Negative LTFTs at WOT, Fix???
Negative LTFTs at WOT, Fix??? Hi, I'm trying to figure out why my 402 is randomly going lean. I noticed that my Long Term Fuel Trims are going from 0 to -15 at WOT and this is when the car starts to go lean. You can actually watch the injector duty cycle go from 66% down to 53% when the LTFTs drop. How can I fix this?
I can email anyone the graph of this taking place as a powerpoint file if this would help. Thanks, Brian
I can email anyone the graph of this taking place as a powerpoint file if this would help. Thanks, Brian
Yes, this sounds more like you are never getting to open loop at WOT. You should log the FTC at WOT and make sure that it's 15 or 22 (more likely, the latter). If not, then you need to dig into what switch is keeping it out of open loop (e.g., TP%, Engine Temp, etc.).
Originally Posted by Fran D
Yes, this sounds more like you are never getting to open loop at WOT. You should log the FTC at WOT and make sure that it's 15 or 22 (more likely, the latter). If not, then you need to dig into what switch is keeping it out of open loop (e.g., TP%, Engine Temp, etc.).
I looked at all the sensors that I can think of would cause this and they look great. What gets me is that when this takes place all the sensors stay the same so it makes me think it is tuning related, but I don't know. I notice my lights dim when I go WOT. Could this have anything to do with the negative LTFTs? I think it is from my belt slipping on the alternator.
Originally Posted by 6speeder
I looked at all the sensors that I can think of would cause this and they look great. What gets me is that when this takes place all the sensors stay the same so it makes me think it is tuning related, but I don't know. I notice my lights dim when I go WOT. Could this have anything to do with the negative LTFTs? I think it is from my belt slipping on the alternator.
The dimming at WOT, I think, is a separate issue (unless, of course, the controller supply droops below 4 volts, but I think the car would just shut off then). That's odd... in and of itself. Perhaps a slipping belt.
Please check the FTC at WOT.
Trending Topics
Check your tps% at WOT. If the TPS is messed up it may not know your at wot.
Also check the PE enable table. Always possible a wrong value has been entered forcing it to stay in closed loop.
Also check the PE enable table. Always possible a wrong value has been entered forcing it to stay in closed loop.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Five Reasons the Camaro Was the Most Pivotal Player in the Pony Car Wars 2.0
Brett Foote
10 Reasons the LS7 Is GM's Most Extreme Naturally Aspirated V8 Engine Ever
Verdad Gallardo Ok, I think the dimming is coming from the alternator slipping because there is rubber next to the pulley on the alternator, but it still does drop to 11.4 volts as soon as I get on it. I logged it last night and the cell it was in for the most part was 22 at WOT.
Originally Posted by 6speeder
Ok, I think the dimming is coming from the alternator slipping because there is rubber next to the pulley on the alternator, but it still does drop to 11.4 volts as soon as I get on it.
Originally Posted by 6speeder
...I logged it last night and the cell it was in for the most part was 22 at WOT.
If you have a contiguous stream of data with TP% at 100 and the FTC is not steady at 22 (without being in a "transition" region, i.e., shift), then there's something that is overriding the PE Enable TP% vs. RPM table. That's probably the first place to check. Have you done something with the tune, recently, to cause these issues? However, if you have a contiguous stream of data with TP% at 100, FTC at 22 and LTFTs at -15, that's a problem that would extend beyond the capabilities of any tuning software, that I know of, to deal with. There may be a problem with the PCM. I hope that's not the case.
I hope all this rambling is helpful and not confusing. Good luck!
