4l60 going bananas ! (maf sensor?)

[Boost]

I have an '07 Silverado (new style) regular cab shorbed witha 4.8 litre "C" engine. Of course it is untuned yet, I can't wait! It has 700 miles on it so far, already Mobil 1, lost the spare & tools, catback exhaust, and cold air intake.

My transmission is acting as if it's very badly broken. It slams EXTREMELY hard on the upshifts while cruising. I don't mean "good" hard. I mean it feels like a freight train rearended me, and can almost cause a concussion. I suspect the Mass Air Flow sensor.

Although the truck is not EFILive tuned yet, I would really appreciate some input from those of you with more experience than me with the 4L60.
I came across a used cold air intake from a 2500HD, and forced it to fit. In the process, it appears the MAF mesh part (honeycomb) got dented and slightly damaged. The check engine light keeps coming on, and the codes are
P0171 & P0174 (lean bank 1 & 2). I was wondering (hoping) if this could cause the horrible shifting.

As far as the intake is concerned, at first I thought I overoiled the filter. But there is also the possibility of the MAF damage causing the problem, or the little hose that used to plumb into the stock intake (looks like a PCV hose, I just put a breather on it, I think it still has the check valve).

The problem is intermittent, but seems to be increasing in frequency. Any thoughts would be greatly apprectiated.

[joecar]

Are you getting MAF codes...?

Any MAF codes may cause the PCM to put transmission into "fault" mode (Throttle Pressure is command to max causing Line Pressure to go to max)...

With the tune tool, go to Transmission Diagnostics and in all the tables you see there edit the MAF DTC's to "No".

You'll see in these tables (Fault Enablers, Max Pressure Fault Enablers, Fault Pressure Modifiers) all the DTC's that will tell the PCM command max pressure in the trans.

If the MAF is dirty/oiled/tampered, you may get lean DTC's... as you would if you had an air leak.

[Boost]

I cannot access or tune this truck with EFILive yet. It is an '07 new style. There are no MAF codes, just lean codes (171&174). Boy I am really hoping that by replacing the sensor tomorrow this will stop. It will eliminate the physical damage and the possible over oiling, only the PCV line and the aftermarket intake will remain. I sure hope my tranny is not broken at 700 miles ! Thanks

[ScarabEpic22]

Well, Im thinking maybe you are getting the lean bank codes because the CAI is giving the engine more than it can take, causing the ECM to see a way lean condition. There are some LL8 guys seeing this problem now as well, and it starts right after they get a CAI installed. Maybe pull the CAI for a little bit and see if it changes, then when EFILive can tune it put it back on.

[Boost]

Yes, but could a generic lean code cause my tranny to shift VERY VERY BAD?
Or did I break my tranny?

[ScarabEpic22]

I dont know for sure, but as joecar said, there could be a malfunction of the MAF sensor causing the trans to resort to high line pressure.

Im not an expert by far, just throwing ideas out there to see if something works until you can tune her and fix this problem. Also, if you pull the intake off and it still throws the code, see if you can get it reflashed at the dealership under warrenty.

[Boost]

Thanks for the ideas guys, that's exactly what I need, just different possibilities to keep me thinking more like the tech I am and less like a panicing customer.

I find today that I can manipulate the truck into not doing "it" by being very gentle on the throttle, and letting off on the shifts. Any steady throttle though, and BOOM, it tries to blast you into the Twilight Zone when it shifts. Feels like it's executing WOT full line pressure shifts all the time. This all makes me think that it IS throttle related. Also, perhaps a broken part in the tranny wouldn't be too intermittent.

As far as putting back the stock intake, well I kind of screwed myself out of that one. You see I traded it for this aftermarket one with a used car we have on the lot. Thanks, I'll keep you posted.

[Chevy366]

I do know from the AutoVE tuning on my 4l80E that with the MAF failed without turning off the line pressure increase like joecar stated it will bang real hard as you described .

[Boost]

Cool ! I'll replace it tomorrow and then have the tranny specialist drive it.

[Boost]

FIXED !

Replaced the broken MAF (Mass Air Flow Sensor) - apparently I broke it by overtightening the hose clamp on the aftermarket intake.
Cleared the codes, and now everything is normal. What a relief.

Thanks!

[ScarabEpic22]

Glad to hear you got it fixed on your new truck!!! Its so frustrating with things like this, but now you can get back to waiting for the cals to tune it.

[Boost]

Yes sir ! I may be one of the first to have a rough tune on one of these, as I am surrounded by them. Thanks for all the help as usual. :)

[joecar]

If you weren't getting any MAF codes, then possibly the PCM was failing the MAF rationality test (which I thought would throw a code) and placing the trans in fault mode.

Glad you got it fixed... :cheers:

What exactly did you do when you broke it (we can all learn something from this)...?

Cheers
Joe
:cheers:

[Boost]

I overtightened the hose clamp on the MAF for the aftermarket intake, since there was not much else holding it in place. It crushed the sensor and the honeycomb mesh in the front got out of shape.