Alright I changed the MAT table and plugged the leak and the BLMs HAVE come down. I'll attach a log. (hopefully it works this time)
The jerky driving has not stopped or lessened at all. It really feels like a misfire, It's just weird to me that I only feel it at low-mid throttle.
Although the fact that the BLMs have come down (although they are still high) and the problem hasn't changed make me think its not tuning-related. What do you think?

 

Can you email me your xdl file and your latest bin. Looking at the csv, it seems like the BLMs are still very high. I want to play the log and look at the BLM history table.

BTW, I'd also reset the ECM by removing battery power, before taking the log. That way you don't have residual high BLMs potentially corrupting the data.

 

They are still very high. However they are no longer pinned at 160. I'll email you the bin and log. All I did was change the MAT table in the bin (and plug the exhaust leak). I did also reset the ECM before taking the log, although I let the car idle until it went into closed loop before I started the recording.

 

Re-reading this thread...

Looks like you also removed the AIR system. You need to disable it in the bin as well. When the AIR system comes on, the ECM applies a 100mV offset to the O2 voltage reading. That could also be throwing off your BLMs.

In the Constants section, find the parameter AIR, Divert AIR if Coolant Temp < and set it to the maximum which I think is 300F. This will ensure the ECM never attempts to activate the AIR system. For good measure too, find the parameter AIR, o2 Rich/Lean Reduction Volts when AIR Diverted and set it to 0 (it's 100 mV from the factory).

The injector offsets in your bin are still the factory values, but they're not that far off from the Bosch-III offsets for the p/n you have... just a few microseconds. Not enough to drive your BLMs to 160...

I will say your BLMs are swinging wildly. Wondering if has to do with when the AIR system is being commanded on and off.

Except for the relocated MAT, the removed EGR and AIR, and the injectors... is there anything else that you know of that's non-stock?

If everything else is stock, and this final change to the AIR values doesn't solve your issue, then yeah I would think that your issues are not tuning related.

The only other thing I can think of is your fuel pressure is varying while driving (not sure if you've been able to check that). If your pressure regulator is intermittent, that could explain the swinging fuel trims and the jerky feel at mid/low throttle.

 

I will address the air system. I also can change the injector offsets. Can you post a picture of the offset table? I'm not sure how to open/read the file you sent a while ago. The only way I could figure was to open it in notepad and it was just a bunch of symbols.

The car has straight pipes, (but stock headers), and it has aftermarket heads (Brodix IK180). I didn't mention the heads because I don't think they are making any difference. They've been on about a year, the compression ratio is the same, and the intake manifold, runners, and plenum are stock. (I did not replace the rockers/pushrods/lifters either). I replaced them for maintenance more than performance. It also has the 4-wire O2 as I mentioned earlier. Besides those things, to my knowledge everything is stock. There are several things that were broken that I replaced, but just with stock replacements.
I will say the plug wires are new and were put on the car after the fuel injector issue began, so they could be grounding somewhere. If they are, it's either not happening at idle or not enough for me to see.

It's kind of hard for me to check fuel pressure while I'm driving. The hose on my pressure gauge isn't long enough to come out of the hood. So I haven't checked it. If tuning doesn't fix it, I can find a way to check it. However, the problem seems too consistent to me to be an intermittent issue. It's very consistent with when and how it happens. I hope its a tuning problem.

 

I think I'll also try driving the car in open loop, before it warms up and see how it acts. So far I've only driven it after its up to OT

 

yeah, the heads aren't going to make a difference here.

But, 4-wire O2... hmmmm...

So the thing to know about the O2 circuit on 8D (7727 ECM for Vettes, 7730 ECM for Camaros) is that the ECM's O2 sensor ground is not actually the ground of the O2 sensor. It's an "implied" ground by assuming that the grounding of the sensor body to the exhaust manifold is good, and that the manifold's ground to the engine is good.

The O2 sensor ground wire coming from the ECM is merely connected to the engine.

This can become a problem if the ground path becomes higher resistance between the O2 sensor and the physical grounding point of that O2 ground reference wire from the ECM.

I too have a 4-wire O2, but I actually took the sensor ground from the O2 and hooked it up to that tan wire, such that the ground reference in the ECM is the true sensor ground.

The heater ground can be connected anywhere on chassis or engine as it's not that critical.

https://www.gearhead-efi.com/gearhea...727V8TPI-3.jpg

At the top, see the oxygen sensor circuit.

So the question is where did you tie the O2 sensor ground coming off the 4-wire?

 

What you might do is check the resistance between pin A22 at the ECM and wherever you tied your O2 sensor ground to.

It shouldn't be more than a couple of milliohms.

Given the heads have been changed and stuff like that, not sure where all the factory ground wires ended up.

 

Sorry, i was wrong its a 3-wire, not a 4-wire sensor. I bought a harness adapter to plug it in. The heating element is grounded to the exhaust manifold, and the O2 signal wire plugs into the original 1-wire harness (to the ECM). So the circuit should operate just as it did stock, only the O2 is heated. Sorry, I thought it was 4 wires but I was mistaken.

