I'm running an 85 ECM in my 87 GT because I wanted the knock sensor capability.
I'm trying to track down an annoying hesitation when the throttle is pressed that I've had for some time (just lived with it). I connected WinALDL to check out the sensors with engine normal running temp at idle.
If I set Win ALDL to the 7170 ECM (stock 87), the MAT reads 64C (about 150F) which I would say is normal considering engine bay heat of an idling motionless car. The temp started at room temp and rose to that as the engine heated up as expected.
But when I change WinALDL's configuration to 85 2.8 ECM (what I actually have in the car), the MAT reads -5.0C (about 22F) which is WAY off.
Why the difference?? According to rockauto.com the same sensor was used with both ECMs. The 87 ECM seems to indicate the sensor is OK, while the 85 ECM seems to say there's something wrong there.
ALL I can think of is maybe the ECM pinout is different. On the 87's 7170 ECM the MAT is connected to A11. Can someone please verify that the 85 ECM is the same? Any ideas?
The Fiero Engine Control Module (ECM) was used in several GM cars besides the Fiero but the PROM (Programmable Read Only Memory) chip within the ECM is unique to the Fiero. If an ECM is salvaged from another vehicle and installed in a Fiero, be sure to install the correct Fiero PROM. The PROM is unique for each engine/transmission combination. A PROM from a Fiero V-6 with manual transmission will not work in a Fiero V-6 with automatic transmission. Also, a PROM may not swap between years even if the engine/transmission combination is the same.
The cars below have ECMs that will swap into the Fiero.
-------------------------------------------------------------------------------- '85 2.8L: This ECM is unique to the 1985 Fiero. -------------------------------------------------------------------------------- '86-88 2.8L: This ECM is unique to the 1986-88 Fiero.
2.8L ECM is the 12276870 or 7707 used in the MAF 2.8L engines (Camaro, FB, FWD cars in 85/86.)
Same ECM hardware but difference embedded program code and thus different ALDL data stream. The 6869 and 7170 used in the Fiero is the same stream but different from the 6870. The 6869/7170 stream is unique to those.
[This message has been edited by TK (edited 05-11-2009).]
IP: Logged
03:31 PM
fierosound Member
Posts: 15217 From: Calgary, Canada Registered: Nov 1999
2.8L ECM is the 12276870 or 7707 used in the MAF 2.8L engines (Camaro, FB, FWD cars in 85/86.)
Same ECM hardware but difference embedded program code and thus different ALDL data stream. The 6869 and 7170 used in the Fiero is the same stream but different from the 6870. The 6869/7170 stream is unique to those.
Thanks TK. Could you tell me why Advance shows 88.58 degrees at idle ?? Shouldn't this be the 10 degrees that the timing is set at?
[This message has been edited by fierosound (edited 05-11-2009).]
IP: Logged
05:07 PM
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
The timing advance that the ECM uses is different from the timing advance that you set with the distributer. The distributer sets the "base timing advance" (which doesn't change), and the ECM also adjusts the timing advance on the fly. So, for example, if you have the distributer set for 10° BTDC, and the ECM commands 20° BTDC, the total timing advance will be 30° BTDC.
Although, 80° BTDC seems pretty excessive.
IP: Logged
06:26 PM
tjm4fun Member
Posts: 3781 From: Long Island, NY USA Registered: Feb 2006
If you are showing an 80 advance at idle, then I have to suspect that you have an issue with your aldl setup. there is no way that there will EVER be 80 degrees of advance. you have to verify that your setup is correct, and that your ecm is really whaqt you think it is. then go from there.
If you are showing an 80 advance at idle, then I have to suspect that you have an issue with your aldl setup. there is no way that there will EVER be 80 degrees of advance.
.
It only shows 80+ degrees at idle. When the throttle is blipped or held down, it then shows values more in line with what it should be in the 24-30 degree range.
IP: Logged
12:50 AM
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
Since WinALDL gives correct readings when you use the '87 V6 setting, just go with that. It doesn't really matter what ECM your computer thinks it's connecting to, as long as you get accurate data.
IP: Logged
01:39 PM
fierosound Member
Posts: 15217 From: Calgary, Canada Registered: Nov 1999
