Data logging --> low Spark values.

[SVTContique]

So ive been having issues with my car lately, namely it seems to be really down on power under load (like it pulls normally until i put a decent amount of load on and then it falls on its face) so i decided to data log and see if i could find any anomalies.

When i did a pull the car was pulling fine and then had a sort of "hicup" around the 3200rpm mark (this is where its been falling on its face) on the data log i can see spark values and everything seems normal, than in an instant the spark value just drops from 21 to 14.5, as soon as i lifted it went back up.

Is this my car pulling timing due to detonation?

Edit: Should also mention that short fuel trim dropped from 1.01 to 0.82 around this time (no idea why).

I also noticed that the AFR jumps up at that point as well from around 11.5 to 12.6ish.

 

[01yellercobra]

Can you post the datalog?

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[SVTContique]

How can i upload the CSV file?

 

[encasedmetal]

datalog can usually be uploaded in excel form. however it sounds you could have a few possibilities.
1. knock sensors are pulling timing due to vibration somewhere (not neccessarily knocking but even exhaust vibrations can trigger the knock sensors)
2. your fuel trims are going into WOT fueling way too early as it seems you're in open loop as your STFT just read 0.82 when in open loop and your timing will be reduced at WOT values- so how close was your tune before this issue?
and a few other ideas I have but would be interested to see the logs as well. you should be able to datalog the knock sensors as well. also- do you have IMRC's still on the car- and are they tuned out if not?

 

[SVTContique]

I cant imagine it being a vibration otherwise wouldnt it do it at all kinds of load? this seems to happen only when i apply load (this implies open loop right?)

The tune was spot on for 2+ years and i havent modified the car at all in the last year other than maintenance.

I was thinking about the IMRC's being the problem, i havent gotten a chance to check them out but they always worked fine before.

Although if they werent opening, wouldnt my AFR be low rather than high?

 

[racebronco2]

I had a similar problem. I thought i gapped my plugs at .028 but the were gapped at .038 and on the dyno i hiccuped at 3200rpms and again at 5800rpms. Regapped the plugs and no hiccupp any more.

 

[SVTContique]

Now im having totally different issues...

The Car has a WACK AFR. Like at idle its running 10.8-9.8, if i give the throttle a little more than cruising speed the AFR jumps up to 13ish(just light throttle). And if i let off the AFR just jumps up to 15ish not 20+ afr which it normally would.

Its not my gauge because the car is definitly down on power.

Ive changed the plugs, the fuel pump.... the only thing i can think of now is the MAF is totally ****ed (ive reloaded my tune).

Is there anyway to check if the MAF is acting weird through a data log? Or should i just pull it out and try cleaning it with some contact cleaner...

I really cant be dumping money into another MAF as well... yeesh.

 

[johnnyrambo41]

Are the short fuels doing the same thing on both banks? if not maybe a lazy O2, if both side maybe a small vacuum leak, first of what car? NA? boosted?