hesitaton problem

[zmanx]

The car runs fine in open loop, In closed loop it hesitates when you hit the gas wether your in park or drive. What could be the problem? Both 02 sensors are good and I have an SLP maf. I also have long tubes and an 80mm throttle body.

[EC_Tune]

SLP MAF...
Dump it and put a stocker back on. There is no benefit to aftermarket MAF's except the ones that utilize the LS7 MAF sensor within a standard MAF type (round) housing.

It's the tune that causes stumbling. Get the AFR & spark correct and it won't do that anymore.

But get a stock MAF on it first.

[zmanx]

Really, SLP is bad ? But will the stock work ok with the 80mm TB.
I had a feeling it might have some thing to do with that MAF.

[EC_Tune]

I generally don't like any aftermarket MAF's unless they are using factory elements inside. The SLP has a resistor attached to it but otherwise it's a stock MAF (IIRC).

If you have a truck 85mm MAF with the integrated IAT sensor you can use it with a MAF harness adapter. Don't descreen the 85mm MAF with the very short airpath of your F-Body.

Here's a config and multiple histograms you can use to tune the MAF and it works on most all LS1 series engines. It will probably work on other applications with mods for that application. Get my MAF!LTFT.cfg config and histograms HERE Should be near the bottom of that post. Read through the custom histograms/configs post as well. You might find something else you like there.

Save the config to:
C:\Program Files\HP Tuners\VCM Suite 2

Save the Histograms to:
C:\Program Files\HP Tuners\VCM Suite 2\Histograms


Don't try to open the config or histograms with anything but the scanner.
File > Open Config > MAF!LTFT.cfg
Do this FIRST!

A little info about narrowband o2's first.
If you don't have a wideband or access to one, don't work on WOT without a wideband. Narrowband o2 sensors are only accurate at stoch, are affected by heat and exhaust pressure, and have no voltage to AFR correlation at all except that they switch from low to high or high to low in a "narrow band" at stoch. That narrow band is generally less than 30 mVdc and is equivelent to 14.7 AFR with non-oxygenated gasoline.

Now on to tuning.
-----------------------------------------------------
MAF tuning is quite easy. Here's how I do it:

1. Open your file in the editor and turn off the LTFT's in the Engine > Open/Closed Loop tab. Either select the Enable/Disable switch or set the Min Temp to Enable to 283F or do both if you wish.
A. Save this file as Rev 1x.hpt or whatever you like. Just make sure it's a different file name and don't write over your stock file!!!
2. Program the cal to the PCM using "Write Calibration Only"
3. Turn on the key, open the scanner, start scanning and open the "VCM Controls"
A. Go to the "Fuel & Spark" tab and press "Reset Fuel Trims" to clear out any LTFT's that were stored.
B. stop scanning - no point in logging a non-running engine.
C. Go to the MAF - STFT histogram(s) and then click on the [C] for cell counts.
D. Restart scanning.
4. Start the car & drive. Try to overlap MAF regions with different RPM's so that you get a very good average with different RPMs.
5. When you have at least 100+ hits (I shoot for 150+) in all of the lower Hz (below 4500 Hz) and tapering down in hit counts above 4500 Hz. I generally don't like hit counts with STFT's below 20.

Note: You can usually get to 6600 Hz without tripping PE fueling but my config filters out those PE fueling hits anyway.

6. Once the data is aquired, click the [A] for [A]verage STFT, select the entire MAF -STFT Filt5 histogram and copy all the data from there (Control - C).
7. Open the editor with your current file and go to the MAF table under Engine > Airflow.
8. Select the entire MAF table and right click, Paste - Special Multiply %
9. Save as a new file (Rev 1b.hpt etc...)
10. Write to the PCM with a Write Calibration Only.
11. Repeat as necessary until the error is in the +/- 1-2% range.

Now you have tuned your MAF! Enjoy the ride.

[zmanx]

Thank you, this should definetly help

[SS_bnoon_SS]

OK, EC Tune, I've used your config MAF!LTFT and the MAF -STFT Filt5 histogram yesterday and today. After driving, minimum 100+ hits, then paste special multiply %, I graph the new MAF settings in the tuner and it's ALL OVER THE PLACE. It looks like a mountain range going up and down, then tapering off in the upper ranges that were left stock. Granted I've only done it twice, but is this normal in the beginning??? I don't want to hurt anything...

By the way, MAF is unscreened by previous owner, so I know it should be a little unstable, but DANG! It's 15" away from the TB on the end of a CAI pipe, I thought it would be a little better than that.

[zmanx]

I decided to go the route of removing the SLP resistor and using a 6.0 truck MAF table. Runs way better. and also found that my EGR pipe was leaking.

[EC_Tune]

SS boon SS - Have you modified your VE table yet? That is usually the first thing I tackle in conjunction with any idle issues. If it's way off, your MAF table will be off (might not be WAY off though).

IF you saved them, post up your last log and your last tune(s). I'm not averse to smoothing the MAF table as it is affected by the VE table especially at the lower end. I hand smooth as well once I get the general curve of things. And I always compare the current MAF table to a stock MAF table for that vehicle. It gives me a general "sanity" check for the values at hand.

zmanx - Good catch on the resistor. I think that's all SLP does to the MAF IIRC. And a good find on the EGR pipe. That is a direct vacuum leak if it was the intake side of the pipe.

[zmanx]

SS boon SS - Have you modified your VE table yet? That is usually the first thing I tackle in conjunction with any idle issues. If it's way off, your MAF table will be off (might not be WAY off though).

