2003 GAGT 3400 lots of knock

[mr.rogers]

So i just picked up this car, its got 150kms on it and seems to be in pretty good shape. I haven't pulled it into the shop to get into much yet but i did find that it has a K&N filter in the stock box and there were 3 or 4 honeycombs smooshed in the MAF. I straightened them out as best I could, not sure if that is a big deal or not. This is the first car I have had with a MAF. The guy sold it cheap because he thinks there is a transmission problem but I was thinking its the MAF needing some cleaning. I sprayed it with carb medic, and cleaned up the air filter, took it for a drive and noticed tons of knock and fuel trims.
Oh i did throw half a can of seafoam in there, maybe it is causing the kr?
So how would one go about testing parts out?
Would a K&N make it that lean?
I don't know if i'm going to keep it yet so I probably won't tune it yet, and it should be in good condition before i start anyhow.
I have the dtcs that were on it from before with the stock tune and the config i used. Also if someone has a set of histograms and a config that works well for this car i would really appreciate it
Thanks, Mark

[planethax]

First and foremost you will want to make sure mechanically everything is in check before any tune.
A broken honeycomb can effect Maf readings.
150kms, you may want to start with plugs/wires/fuel filter etc first if they have not been done.

Then check condition of O2s

[mr.rogers]

i went and filled it with premium last night and bought a fuel filter for it that i will replace tonight. Think i might even have a spare maf laying around i could toss in. Ya i should have grabbed plugs for it too... here is the log on premium to work.

[mr.rogers]

and here is the lunch log. definitely running better but the knock is still there

[planethax]

Fuel trims off but I only see Bank1 o2 and bank 1 lt st

post your config file as well.

[mr.rogers]

I think i was using default metric or the ecotec one.
I just found the gtp one on here is that a good one for these cars?

[mr.rogers]

here is the drive home using this config, but i dont have the wb o2
Like i said I'm new to this and don't know how to use this software completely but i get the theory. so any settings you can recommend would help a lot.

[GeoJB]

Your Fuel trims are all over the place.
PM me your E-mail address & I can send you a "how to" for tuning the V-6.
Although it's for the 3.8, I believe you can use it for your car.

[GeoJB]

Oh ya, Just looked at your editor file.
You can use it.

[mr.rogers]

tonight i gave the intake a seafoam bath, changed the oil and fuel filter and maf again. reset the trims and took it for a drive and still got the same results. by looking at the log is it safe to say the O2 sensor is working properly? because there is a code for it and i was going to change it out next with a new set of plugs and maybe wires. after all this if its still not running properly does anyone have any suggestions as to what might be causing it? what are the chances the fpr has gone bad and is causing the lean condition on accel. or is the next step to just tune out the issues...

[planethax]

You will want to log Bank 1 Sensor 1 and Bank 2 Sensor 1,
Forget about Bank 1 Sensor 2 that just checks the Cat

[Russ K]

You will want to log Bank 1 Sensor 1 and Bank 2 Sensor 1,
Forget about Bank 1 Sensor 2 that just checks the Cat

This car doesn't have a B2 S1 O2 sensor. First test the fuel pressure at WOT, if ok replace the Maf sensor. The AFR is very lean under load as the B1S1 O2 drops to 30 mv. This will also cause an O2 low voltage or a lean fuel trim code.

And you need a wideband to tune the WOT AFR.

Russ Kemp

[mr.rogers]

what if i unplugged the maf and tried a log running off ve. that would take the maf out of the equation right? I will see if i have a pressure gauge around too. if the plugs were bad it would be showing up rich also, so maybe the injectors are plugged?

[planethax]

This car doesn't have a B2 S1 O2 sensor.....

Russ Kemp

Correct, I needed more coffee.
Thanx for the correction.

[MMGT1]

Those scans sure look like it has the crank position sensor issue happening to me. The 7X sensor in the 3400 is at the back of the engine, closest to the firewall. The heat back there is really harmful to the plastic casing that GM used to house the sensor. Over time it develops cracks and will skew the sensor output, resulting in the type of scan I see there. The other common problem is the connecting harness between that sensor and the spark module. From the heat I mentioned, the wire, which is a two wire lead, will sometimes fuse and cause skewed readings making the car go nuts at highway crusing speeds. Even stalling when coming to a stop from said speed range.... just a thought here, could be something to look at though for sure

[mr.rogers]

I will definitely take a look at that, but i believe the problem has been solved.
I grabbed 2 MAFs from the jy today and cleaned them up good. This is the log with the clean maf in and it seems to be much closer. only 1 or 2 degrees of knock and it shifts better and pulls harder now. I think I will take a stab at tuning it now.

[Russ K]

Looks a lot better, I've had several bad mafs cause the same issues. Lean AFR, spark knock & soft trans shifts.

Russ Kemp

[mr.rogers]

I completed the ve tuning portion last night and got a pretty smooth curve and trims +-4 or so on a quick drive. man it sure bangs the gears when the maf is disabled... I need to calibrate the maf now but im a bit lost on this step. the guide is for a 3800sc and the 3400 is a lot lower. also the cylinder skew is it worth while? if so how do you determine what is required. I will post the tune tonight for review if anything pops out. I just want to tune it on regular fuel as a dd so maybe i should use the LO table to start with?

[GeoJB]

keeping it stock? leave the scews alone.......for now..... Play with them later if you want too.
I would think the #'s you are referring to don't matter.
It's more of a matter of getting the trims within & inline with the 5% that you have the VE tune.

Go with the Lower timing table while bringing the trims inline.
If the car has a PE mode "turn it off" And don't go WOT at all.

AFTER the trims are where you are satisfied, then go for the timing table adjustments.
Keep the KR down while tuning by keeping the table on the low side.

Keep going.

BTW, now that you have the car running great for summer, you might need to re-adjust for winter.......

[mr.rogers]

This is a log of were I'm at right now, I tried the ve tuning but it looks like the knock is back. Its definitely still shifting fine there is so much knock. any suggestions? same config as before.