throughly confused

[gojo83]

well I am working on learning the program better and have had a few ppl that have been a Godsend but here is where I am confused in the highway scan i was merging onto the highway and saw 5.71* of kr. watching the TPS and where pe mode starts it is rich then all of the sudden switches to lean. I didn't even go WOT any advice would be great as i don't get it at all. for the record the mod list is a P&P lim and gen v, 1.8 RR, intake and full exhaust with headers the pulley on it is a 3.5 and max boost I have seen is 7.7psi. any idea why it flipped why it did and how to change it would be great

[jackedupcanyon]

Is your wideband working? Why are you commanding 12.57-12.58 all the time? I did not see any PE or any lean points.

[gojo83]

the wideband is not working currently I will be working that issue this thanksgiving break

[n0dih]

Your datalogs are showing nearly exactly what mine are seeing.

Try this. Move PE mode up to 70%. You will probably note that the KR issue doesn't happen till 70% TPS now. Of course, you can't leave it like that, but I even ran mine to 100%, and KR didn't happen till 100%. It gets a bit better if I move it down to 30%, but the issue is still it pings....

the wideband is not working currently I will be working that issue this thanksgiving break

[Perforator]

I looked at the first scan and didn't see it go lean at wot. Are you sure you don't have something hitting like the downpipe or something?

[gojo83]

could it be as simple as the station I am getting the gas from is not truely putting premium in the pump but low octane gas instead. also I live at 6k feet in theory I should be able to go further then this based solely off altitude

[n0dih]

Remember, high alt reduces the octane requirement, 1 octane point per 1000 feet. So 93 at 6000 feet like it was when I was living at the base of Cheyenne Mountain is like 99 octane there. So even the 90 octane there was fine for my 10:1 455 Pontiac.

I have got gas from every station around, even went to E85, I still had this KR issue. E85 is 105 octane.... Mine has got worse and worse, I am seeing as high as 15 degrees KR! But taking off the Knock Attack to 0, I do NOT hear audible ping. But yet, calling it false, I don't as the movement of PE mode that can move the KR start point proves to me it is not FALSE knock, it must be real, but pulling timing out isn't curing it, so there MUST be a mechanical issue going on somewhere...

[n0dih]

Looking deeper at your datalogs, you have the EXACT same type issues I am seeing. Export to excel, looking in HPT isn't helping much, you need to look closely in Excel.

Look at the moment the KR starts, the MAF values are going DOWN yet, TPS is still up, KR increases and rpm increase momentarily stalls.

I am wondering if we are seeing something that is "backing" up and causing standing waves to impact the MAF readings. I am ready to go with a different MAF to test with (I have one from my Cadillac that I can use for testing that is a 3" MAF). I did try OL and SD mode, no dice, helped, but not the ISSUE.

I still wonder if I have a partially plugged up cat, I see mine run up to 6000 rpm just fine, but maybe I have partial flow?

[gojo83]

I have no cat and a 2.5 cat back that is what is really confusing me I should have flow like no other and header with that too

[n0dih]

I am running stock tune and having problems, where I didn't in the past. I went down to NGK TR5's then TR6's, no help, the only "mod" I have is gutted air box. I can't imagine that the air box would cause this many issues....

So rule out cat....

[gojo83]

I got a shop at my grandma's house i will go over everything with a fine tooth comb this break and see if I can pinpoint something

[n0dih]

Things I have learned:

1. Moving PE Mode threshold has largest effect bar none.
2. Colder plugs has no effect
3. E85 has very little effect, but some. just not as bad, but still there.
4. Different stations for 93 octane, no help. (Remember GM designed around 91)
5. Reducing timing helps very little
6. Adding fuel helps very little
7. Moving TCC points up or down, no effect
8. Turning on Burst Knock little effect
9. Adding more Accel Enrich, even extending the time Accel Enrich is on, no effect
10. 90-100F intake air vs 30F intake air, no effect.
11. Turning off knock control, eliminated KR, no audible KR. False Knock? But in all reality, how can it be false if PE mode thresh moves it?
12. Stock tune, modded tune, nothing helps.
13. (note I do NOT tune by NB's) I have run with NB's reading in PE Mode anywhere from 880-950mV, no change. Sorry, no bung yet for WB...
14. Open Loop, no change
15. MAF Mode vs SD Mode, no change
16. Transient Fuel modes, none make an effect

I am sure I have tried more.... These didn't do enough to eliminate it.

