OBDII Scan - What to Look For?
 

So my scan cable didnt arrive as early as I would have liked, but it has finally arrived and I will be scanning the car tonight. The problem is, I have no clue what to look for, or what parameters certain sensors should be operating within.

To give a general rundown of what the car is doing without going into as much detail as the last post:

Car starts and idles great. It will idle in the garage and rev freely with no hiccups at all for 5, 10, 15 minutes or however long I let it idle for. When I back it out of the driveway and go for a drive, the car pulls hard initially but starts to lose power linearly over time, with it eventually wanting to drop below idle and die when i let off the gas after a minute or so if driving. The car does'nt throw any codes, and there doesn't appear to be any misfires, the car just wants to die unless I play with the throttle for a few seconds. If I let it die then start it back up, the idle will fluctuate for a split second then go back to normal and I have full power again until I put it in gear and start to drive it again.

Recent Repairs:
-Entire fuel system replaced minus the injectors which were sent off and cleaned/flow tested. According to a fuel pressure gauge that I hooked up, I have 35+ PSI at all times, during driving and during the stumbling/stall.
-New plugs and wires
-Checked all vacuum lines

So this is where I need ya'lls help. I'll be checking readings for the MAP, MAF, O2's, IAT's, Ltrims, Strims, but I'm not entirely certain what the readings for each of those should be or what I should be looking for when scanning the car. Can anybody give some helpful information on what the operating parameters are for each, or at least what to look for when viewing the live readings?

I will make a data-log if that helps, but what parameters would be helpful to log and at what point during the drive?

Any help is greatly appreciated guys!

That is FANTASTIC, big thanks!

VERY helpful 411 Rob, thanks

Op

STFT should be 0 or a very low # if they do change. If they are + or - 25 than you are either running big time rich or lean depending on if the # is preceded by a + or -. My scanner only notes the - so the plus is just the #

A + condition means rich and is often caused by a vacuum leak....BUT not all the time.

I chased and checked every sensor and vacuum leak possibility and my issue turned out to be a bad ICM. All symptoms were not typical of a failing ICM nor does my scan tool even monitor it. IDK if any scanner does. The bad ICM did however cause my STFT to be pegged

Not saying your issue is ICM (although may be)

Fred (Injuneer) gets all the credit.

Thanks, Ill keep an eye on those.

Oh MAN, I dont even know where to start.

SO there are two options for STFT: Short Term Fuel % Trim, and Short Term Fuel Trim. Which should move less than 1?

Regardless, my STFT(not percent) is all over the place. At 30000 RPM's im getting +20 on one bank and +13 on the other. Driving steady at 1500 RPM's "Bank 1" is -7 and "Bank 2" is +3. Maybe the car hasnt relearned the heads and cam after it sat so long, I dunno.



Mass Airflow numbers appear to be reading correctly at 1.3 lb/min at idle and raising appropriately.

Attached is a 10 second data log with me starting in first, shifting to second, and accelerating through second. Does this look correct.

https://cimg0.ibsrv.net/gimg/ls1tech...9e203726ac.jpg