When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have a termX on a 78 vette with a 5.3 and a summit stage 1 8719 high lift cam. Car is running pretty good where I'm driving it on the road to figure out all the little issues. This is not my first TermX LS setup as I have one in a 3rd gen firebird with a 5.3 and a turbo. My issue is at light throttle The engine revs/accelerates just fine through the RPM 3k+ through all gears (700r4). But when I give it more throttle say half or heavier after like 2000-2500rpms it like hesitates and breaks up basically falling on its face till I let out or get above that 3000-3500rpms. I also floored it when this happened and the car felt like it had no power but the car feels faster sometimes depending on when I stab the throttle and depending on the gear I'm in. I did a datalog of one of the runs and Its very weird... looks like its dropping out of closed loop and going to open loop? Then when I come off the throttle the closed loop comes back on. I verified the closed loop is enabled but it wasn't set to a min temp or rpm or anything... the closed loop box was just checked off. I set it to come on after 140*F coolant temp just like my other car. I'm not sure what is causing it to randomly drop out of closed loop but looks like it goes rich and maybe thats whats causing it to break up/hesitate and feel dead like RPMS and power don't climb. I'm not the best with the holley data logs but I attached it if someone could take a look. I also adjusted my closed loop learn values from 50/50 to 15/15 as the tune fuel learn table only shows a 5-8% swing. My timing isn't crazy when the break up is happening like 22-25* If I remember. Its also like my fuel lb/flow drops too like its cutting fuel?
Let me know what you think and what would be a good starting point. Like I said its only on med/heavy throttle and the car really drives fine otherwise (maybe a stall here or there every couple of drives) but I still need to adjust and get the IAC below 40 steps at drive idle.
I have a termX on a 78 vette with a 5.3 and a summit stage 1 8719 high lift cam. Car is running pretty good where I'm driving it on the road to figure out all the little issues. This is not my first TermX LS setup as I have one in a 3rd gen firebird with a 5.3 and a turbo. My issue is at light throttle The engine revs/accelerates just fine through the RPM 3k+ through all gears (700r4). But when I give it more throttle say half or heavier after like 2000-2500rpms it like hesitates and breaks up basically falling on its face till I let out or get above that 3000-3500rpms. I also floored it when this happened and the car felt like it had no power but the car feels faster sometimes depending on when I stab the throttle and depending on the gear I'm in. I did a datalog of one of the runs and Its very weird... looks like its dropping out of closed loop and going to open loop? Then when I come off the throttle the closed loop comes back on. I verified the closed loop is enabled but it wasn't set to a min temp or rpm or anything... the closed loop box was just checked off. I set it to come on after 140*F coolant temp just like my other car. I'm not sure what is causing it to randomly drop out of closed loop but looks like it goes rich and maybe thats whats causing it to break up/hesitate and feel dead like RPMS and power don't climb. I'm not the best with the holley data logs but I attached it if someone could take a look. I also adjusted my closed loop learn values from 50/50 to 15/15 as the tune fuel learn table only shows a 5-8% swing. My timing isn't crazy when the break up is happening like 22-25* If I remember. Its also like my fuel lb/flow drops too like its cutting fuel?
Let me know what you think and what would be a good starting point. Like I said its only on med/heavy throttle and the car really drives fine otherwise (maybe a stall here or there every couple of drives) but I still need to adjust and get the IAC below 40 steps at drive idle.
It looks like it has as a misfire on the side the WB02 is on.
Fuel pressure is solid,
It goes open loop on quick throttle transitions. That's why it's important for the fuel table to be actually tuned and not carried by the WB only.
It kind of felt like a miss fire but it seems like its only under decent load more than 1/4 pedal. The WB02 is in the pass side collector on long tubes. I just did custom 8mm wires, TR6 plugs and used GM square coils but they worked before. The fact that it seems like its smooth on light ish throttle makes me think the WB02 is dropping out and going rich. I checked the WB02 and the plug/wire is kinda taught but I can move it alittle.
I've just started driving it so I'm in the process of letting it adjust fuel and transferring the learned fuel table over. It feels like a miss or over fueling. I don't want to be chasing my tail tho and moving the fuel around crazily without fixing the issue. On the new tune I removed the 50/50 and made it 15/15 on the learned tables for fuel correction. I'm tempted to check the coil wires again and make sure all is good. I could swap coils as well but its not as easy if it was on the valve covers.
So just so were clear going from closed loop to open loop on throttle transitions is normal? When is closed loop enabled?
Post your tune up. Verify your injector data. You've got major swings from rich to lean. Appears that you've got a fuel delivery issue
Injector data is good, they are GM take offs from a vette 42lb. Fuel system is a walbro 255lph HP with a single -6an to a LS Vette combo filter/regulator with a short return back to the tank. From the filter/regulator its a single -6an PTFE line to the pass front rail, billet fuel rails with crossover in the back and deadheaded on the driver front side. Fuel pressure is monitored in the rail with a low dollar motorsport 100psi transducer.
I could cut lots of fuel in the 2500rpms+ range above 75kpa and see if that helps.
The reason it's going rich, is its hitting a part of the VE table that's like 119, the 02 tries to achieve the target AFR, takes a bunch of fuel out, over compensates, then it starts swinging back and forth.
It kind of felt like a miss fire but it seems like its only under decent load more than 1/4 pedal. The WB02 is in the pass side collector on long tubes. I just did custom 8mm wires, TR6 plugs and used GM square coils but they worked before. The fact that it seems like its smooth on light ish throttle makes me think the WB02 is dropping out and going rich. I checked the WB02 and the plug/wire is kinda taught but I can move it alittle.
