Alright.. here's a pic of whats going on -

and the datamaster file http://www.harringtonfire.com/files/newr4n.uni

I'm not sure why I'm so rich at lower RPMs and good up higher. it avarages around 110 in the lower RPMs on the left side, with a slight split of 5 or so higher on the right.

I have replaced FPR, coil, plugs, wires, fuel filter.

car has PCM programming by herter, as a side note, I feel like I lost some lower end torque with his program, but gained a bunch on top. maybe related? I havn't contacted him as I havn't ruled out it being a problem with my car yet.

I have a slight miss occasionally at idle.

my car has intake, 2.5" dual exaust, 1.6 rr & new springs.. that should be about it as far as this is concerned.

any ideas?

 

If you post your DataMaster files in ".csv" format, those of us who prefer to use Excel can read them.

How long since the last time you "reset" the PCM? If you reset it recently, it might simply be a case of having spent more time in the low RPM/low load cells, and having them more fully "developed" than the upper range cells where you haven't spent a lot of time driving.

If it hasn't been reset for a while, and you feel those cell reading are representative of a full range of driving conditions, it could be something that is more pronounced at low loads. Leaking injectors would be a possibility.... they will affect the O2 readings more at low loads, when they have more time to drip. Possibly an EGR problem, since that will cause a rich condition, and would be less of a problem at higher engine loads, where MAP is higher and the EGR flow represents a smaller portion of total flow. A "miss" at idle would point to either of these problems as well.

Has your MAF sensor been molested?

 

Thanks for th quick response.

here is the CSV file

The PCM has not been reset for a few thousand miles. I see the problem in older scans aswell. I have not considered EGR as I have no stumble associated with quick throttle changes, and my highway mileage is good at about 26mpg. seems wierd. I'll have to research EGR problems some more.

as for the MAF, the screen is intact, and the only molestation has been a good cleaning with Q-tips and alcohol, which resulted in no change. I have tried running with the maf disconnected, aswell as running with my old non programmed PCM and I still have the same slight miss at idle (random, every 3-10 cycles, randomly but evenly distributed between the right and left tail pipe). I assume this is from too much fuel as when I change spark plugs it will run better for a mile or two before the miss returns, even though the plugs look fine.

I originally thought that this was due to a possible manifold gasket leak or something until I realized that that would make the mix appear more lean and cause the PCM to dump more fuel into the mix.

the blms arent bottoming out at 108 thought so I think that maybe whatever the problem is, the PCM is able to adjust for it, if that means anything.

so... looks like I need to get a new EGR valve and solenoid, along with a couple O2 sensors for good measure. those sound like a good shot?

Thanks for the help. I've been hunting this one for too long on my own & I cant seem to find any other posts with the same problem as this.

Ryan

 

You seem to have ruled out the possibility of a leaky injector (or several). Why not pull the rails up with the injectors intact, turn the key on (do not try and start it) to pressurize the fuel system, and look for drips from the injectors.

 

no, didnt rule 'em out, just forgot to mention that. no, I hadnt checked that, so I did that today. boy, those fuel rails were stuck in there, but no, turned the key to prime the pump, and no drips. (as a side note, the bolts that hold down the fuel rail were not there! scary. I found the right thread at the hardware store in the mean time, and ordered another set of bolts from gm.

I tried pluging the vacuum hose for EGR, no change.

I have no vacuum leaks, cood idle vacuum. around 19-20.

any other ideas? I've been hunting this idle pop / rich condition for a year now. not sure what to relace next :/

 

Hi, got your email.

You log does look similar to how mine did, BLM's idling around 108-110 and nearing 128 as air flow picks up. I've altered my MAF tables and am seeing around +-5% now centered on 128 BLM.

I will look at your csv tomorrow as its 1am ATM. Do you have tuning software ? Can you show me the MAF boundary tables for your tune ?

