CEL MAF Implausible Signal

[amcocr]

Hi

I recently purchased an '03 RS6/50k miles with a Unitronic Stage 1 tune. Meticulously serviced by the previous owner with all records. Purchased in Charlotte, NC and driven back to Colorado with no issues. A day after I arrive in CO, the CEL comes on in the morning. I pull the code, generic P0101 "Mass or Volume Air Flow A Circuit Range/Performance." and specific code, DTC17416 P1008 "Mass air flow sensor 1/2 implausible signal." DTC Status sporadic: Open Circuit".

So far my mechanic has performed the following: 55k Service, replaced MAFs and Gaskets. Replaced Air Filters and ensured Air Box was sealed. Smoke test for air leaks. A small hole in the drivers side inter cooler was found. Unitronic Re-flash of the ECU.

So far nothing has fixed the issue. The car seems fine most of the time but their is occasional hesitation when I accelerate. Also note that the CEL goes out on its own and can stay off for a couple of days and other times it comes on and stays on for over a week. I think I've addressed the obvious culprits. Now I'm at a bit of a loss where to look next so any input to this problem is greatly appreciated.
18203

[mrdave]

Check the maf wires and plugs. The airbox traps a lot of heat from the turbos and can cook the wires underneath over time. Additionally, there's a hard bend coming off the driver's side maf harness that further fatigues the wires.

[amcocr]

Check the maf wires and plugs. The airbox traps a lot of heat from the turbos and can cook the wires underneath over time. Additionally, there's a hard bend coming off the driver's side maf harness that further fatigues the wires.

Thanks for the advice. I forgot to mention that Bank 1's MAF connector was fatigued and was rebuilt. So you think it could be further back in the harness?

[mrdave]

It's possible. There's a small metal "shelf" on the firewall that has a large bundle of wires routed over it. I had an ignition coil wire short out due to rubbing on that shelf.

Otherwise, have you tried switching the MAFs around and seeing if the code follows the MAF?

[amcocr]

It's possible. There's a small metal "shelf" on the firewall that has a large bundle of wires routed over it. I had an ignition coil wire short out due to rubbing on that shelf.

Otherwise, have you tried switching the MAFs around and seeing if the code follows the MAF?

Yes we did that. The issue stays on bank 1. It's consistent as far as the error is concerned. What's not consistent is when it triggers and that it clears itself.

[amcocr]

So in talking to my mechanic last night, he seems to think that the hole in the intercooler for bank 2 could be throwing off the MAF signals which is triggering the implausible signal error from the MAF on bank 1. Replacing the intercoolers is a costly repair for a "maybe" fix. Does this make sense to anyone? Thanks again.

[bethridg]

I'm no expert but it seems to me that it would require a LOT of air entering the system post MAF to trigger that error. Meaning a significant hole or disconnected boost hose. The stock intercoolers are known to leak from pin holes in the end tank welds. A common diy is the use of JB weld to seal the tanks. I used this method shortly after purchasing my car. I'd start there before throwing buckets of cash/parts at the problem.


http://www.rs6.com/showthread.php/21018-Intercooler-refurbishment-and-replacement-pictures

[amcocr]

I'm no expert but it seems to me that it would require a LOT of air entering the system post MAF to trigger that error. Meaning a significant hole or disconnected boost hose. The stock intercoolers are known to leak from pin holes in the end tank welds. A common diy is the use of JB weld to seal the tanks. I used this method shortly after purchasing my car. I'd start there before throwing buckets of cash/parts at the problem.


http://www.rs6.com/showthread.php/21018-Intercooler-refurbishment-and-replacement-pictures

Many thanks for the comment and the link. I'm going to question the size of the hole and go from there. Unfortunately I'm not mechanically gifted to perform repairs like you did. If I was going to change the intercoolers, do you have an opinion on Apikol?

[lswing]

Apikol, Wagner, or even checked and sealed stock intercoolers are fine...

Edit; if not already, upgrade all IC boost hoses to silicon, kit like Venair or Wagner, seals it up great and they don't pop off.