Restoring MAF to a mail order tune

[radiogareth]

Hi, I'm over in the UK and have a L33 Vortec 5.3/4L60e running in a Mazda RX8. Its been upgraded with a 2004 LS2 cam, LS6 intake, corvette pump, pulley and exhaust manifolds. I started off with a mail order tune (MAF-less as I didn't get one with my engine, a salvage purchase here in the UK. I needed to change the throttle curve, (DBW) shift points and speedo etc so I've bought a copy of HP Tuners. I have managed to make the car far more drivable by altering these small bits. Its been really reliable up until recently when it suddenly started running on 4 cyclinders, with no throttle control - idle only. I'm assuming this is failsafe mode. Looking at live data on an OBD2 scanner showed occasional MAP 'no data' messages and I can't seem to view it in live view diagnostics. I'm seeing rpm, tps etc....
So I have a MAF from a Northstar that plugs into my loom and provides readings on my OBD2 reader. How can I re-enable the PCM to use MAF data and MAP? I'd have thought it would be a tick box, but I can't find it even in advanced.

Suggestions please.......TIA....

Gareth

[Z06-Hammer]

Post your tune so we can see what all is turned off in it.

[radiogareth]

OK, I guess that would help....

Here is the tune I've pulled from the car......other than shift points and throttle pedal curve, its as my mail order tuner sent it.

Thanks

Gareth

[Z06-Hammer]

The MAF is not turned off in your tune. What have you changed under electronic throttle as those tables can cause some serious issues when modified. I would put them back to stock and reset your dtc's with the scanner.

[radiogareth]

OK, I'm puzzled then. All I changed was % pedal/throttle and moved the shift behaviour to stop kick-down. Its been driving 'spot-on' ever since I first turned the key over 1,000 miles ago. (without any MAF, just an IAT sensor and MAP sensor). The other day I noticed a slight stumble and then it lost any throttle (DBW) and was running on 4 cylinders. (Is this 'fail safe'??) After 3 restarts it returned to 'normal' and I drove it home OK. But its not 'right', I can feel the occasional small 'stumble' through the seat of my pants, hence I thought I'd try a MAF I have that fits off a Northstar (engine for my hotrod, work in progress). I can see gr/min MAF in the live data (but NO MAP??), my mail order tuner said that it (MAF DATA) was being 'ignored' by the PCM.
So shall I reset the ecu, and take it for a drive with logging and see if I can catch a fault?

Thanks

[mbray01]

sounds like you are having an internal fault within the throttle body. Either the throttle body itself or the connect. Its actually really common. Not sure if the northstar will read correctly for your vehicle. Even though it reads doesn't mean it reads correctly. The maf does not have to be turned off in the tune, just unplugging it will work, as yours has been

[radiogareth]

OK, I'll give it a really close going over. Its a low miles engine and loom, 25,000 only. Up to now I've been very impressed by the drivability.
For a replacement MAF, should I source a unit from the original vehicle (2005 Sierra 1500 4x4) or something a bit closer to the engine spec now (LS2 cam LS6 intake).
Thanks

[Z06-Hammer]

OK, I'm puzzled then. All I changed was % pedal/throttle and moved the shift behaviour to stop kick-down. Its been driving 'spot-on' ever since I first turned the key over 1,000 miles ago. (without any MAF, just an IAT sensor and MAP sensor). The other day I noticed a slight stumble and then it lost any throttle (DBW) and was running on 4 cylinders. (Is this 'fail safe'??) After 3 restarts it returned to 'normal' and I drove it home OK. But its not 'right', I can feel the occasional small 'stumble' through the seat of my pants, hence I thought I'd try a MAF I have that fits off a Northstar (engine for my hotrod, work in progress). I can see gr/min MAF in the live data (but NO MAP??), my mail order tuner said that it (MAF DATA) was being 'ignored' by the PCM.
So shall I reset the ecu, and take it for a drive with logging and see if I can catch a fault?

Thanks

Sorry, thought you had messed with the electronic throttle table by the way you worded your post. Now I realize you modified Part Throttle Shift> Throttle Position% in Trans table.

[mbray01]

maf for whatever os you are using
if its using the truck strategy still then use a maf specifically for it

[radiogareth]

Michael, I can understand how the end application affects a particular tune (towing truck compared to lightweight car for instance) but surely a MAF is only related to how much HP an engine is capable of (i.e. the air it needs) plus of course it needs to fit the plug on the loom. I agree the Northstar unit may not be correctly calibrated for my engine although my understanding of how they work should mean that if the circuits are OK and working, and its operated within the design flow-rates the data should be good. The N* it came from was rated at 300/300. My 2005 5.3 L33 (799 heads) was I believe factory rated at 310. But I have changed the cam and springs to 2004 LS2 (405 HP) and added an LS6 intake, CAIT and de-cat. So maybe I need a MAF from an LS2?
Advice welcome. I understand what's going on but I'm not a GM specialist, its hard to get LS stuff here, everyone over here still thinks a 350 SBC/TH350 is the only way :-(

[matty b]

Check your fuses and wiring for the swap. I bet the swap harness is at fault, but without being there to go over it, can be for certain.

[radiogareth]

I'll do a pin for pin check, (it was three years ago that I worked the harness) but from what I recall, that wiring was left untouched, just re-loomed once I'd finalised layout. Do TACS modules regularly go faulty, or the actual throttle drive assembly, or the pedal itself??

[radiogareth]

Well I pulled the plugs and it all look like new. I fitted the MAF, reset the ecu (battery off for half an hour) and took it for a drive. Big difference, hard to actually qualtify but the car just feels more refined. I guess more data is better. Be interesting to see if the MPG gets any better too.