[TGP-37]

NB's are only good for stoich. It should be 14.7 AFR but I found my stoich is 14.5 due to ethanol added to the fuel.

I have read AFR's at 14.5 to 12 from the Wideband and the NB reads high 800's-low 900's. Point is, your NB readings mean nothing outside of stoich.

It can indicate a lean condition at WOT if NB is less then 850mv (guessing) but your AFR's could be way far off.

I would get knock at 12 AFR and slight knock at 11.6 in PE mode (boosted). 11.4 no knock period. Point given, the NB read about the same for all those different AFR's.

I'm just a beginner as well but I can tell you get your Wideband scanning to get a REAL reading of your AFR at PE. You may be slightly lean.


long story short: You really need a wideband scan.

[n0dih]

Found what fixed my problem, MAF. I went SD mode because I started getting MAF Low faults, and voila, the problem is 100% GONE.

I am in the middle of working on a LQ4 MAF for it, but the MAF wasn't reading, checking wiring when I can get time on the car (it is the main driver). Hope to get out there this afternoon and see if I can turn the MAF back on and get it working right.

NB's are only good for stoich. It should be 14.7 AFR but I found my stoich is 14.5 due to ethanol added to the fuel.

I have read AFR's at 14.5 to 12 from the Wideband and the NB reads high 800's-low 900's. Point is, your NB readings mean nothing outside of stoich.

It can indicate a lean condition at WOT if NB is less then 850mv (guessing) but your AFR's could be way far off.

I would get knock at 12 AFR and slight knock at 11.6 in PE mode (boosted). 11.4 no knock period. Point given, the NB read about the same for all those different AFR's.

I'm just a beginner as well but I can tell you get your Wideband scanning to get a REAL reading of your AFR at PE. You may be slightly lean.


long story short: You really need a wideband scan.

[TGP-37]

Found what fixed my problem, MAF. I went SD mode because I started getting MAF Low faults, and voila, the problem is 100% GONE.

I am in the middle of working on a LQ4 MAF for it, but the MAF wasn't reading, checking wiring when I can get time on the car (it is the main driver). Hope to get out there this afternoon and see if I can turn the MAF back on and get it working right.

I had a dirty MAF once run me in circles until I decided to spray clean it. Such a delicate sensor for such an important reading.

Good Luck!

[n0dih]

Was the output low or dead 0? Mine is reading zero, null, nix, nada, nothing.... I might go see if I can get some cleaner, but with a dead output I am suspecting it is a dead sensor unless that is how they fail just by being dirty. I haven't had a bad MAF before.

Anyone ever actually take one apart?

I had a dirty MAF once run me in circles until I decided to spray clean it. Such a delicate sensor for such an important reading.

Good Luck!

[TGP-37]

Was the output low or dead 0? Mine is reading zero, null, nix, nada, nothing.... I might go see if I can get some cleaner, but with a dead output I am suspecting it is a dead sensor unless that is how they fail just by being dirty. I haven't had a bad MAF before.

Anyone ever actually take one apart?

I can't say for sure. I do believe I had an altered signal. Sometimes wires break at the terminal area. Especially if they are old, moved often and pulled on hard at some point during repairs.

I would use a multi meter to test for open circuits from the female plug at the sensor to the PCM terminal. If all wires are good, you probably have a dead MAF. I'm not sure if there is any way to fix it. I'm sure there are other ways to test the MAF but I just don't know them of hand.

If you alter the PCM, did you check the MAF fail frequency?

Did you check all grounds are good? Some sensors do crazy stuff if a ground is failing.

And maybe, just maybe, cleaning it would fix the issue.

[murphinator]

I had a maf that was completely dropping out on me , ended up being corrosin internally in the connector - green crud , a co worker had the tools to take the connector apart and clean it from when he worked at a gm dealer no issues after

as far as cleaning the sensor use maf specific cleaner , its a sensitive sensor CRC makes a maf sensor cleaner

[TGP-37]

I had a maf that was completely dropping out on me , ended up being corrosin internally in the connector - green crud , a co worker had the tools to take the connector apart and clean it from when he worked at a gm dealer no issues after

as far as cleaning the sensor use maf specific cleaner , its a sensitive sensor CRC makes a maf sensor cleaner

I like to use dielectric grease for such connections. Especially 5v ref terminals. It helps prevent that green crap.

Spray MAF cleaners work great, just NEVER touch the wires that reads the air flow. The slightest finger grease can throw readings off enough to screw up LTFT's.