I know the forums are flooded with questions and info about the TBI 427 MAF Swap so I appologize if I ask a question that has already been asked, especially if the answer is lurking on here somewhere.

I recently swapped from the 299 Truck PCM to the 427 out of a 95 4.3 Truck. I believe everything is pinned right cause it doesn't throw codes and it starts right up. I used the MAF and IAT sensors from a 97 Vortec 5.7. I'm sure the scales are screwed up as I am using Dimented's code that is tuned for a 5.3 I believe.

It backfires out the intake when I hit the gas. After it idles for about 30 seconds it will idle down and start running richer. I have noticed that it idles better when I unplug MAP sensor. I have TunnerPro Running and can see some data but lack of knowledge prevents me from doing anything with it.

I don't have an ADX file for ScannerPro so if someone has one that works with the MAF Code and they could send it to me that would be great. I would post my log file for someone to glance at and see if it is something simple or involved. I wouldn't know either way. I need to learn to do this stuff so I am not such a nag.

It was stupid of me to dive into such an advanced project as I haven't done any tuning before. Any and all help is greatly appreciated. This forum has gotten me so close to getting this truck done. Help push me over the hill and get moving again on this.

 

Dimented can hook you up with the correct MAF values for the MAF you have, he has the L31 vortec info, PM him and get that fixed first.

Is the backfire a true backfire from spark or a lean pop? Send me your log to danny@columbus.rr.com.

 

Thanks...That sounds good. I was just about to start searching for the L31 Info

 

Sorry for not getting back to you sooner. Yes, the tables there are incorrect for the MAFs from the vortec trucks. Here is the correct table from my vortec PCM. The tables are aligned differently, so you will have to interpolate a little bit, but it should get you much closer (to expand the pic, double click on it again when open and zoom in)

 

The backfire could be due to two things. Too much spark, or not enough fuel on tip-in.

When you put the right MAF table in, observe how the truck runs when you hit the gas. If it stumbles for a few seconds after the backfire, it could be not enough MAP acceleration enrichment. If it pops, and then takes off normally, then you may need more TPS acceleration enrichment. This is because the MAF sensor does not respond instantly to the airflow due to the pulse accumulation. All GM MAFs will do the backfire out the intake thing w/o correction during tip-in when in MAF only mode.

 

Hey thanks for all the help guys. Does anyone have the ADX file for scanner pro or do ya'll log with TunerPro?

 

I have an $0D adx but its not MAF specific like you said you were looking for. If you still want it Ill email it to you.

 

I have an ADS for the MAF for tunerpro RT. I thought it was included with the MAF code attachment in the sticky, but maybe not. The ALDL transmission has been modified in the MAF code to allow for the MAF flowrate to be transmitted, as well as the WB O2 AFR if you ever hook up a unit.

 

Also, how big is your current MAF? The one I have from a Yukon is 3.5" in dia. Should be plenty for most street motors.

 

3.5 is what mine is. I think the math I worked said it would flow 700 or 750 cfm. granted that is no obstructions, turns or anyting of that sort.

 

You mean there is no turns in the intake pipe? For the MAF to work best it should not be right before or after any straight sections of ducting and mounted horizontally.

 

Drummer brings up a good point that long, straight runs of piping are not the best with MAF. This can cause the engine to stumble on tip in due to the pipe resonating. Best setup is a short, non-uniform cross-section air intake, or just a cone element on the end of the MAF.

The MAF you have now is good. That will max out flow wise at around 700 CFM at the same time it will peg the MAFs output, which is 400+ grams/sec. Also, dont try to remove the screens like people have done with the old garbage Bosch MAFs. It really screws up the MAFs calibration and operation, and they are not a restriction, anyway. You probably wherent planning on it, anyway, but youd be surprised how many people try it, and screw them up.

 

Right now the MAF is hooked straight to the Caddy Bonnet with a piece of Rubber Flex off the Caddy to be precise. I am planning on making an airbox for a filter and then hooking that to the fender of the truck like from the factory. However I have removed the terribly small duct work from inside the fender. Should provide respectable air temps.

 

That is cool man! I really like that!

 

I know have the MAF off an 04 5.3. Hooked it up and all data is coming into the PCM so there's a good start. It was still having problems and I was messing with TPS stuff and noticed on a test run in the driveway on launch that the timing dumped to 0 degrees. A quick inspection of the Base timing value revealed 9.83, I am set to 0. A quick change to match my settings and an instant difference, now it seems to be slightly lean or rich. Haven't investigated enough as I got a call from work and had to leave. It is stumbling a little and then takes off. AFR was around 16.4 if I remember correctly

I have already been helped so much anything else is just more beer in the fridge (I don't like icing or cake really).

Thanks all

 

The lean stumble is most likely a lack of MAP AE. The fuel tends to settle out when the intake is cold, and it will cause a stumble until a coating of fuel has been established.

Also, the PCM has some launch timing controls where it pulls SA on tip-in to prevent detonation. I think its defined in the XDF (ill post it up later). IIRC, the timing is pretty conservative in teh stock calibration.

