AdsoYo

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I'm sure I've said this before and I'll say it again. Bucking while cruising around town has been my arch nemesis since day one with this engine. I recently added a new weapon to my arsenal in the fight for all that is good and just: Ballenger Motorsports AFR500. It is literally a re-stickered NGK Powerdex AFX, and is the official continuation of that wide band. I bought the NTK calibration grade sensor to go along with it so there is no question about the wide band's accuracy.

It looks like the sensor has provided a clue towards a contributor for the bucking: lean cruise. I always suspected the car might have been running lean and the wide band confirmed it, showing an afr of 15:1 +/-0.2 for the cells I cruise around town in. 95% of the other cells that matter are 14.7 +/-0.2. Does anyone have any ideas for how I can fatten up the cells I cruise in? Mods are in the sig.

Base idle airflow was set with Russ K's config file. I tuned MAF and VE to death over the course of the last 9 months. Today I logged with the wide band then did Paste Special>Multiply by % for both MAF and VE tables. That didn't make any difference in my MAF and VE AFR error histograms afterwards. I changed MAP, LTFT, and RPM zone boundaries. My injector data isn't exact but it's close. I adjusted EOIT so that during cruise all fuel is injected AFTER the cam's overlap event so nothing gets sucked out the exhaust. Target AFR is set to 14.42254 since my local gas stations have up to 10% ethanol. Made some minor adjustments to the closed loop proportional and integrator tables for the mid length headers. Finally, I'm using a stock LT1 spark table.

I'll post my current tune and my latest log for those with hptuners. This log was done during some WOT tuning, after multiplying the VE and MAF tables by the AFR Error histogram.

ACE1252

I would have to have to re-verify this by hooking up my AFX wideband, but I think I saw 16's when I was cruising as well with my CC503. I don't have any bucking issues with it other than tip in at around 5 mph in a parking lot(when the engine is pulling the car at idle, no throttle). Locking in it speed density I can make the tip in problem go away with a 12.5:1 mixture.

One thing I have yet to do is to characterization the MAF curve on a dyno(steady state loading) along with the VE table.

I've been looking at your program and nothing is really jumping out to me as a major problem(I still need to do some more comparisons).

I've been keeping track of how you are doing and I'm really surprised that you are having these bucking problems. Did that 383 ever run on an LT1 PCM(I can't remember)? If so, was it okay?

AdsoYo

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And I appreciate the constant help, thank you! I can't believe you were cruising around at 16:1 AND didn't have any bucking issues. I was using an LT1 pcm up until last summer when I went 24x. I had it professionally dyno tuned on a mustang dyno and was having the same bucking issues I'm having now.

Shownomercy

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My car doesn't buck or anything at all, cruising is 16:1 area and any throttle quickly drops it to where it should be. Dat mpg lifez!

revolutions

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The fact that you had the same problem with the LT PCM should tell you it is not being caused by the tune or any component that was swapped. I don't know where to tell you to start since I don't know what has already been done but my first thought is a intermittently bad TPS, MAP or MAF. If you have access to a scanner that can record the waveform of sensors take a drive and then look for any anomalies in the recorded data.
There are many vehicles running around with a cruise AFR much leaner than 15.1:1 with no drivability issues.

AdsoYo

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So jelly...

I agree. My logs show those sensors working properly though. One of the reasons I'm convinced this can be solved through the tune is I've done it accidentally a few times. The PCM relearns its old habits within a few minutes though.

BIGsmokey10

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Agree with shown no mercy. Lean cruise is not your issue. My buddy Brians 700 whp turbo blazer goes down the road at 17:1 with 50 degrees of timing and it's smooth as butter.

I think its safe to assume you have another issue.

revolutions

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A log may not catch it that is why I asked if you had access to a scanner that would record a waveform. A log is *digital* for lack of a better term what I mean by that is it has a defined update rate but a scanner that can record a waveform will give you an *analog* recording. Think of it like this: if you were to data log the electricity in your home (60Hz) and the logger had a refresh rate of 120 frames/captures per second and you started the capture exactly at a peak the log would only show +120 and -120 alternating back and forth (square wave) but if you recorded the waveform you would see a sine wave save for some distortion.

Back when I was turning wrenches for a living I chased a stall problem for a few weeks driving a customer car at lunch everyday and never saw anything abnormal or got a SES light but I started systematically recording the waveform of sensors and ended up finding what I would describe as distortion in a crank sensor waveform. I did not mention your crank sensor in my original post since you didn't have it prior to the 24x conversion.