IF you saved them, post up your last log and your last tune(s). I'm not averse to smoothing the MAF table as it is affected by the VE table especially at the lower end. I hand smooth as well once I get the general curve of things. And I always compare the current MAF table to a stock MAF table for that vehicle. It gives me a general "sanity" check for the values at hand.

zmanx - Good catch on the resistor. I think that's all SLP does to the MAF IIRC. And a good find on the EGR pipe. That is a direct vacuum leak if it was the intake side of the pipe.

Yea, it was on the intake side and the pipe was not seated right. Its like a whole new car now.

[Braemerz28]

-----------------------------------------------------
MAF tuning is quite easy. Here's how I do it:

1. Open your file in the editor and turn off the LTFT's in the Engine > Open/Closed Loop tab. Either select the Enable/Disable switch or set the Min Temp to Enable to 283F or do both if you wish.
A. Save this file as Rev 1x.hpt or whatever you like. Just make sure it's a different file name and don't write over your stock file!!!
2. Program the cal to the PCM using "Write Calibration Only"
3. Turn on the key, open the scanner, start scanning and open the "VCM Controls"
A. Go to the "Fuel & Spark" tab and press "Reset Fuel Trims" to clear out any LTFT's that were stored.
B. stop scanning - no point in logging a non-running engine.
C. Go to the MAF - STFT histogram(s) and then click on the [C] for cell counts.
D. Restart scanning.
4. Start the car & drive. Try to overlap MAF regions with different RPM's so that you get a very good average with different RPMs.
5. When you have at least 100+ hits (I shoot for 150+) in all of the lower Hz (below 4500 Hz) and tapering down in hit counts above 4500 Hz. I generally don't like hit counts with STFT's below 20.

Note: You can usually get to 6600 Hz without tripping PE fueling but my config filters out those PE fueling hits anyway.

6. Once the data is aquired, click the [A] for [A]verage STFT, select the entire MAF -STFT Filt5 histogram and copy all the data from there (Control - C).
7. Open the editor with your current file and go to the MAF table under Engine > Airflow.
8. Select the entire MAF table and right click, Paste - Special Multiply %
9. Save as a new file (Rev 1b.hpt etc...)
10. Write to the PCM with a Write Calibration Only.
11. Repeat as necessary until the error is in the +/- 1-2% range.

Now you have tuned your MAF! Enjoy the ride.

Sorry to jump in on the thread, but I've got a "noob" follow-up question...
I just did exactly what is suggested above on my 4.3L Sonoma (same basic programing as the LS1's). I've got every cell under 7200 Hz set to report less than 2% error, most cells with less than 1% error. Turned LTFT's back on after the tune and measured 1.1 or less with most being 0.5 or less. So, doing pretty good there (I think).

Question is: what's the best plan to adjust the cells above 7000 Hz? Or is this not needed because something else takes over?

I've got the wide-band in the tool box ready for the VE tuning step. This is starting to be fun!

Thanks!

[EC_Tune]

Question is: what's the best plan to adjust the cells above 7000 Hz? Or is this not needed because something else takes over?

I've got the wide-band in the tool box ready for the VE tuning step.

That's what you want to use for Power Enrichment tuning. It's pretty much the same but you will be using the MAF vs AFR error % histogram instead of fuel trims. I usually set a filter so that the MAF vs AFR Error% only reports when PE is active (Commanded AFR < 14.6). I think that histogram is in the GEN III V8 config repository as well. You will have to replace the "DynoJet" wideband in my config with the config for your wideband but that's essentially all you have to do besides plant the throttle...


You'll want to set up a VE tuning specific config & histograms and do that first before tuning the MAF.

[Gh0st]

That's what you want to use for Power Enrichment tuning. It's pretty much the same but you will be using the MAF vs AFR error % histogram instead of fuel trims. I usually set a filter so that the MAF vs AFR Error% only reports when PE is active (Commanded AFR < 14.6). I think that histogram is in the GEN III V8 config repository as well. You will have to replace the "DynoJet" wideband in my config with the config for your wideband but that's essentially all you have to do besides plant the throttle...


You'll want to set up a VE tuning specific config & histograms and do that first before tuning the MAF.

Ah, so when I'm trying to dune my MAF for WOT I want to use the MAF vs AFR Error % but when I'm tuning for just cruising and stuff I want to use the method you described above? Why not just use the MAF vs AFR Error % to do both?

[EC_Tune]

If you have the car in Open Loop you will be using AFR Error% exclusively.

[Red04RegencyRST]

Ah, so when I'm trying to dune my MAF for WOT I want to use the MAF vs AFR Error % but when I'm tuning for just cruising and stuff I want to use the method you described above? Why not just use the MAF vs AFR Error % to do both?

If you have the car in Open Loop you will be using AFR Error% exclusively.

so, if your going back into closed loop you dont want to tune your entire maf table this way? just above 7000hz, is that right?

[EC_Tune]

You want to verfiy the STFT/LTFT are in range but use the AFR ERR% for WOT only. You can have filters that keep closed loop data off the AFR Err% histograms so you can do both at once.

[ls1_doc]

So what happens when you take the average and it all goes to 0's ?

[EC_Tune]

Never happens. You did something wrong.

[Eat-Pez]

I'm a noob. How do i do this?

2. Program the cal to the PCM using "Write Calibration Only"

[Phil'sC5Vette]

I can open a configuration in the scanner and I see it, but when I open a tune and play it, the config doesnt work.

Is it because I did not have the configuration open and running durign the scan?

I was trying to use the MAF CFG

[EC_Tune]

You will copy the error term (LTFT, STFT, or AFR Error%) into your MAF table. If you re-open the scan file just right click on any histogram and select Load All Data.