I've just started driving it so I'm in the process of letting it adjust fuel and transferring the learned fuel table over. It feels like a miss or over fueling. I don't want to be chasing my tail tho and moving the fuel around crazily without fixing the issue. On the new tune I removed the 50/50 and made it 15/15 on the learned tables for fuel correction. I'm tempted to check the coil wires again and make sure all is good. I could swap coils as well but its not as easy if it was on the valve covers.
So just so were clear going from closed loop to open loop on throttle transitions is normal? When is closed loop enabled?
That "typically" indicates an ignition misfire because it loads the system so much. Also with as spiky and drastic as the 02 is, I'd suspect ignition too.
The reason it's going rich, is its hitting a part of the VE table that's like 119, the 02 tries to achieve the target AFR, takes a bunch of fuel out, over compensates, then it starts swinging back and forth.
it was the base tune VE. I’ve been chipping away but if you have a better number or percentage to take out let me know and I’ll take some out. I was hoping the WB02 would do the work over a couple the drives except it’s not driving well in those ranges to get good data. If you have a better VE post a pic or the tune and I’ll give it a try.
it was the base tune VE. I’ve been chipping away but if you have a better number or percentage to take out let me know and I’ll take some out. I was hoping the WB02 would do the work over a couple the drives except it’s not driving well in those ranges to get good data. If you have a better VE post a pic or the tune and I’ll give it a try.
What is really surprising to me is, at 600rpms, with 15% throttle it's hitting 80kpa. I don't even see how that's possible with an auto w/ a stall. It should not have that much load on it at that low of TPS and a stall.
If it was a manual and you were lugging the **** out of it, I could see it, but not with an auto.
What is really surprising to me is, at 600rpms, with 15% throttle it's hitting 80kpa. I don't even see how that's possible with an auto w/ a stall. It should not have that much load on it at that low of TPS and a stall.
If it was a manual and you were lugging the **** out of it, I could see it, but not with an auto.
not sure where you are seeing that but it’s a 2000stall 12” stock converter 700r4. I don’t lug it that low but will on the highway at like 1200 rpm’s at 60mph. With a locked converter you can get the load up pretty quick.
Originally I created the startup tune with the handheld as It was my first term X system and wanted to get it running. I decided to start fresh with a base cal from the TermX with the 24x tune with no tranny. I loaded it up and used the comparison tool to verify differences between the last tune and this one. Big changes in fuel table and something weird with the new injector off time. I verified the injectors are short USCAR LS3 41lb 12576341. I set the tune and just verified nothing crazy was off. I loaded the new base and started it up. Running pretty rich with the base tune fuel and in open loop but started up. I let it get to about 150*F but it never went into closed loop (enabled in tune to start at 140*F) and set ;learned correction to 20/20. I gave it some revs and it reved fine but in the enclosed garage It got my eyes burning pretty quickly. before startup I verified the plug wires were fully seated in the coils and plugs on the pass side (WB02 side). I shut it down and now posting this. I thought it was weird that it didn't go into closed loop after 140*F... I did see it blip back and forth for a split sec while free reving.
I zipped the files and attached to this post if you want to take a look at the tune and the quick log.
Took the car to work (mix of highway and city driving) and the car ran decent. I seems like the hesitation/load up wasn't there anymore. I think the lower fuel on the base map was helping in the upper ranges. Idle however was rich and you can see that in the attached images. I took a screenshot of the fuel learn table to see what the fuel it was wanting. Removed 18% in the idle area but added big time in the 2500rpm range in the 75+kpa area (maxed out the 20% I allowed). When I was ready to leave work I transferred the learned table to the ECM which is what you see. Started up and idle was better AFR wise but felt like it was lean when cold. On my way home I thrashed the heck out of it to see if I could populate more of the VE table and I did. Car wasn't "breaking" up but you could feel it load up a bit in the 2500 range still. I think what is happening is the 700r4 2nd gear isn't great and with the 255/55r15s and the stock LOW 2.70 gear its just trying to overcome the poor mechanical leverage. When I parked and shut down I pulled the fuel learned table again and it looks like it wanted more fuel in the 1400-2500 range in the higher 75kpa+ map ranges. I transferred that over as well and then thought about the lean condition when cold but not hot in the idle rpm areas. I decided to increase the afterstart enrichment a but between 80-140*F to see if I can assist int he 15-17.8:1 AFR i was seeing on the handheld and I could also hear it in the exhaust. The car doesn't seem as fast as my other 5.3 with with a stage 2 218/228 cam but this is a smaller cam and its NA and the stage 2 with a tiny 70/70 billet turbo comes into boost really easily. It might just be the NA of this combo and the low gearing making it feel a bit like a dog.
Some other things I learned was my Tach is off by 100or so rpms at idle and 300-400rpms in the RPM band. So when I thought I was cruising in 4th at 70mpg at 2200 I'm really at like 1875 or when I think I'm hitting 5500 on the shift its really 5100 or so. At idle I thought it was weird that I was at 750 or so when I'm commanding 650 and it is actually getting to 630-650 but the tach is just reading 100rpms higher.
I find it weird that I have a huge fuel bump in the 2000rpm range at high MAP values and then it drops off as RPMs increase.
I took a log but I haven't had a chance to download it from the handheld yet but will post it when I get the chance. I will also post the tune.
EDIT: I've added the tune and data log. This was a highway drive and its weird 100% TPS but No real increase in RPM. I looked down at the speedo and I was doing about 100mph in 3rd so I had to let out but it didn't feel like it wasn't "moving".
this was the first fuel learn from the morning drive from home to work on the base fuel map This is the return drive from work to home or the 2nd learn from the modified base. This is the total VE after all driving today and how the tune currently sits. All fuel learn values have been added and updated here.
Last edited by customblackbird; 06-28-2024 at 08:32 PM.
06-20-2024, 09:24 PM
TermX tuning issue 
