oldred95

I've already contacted dimented and I hate to steal his thunder but I'm kind of in a pinch and would like to get my truck going this weekend if at all possible. Anyway it starts and runs on it now, but its so rough its not funny and all it will do to stay running. At first it was lean and would hit and die, now I've got it to stay running but only under heavy throttle. I'm running 25 psi on 61# injectors and using the flow rate to mass tweak the fueling just to get it to run. I've tried everything from 11.24 gm/sec flow rate to 7.0 gm/sec and so far 8.65 has been the best. I can't seem to keep it going long enough to hit closed loop. I did one time and it showed BLM's of 128 and one time it dropped to 118 for a split second. The injector pulse width is 5-6 millseconds at idle and the MAF is showing 3000-4000 hz and 14-18 gm/sec flow rate. Also the IAC counts are pegged at 250 like its all it can do to sustain an idle which is exactly what its doing. I'm not too sure what to do at the moment or what it needs. I can't tell if its rich or not by the exhaust. I have no cats and to me its always smelled rich and will make your eyes water if you breathe too much of it but now it smells no different then it ever did. I don't see any black smoke or anything. One last thing, MAP is anywhere from 50-70 KPA. To me it acts like its lean but then giving it a pretty significant amount of fuel doesn't seem to do anything for it. Any ideas?

dimented24x7

iTrader: (2)

Its going to be hard to tell without a wideband. Like I said earlier, I had all these same issues. There are literally dozens and dozens of different MAFs available, all with vastly different calibration curves. It doesnt take much to make the motor run bad as far as the MAF table goes since the table controls the fueling almost entirely. The two clues you have at your disposal now are the spark plugs and the NB O2. Its sort of useless, but if its higher than .450 V, your richer then 14.7:1. If its lower than that, your leaner then 14.7:1. Pull a few plugs after it runs for a bit. If theyre white its lean. If theyre a grey color without much soot, its so lean that its misfiring, or possibly misfiring from some other issue. If theyre a dark sooty color, its too rich, like 10:1 or richer.

Also, you're using the bin I sent, correct? That one has all the specific info in it for your truck. Just make sure you use your spark tables and such for both the CLOSED and OPEN throttle spark tables. If the closed throttle table used during idle is wrong, it can cause the motor to run poorly. Setting the entire closed throttle spark table to 18-20 degrees for now will make it easier to diagnose the problem.

dimented24x7

iTrader: (2)

Also, dont use the injector flowrate constant to tune. This can improve one area, but cause another area to be incorrect. If one part of the MAF table is too lean or rich, the engine can get stuck there. Set the injector constant to be what it should and use the MAF table to tune. Basically you look at the frequency your idling at and adjust the cooresponding flowrate. For example, if you have 3000 Hz or so at idle and you want to lean it out a bit, lower the flowrate around the 3000 Hz area. Also 5-6 msecs at idle could be too high. Should be like ~2 msecs or so, but may be higher if the motor is at a high MAP or low RPM. Look at the plugs and use those as a guide.

dimented24x7

iTrader: (2)

Additionally, as a general rule of thumb, if the MAF table is ok at lower flowrates, but too lean at higher flowrates, the engine will do what its doing now. Idle worse and worse the more you open the throttle due to the engine being lean at higher airflow rates. If the table is ok at higher flows, but too lean at lower flowrates, itll surge up and down as the engine levels off, leans out, and then riches up again when then IAC opens to maintain the idle speed. Also dont forget to keep an eye out for other things like loose wires and such. Nothing worse then trying to fix one problem when its something else.

rhuarc31

Amen to that last bit dimented

oldred95

Finally got it to run. Pulled a plug and it was so black you'd swear it was burning diesel and loaded up like no other. I ran it in speed density so I could get it cleared out a little bit and get the plugs cleaned off then found the correct MAF flow table and used it and it was still pig rich so I just cut the whole table in half and it cranked right up and idled good. I know it will be insanely lean if I open it up but I just wanted it to run and sure enough it did. Now the big problem still remains, the transmission will not shift and I am using the MAF code for the auto trans.

dimented24x7

iTrader: (2)

Ill take another look at it on the bench tonight and see if I can find the issue.
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Also, what happens when you use your stock SD bin, and check off the option byte to use the magnetic VSS pickup as discussed earlier ($5D02, b4)? This way at least we can establish that everything is working, and that its some issue in the software.