AdsoYo

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Interesting! Well it does it in speed density, open or closed loop. It seems to smooth out if I fatten up open loop, still need to find a pattern. Bought a new MAP sensor in 09 for the new engine, TPS is original with 230,000 miles on it. So you think one of my sensors is tweaking and I just can't detect it?

revolutions

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Yes I do.
I would start with the TPS.
Disconnect it and using an analog ohmmeter probe the pin that would have the blue wire connected to it and one of the other 2 pins.
Then slowly roll through the the accelerator watching for the needle on the ohmmeter to jump. I say use an analog meter because
they respond instantly and it makes it easier to find a glitch. If you don't see anything abnormal try doing a tap n wiggle test.
If still nothing with the TPS connected, the key on and using the dc volts setting of the meter connect the red lead to the blue wire and black lead
to the black wire perform the sweep and tap n wiggle tests again watching for voltage fluctuations.
It is recommended that you only do voltage tests with a digital meter as they have high internal resistance and there is no chance of overloading
a computer circuit on the other hand an analog meter may have low resistance which can damage a ckt when taking voltage readings.

The next thing I would check would be the MAP sensor.
Disconnect the MAP sensor’s electrical connector. Back probe terminal B (lt green) place the meter's red lead on the probe and the black lead on a known good ground.
Turn the ignition key ON voltage should be 4 to 5 volts with no vacuum applied. Apply vacuum to the MAP sensor’s with the hand vacuum pump slowly increasing the
amount and watch for a fluctuation. Do not exceed 20" of vacuum it can damage the sensor.
If all good including a tap n wiggle I will give it some more thought, I love a challenge and from the sounds of it this one has been a major thorn in your side.

moehorsepower

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[QUOTE=AdsoYo;18880544]I'm sure I've said this before and I'll say it again. Bucking while cruising around town has been my arch nemesis since day one with this engine.

. I always suspected the car might have been running lean and the wide band confirmed it, showing an afr of 15:1 +/-0.2 for the cells I cruise around town in. 95% of the other cells that matter are 14.7 +/-0.2. Does anyone have any ideas for how I can fatten up the cells I cruise in? Mods are in the sig.

Firsts off you need to know what you are doing, running you say 14.7 + or - 2 and running 15's is not lean, The motor is running in a no load condition and this is fine, as said some run up to 16 with no problems, I suspect you may have too much timing or you are going the wrong way with your AF, some people think that they are lean when in reality it is rich and the PCM correction factor is pulling fuel, then it adds, results..surging

AdsoYo

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This has been a major thorn since 2009. I'm glad you love challenges because I'll take all the help I can get. I'll try your ideas asap.

I don't think I'm misinterpreting my AF. Narrowbands are keeping the motor at lambda=1 which my wideband shows as 15:1. Now that others state their ride runs fine lean, I'm going to pursue other causes. Timing is okay, I've spent hours doing trial and error with my spark table and saw no results. I ran the car down to 19* and all the way up to 50*. The bucking was present all throughout that range of timing (actually got noticeably worse down low). I'll give revolutions' ideas a try as well as mess with EOIT and injector data some more. I'm also going to continue adjusting the VE and MAF tables with the new wideband.

moehorsepower

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If you want to fatten up down low and you are still running a MAF then log at what KPA vs TPS and or MAP you are in at cruise and go into those hz and add fuel, if you are SD, do the same with the VE tables. Since I am the opposite, I rune 96lb injectors and use the MAF to lean it out at idle and cruise.

ACE1252

Is it only doing this is 6th gear or is it happening in all gears? What speed? Is it surging or bucking steady state, tip in, or both?

AdsoYo

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When adding fuel with the MAF table, you decrease the values correct?

It's actually fine in 6th. The car shakes side-to-side ever so slightly at 60mph but as I go faster it smooths out quickly. 65mph is almost totally smooth and 70mph feels perfect. My main problem area where I do a large portion of my driving is 4th gear at 30-40mph (about 1800-1900 rpm), steady state. Tip in is fine.

revolutions

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I assume when you say bucking you mean it is like it stalls for a split second or it is like you get multiple consecutive misfires not just a simple miss.
Does weather effect how severe or how often it bucks. Do you drive it in all types of weather or only nice days.

moehorsepower

iTrader: (3)

[QUOTE=AdsoYo;18886594]When adding fuel with the MAF table, you decrease the values correct?


No, you increase the hz..Start slowly..

Purple Poncho

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[QUOTE=moehorsepower;18887260]Just to add to this: make sure every following number in the HZ field is higher then the last or you will get a hesitation at that RPM point.

RixTrix

What weight flywheel is on your motor?

moehorsepower

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??? what does that have to do with it...