New guy, idle issues on a cam swap lq4

[72cutlass]

Backstory, wrapping up a very long saga of an LS Swap. ECU was "Tuned" by a very prominent company and person. I wont put them on blast because this project has dragged out years and life goes on. Engine was running terribly and smoking like a train. I thought the amazon special 8.1 injectors were at fault, bought new "42lb" ones from FIC (connection), along with the fuel pressure regulator and it was still smoking. At that point I said F' it and bought HPtuners today and within about 5 minutes realized suspicions were correct and the stock injectors were in the tune, so it was dumping double or more the needed fuel. Oil was full of gas, spark plugs were black, etc. On the upside my fears that the smoke was rings or valve seals was alleviated. "tune" wise it looks bone stock from what I can tell. VATS and standalone modification were done by LT1Swap Brent prior to a quick refresh and cam swap.

Specs:
LQ4, Stage 3 truck cam, headers, dual 2.5 exhaust in a GM A-Body. 42lb FIC injectors, actually flow 50ish at 58lbs, truck rails and return style regulator. 700r4 transmission, so no tcu components. I've also attached that spreadsheet I received.

Where I am now: I changed the injector data with the data supplied by FIC. No smoke and it idles better but is not steady and has popping from the exhaust. What I've attached here are the tune as received and the iterations thus far along with a long of the latest idle. There's something up with B2S1 o2, and I replaced it but it remains stuck at 1v. I'll be troubleshooting that for a possible harness issue next weekend. If I understand things correctly though in open loop which is it currently is, it is not using the o2 sensors so the bad idle and occasional pop would be tied to the tune, either not enough timing resulting in fuel burning in the exhaust, or it is lean popping.

I really don't plan to get to heavy in this, just need it idle okay and drive like a useable car for right now. I'm usually pretty good with software and learning things but definitely in over my head for the moment. Within a year I'll either be doing heads/cam or a supercharger and at that point get it over to a shop on a dyno and try to push all the power out it can.

I've been saving as I go with rev numbers to avoid f'ing anything up irreversibly. Attachments have revision numbers. I'm pretty busy during the week so it'll be next weekend likely before I can get anymore log data up but for anyone willing to help I will certainly do my best to get any log info I can when I can.

As-Received is as received
Rev1 I changed the injector flow rates
Rev2 I changed the volts and offsets per the spreadsheet
Rev3 I went up 10% on the idle airflow. It seems to be lean and a larger cam, so I figured upping the idle airflow would get it richer.

Log is after Rev3 was written to the ecu.

Thanks

[blindsquirrel]

Returnless fuel system with constant 58 PSI, verified with a reliable mechanical gauge at the rail? And it maintains 58 PSI even on snap throttle and while driving under load?

You forgot to put in the Short Pulse Adder data from the sheet.

Fix whatever's wrong with the upstream O2s and put it in closed loop. The steady 1108mV on B2S1 is a short to voltage somewhere, to find out if it's in the sensor or in the harness, unplug that sensor and key-on; if B2S1 goes to the ~450mV bias voltage and goes back up to 1100 when you plug it back in, it's the sensor. If it stays at 1100 no matter what, it's in the harness.

Log also has a P0200 - Injector Circuit (pending)

[72cutlass]

First off thanks for responding.

Every reason to believe fuel pressure is good, brand new regulator and walbro. Will confirm this evening with a gauge though.

O2 pretty sure it's a short to voltage on that sensor, simply because I had the one that was in there when it was being flooded, then a new one now. I'll do the confirmation check as you described the. Look for the short with a meter this weekend.

On the short pulse adder I remember now, I couldn't figure out what units it was in. So what units is on the spreadsheet?

[blindsquirrel]

Short Pulse Adder is just find the one that has the same axis labels as your tune file, then copy and paste. Units are milliseconds, I can't imagine how you would ever find a reason to change it to anything else, considering what that table is.

To me, 'brand new regulator and walbro' would mean just the opposite - no reason to assume it's any good and only trust it after checking. But I'm weird I guess.