 

I assume I adjust that in the Delta MAP AE table? How much would I want to adjust it by, I'm unsure of how it scales and I don't wanna completely screw it up. Sorry I have very little of a clue on what I'm doing. I think I might know enough to be dangerous. I was paying someone to make a chip for me and that just hasn't panned out hence why I swapped to MAF so that tuning myself might be easier.

 

The delta MAP AE is a function of injector duty cycle (or delivered fuel mass). Theres no real explicit way to find out how much is needed with a particular intake manifold, and varies quite a bit with the coolant temp.

For example, when the manifold is cold, it will need a lot of AE as teh fuel readily settles out on the manifold walls when the vacuum drops. The ammount that can settle out is a function of temperature and vacuum. As the temperature increases, you need to scale back the MAP AE as the lighter components can no longer settle out. Eventually if the intake manages to reaches full operating temperature, none of the fuel can settle out, so no AE will be needed. This happens with MPFI, but not necessarily TBI as there is always fuel in teh intake, which can cool the intake back down under certain situations.

Ive found that the following empirical table works well to linearize the MAP AE fuel quantity with respect to temperature. This works on both my MPFI manifold and worked with my old TBI manifold. Type these values into the cool temp based MAP AE multiplier table if they are not already there, and it will take care of that part. As long as the manifold is at the temperature that the coolant temperature is at, this will provide the proper compensation as temperature changes.

 

You will have to keep in mind, though, that with TBI, the manifold temperature can change dynamically due to the fuel in the manifold. You may find that at some points the engine will be rich on tip-in, while others it will be lean. There is an option in the code to allow you to add a temperature sensor for the intake manifold itself. I found that this really helped take care of all the drift in the AE. This is especially important with a manual as you utilize the AE each time you shift and get back on the gas. If its not right, it will make driving a real drag.

See how it works, though, before you resort to this. If your taking in air from the engine compartment in teh cooler months, then the manifold will remain at a more constant temperature.

Also, having a wideband makes tuning much easier. Especially when it comes to setting up the duration of the AE. Otherwise, your pretty much just guessing.

 

I don't think I have the most recent version of the bin. I do not have a table for that.

And another thing, My MPH in the computer isn't working. I unhooked it from F2/F3 and the computer shows 4.** MPH at idle. when I rev it, it goes down. It acts like it is getting the speed input from something else. Unless the ads is showing the MAF input on the MPH display on the Dash. My Speedometer works though.

 

Sorry, its been a while since I used the $0D_MAF code. The tables are called sync AE temp correction vs. manifold or cool temp and async AE temp correction vs. manifold or cool temp in the XDF. Just plug the above into each of the AE temp correction tables and you should be good to go.

The actual ALDL parameters are configurable in the $0D_MAF code. IOW, you can define what will be transmitted thru the ALDL port. There is a table at the start of the XDF called ALDL scan too xmission address table with 60 some odd addresses in it. Let me have a look at the ADS file and I'll post up the table with the desired addresses for the ADS you have. If you want to see something else, you can re-define the addresses as desired. I'll go into more depthas to how to do this when I post the table. Also, I can post up my last manual bin that I was using. DONT use it directly as its for a manual, but you can steal info from it to try to see what works best.

 

I have a manual 5 speed in my truck

 

Sorry I haven't had a chance to get to updating the ALDL transmission table. I'll try to get to it this weekend and post up the correct table. All you'll have to do is type in the addresses and you should be able to see the correct data.

Other than that, how is it working so far?

 

I think the MAF is making this tune easier than I know. I am working to get the Timing and Delta MAP and TPS right. I am getting a high idle after I let off the gas and put it in neutral, even if I lug it down and then put the clutch in. I bumped my fuel pressure to 21psi to try and make sure I am getting enough fuel cause I thought I was possibly running out of fuel at one point cause it seemed to fall on it's face at WOT and up in the 3500rpm+ range. I have the 90 lb/hr 454 injectors so I think the fuel isn't a problem now. I know the quick WOT throws it for a loop. Not as hard as I thought it would, but I have read over and ever not tune by the seat of your pants. So again, the WB02 would be very helpfull to know what is goin on.

If I can get some help gettin the speed, IAC, and 02mv to show up in TunerPro I will take a log and post it to see if anyone knows whats up. My problem is that I have never done this. Is there a special definition that WinBin needs to open up this code or will a $0D def work?

Thanks for Ya'll do

 

I'll get the proper address table later on when I get back on my home PC.

You really do need a wideband to tune properly. Its probably one of the most important tuning tools you can have. The MAF will make the fueling consistant, but if the injector flowrate differs from what is in the code or the MAF calibration is off, it will be consistantly wrong. Its especially important to have it for tuning the AE, as thats the most difficult part of the fuel tuning. Id make it a priority to get one. Right now, you can only guess at what changes need to be made.

The MAF code allows you to wire the output from a wideband directly into the EGR voltage input and also allows you to convert it to actual AFR. This will allow you to have the wideband AFR in your datalog.

