TBI tuning help

[bp71k5]

So I thought i'd start a new thread to make this easier.

I have a TBI with the following symptoms:
1. Consistant ESC code after engine reached operating temp and driving at speed.
2. An intermittant stumble on hard acceleration in high gear.
3. Pinging when engine is under moderate and high load (doesn't happen at idle).

I did another datalog with the truck not moving, but let it idle and brought it up to 3200 rpm a couple times to let it collect enough data.

Here's the BLM and a screenshot of the sensor data at idle. It seems like my trouble is more when the truck is moving and not at idle since the BLM numbers seem pretty close to ok?

Edit: I do not yet know what the fuel pressure is, but am working on checking that in the next few days.

 

[4X4HIGH]

Did you finally get a VSS hooked up properly?

 

[bp71k5]

Yes, I *believe* it is hooked up properly. I don't get any VSS codes anymore and I hooked it up as the instructions told me to. One wire goes to the ECM and the other to ground. (It's a "painless" VSS which doesn't need a buffer module)

Also, are there any other causes for a lean mixture (other than low fuel pressure) I can look for while I wait for my pressure guage to get here?

 

[bp71k5]

I also just checked the spray pattern with a timing light and I'm not quite sure what it should look like.

At idle, both injectors look about the same. It looks like a cone with little tiny droplets of gas. It's not a solid stream.

When I move the throttle, one injector looks the same but the other has a more solid stream at the injector nozzle and then changes to the tiny droplets shape as it gets farther away.

Does anyone have any pictures of what the spray pattern looks like? If anything, I'd think both injectors should look similar?

 

[4X4HIGH]

They should have a nice conical shape and even spray pattern and both injectors should be the same.

A bad 02 sensor could make the engine run rich or lean, bad regulator spring, bad fuel pump, bad injectors or clogged injectors, those are to name a few things.

 

[eagle mark]

They should have a nice conical shape and even spray pattern and both injectors should be the same.

A bad 02 sensor could make the engine run rich or lean, bad regulator spring, bad fuel pump, bad injectors or clogged injectors, those are to name a few things.

Yup what he says.

Is the motor stock? ECM that came with motor?

TPS should be .54 yours is .69

BLM is a little lean even at idle, under load is easy to go lean when there is an issue like low fuel presure, clogged filter or dirty sock in the tank. Won't be able to tell till you get fuel presure. I know every one quotes 9-13 PSI as the manuals say but if it ain't 12-13 it ain't gonna run right.

 

[4X4HIGH]

Any TPS reading under 1 volt is fine. He has a new filter and sock. I built his engine and installed a cam for an 89 blazer with TBI and i sold him the ECM and wiring from an 89 blazer. The only other thing i can think of that could affect him is that the chip in the ECM is for an Auto trans and he's running a manual. We're going to assume for now that the VSS he installed is working properly.

 

[bp71k5]

bad injectors or clogged injectors

Does the fuel injector cleaner stuff at the auto parts store have a chance of fixing clogged injectors?
If you were going to throw a bit of money at it, where would it go knowing my fuel pressure guage is on the way soon? I want to wait to test the fuel pressure and the other stuff before I buy new injectors.

I think my money is on the fuel pressure at the moment. I also did the adjustable regulator modification last night found here: http://www.thirdgen.org/tbi-afpr

I turned up the pressure just a bit to see the difference. Has anyone done that and is there any trouble keeping the screw from turning after a while with the engine vibration?

 

[bp71k5]

So after increasing the fuel pressure the injector spray pattern is noticably different. I'm going to leave it where it is until I can test what it actually is.

I also did another datalog. The engine seems to have a little more guts down low, but I still think I heard pinging.

Since I needed gas, I also filled up the tank with 91 octane instead of 87 this time and took another reading on the way home. During that time I also got my ESC code enabled like I expected. I've attached the datalog from before and after here. It looks like the knock counter went down after the fillup, but I still got a code.

It's hard for me to tell, but is it running any less lean?

 

[eagle mark]

The 87 octane log file looked closer to 128 to me.

 

[bp71k5]

Update:

I did some pretty serious troubleshooting. Ended up replacing the O2 sensor and the MAP sensor. No change in performance but I did discover a few things:

1. My manual tranny makes noise similar to what happens when I bang on the block with a hammer (gently) to simulate a knock. The knock count goes up when I clank on the tranny as well. All that noise in the drivetrain could be causing some of my knock counts to go up.

2. The stumble I have been experiencing is somehow related to the timing being retarted very quickly when the throttle goes from idle to about 1/2 throttle even when the truck is sitting still. Watching the timing mark, I hookup the timing light and turn the throttle up real quick for a second and the timing mark drops down past 0 to about 4-6 ATDC. Once it does this I get the a pop\stumble.

3. When I tap the cylinder head with a hammer, I don't see the timing drop. It could be dropping a little, but the marker fluctuates between 14-17 degrees at idle so it's hard to tell. Maybe the new knock sensor is bad, but that seems unlikely.

Problem #2 concerns me the most since I've never seen the timing change like that on any other car I'd had. Anyone have suggestions for that?

It's starting to feel like I'm chasing my tail. I think I may let it sit and wait for the fuel pressure guage fitting and go from there.

 

[bp71k5]

Since someone pm'd me about this I thought I post what fixed this. Once I got a new chip for the ECM, it worked a lot better. I believe the timing map was way off. The stumble was caused by the timing retarding too much.