump feed line. Its a rubber fuel hose that fuel passes through on the pump. Its prone to cracking and leaking and will cause loss of power and a miss.
Have you checked the timing? the timing chain is an item that is a wear item and can stretch causing power loss and missing.
Starting with the basics is always the first place to start. Cap, wires, plugs, rotor, air and fuel filter, intake and vacuum leaks. Check the the fuel pressure and ensure both injectors are operating properly. The injectors do clog up and need cleaned. Check the connections on the distributor and check the plastic vacuum barb that threads into the intake plenum on the left side near the firewall. Its prone to cracking and causing a vacuum leak.
Another area to check is the fuel pump feed line. Its a rubber fuel hose that fuel passes through on the pump. Its prone to cracking and leaking and will cause loss of power and a miss.
Heel & Toe
Joined: Aug 2013
Posts: 22
Likes: 0
Here is your fix. It is 2 things.
Map senor is bad or vacuum lines are leaking.
I had the same thing happen and mine was cracked and broken vacuum lines one we replaced all lines corrected everything! This was even throwing my check engine lite. At the same time I did replace the air pump.
Also look and see if your headers are getting red hot. If show your cat is stopped up.
Map senor is bad or vacuum lines are leaking.
I had the same thing happen and mine was cracked and broken vacuum lines one we replaced all lines corrected everything! This was even throwing my check engine lite. At the same time I did replace the air pump.
Also look and see if your headers are getting red hot. If show your cat is stopped up.
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Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
http://www.chevythunder.com/codes_5152_55.htm
A MAP sensor or vac to it problem would give you a DTC 33 or 34
Thread Starter
Intermediate
Joined: Jan 2014
Posts: 48
Likes: 0
That is what I had thought which is why I am now looking for a 84 automatic ecm and prom chip in working order for a good price also interested in someone burning me a factory chip and possibly some other chips which different tunings i could try
Instructor
Joined: Apr 2007
Posts: 225
Likes: 1
From: Highland Village texas
The ecm is dramatically more unreliable then the prom chip. If the early computer is built like the 165 its guaranteed to fail eventually.
the coating over the electronics flexed with temp changes and eventually breaks the solder joints on the ic's flush mounted on the boards. All the remans are solder reflowed and use a updated coating that doesnt cause stress on the ic's. This is what happened with the original 165 ecms. Im sure yours is in the same boat. Since you have a hard ecm fault start with the ecm.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
Very few play with those ECM's these days because they are so slow and there is little support.
Most upgrade to a TBI truck ECM with all the benefits that come from fast modern technology
or the EBL setup
http://www.dynamicefi.com/EBL_Flash.php
that lets you adjust the tune straight off a laptop just like a LS1 engine
Most upgrade to a TBI truck ECM with all the benefits that come from fast modern technology
or the EBL setup
http://www.dynamicefi.com/EBL_Flash.php
that lets you adjust the tune straight off a laptop just like a LS1 engine
Thread Starter
Intermediate
Joined: Jan 2014
Posts: 48
Likes: 0
I've been told this about the ecm upgrade by everyone my only problem is I wouldn't know where to begin and believe that to possible b beyond my capabilities lol I'm just trying to get the original car running good that's all
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Here is your fix. It is 2 things.
Map senor is bad or vacuum lines are leaking.
I had the same thing happen and mine was cracked and broken vacuum lines one we replaced all lines corrected everything! This was even throwing my check engine lite. At the same time I did replace the air pump.
Also look and see if your headers are getting red hot. If show your cat is stopped up.
Map senor is bad or vacuum lines are leaking.
I had the same thing happen and mine was cracked and broken vacuum lines one we replaced all lines corrected everything! This was even throwing my check engine lite. At the same time I did replace the air pump.
Also look and see if your headers are getting red hot. If show your cat is stopped up.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
So what are you after ; just to drive the car or restore it to stock.
How long have you had it ,did it ever run well ?
You are heading down the right path trying to find a known good ECM and prom to test it with but as you have found out they pretty thin on the ground
At the risk of
from Tom I would suggest you throw a carb on it it if all you want to do is get it running?
You could then source a good ECM at your leisure if did want it factory original
How long have you had it ,did it ever run well ?
You are heading down the right path trying to find a known good ECM and prom to test it with but as you have found out they pretty thin on the ground
At the risk of
from Tom I would suggest you throw a carb on it it if all you want to do is get it running?You could then source a good ECM at your leisure if did want it factory original
Melting Slicks
Joined: Jan 2008
Posts: 2,054
Likes: 120
From: AZ
Very few play with those ECM's these days because they are so slow and there is little support.
Most upgrade to a TBI truck ECM with all the benefits that come from fast modern technology
or the EBL setup
http://www.dynamicefi.com/EBL_Flash.php
that lets you adjust the tune straight off a laptop just like a LS1 engine
Most upgrade to a TBI truck ECM with all the benefits that come from fast modern technology
or the EBL setup
http://www.dynamicefi.com/EBL_Flash.php
that lets you adjust the tune straight off a laptop just like a LS1 engine
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
LOL...that was funny. 
Not a bad idea to get it running in the interim. I'm not against that at all.
It's the guys who say "you can swap to a carb cheaper than fixing it". Or "you can go faster w/a carb/manifold (only) swap than you'll ever get the CFI to go". Those are the posts that irritate me.
Not a bad idea to get it running in the interim. I'm not against that at all.
It's the guys who say "you can swap to a carb cheaper than fixing it". Or "you can go faster w/a carb/manifold (only) swap than you'll ever get the CFI to go". Those are the posts that irritate me.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
Then reinstate the CFI with the stock ECM or upgrade to a TBI /EBL once he has a better understanding of the limitations of the stock ECM
which has never been hacked for tuning purposes
