New to TBI Data logging and such.

**georgeb** · 06-15-2015

Ok, I drove the beast to work today and idled in the lot for a few minuets before recording this log. I goes into closed loop while I am driving or off idle but goes back open at idle. It also cools down a bit when idling......

**georgeb** · 06-16-2015

It also seems rich at idle. The exhaust is rather strong smelling and makes my eyes water if I idle in the shop for any amount of time. I don't have cats on the truck if that makes a difference. The doors are open of course.

**jim_in_dorris** · 06-16-2015

Okay, I see a couple of things. First, your IAC at warmed up idle is 0 steps. That usually means that you either have a vacuum leak, or you need to close the throttle blades a 1/4 turn. the second thing I notice is that yes you are in open loop, and your factory bin might be an open loop idle bin. Nothing really wrong with that, it just makes tuning idle a little difficult. In open loop, we can't see what fuel corrections are needed, because the BLM's and INT's are essentially locked. try to get your IAC steps into the 10 to 20 range then relog.

**georgeb** · 06-16-2015

OK, I closed the throttle plates about 1/3 of a turn on the stop screw to get to the IAC counts I have. I may need to re-bush my throttle shaft at some point because I know the plates are almost to the point they want to stick in the bore and I have some noticeable play in the shaft. I also noticed the plates seem to have corroded along the lower edge (the side that travels down as the throttle is opened). This poor thing was really neglected by the previous owner.
Again, thanks so much for your help! I have learned a great deal already!

**jim_in_dorris** · 06-17-2015

ok, the next thing you may want to do is see what your fuel pressure is. Because you are rich at idle, it may be okay, but you should still test it. Then do a log warmed up and driving normally. That will give a good indication of what is going on

**georgeb** · 06-17-2015

Ok, will do. I will need to get a fitting for the fuel pressure tho. I was thinking of a permanent gauge anyway.

**georgeb** · 06-18-2015

One more thing. I currently have the timing set at 8 deg advanced over the spec 0 deg. It seems to run better there. I assume it would be best to set it back a 0 correct?

**jim_in_dorris** · 06-19-2015

yes it would. What happens is that the 8 degrees you have set in timing gets compensated for by the tune, and so you don't gain anything. If it really runs better at 8 degrees, it would be best to actually put it in the tune.2-4 degrees doesn't matter too much, but beyond that it does. I can't remember correctly, but i think it takes out that 8 degrees of timing in the tune. It would be like pulling timing by 8 degrees across the board. the best way to play with timing is in the tune.

**georgeb** · 06-20-2015

Ok, here is one of a drive out of town and back with some in town driving. I have the timing back at 0 DEG and I measured my fuel pressure at 10-11 PSI.

**jim_in_dorris** · 06-20-2015

All in all, not too bad. At a steady cruise your BLM is right where you want it. However when you stab the accelerator, you are going lean. The first thing I would look at is your injectors. At a dead idle, are they dripping? does the spray pattern look good? when you hit the accelerator (in park) does the spray pattern look good and does it appear to add more fuel? If your injectors look good, I would consider bumping your fuel pressure. Take your injector pod off, and add a washer to bump it to 12-13 #'s and see if your hard acceleration BLMs are a little richer. I wouldn't worry too much as long as you aren't racing, I ran leaner than that for years without a problem.

**georgeb** · 06-21-2015

Ok, I will check those things. The injector spray looks ok at idle with no dripping however I think I may try to clean them anyway. I will look for it to add more when I open the throttle. I am also going to try the washer add for more fuel pressure and see if it comes up a bit. When you have the time could you explain how you determined the lean condition? I imagine you saw the blm drop off when the throttle is opened and then recover. I don't fully understand how this all works but in order for me to continue with a TBI system I need to understand it and be able to tune it. I am just a bit spoiled by having the ability to tune my Q-jet. I have learned a great deal already and really appreciate all your help!!!!!

**jim_in_dorris** · 06-21-2015

anything above 128 in the BLM's (long term fueling) is lean (not really too probamatic until about 138, and not serious until above 145. below 128 is rich. The BLM change on throttle stab is AE (accel enrichment, think pump shot on a carb.). That is an area that frequently needs work to make a tune work like a gearhead wants. The other is DFCO, decell fuel cut off. when you get ready to tune your truck, there is an excel file that Dave W. built that lets you make fuel corrections to the tune.

**georgeb** · 07-17-2015

I know I let this thread go dead for a bit but I have switched gears to working on the body of the truck. I picked up a southern cab and am in the process of prepping it for paint. Wont get it done before the snow flies tho. Anyway after running this truck with the initial timing at zero degrees since my last post I have become convinced that it runs like crap set there so I put it up at eight degrees. WOW, it runs so much better there. Pretty sure it's masking the issue but I'm good with it for now. Not sure what it did for my elusive surge during warmup that goes away at operating temperature. But I will run it in the drivway to see. I currently have no idea what to look at to locate the problem but I suspect the map sensor may be flaky. I need to try and diagnose it before I up and replace it. Well for now I am on body work and will most likely return to the drivability issues this fall. I need to replace the engine because of a bad block casting but would like to know if I can get the TBI to work properly before I make the change. Partly because I am inclined to ditch the TBI for a carb if I can't get it to run correctly. Thanks to all who helped! I will be back to pick up on this in the fall.

**georgeb** · 08-10-2015

$42-1227747-V5.2.adx (85.7 KB, 524 views)
$42-1227747-V5.9.3.xdf (344.8 KB, 612 views)

I have a question. I was attempting to connect to a 91 suburban using these files to view live data but was unable to do so. Are these the wrong files for connecting to that truck? Did I need a different definition file?

**fastacton** · 08-11-2015

Did the Suburban happen to have a 4L80E? Normally you shouldn't have a problem using those files unless it has the '7060 ECM ('91-93 with 4L80E) in it.