dimented24x7

iTrader: (2)

Also, does it feel like its stuck in 3rd still, or is it in first and wont upshift? That will at least tell me where to look.

oldred95

I drop it into OD like normal and it will take out just fine but then won't shift out of 1st gear automatically. I can pull it down to 2nd gear (second gear start with the 60E) and it goes right into 2nd gear just fine. I can pull it down to 1st and it works just fine. Reverse works fine too. Basically there is no automatic upshifts, only manual upshift and downshift from 1-2 and 2-1 works. When I put it into 3rd or OD after I'm going down the street it "shifts" but then there is nothing there.

I have never seen any place in the XDF to change the option bits like you mentioned or I would try that. All I can say is that before I ever messed with it it was working fine. My guess is unpinning F12 has something to do with it. I swore fast355 said he was running a MAF and 60E on something of his and it was working fine. But then again anything he does works fine even if it was put together backwards upside down and sideways on friday afternoon at 4:59 pm.

dimented24x7

iTrader: (2)

Actually, I think its my fault for it not working. Id be willing to bet that I forgot to change the TOS params back for the 4L60-E. Theyre probably still set for my TKO.

Go into tuner pro with the MAF XDF and bin and at the very end of the constants section, there should be two for the transmission output speed (TOS). Open up your stock bin as a compare file and match these two constants in the MAF bin to your stock bin using the copy button in compare mode. Thats probably why it wont shift now. Its no longer stuck in 3rd, but now wont shift because the constants are off.

oldred95

I found the time to wait for TOS pulses set to 60 msec in the MAF bin and 20 in the stock untouched SD bin. Also the ratio for calculating mph from TOS rpms wasn't quite the same either. I'll do out and see what it does and be back PDQ with results.


Have you got any super slick way for editting the frequency to correct fueling? Datamasters histogram made this so easy for SD. Any such thing for MAF?

dimented24x7

iTrader: (2)

Sorry about that. I forgot to change it back. Also make sure to change the number of pulses per rev from 12 back to 40 for the 4L60-E.

With a wideband, calibrating the MAF table takes about an hour or so. You drive the car at various loads while datalogging the MAF frequency and wideband O2 output. Once you have enough samples, you then multiply the airflow at each point you datalogged by the corrections you obtained from the wideband data. For example, if the engine is at 6700 Hz and your desired AFR is 14.7:1 but the wideband is reporting 16:1, you go to the entry at 6700 Hz and multiply the airflow there by 16/14.7 to obtain the true airflow. If you have enough points, youll notice that they appear to fall along an imaginary curve. This curve is actually the true calibration curve of your sensor. You then interpolate the entire MAF curve through these points (see pic below for an example). You repeat this maybe three or four times to dial it in, and thats pretty much it. So long as the sensing wires remain clean and there are no problems with the sensor, you never have to do it again. At most itll be tweaks if you decide to change something in the intake tract.

oldred95

So is there any reason why the POS refuses to start and stay running when its cold vs when its hot? I can not get the damn thing to run more then a few seconds at a time. Do the choke settings and everything from the speed density still work the same with the MAF?

dimented24x7

iTrader: (2)

Yes, it all works the same on the choke settings side, but you may want to import your settings over from your bin. Also, untill the MAF is calibrated, it may give you some trouble when its cold if its running lean or rich. Also, go to the min and max allowed saved BLM in the constants section and change it from 128/128 to something like 112/140. This will allow the PCM to self calibrate the lower portion of the MAF curve from 0-128 grams/sec using the CL data and these settings will be saved after you shut down. This may aleviate some of the problems in the short term while we iron out the kinks.

Also, please dont forget to set the TOS pulses per rev from 12 to 40.

oldred95

Still won't start and stay running. Doesn't matter what I try and I checked and the cranking BPW and choke afr tables are all set to what they were with speed density and it always cranked right up on speed density. What I don't get is how it can run so good when warm but when cold it turns a cold shoulder to me and won't do anything. It makes no sense to me. And how well am I going to be able to tune it (assuming it runs at some point) with a narrow band 02 sensor? I need a wideband and an emulator before I can get anything done worth mentioning but I don't feel like spending another 400 when it will just give me more headaches anyway. I'm so discouraged with it now I don't really care at this point.

dimented24x7

iTrader: (2)

No need to get the emulator. Its not absolutly necessary. I still have yet to buy one. I tuned with just a PPII. For the MAF it wasnt an issue, but for the transient tuning, it got rather annoying due to how much transient tuning is required with TBI, regardless of the system in use. A wideband is absolutly necessary no matter what you'll be doing. You can tune using the BLMs for now. Youll have to do it cave man style during PE, which can get you fairly close if you read the plugs and such.

