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Quenstion in reference to MAF scaling

Practical Reflash Tuning

Discussion and questions related to the course Reflashing

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Hello again! I have been watching your course material and made it to the practical reflashing. I have a 1987 Chevy S-10 that I have successfully installed a Gen 3 LS 4.8 into. I have done a few modifications to the engine, most notably a custom ground camshaft. It is a ISKY triple 12 camshaft, here are some specs: 212/212 110LSA, Intake lift: .561 Exhaust Lift: .561 with 40 degrees of overlap. I assume after looking at your course material that I will need to rescale the MAF, so that the rest of my tune falls into place accordingly. I took it upon myself to use the search button (haha) and found your webinar : 099 | MAF Rescaling with HP Tuners

Using the info from this along with earlier suggestions in your course material, I need to calibrate my MAF first thing. When I put the truck into gear from idle it dies. So, to me it seems I need to calibrate it at idle once its up to temp? Can I use the same method you applied in your webinar to tune this sensor at idle? Then go through with the same method again for the cruise part of it?

Another think I think worth mentioning is that with the stock file on the PCM, the truck will not fire up without blipping the throttle, if I barely hold the throttle open (maybe 25%), then slowly bring it down to closed, it will idle on its own. Vats has been disabled as I am not using a BCM.

I am using HP Tuners 3.0 mpvi pro

I hope I gave you enough info for a decent start to this "problem" if you need any more info don't hesitate to ask for it. I have built this engine from the ground up and I have any info you may need.


Did you check for vacuum leaks?

I have not checked for vacuum leaks, I'll have to hook up the mighty vac guage when I get home and see what she is reading.

You need to spray around the intake system with carb cleaner or pressurise the system with an air compressor.

Yeah, I was at work til late last night. But I intend on doing that first thing this morning. Let you know my results, if I do not have any leaks though, what do you think would be the next logical approach

:update: started the engine, had to blip the throttle again. Sprayed starting fluid everywhere where the intake mounts to the heads, including vacuum hoses, throttle body, map, everywhere! No change in idle pitch anywhere.

Another update, took my hose off for my brake booster and plugged it with a socket and it fired right up! Must have a leak in the booster somewhere. So now that that's known. In reference to the MAF scaling, do I use the same method described in the video to scale it at idle? And another note, when I plugged the hose, I was able to put the truck in gear without it dying! Yes!!

good news.

start with the method in the video and report back.

You got it! Thanks for the help so far. My Innovate wideband came in today and I've been making the exhaust today for the mounting of it, it's about 26 inches from the collector at as close as I could get to the 12 O'clock position. Just gotta get the relay wired up and I'll be able to finally see in real time what she is doing..

Hey guys! Haven't forgotten about you guys! I work on the weekends though (Fri-Mon) so I've had little time to mess with my truck. I did get my innovate wideband bung welded in and got my relay wired up. So hopefully tomorrow morning I should be getting my first real MAF error log recorded. Gonna get it up to temp and start logging my idle numbers

Alrighty, so I tried to take some measurements for my AFR error in open loop mode and it started off almost immediately lean by about 14% at 3250hz, 13% at 3375hz and 10.94 at 3500hz so I shut it off. This was after it was brought up to temp and everything was stabilized. I'm commanding 1.00 for my open loop F/A vs Coolant temp vs MAP as instructed in the webinar 99 MAF resealing video. Do I need to command a more rich AFR to fix this?

Edit: I had my short term fuel trims enabled like a dummy! I turned those off. Sure enough its sitting about right where it should now as far as where its idling. It is displaying lean still, but a much lower percentage: 3250hz I have 6.12 lean and at 3375 hz I have 2.12 lean each with over 1000 counts on them

Thanks in advance!