I'll get back to you tomorrow if i can

Mitch

 

Hi again , it's 7.45 i'm off to work , so a shortish post.
I've run your csv through my prog (Not filtered coolant_temp or MAP)
As you can see the L&R averages range from about 10% upto 0 just like mine did with the buggered MAF
THIS is mapped against the STOCK MAF setting, so i'd need to know what figures you actually have as cell boundaries.
AFAIK i can't get this data directly from any software , so have to make a table up manually for my program.

Hope this is if some use. (Not sure if it will view properly but can email it of desired )
Table of AFGS Boundaries Vs ALL BLM's -%age = RICH ( BLM<128) +%age=LEAN (BLM >128)

Freq AFGS LAvg RAvg Hits NewValue
1488 2.45 | L: 0 R: 0 Hits: 0 1488 2.45
1616 2.88 | L: 0 R: 0 Hits: 0 1616 2.88
1744 3.34 | L: 0 R: 0 Hits: 0 1744 3.34
1872 3.87 | L: 0 R: 0 Hits: 0 1872 3.87
2000 4.45 | L: 0 R: 0 Hits: 0 2000 4.45
2128 5.12 | L: 0 R: 0 Hits: 0 2128 5.12
2256 5.85 | L: 0 R: 0 Hits: 0 2256 5.85
2384 6.64 | L: -9.375 R: -7.812 Hits: 172 New: 2384 6.0694
2512 7.49 | L: -10.94 R: -10.16 Hits: 328 New: 2512 6.7
2640 8.41 | L: -10.16 R: -9.375 Hits: 659 New: 2640 7.5887
2768 9.4 | L: -10.16 R: -8.594 Hits: 193 New: 2768 8.5187
2986 10.46 | L: -8.594 R: -7.812 Hits: 158 New: 2986 9.602
3024 11.6 | L: -10.94 R: -9.375 Hits: 72 New: 3024 10.422
3152 12.82 | L: -12.5 R: -10.16 Hits: 86 New: 3152 11.368
3280 14.11 | L: -11.72 R: -8.594 Hits: 115 New: 3280 12.677
3408 15.48 | L: -13.28 R: -9.375 Hits: 120 New: 3408 13.726
3536 16.98 | L: -14.06 R: -9.375 Hits: 129 New: 3536 14.99
3664 18.6 | L: -12.5 R: -8.594 Hits: 146 New: 3664 16.638
3792 20.34 | L: -13.28 R: -8.594 Hits: 96 New: 3792 18.115
3920 22.22 | L: -13.28 R: -8.594 Hits: 72 New: 3920 19.79
================================================== ====================================
4048 24.23 | L: -10.94 R: -7.031 Hits: 58 New: 4048 22.053
4176 26.35 | L: -10.16 R: -7.031 Hits: 225 New: 4176 24.086
4304 28.6 | L: -9.375 R: -6.25 Hits: 130 New: 4304 26.366
4432 30.97 | L: -7.812 R: -4.688 Hits: 47 New: 4432 29.034
4560 33.43 | L: -7.031 R: -3.906 Hits: 78 New: 4560 31.602
4688 35.99 | L: -7.031 R: -3.906 Hits: 83 New: 4688 34.022
4816 38.69 | L: -7.031 R: -3.906 Hits: 74 New: 4816 36.574
4944 41.54 | L: -7.031 R: -4.688 Hits: 67 New: 4944 39.106
5072 44.52 | L: -6.25 R: -3.125 Hits: 64 New: 5072 42.433
5200 47.66 | L: -6.25 R: -3.125 Hits: 58 New: 5200 45.426
5328 50.97 | L: -5.469 R: -3.125 Hits: 20 New: 5328 48.78
5456 54.42 | L: -6.25 R: -3.125 Hits: 10 New: 5456 51.869
5584 58.04 | L: -5.469 R: -3.125 Hits: 30 New: 5584 55.546