Also make sure that the injector constant matches the flowrate of the injectors at the current pressure. This is important as the injector flowrate is used to directly calculate the mass of fuel required from the mass of air taken in by each cylinder. With MAF, everything should be set as close and held as consistant as possible (injector constant, fuel pressure, etc.). Even if some things are only off by a little bit, they can cumulatively add together to throw the fueling way off.

 

Do you have a recommended brand for a wideband?

 

Ive been using the Innovate LM-1 for the past 5 years or so with no issues with the unit. The LM-1 is a hand-held unit with integral display. They also make an LC-1, which is just the controller. You could purchase just the controller itself and simply connect it to the PCM and use that to read in the wideband data in the datalog. The controller just has the circuitry, no display. You would power it from teh cig. lighter and use the EGR input to read in the WB-O2. Some people install the LC-1 permanently into the car, but I would not recommend it as it not only wears on teh wideband, but some people have had issues with them malfunctioning in the long term.

There are also other options, such as gauges with integral controllers that you can install. The gauge will show the AFR from the wideband, as well as have some other options.

As far as the ALDL goes, here is the table of addresses. Type these into your ALDL scantool address table in tunerpro and use the above attached ADS file. You should then have the right info in the datalog.

 

I ordered the LC-1 up and plan to just read it from the PCM. I got it for 129.00 so I couldn't complain and that is with warranty. Gotta Love Time Automotive, they are really competitive. Thanks for the tip I was going to just install it but I will order a bung that has a plug so I can remove it.

Thanks for the address table. I will get that plugged in asap

 

Alright here is the latest with my situation. I have my throttle follower working...now if it's right is beyond me but it seems to do the job. It looks like my timing is what was keeping it from working. Too much or not enough advance I don't know. I set the entire open and closed throttle SA tables to 25 degress. The truck starts right up and seems to idle fine...when it is cool it will start to drop the rpm but catch itself and idle fine after that.

So I need to rework my timing tables, any tips there? I am attachting my bin that is currently running in the truck. I will say that around town drivability is better locked at 25 but the power isn't there anymore. I know how to change weights in a vaccum or mechanical advance distributor but TBI works a little different.

Thanks everyone

 

So its still working Ok for you?

You can still tune the timing the same as an old dist.

Set the throttle closed table to whatever you like at idle. If you want, you can just set all teh values to the same thing, say, 22 deg.

The open throttle table can be tuned by basically setting the cruise timing, low speed/off idle timing, and max WOT timing to what works best. Then, just blend the areas of the timing table together so the transitions are smooth. In a simplified fashion, the timing works pretty much the same way, except the PCM uses tables instead of springs/weights to do it.

Instead, the engine RPM and load are used. 30-40 kPa is low load, kinda like cruise with the vac. advance. 80-100 kPa are high load. This will be sort of like your total advance with the vac advance plugged. Its not as hard as you might think. Just takes a little getting used to.

 

Thanks dimented,
I have trouble with the idle when I first start it up warm or cold. It won't hold the idle but after you drive it for awhile it will idle, but low...around 500 instead of 750. Shut the truck of and start it back up and boom idle problems again. A/C idle won't work for anything and in most cases will end up stalling the truck out. I am wondering if it is due to IAC Gain or the 02 tables are bad and it is flying between lean a rich??

Other than that it seems to be running fairly well. I need to hook my WB02 back up and look at the AFR's to see if it is running rich or lean and where, the timing has been making a huge difference in the way it runs.

Is there any way to look at the knock count on the 427 PCM, on my 299 ECM it would show a knock count for that engine run session in WinALDL.

Thanks again for all the help.

 

What does your MAF table look like? Many idle problems are due to the AFR being too lean. Keep in mind that while MAF makes tuning easy, the MAF table dominates the fueling as the fuel is directly calculated from the MAF sensor and calibration. If there are cells that are reporting too little flow, the engine will go lean whenever it enters those cells. At idle, this manifests itself as the engine surging up and down and then a stall. As an experiment, try increasing all the airflow values from 0-20 grams/sec by 15% and see what that does. if the idle dramatically improves, then you need to redo the MAF table. Your BLMs can be a help, too. Take a look at them at idle. It sounds like closed loop is whats keeping the truck idling. There are limits to how high/low the BLMs can be to be saved. If the BLM is way out, the PCM will not save that value, but a default max instead. Hence, the poor idle on restart.

As for timing, it will have no effect on the fueling with MAF. But, you should put the engine into open loop and verify as much of the MAF calibration as possible. It sounds like the fueling is off in certain spots.

As for the knock, yes, it can be datalogged. You will need to edit the ALDL transmit table to include it in place of something else, and then edit the ADS file to show the knock. Lets get the fueling solved first, then we can move onto the knock.

 

Also make sure you ahve the correct injector constant put in. Avoid chaning the fuel pressure to tune. That will throw everything out the window. Select the fuel pressure you want, and enter the adjusted flowrate for the injectors. After that, leave the fuel pressure as is. Its imperative that the correct injector constant be entered, or the MAF table will not reflect the actual airflow.

Once you do this, you will need to recalibrate teh MAF table. I suspect that a lot of the idle issues will resolve once the MAF is properly calibrated.