The system does work well, but like anything else, it requires time to set up due to the fact that I just have a generic tune in there. Basically, this is like calling a tailor, telling him you want a suit made, and that your six feet tall, and then hanging up. Naturally, the suit wont fit quite like you want it to without some additional adjustments. This is the part where a wideband really helps. Plugging the wideband into an external power source and watching it while you start the car can tell you a lot. With the engine cold it wont be as accurate, but it will tell you if your overly rich or lean, and what needs to be adjusted. Also, take a look at the crank to run AFR table. I remember taking a lot of fuel out of that due to the fact that it would drown the motor in fuel. Its possible that in stock form, it could be required to get the motor to start without stalling. Match it to your stock bin and see if it fires up. Ive used this system from the dead of winter (-5 degrees F) to over a 100 degrees F in the summer without any issues. BUT, I had to tune it first to make it start and run well.

dimented24x7

iTrader: (2)

Also, keep in mind that MAF and speed density are not equivelent with TBI due to the fuel dynamics. SD can be inaccurate at certain operation points due to the fact that the intake charge temp is affected by the fuel. MAF doesnt see any of that. With MAF, WYSIWYG as its independant of all of the fuel dynamics. Thats why MAF TBI exists in the first place.

oldred95

I found some pretty significant crank to run AFR drownage, say around 3-6 points AFR being added. Its no wonder it cranks up smooth but after a half second or so goes to chit and smells rich as can be. I'll fiddle with it a little more tomorrow and see what I can come up with. I know I need a wideband bad but right now I feel like I've got 38 variables that may or may not make it run and that would only add to my confusion, that and they cost 200 bucks for the PLX and it still only comes with a junk bosch sensor.

dimented24x7

iTrader: (2)

Take a look at that transition table. I reduced it quite a bit, but the car still would dip momentarily, but recover. If the motor starts but stalls immediatly, you might want to look at that table. This seems to be a common problem for most TBI motors. My theory on it is that the manifold holds onto a lot of fuel when cranking that causes the motor to go rich when it catches. The higher the AFRs in that table, the richer it will be as that AFR is subtracted from the desired AFR to richen the transition, but there is a threshold that determines when the AFR is either added or subtracted out. Ill check later to see how its handled, but at cooler temps, its subracted out to richen the AFR. If the engine does what I described. Try zeroing out the table and see if it helps any.

oldred95

I zero'd out the upper 1/3 of the table and then dropped the rest of it to where the most AFR that will be added at any temps that we will see around here is 1-1.5 points AFR. I think but don't expect it to start and run decently tomorrow morning. And yes I know all about the die down and recover transition on startup. Setting my IAC park counts high seemed to help that some along with tweaks to the choke and crank BPW settings when I ran speed density. The MAF XDF is starting to make more sense but I think it will be a while before its truelly drivable.

dimented24x7

iTrader: (2)

I have a feeling that getting the MAF table right will go a long way to making it start better. One reason it probably runs good warm is that the closed loop is kicking in and correcting the fueling. But, since the saved BLM thresholds are set at 128/128 as a default, the corrections to the MAF table arent saved, and your back to square one when you go to restart. If you set the upper and lower allowed limit for the stored BLMs to some other threshold to allow the BLMs to be saved. The PCM will recurve the MAF table using the BLMs and do a good deal of the tuning for you, likely making the next restart easier.

The MAF is less intuative, and requires you to adjust how you think since its grams per second and not RPM and kPa, but it pays for itself when you go to swap a cam or the heads. You can just slap it together and drive away without having to touch anything. Also, the MAF is precise enough that closed loop isnt required, which comes in handy with larger cams with overlap.

