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Old 11-08-2010, 02:41 PM   #1
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Default L67 tuning help

I'll admit I'm new to a lot of this, but this has me confused.

I was trying to tune VE tables, and had very little success doing so. I've read a few tutorials showing how to do it, but it doesn't seem to work quite right for me. The reason for that is that with the MAF unplugged and the PCM presumably in speed density mode, I can raise my VE table numbers to their maximum of 200 and LTFTs will still be positive and in the red.

What am I doing wrong? When the MAF is plugged in, everything is working just fine and the engine is actually running a little too rich.
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Old 11-08-2010, 03:51 PM   #2
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each time after you flash and before you datalog more are you resetting the fuel trims?
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Old 11-08-2010, 03:55 PM   #3
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each time after you flash and before you datalog more are you resetting the fuel trims?
I'm not resetting them after I flash, but I am before I datalog.
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Old 11-08-2010, 04:25 PM   #4
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If I remember right, when doing a VE tune, you reset the fuel trims only one time.
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Old 11-08-2010, 04:36 PM   #5
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you have PE disabled, right?
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Old 11-08-2010, 04:46 PM   #6
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you have PE disabled, right?
Nope. I thought PE was supposed to cause the car to run more rich under acceleration above a certain point, not run asininely lean at idle.
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Old 11-08-2010, 05:43 PM   #7
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You need to follow all the steps for a VE tune.
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Old 11-10-2010, 11:34 AM   #8
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Bob, Cam'* tune is identical to mine in every single way with the exception of the disabled DTCs and the trans tune. Regardless, I tried flashing it and it made no difference, aside from forcing my trans to run in limp mode from the moment it started up.

I found some dude'* very comprehensive tuning guide on 60degreev6. Forgot what his name was, but it seems everyone'* using his tutorial.

I want to VE tune. Unless someone can prove to me that it does absolutely nothing, I want that dialed in.

The PCM is a 99 Monte Carlo L36 PCM. This is an L67 swap in a 95 Regal with headers, 3.4 pulley, CAI, autolite 104'*, 3" high flow cat, 2.5" exhaust, and 3.29 gearing.

Now here'* what happens. I disable PE, and I fail the MAF by unplugging it. The tune instructions show that I should be able to fail the MAF in the tune, but I don't have those options available to me when I go in there in hptuners. Not sure why, as many tabs are completely blank. Anyways, that'* where I'm at. When I turn the car on, it takes a long time to crank. Actually, it always takes a long time to crank, with or without the MAF plugged in. Once it starts up, the idle is very, very rough and I have to keep my foot on the gas to keep the engine alive. During this time, a very loud howling/suction noise is coming from the engine bay. I've determined this to be the IAC valve being wide open. Here'* the problem. If I let it sit for a while and give it some gas, after abotu 5-10 minutes, eventually that howling noise will go away. I can then sit and rev around a bit, and as the scanner is populating the LTFT cells, that noise comes and goes a bit, but not as loud as in the beginning. I can then get it to the point where if I just sit in idle, I will have a great, steady idle.

However, the moment I start driving around again, that howling noise comes back.

Here'* the problem. When that howling noise comes on at first, it causes my STFT'* to run off the scale as extremely lean. At the same time, the O2 sensor is reporting very low numbers (60-80), and there is a very strong and obvious smell of gas out of the exhaust. When that howling noise goes away, the O2 sensor starts reading rich, and the STFT'* go in the other direction and also read very rich. All it takes is for me to start driving around again, and the IAC will open up and throw off all of my data.

Here'* another thing. I can command a certain RPM using VCM controls in the hptuners scanner. With the MAF plugged in, it will run at the commanded speed. However, in SD mode with the MAF unplugged, if I command 800 RPM, the IAC valve will open wide again and it will idle between 1200 and 1700 despite being commanded at 800.

I have no clue what'* going on here. It seems to be working fine with the MAF plugged in, but that'* about it. Any idea what this could be?
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Old 11-11-2010, 12:38 AM   #9
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Very odd, it sounds like a huge vacuum leak. This is why your coming in as lean. What'* funny is I just tuned a top swap this last Sunday and the scans looked a lot like what your describing. Scan say lean, O2 running in double digits, and I could smell gas from the exhaust. Turned out being plugs 2 and 4 had the wires switched. Are you sure all the wires are connected right? This seems like a sensor problem more then a tune problem.
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Old 11-11-2010, 01:34 AM   #10
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Very odd, it sounds like a huge vacuum leak. This is why your coming in as lean. What'* funny is I just tuned a top swap this last Sunday and the scans looked a lot like what your describing. Scan say lean, O2 running in double digits, and I could smell gas from the exhaust. Turned out being plugs 2 and 4 had the wires switched. Are you sure all the wires are connected right? This seems like a sensor problem more then a tune problem.
Yes, except with the MAF sensor plugged in, I can beat a 2008 Audi S4 from 0-60 (which actually happened on my birthday). The only problem with this engine comes only when the MAF is unplugged and I'm trying to tune in SD mode.
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