[blindsquirrel]

Also... 'new regulator' doesn't specify whether it is manifold referenced or nonreferenced/returnless. The two types need the injector data set up different.

[72cutlass]

Short Pulse Adder is just find the one that has the same axis labels as your tune file, then copy and paste. Units are milliseconds, I can't imagine how you would ever find a reason to change it to anything else, considering what that table is.

To me, 'brand new regulator and walbro' would mean just the opposite - no reason to assume it's any good and only trust it after checking. But I'm weird I guess.

I did not put it in the first post and will edit to reflect, but this is on stock truck fuel rails with a return.

Given my history with this car I should not be making assumptions like fuel pressure being good I suppose and will confirm with a gauge. I have one sitting 3 feet from the fender, just to hardheaded to check it.

I understand the offset unit now is ms, not sure how I overlooked that yesterday but was day 1 on a long journey. I remember looking at the numbers on the spreadsheet and they were so different than the ones in the table I was worried I may have had the wrong units pulled up. I'll get that in there and report back in a few days when I've had time to chase down the o2 issue and confirm fuel pressure.

[blindsquirrel]

So, the full data in the datasheets is assuming a returnless/nonreferenced fuel system. To use the data with a referenced/return style, you use ONLY the data in the "0 kPa" column, for both the flow rate AND the offset vs volts vs VAC, and paste that column into every column all the way across both tables. See the injector spreadsheet in my sig for very clear examples of what those tables look like, comparing referenced to returnless.

[Alvin]

Short Pulse Adder is just find the one that has the same axis labels as your tune file, then copy and paste. Units are milliseconds, I can't imagine how you would ever find a reason to change it to anything else, considering what that table is.

To me, 'brand new regulator and walbro' would mean just the opposite - no reason to assume it's any good and only trust it after checking. But I'm weird I guess.

I had a guy argue with me cause I called him to tell him he had no fuel pressure at all.
"thats impossible I just put a new pump in before coming there"

I said I don't care if it drove to egypt and back.. it has no fuel pressure now.

LOL carry on.

[Alvin]

This has a injector circuit code pending.

Along with a suspiciously high 02 reading on one side. Since this is a swap harness I'd take the time to pinout all the injectors back to ECM. Make sure all the pink wires have 12 v ign.. etc.


That code isn't one that pops up without good reason.+

[RDF1]

I had a guy argue with me cause I called him to tell him he had no fuel pressure at all.
"thats impossible I just put a new pump in before coming there"

I said I don't care if it drove to egypt and back.. it has no fuel pressure now.

LOL carry on.

How many times do you have to tell people that "Just because its new doesnt mean its good"?

[72cutlass]

How many times do you have to tell people that "Just because its new doesnt mean its good"?

Trust me I get it. If things can go wrong, it'll go wrong on this car.

Thanks for all the help, I'll do my best to figure out the o2 and fuel injector error issue, along with verifying the fuel pressure this weekend. It's not great but it's already far better than it was. I suspect the ECU was never tuned by the shop that did the tune on it and it went from the to do pile to the done pile accidently. I have that kind of luck in life with this car. On the initial look it seems like all the parameters in the as-received.hpt file were for a totally stock engine. Things happen, it just sucks to have wasted that money.

Can I just pull the pin out for the high signal side run a new wire and be done with it? If it is still showing 1.1 at that point then the ECU would be the source of excess voltage right?

This has a injector circuit code pending.

Along with a suspiciously high 02 reading on one side. Since this is a swap harness I'd take the time to pinout all the injectors back to ECM. Make sure all the pink wires have 12 v ign.. etc.


That code isn't one that pops up without good reason.+

Hypothetically here if you are dealing with a completely incompetent jackass what would be the way to check the issue on that injector? You know just just hypothetically speaking... Do it with the motor running or just key-on?

[gtstorey]

Hypothetically here if you are dealing with a completely incompetent jackass what would be the way to check the issue on that injector?

I'd take the time to pinout all the injectors back to ECM. Make sure all the pink wires have 12 v ign.. etc.

