I just purchased hp tuners and so i'm a complete noob to tuning. i'm hoping for someone with some experience to take a look at my tune file and give me some input on what to change. I really want to start tuning the car myself instead of taking it to a shop everytime I change a blower pulley or do anything. Right now it's tuned with a MAF, eventually I want to go SD, I just have no experience yet. it has been tuned by several shops but the last tune was at EPP, now brutespeed, way back in 2006ish. the car has just been in the garage for the last decade and I've just recently started getting back into it. so here's my problem: the car runs excellent at wot with an afr about 11.5. it's the part throttle that has always been an issue and no one has been able to get right. at part throttle my wideband afr spikes really lean and the car sputters and hesitates for about a second. it used to spike to around 18, recently I've seen it climb to 30. i'm guessing I just need to add fuel somewhere, but I honestly have no idea. it's not restricted to a certain RPM, it happens anywhere and anytime at part throttle, especially if I let off the gas and get back on it. If I unplug the MAF, the car drives great at part throttle. I've changed the MAF and O2's so that's not it. no vac leaks either via a smoke test. Major mods are in my signature. Any help is greatly appreciated and thanks in advance!

 

Well, since nobody chimed in I'll throw you my suggestion. I am assuming when you say part throttle, it's not enough throttle to kick it to PE mode. It's still using tables and trims.

So first, look at all your sensors as you are driving. If it has been sitting, you may find (for example) that your TPS sensor is glitchy and when you hit a dirty spot at part throttle it reports something way out of whack, so graph it with HPTuners scanner and all other basic sensors and see that they all "make sense" and look right.

But if you think there are no mechanical problems and you think this problem is all in the tune, then I think what you might want to consider is just start tuning SD mode now since you said that's your goal. If it were me, I'd pull the plug on the MAF and that'll kick it over to SD mode and just start doing SD tuning like many articles on this site describe. Basically you need to drive the car normally while using Hptuners scanner set up with the right graphs, and it'll do the math using your wideband and show you the errors in your tables based on commanded AFR and your resulting AFR and the fuel trims that the computer had to use to get the AFR right. You then apply the calculated graph corrections to your tables, burn the tune to the car, and do it again over and over until the errors are very low. That's how you generally get all the part-throttle tables cleaned up and efficient.

I would be very careful to not go WOT much in this mode because (if I understand things correctly), since you are still running a MAF tune, your current WOT AFR was based on your MAF flow table to get it to your 11.5, you may find that with no MAF and it fails back to SD mode the resulting AFR is WAY off and it won't use trims to correct it at WOT and you could damage things. That too will need tuned, but from what I read you do the WOT tuning last once you have all your other tables valid.

If you don't want to dive into an SD only tune yet, then I think the MAF tuning is what you need to look at. I'd still do the SD/VE tuning first but once you do that then you plug the MAF back in and basically do the same thing but this time you have your HPtuners scanner watch for the MAF FLOW and the corrections for that. You apply those errors to the MAF table the same way as you did with the SD table over and over until the error gets very low..

Again, I am somewhat new, just trying to give you some general direction. If my advice is wrong someone please correct me.

 

 

If when you unplug the MAF the car runs perfect means I think you should probably be looking at the MAF table. It's just a 1-dimensional table that equates Hz to airflow. It should look like a very smooth curve when you look at its graph in hptuners.

I do know that very miniscule adjustments here made large differences in my tune. Maybe do a quick SD tune just to make sure it's good then do a MAF tune, now that I realize it runs good SD and bad MAF, I bet that's where you're problem is, the MAF tune.

I'd be more confident in my suggestions here if you were N/A since I just went through all this myself, but there are all sorts of nuances and things with F/I that make me think there may be way more to this and I'm giving you bum info LOL...I hope I'm not.

I tried to peek at your tune but it tells me you are using a new unsupported version, and I'm not upgrading for a while for, well, long story LOL.

https://ls1tech.com/forums/pcm-diagn...-heads-up.html

 

 

When I went to cammed LQ4 my MAF table was way off, but it only took very small changes to bring it into tune. Drive around logging your MAF HZ and MAF Airflow, and log other items you'll see in MAF tuning docs and I bet you'l lfind your airflow-to-hertz mapping is off right at the airflow spot where your glitch is, and doing your error correction will look like very tiny increments/decrements on the graph but will make large differences.