5712 61.81 | L: -5.469 R: -3.125 Hits: 22 New: 5712 59.154
5840 65.77 | L: -5.469 R: -3.125 Hits: 32 New: 5840 62.944
5968 69.92 | L: -3.906 R: -2.344 Hits: 50 New: 5968 67.735
6096 74.27 | L: -4.688 R: -2.344 Hits: 31 New: 6096 71.659
6224 78.82 | L: -3.125 R: -1.562 Hits: 22 New: 6224 76.973
6352 83.59 | L: -3.906 R: -2.344 Hits: 23 New: 6352 80.978
6480 88.58 | L: -2.344 R: -0.7812 Hits: 29 New: 6480 87.196
================================================== ====================================
6608 93.8 | L: -2.344 R: -0.7812 Hits: 29 New: 6608 92.334
6736 99.25 | L: -2.344 R: -0.7812 Hits: 11 New: 6736 97.699
6864 104.93 | L: -1.562 R: -1.562 Hits: 5 New: 6864 103.29
6992 110.88 | L: -1.562 R: -1.562 Hits: 10 New: 6992 109.15
7120 117.04 | L: -6.25 R: -6.25 Hits: 3 New: 7120 109.72
7248 123.42 | L: 0 R: 0 Hits: 1 7248 123.42
7376 130.03 | L: 0 R: 0 Hits: 0 7376 130.03
7504 136.87 | L: 0 R: 0 Hits: 0 7504 136.87
7632 143.92 | L: 0 R: 0 Hits: 0 7632 143.92
7760 151.14 | L: 0 R: 0 Hits: 0 7760 151.14
7888 158.63 | L: 0 R: 0 Hits: 0 7888 158.63
8016 166.31 | L: 0 R: 0 Hits: 4 8016 166.31
8144 174.03 | L: 0 R: 0 Hits: 4 8144 174.03
8272 182.36 | L: 0 R: 0 Hits: 2 8272 182.36
8400 191.01 | L: 0 R: 0 Hits: 1 8400 191.01
8528 200.07 | L: 0 R: 0 Hits: 3 8528 200.07
8656 209.43 | L: 0 R: 0 Hits: 7 8656 209.43
8784 219.12 | L: 0 R: 0 Hits: 5 8784 219.12
8912 229.15 | L: 0 R: 0 Hits: 1 8912 229.15
9040 239.52 | L: 0 R: 0 Hits: 0 9040 239.52
================================================== ====================================
9168 250.23 | L: 0 R: 0 Hits: 0 9168 250.23
9296 261.3 | L: 0 R: 0 Hits: 0 9296 261.3
9424 272.71 | L: 0 R: 0 Hits: 0 9424 272.71
9552 284.48 | L: 0 R: 0 Hits: 0 9552 284.48
9680 296.61 | L: 0 R: 0 Hits: 0 9680 296.61
9808 309.1 | L: 0 R: 0 Hits: 0 9808 309.1
9936 321.96 | L: 0 R: 0 Hits: 0 9936 321.96
10064 335.2 | L: 0 R: 0 Hits: 0 10064 335.2
10192 348.8 | L: 0 R: 0 Hits: 0 10192 348.8
10320 362.77 | L: 0 R: 0 Hits: 0 10320 362.77
10448 377.14 | L: 0 R: 0 Hits: 0 10448 377.14
10576 391.88 | L: 0 R: 0 Hits: 0 10576 391.88
10704 407.02 | L: 0 R: 0 Hits: 0 10704 407.02
10832 422.55 | L: 0 R: 0 Hits: 0 10832 422.55
10960 438.46 | L: 0 R: 0 Hits: 0 10960 438.46
11088 454.78 | L: 0 R: 0 Hits: 0 11088 454.78
11216 471.51 | L: 0 R: 0 Hits: 0 11216 471.51


OK Can explain in more detail if needed.

HTH - Mitch

 

bugger the formatting has been lost, anyway, you can see the negative values around -10% reducing upto 0 as the airflow gets bigger.
BUT this is only true whilst the MAF boundaries are correct.

Any feedback welcome.

Mitch