this isnt another dumb question thread so please read on...... I need some serious help figureing this out, well let me start at where it seemed like it all began, I got some gas at a chevron station that I've gotten bad gas at before, and about 15min. after getting gas this time I went to do some wot runs and at low rpm under throttle I got some major detonation, I thought it wuz the gas and seeing as how it wuz only 5 bucks worth I just didnt do any hard runs till I could get more gas run though the engine, well I filled it all the way up afterwords at another gas station and ran through that tank and when it wuz just about empty I put another 20 bucks worth in figureing that it would be all gone, I even changed the fuel filter today just incase, I went to do some more wot and I got the same detonation feeling, the other day I tried it in 3rd goin up a hill and went wot and the car detonated and accually stalled out, only took a couple seconds to start back up, well I babied it some more till I could get my efilive hooked up to see what wuz going on, there IS and was NO codes being thrown, no check engine light and no codes thrown when hooked up to efilivev5pro, I did some data logging today and when it detonates its not showing any KR, wtf?, sometimes it shows kr but its about 50/50, I got a 6.xx something kr at about 2k rpm and 50% throttle wich is very odd, I need somebody to look at this log I did and let me know if you have any ideaws, you'll have to reset your guage and chart config to view what I have logged,

I'll try to answer any common question but if you have anymore please let me know..

it seems only around 2k at 50% or more of throttle it detonates and I'm quik to lift off

if I go easy to higher rpm's it dosent seem to have any problems but I've only gone higher rpms maybe 2 times cause I'm scared of what would happen if it detonated at 5k

the exhaust plug is out and has been out for quite some time

I did not do any hard running of the engine before hand

the car has a mild cam and headers but they've been in for allmost a year w/ no tune and no previous problems

I'm going to check my plugs shortly havent had time yet,

there are no other leaks or loose vaccume lines or wires unplugged or loose ground wires



clicky for those of you w/ efi live, right click and save as "detonation.efi" and it should work

 

ok, guess I'll continue to try and figure it out on my own, thanks anyway

 

Honestly, it could be alot of things.

Just to name a few:
Crank Sensor
Cam Sensor
MAF Sensor
Ignition System

What is your MAF signal doing? If the MAF signal collapses (for whatever reason) you will about bounce your head off of the steering wheel on a hard run.

Are you sure it's detonation? If it is rattling or "marbles in your engine" sounding, it may be something mechanical like your valvetrain.

Good Luck

 

I think if I wuz at higher rpm's I would get that "head bounceing off steering wheel" feeling, it def. dosent sound like something rattleing, I can feel the whole car jerking when it does it, if it were any of those sensors wouldnt it set a code?
Here'z a few screen shots

 

That lean spike in the bank 1 O2 sensor on your first chart looks bad. But, it doesn't seem to happen every time you go to WOT...
The 2 part throttle KR's on the second chart also look to be a little lean, based on the average O2 sensor values.
It also looks like your fuel trims bounce around a bit from cell to cell... look at the 3rd KR in your second chart. The fuel trims go from -10 to 0 right when the KR happens...
Hope this helps...

 

if I'm under wot, the fuel trims go to 0, so I didnt figure I had a problem, what could cause the fuel trims to bounce around so much under normal driving?

 

Ummmm... I'll try to explain more.
The fuel trims vary by fuel trim cell. The PCM uses the closed loop O2 sensor values to adjust the fuel trims and try to keep 14.7 AFR (closed loop). The fuel trim cells are arranged by MAP and RPM (Main VE Table), so they more or less represent different load ranges of the engine. If all of your calibration tables in the PCM were perfectly accurate, and if the weather was constant, then it might be possible to get 0 fuel trims across the board. Real world isn't like that, so its normal to have your fuel trims a little different in each trim cell.
I have been doing some VE tuning lately - read the sticky thread for more info on VE tuning. Anyway, it seems that having large differences in fuel trims from one trim cell to another can cause stumbling problems at part throttle. This is why I mentioned the -10 to 0 transition from your log. A sudden 10% change in fueling will not be a smooth transition...
If you want to play around with your VE table, I suggest much reading on the subject and much logging to be sure you know what effects the changes are having.
cheers

 

thanks man, what are the frequency range supposed to be for the maf?

 

ok, update, I bought some maf safe electronic cleaner that leaves no resadue, cleaned the maf, cleaned my k&n, put the exhaust plug back in, took it for a test drive and it seems to have been a little better at first but it's still there under power, the banging sound is nowhere near as loud but it's still got the same feel, I have not ruled out clogged cats yet, anybody got something else I should try?

 

If it is an insanely loud backfire, I would start checking your timing / ignition system.

 

damn, this pos stalled out today, when I tried to pass somebody, it seems to happen mainly under low rpm torke, the plugs look good, and I unplugged the maf while it wuz running just to see if there wuz a change in idle and there wuz, so it seems to be in effect, how long does it take for the pcm to reset, 15 min.? there is stil no ses light on (besides the unplugging of the maf), I'ma go *** wit it right now, I'll double check the pcm reset when I get back on, I just plan on taking the + wire off the batt

 

check your fuel pressure.

 

been keepin an eye on that, I've got a fuel pressure guage in the car, it stays at 60psi, going wot it goes down to about 55psi but stays there,

This problem is not present unless under power, in my driveway I just did a log and tried slowly climbing the rev's to about 4k and holding there, no problems, when giving full throttle and revving the engine to about 5.5k still no problems, tried all different types of revving, the neighbors probably thought I wuz a ricer, lol, and still no problems, but if I'm making a pull down the road it feels like it wants to cut off, and still no ses light, I disconnected the batt. when I wuz done, I'm going to leave it like that for a while if I'm too busy I'll reconnect it and try again tomorrow, anymore ideaws?


edit: btw, my car is an M6

 

ok, had the batt. disconnected for over 24hrs., drove around a bit and went to test it out some more and still got the problem, its mianly low rpm at lower speeds in 1st 2nd and 3rd, not really there in 4,5,and 6, I quadrouple checked all the vaccue lines and electrical plugs, could there be any electrical components like the maf or something else that would not throw a code?, I'm tryin not to get overly frustrated but we all know how these stupid things can drive us nuts.. I'll try to list the things I've checked
retreive codes and data logging w/ efi live
checked spark plugs and wire connections
checked all electrical connections and visible wires
checked all vaccume lines and hoses
cleaned maf and air filter
reset pcm (disconnected for 24 hrs)
got good fuel in the system and good psi
oil is good
cant think of anything else right now............ uhh, maybe I need to wash the car and it'll go away, lol............ riiight

 

could one of those stupid ground wires on the back of the drivers side head popped loose and its barely making a connection and when the engine gets a little torke twist it dosent make connection?, what would that feeling be?