Also, just out of curiosity, where is "here"? If its cool to warm all year, then you can take a deep breath and relax a bit as you wont have much tunign to do. In NJ with moderatly cold winters and hot summers, it took me a full six months to calibrate the PCM due to the fact that there was such a wide range of temps involved.

dimented24x7

iTrader: (2)

Also, I tried the MAF bin that I sent you out on the test bench with a function generator to simulate the VSS and looking at the shift solenoid states, the PCM is commanding the transmission to shift at the hardware level in the correct pattern for the given speed and TPS input. In theory, it should shift the next time you try it.

oldred95

"Here" is at my parents house in southern Kansas, "there" is college on the "bayou" of Oklahoma south of Tulsa where it rains every 3rd day and sometimes for week straight. Temps can go from 90 to 50 overnight.


I figured anytime something was changed to the system it would still need the maf table adjusted, for example if I swapped cams again. Guess I was wrong.

dimented24x7

iTrader: (2)

Did you ever get to try the truck and see if the trans was working properly?

oldred95

Nope. It did not want to stay running at all. I said screw it and will mess with it again another time. I even zero'd out the crank to run table and it would not stay running, it tried its damnedest but it could do it. Guess I'll have to tweak some more on the MAF flow chart.


One thing I would like to know is say I get it to run and all is good, I plan on putting a 454 TBI on it with 46# injectors at 35 psi. What will that do to it? Is it just a matter of entering the flow rate or will it drastically throw the fueling off again?

dimented24x7

iTrader: (2)

I stand corrected about the crank to run transition AFR. Its added to lean out the crank to run transition. But, if the engine starts and over several seconds dies out, then this is unlikely to really help. Its there to prevent the classic start and immediate stall that the old TBI cars/trucks had. I have a feeling that the O2 was what helped the engine run good when it was warm.

If the engine starts in speed density OK, you can use that to do the initial tune of the MAF. Speed density and MAF will diverge a bit due the fuel dynamics, but with the engine fully warmed, they will be close enough to be of use. Try this next time you go to tune it. Go in to TP and set the error 17 frequency threshold to 65535 Hz and the error 17 time threshold to 0 msecs. This will immediatly dump you into speed density. Except that unlike the MAF being unplugged, you will still have the MAF frequency in your datalog. Below the MAF frequency, the grams per second will not be the grams per second in your MAF table. Instead, it will be the calculated grams per second airflow from the speed density calcs. You can datalog this and plug the corresponding grams per second into the MAF table at the corresponding MAF frequencies. This may help get it running. After that, you can use the BLMs to tune the MAF table. BLM tuning with plug cuts got me pretty close before I had a wideband.

dimented24x7

iTrader: (2)

No effect on the MAF. Set the constant to the injector flow and thats it.

But it will effect the AE requirements. The one most effected will be the TPS AE if you have a manifold with a large plenum volume. The MAF lags the airflow slightly as its the mean flow over one intake cycle and not the immediate flow, and when you snap the throttle open, the sudden inrush of air into the manifold can leave the motor lean momentarily. This will show itself as a split second hesitation with a snap out the TBI when you stab the gas to the floor. The TPS AE values in there are already set for a BBC TBI with a large manifold. If you have a momentary rich spike, you can just scale the values down a bit. If the MAP AE is ok, then it will remain essentially unchanged as its based on the pressure drop within the manifold more then anything else. All the AE fueling is based off of duty cycle, so its not thrown off by changes in the injector size so long as you enter the correct injector constant. The decel enlean is still pulsewidth based, so it may need tweaking later on.

oldred95

So then all I'd have to do is have the VE tables right and then use that along with the MAF reading to figure my MAF table. I think I get what you're saying. You think the cold starting issue is just the MAF table being so far off or do you think its still in the choke and crank to run settings?

dimented24x7

iTrader: (2)

I have a feeling that the MAF table may still be off. The grams per second term from the VE should get it closer.

dimented24x7

iTrader: (2)

Also, I was thinking about the VSS. If you still have problems with it not shifting, look at the speedo. If its reading nothing or acting erratically, then you may need to swap the wires on the PCMs VSS input. I dont know exactly whats in the buffer box or the PCM, but I have a feeling that the low and high reference of each must be kept segregated or there will be no VSS signal. IOW, having the high and the low of the PCM and buffer box on one wire and the low and the high on another may zero out the signal to both.