This is the harness I'm using.

 

I still think it's a worthwhile endeavor to check the resistance like I mentioned.

Check from the O2 sensor body to the A22 pin at the ECM connector. You can unplug that connector from the ECM to make that measurement as we're only proving out the wiring harness.

A bad ground on this circuit will cause an incorrect voltage reading off the O2 sensor.

 

Here are the voltage offsets for 280155700 injectors...

 

I'll check it. I won't be able to tonight. Thanks for the offsets, I'll get those in the computer as soon as I have the time.

 

I've been looking at my VE tables. I had adjusted them some time ago and have been using that bin as the basis for everything I've been doing recently. I should have mentioned this before -- I just didn't think about it. I was focused on mechanical modifications.
Well I compared the VE tables in my bin to the stock bin. And it looks like I actually removed fuel at part throttle. Again, this tuning was done a long time ago, and my memory is not good. I don't want to change 100 things at once, so I'm first going to load the tune with the AIR disabled and the injector offsets adjusted. I've already made the bin for that I just haven't yet flashed the chip. If that doesn't bring the BLMs down I think I will put the stock VE tables back in, and go from there.
I'll attach a picture of the comparison.

This is the difference between the stock bin and the bin I'm using now. The negative numbers represent higher values in the stock bin.

I'm sure you've found out by now, but I'm not a tuner. Every time I have to mess with the computer I wish it just had a carb. Mechanical stuff comes easy to me, electrical and software does not. So I apologize for being so dull when it comes to all this stuff.

 

Sounds good. Yeah, 160/128 = ~25% So it would take at least a 25% change in the VE tables to get your BLM's up to ~160. Maybe with your VE table mods and cleaning up these other things with the MAT and AIR and stuff, we can get this thing stabilized.

BTW, if/when you get the BLM thing sorted out, what you can do is use my VE tuner. It uses the BLM history tables in TP to dial in your VE tables. Usually within a couple of passes you can it very close. That's if you want to dial in the VE tables after you get past this troubleshooting excercise.

I'll email it along with my ADX file which has the history table set up for it.

 

that would be excellent thank you. I’m thinking I’ll be able to get this chip burned today and see how it does

 

Alright good news. The VE table brought the BLM right down. I'll email you the bin and log again so you can see it.

Unfortunately, the stumbling has not changed. So at this point its probably not in the tune I think.

My fear is that my new injectors are clogged. The misfire is somewhat similar to my previous clogged injector experience, although that got worse with load, and would only get better if the car was driven around 3000RPM with minimal pedal input. Now it only comes around under part throttle, and is smooth under load. I didn't put the injectors on until the fuel coming through was clear, but it may not have been enough. I'm not sure how to diagnose it either, as it doesn't happen in neutral.

I got your email btw, I appreciate that very much, and I'll put it to use.

 

Ok, I'll take a look at your bin and log when you send it.

 

I sent it yesterday. I guess it didn't go through. sending it again now.

 

Dude, that looks WAY better....

You can pretty much leave the VE tables alone at this point if you wanted to. The BLMs are still swinging a little bit, but it's within the range I'd normally expect.. just a few points either way.

In terms of the stumbling...

If you're sure your ignition system is in good working order.. No fouled plugs, plug wires are good, coil is good, etc...

It could still be tuning related in terms of the heads and the straight pipes wanting a little more fuel at low throttle. Most likely you're hitting a lean spot on as the MAP varies a bit.

What I would try is to increase your delta-MAP accelerator enrichment (AE). The top table is the factory bin and what you're running. The bottom table is from a 92-93 LT1. The short runner manifolds like a lot more AE. While you still have a long runner TPI, your modifications may be enough to warrant a little more fuel in this region. You could start incrementally increasing the values in the low-MAP regions to see if that helps. The reason I'm posing the LT1 values is that it's kind of an upper bound on where you should be. If you find that you're going beyond the LT1 values and its not helping, then the problem is probably somewhere else.


Another thing you can try is to disable the Inv MAT table altogether. It may cause your BLMs to go down a bit, but if it solves your stumbling issue, you can use my VE tuner to get the BLMs back in line. In the switches, simply uncheck the flag for the Inv MAT table. This can help rule out your relocated MAT sensor as the cause.

 

One other thing I'm noticing is that you're getting a lot of knock retard in areas that I wouldn't expect to see any... If its false knock, the ECM is going to retard timing unnecessarily, which I'm actually seeing happen in your data. The highly variable timing could also be contributing to your stumbling...

What knock sensor are you running? If you're not sure what the previous owner installed and you can't identify it, you might want to consider getting a true Delco sensor for your year Corvette.

Also, I wonder if its installed to tight (which makes them more sensitive). These things are supposed to be installed to a specific torque (14 ftlb)

I battled false knock for a bit and when I changed out my old Pep Boys special for a true Delco and then re-torqued to the right spec, it cleared right up.