[72cutlass]

The "etc." was the hang up. Etc means "and other similar things" so am I only confirming 12v on all pinks for the injectors or other wires too?. "Etc." literally means "and others" I'm just really paranoid and want to make sure I'm doing this correctly right now.

Also key on, or running?

[blindsquirrel]

You don't verify pinouts with the engine running. You need service manuals, with diagnostics and pinouts and diagrams. You study the diagram, find this wire goes from *here* to *there*, then look at the harness and make sure that is the right wire and that it goes from the right spot at one end to the right spot on the other end.

[72cutlass]

You don't verify pinouts with the engine running. You need service manuals, with diagnostics and pinouts and diagrams. You study the diagram, find this wire goes from *here* to *there*, then look at the harness and make sure that is the right wire and that it goes from the right spot at one end to the right spot on the other end.

Got it. I did the harness years ago myself. Familiar with the pin outs but not the when and how to diagnosis the problems. Used lt1swap back in the day to get it done. Started this project way back before these cheap swap harnesses were a thing. Confirming the components are wired right is simple enough for me. I'm very soft on the troubleshooting basics like when the wires should or should not have voltage and how much they should be reading when though.

The o2 wiring is 100% correct from a this pin to that connector stand point, verified Saturday. Now if there is a short and where it's coming from is where I'm on the struggle bus of how to actually verify. Like check which wire, when, and how much voltage or resistance. That sort of stuff I need someone to spoon-feed me at least for one circuit to understand.

I did the whole chassis harness and everything works like a charm. But that is more straightforward as I know I'm always looking for 12v and it's when this or that switch is hit.

Hope that helps explain where I'm at knowledge wise.

[blindsquirrel]

Does it stay at 1108mV with that sensor unplugged?

The PCM isn't capable of reading more than 1.1-1.2 volts on the O2 signal pins, so it could have 12 or 14 or 5 volts coming from another wire and the scanner would still only show ~1100mV. If it stays high with the sensor unplugged, measure voltage at the O2 connector signal hi terminal in the harness. That will give you an idea of which circuit it might be shorted to.

[72cutlass]

Does it stay at 1108mV with that sensor unplugged?

The PCM isn't capable of reading more than 1.1-1.2 volts on the O2 signal pins, so it could have 12 or 14 or 5 volts coming from another wire and the scanner would still only show ~1100mV. If it stays high with the sensor unplugged, measure voltage at the O2 connector signal hi terminal in the harness. That will give you an idea of which circuit it might be shorted to.

I'll throw that on the battery of tests to check. I'll check it this weekend. Key on- but car not running, i think it dropped to .088 on the log though. The "good" sensor went to 0.

Say if I check and it's pushing 12v through the signal wire or staying 1.1 when unplugged. Then what? Cut the harness open and visually look for a fray?

[blindsquirrel]

The O2s should read 450mV when unplugged, that is the 'bias voltage', produced inside the PCM. The signals here are tiny tiny, the O2 pulls it lower than 450 when lean and pushes it higher than 450 when rich. On one that's working properly you can touch one finger to the signal pin and another finger to ground or B+, and drive the O2 voltage fully low or fully high, it's that sensitive. They will sometimes leak enough voltage across fully good wire insulation to drive the signal high or low, when conditions are right - length of contact between a hot or ground wire and the signal wire, humidity, maybe a little salt... and the O2 signal goes somewhere it shouldn't.

If it was me, and I found it was still pegged out high with the sensor unplugged, I would unplug the PCM and then see if it still goes high with key-on. Voltage could be from a regular switched IGN wire in the harness. This speculation is all kinda silly though before you know what it does with just the sensor unplugged.

[72cutlass]

Silly speculation or not, that was tremendously helpful in understanding the mechanism I'm dealing with. I'll be back here when I have more information to report.

[blindsquirrel]

I would unplug the PCM and then see if it still goes high with key-on.

clarification: not in the scanner, obvs, since the PCM would be unplugged. Meaning checking voltage at the O2 connector with a DVOM, seeing if it was the same voltage with a DVOM as with the PCM plugged in.