Help me understand this Datamaster Scan
Thread Starter
Instructor
Joined: Jan 2003
Posts: 108
Likes: 0
From: Virginia Beach Virginia
Help me understand this Datamaster Scan
Forum,
I’m new to ECM/PCM scanning. This is my first. I’m looking for inputs on my Datamaster Scan (Version 3.5.1). This scan was all done at idle. I uploaded 3 pictures with the beginning, middle, and end of the scan. In the beginning all is smooth until my spark advance goes nuts and the idle gets rather unsteady.
Car:
89 Coupe All Stock
Problem:
After the car warms up for a minute the idle is rough. Constant rise and fall. Vibrations
What I notice in my scan:
AFGS is High…..7.7 – 11. Should be 4 – 7.
Spark Advance goes nuts… Rapid and constant flucuations
L and S Term Counts drop. S returns but L stays at 108…. Should be 118 – 138.
O2 Volt goes nuts…Rapid and constant flucuations.
I’ve given this to you guys because I don’t know exactly what it’s telling me.
Any Theories?
Thanks
Big *****
I’m new to ECM/PCM scanning. This is my first. I’m looking for inputs on my Datamaster Scan (Version 3.5.1). This scan was all done at idle. I uploaded 3 pictures with the beginning, middle, and end of the scan. In the beginning all is smooth until my spark advance goes nuts and the idle gets rather unsteady.
Car:
89 Coupe All Stock
Problem:
After the car warms up for a minute the idle is rough. Constant rise and fall. Vibrations
What I notice in my scan:
AFGS is High…..7.7 – 11. Should be 4 – 7.
Spark Advance goes nuts… Rapid and constant flucuations
L and S Term Counts drop. S returns but L stays at 108…. Should be 118 – 138.
O2 Volt goes nuts…Rapid and constant flucuations.
I’ve given this to you guys because I don’t know exactly what it’s telling me.
Any Theories?
Thanks
Big *****
Thread Starter
Instructor
Joined: Jan 2003
Posts: 108
Likes: 0
From: Virginia Beach Virginia
Sorry about the pictures. I don't know what happen. I inserted links. Copy and paste these links into your browser to view. I can't seem to upload the pictures. Sorry Again.
*****
http://www2.snapfish.com/slideshow/A...34/t_=34584634
http://www2.snapfish.com/slideshow/A...34/t_=34584634
http://www2.snapfish.com/slideshow/A...34/t_=34584634
*****
http://www2.snapfish.com/slideshow/A...34/t_=34584634
http://www2.snapfish.com/slideshow/A...34/t_=34584634
http://www2.snapfish.com/slideshow/A...34/t_=34584634
Race Director
Joined: Sep 2003
Posts: 16,839
Likes: 341
From: Database Error Indiana
Big, the O2 #s are supposed to do that. 
The 108 on the blm means its running rich. Does the exhaust smell rich ?? The screen shots in open loop dont tell much. Its closed loop that counts. Maybe some one else has some ideas. I am thinking maybe leaky injectors or FP regulator. Have you checked fuel pressure?
The 108 on the blm means its running rich. Does the exhaust smell rich ?? The screen shots in open loop dont tell much. Its closed loop that counts. Maybe some one else has some ideas. I am thinking maybe leaky injectors or FP regulator. Have you checked fuel pressure?
Melting Slicks
Joined: Aug 2003
Posts: 3,420
Likes: 408
From: Lakeville MI
The snap shots don't reveal too much information, but here's the obvious:
It appears to be pretty rich in closed loop with the BLM sitting on the 108 lower limit. The ecm is doing all it can to pull fuel.
The MAF flow also appears to be a bit high but not terribly so (it appears to be 8.4 gm/sec at 750 rpm), which is also consistent with the rich blm. I normally expect to see about 1 gm/sec/100 rpm. Too much measured airflow results in too much fueling. The low blm is trying to compensate for this.
Go for a drive at various speed and load conditions and get some data to fill in the histogram. This will give you a good idea if its running rich or lean overall.
If its rich everywhere, consider reducing the fuel pressure by a psi or 2 and re-evaluate.
It appears to be pretty rich in closed loop with the BLM sitting on the 108 lower limit. The ecm is doing all it can to pull fuel.
The MAF flow also appears to be a bit high but not terribly so (it appears to be 8.4 gm/sec at 750 rpm), which is also consistent with the rich blm. I normally expect to see about 1 gm/sec/100 rpm. Too much measured airflow results in too much fueling. The low blm is trying to compensate for this.
Go for a drive at various speed and load conditions and get some data to fill in the histogram. This will give you a good idea if its running rich or lean overall.
If its rich everywhere, consider reducing the fuel pressure by a psi or 2 and re-evaluate.
Thread Starter
Instructor
Joined: Jan 2003
Posts: 108
Likes: 0
From: Virginia Beach Virginia
The car is running rich. I knew that before I scanned it. I can smell it. I don't know what could cause it. I figure I have one key problem which is causing several readings to be out of tolerance. Question is "What's the Key Problem"
* When I first start the car it runs smooth for a minute or two. Then after is warms a bit I get erratic idle and vibration.*
Vacuum is Good
EGR is Good
PCV is Good
Inspected and cleaned Plugs
Big *****
* When I first start the car it runs smooth for a minute or two. Then after is warms a bit I get erratic idle and vibration.*
Vacuum is Good
EGR is Good
PCV is Good
Inspected and cleaned Plugs
Big *****
Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
because it's only a snap shot it is near impossible to say, however I can say in Open loop it is a bit lean at 15.7. The shot of closed while displaying 108 blm shows a 800+ 02 reading. I know you stated 02 is moving quite a bit, but does it do that when in closed loop. If it is hanging around that 800 mark and not fluctuating rapidly, that could be a syptom of a bad 02 sensor which can cause a rich condition. Cross counts should be clicking off quickly, but, if not would be another reference point. Pulse width doesn't appear high, other questions would be where is the fuel pressure set at or has it been increased.
However my first guess from this amount of data, is to have a closer look at the 02.
However my first guess from this amount of data, is to have a closer look at the 02.
Le Mans Master
Joined: Feb 1999
Posts: 9,959
Likes: 40
From: South Carolina
St. Jude Donor '03 & '05
Check mechanicals. Check your IAC. It will not throw codes, but will just die, or run bad as many have found. Scanning only shows what the ecm is telling it to do. It will make your car run like its rich as extra air is coming in acting like a vacuum leak.
http://shbox.com/1/iac2.jpg
http://shbox.com/1/iac2.jpg
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Melting Slicks
Joined: Apr 2003
Posts: 2,150
Likes: 6
From: NS
It doesn't sound like the O2 sensor to me because they are telling the PCM it's rich, which the owner says it is. Since it runs good in open loop off the VE tables my guess would be a bad MAF sensor? Hard to tell without comparing his scans to a known good one.
