Got the plenum spacer and ECU reflash in my 2003 G35 about 1.5 years ago.
Everything fine until July "check engine" registered "multiple random misfire",
I researched the codes, one possible sympton was air leaking from manifold.
I decided to wait and see if "check engine light" came on again before doing anything drastic. A couple of weeks ago light comes on again, my buddy's check engine tool can't connect so I take it to the dealer.

New o2 sensor cleared one code but manifold leak prevents some kind of o2
measurement from clearing. Dealer tried tightening and loosing manifold (with spacer in it) can't get the code (and check engine light) to clear. Dealer says air is leaking from all around spacer. Inspection is due in Oct, in my state a car will not pass with "check engine" light on. ANy suggestions?

 

you should contact motordyne about this they might have suggestions.

 

did you try removing the spacer to see if the code goes away. then reinstall.

 

what spacer do you have, sounds like a skunk

 

+1. Also make sure u torque them down in the right pattern, and to the right specs.

 

The spacer is from altered atmosphere. My concern is that the dealer
over-tightened or tightened in the wrong order. They didn't call me to ask about the spacer, they just started playing with it trying to get the o2 fault to disappear. If they dameged anything, I'm f'ed. Dealer will say it's a non-authorized aftermarket part.

 

Get new gaskets for the spacer.

 

let me know what happens

 

+1, sounds like the easiest cheapest most probable fix.

 

what code are you getting ? I have code #P1444 and still not fixed

 

AAM uses a tapered spacer I think. Best thing is to get it out of there, and make sure you have no leaks stock, before 'upgrading' again. I hope you saved the original bolts. I think it is a mistake to try to fix it with the aftermarket part still installed. It will make troubleshooting more difficult because you are dealing with more unknowns.
If you can get it back to factory configuration and it is sealed, you will not have a problem with warranty. I would probably revert the flash to stock also, at least until you can get everything working normal again. Back to baseline.

 

Talked to AA, they said dealer could ahve damaged spacer and/or plenum by playing around with it. Start the car and spray carb cleaner around spacer and bolts in top, if engine sputters there is a leak. Did this after I got car from dealer, didn't notice any sputtering. Loosened all bolts in reverse order, then re-tightened in correct order. Again sprayed carb cleaner all around spacer and on bolts on top plenum, didn't notice any sputtering.

Check engine light is NOT on as dealer originally told me. They said car was running too lean, could lead to engine damage and burned out valves. I believe the measurement they referred to was the o2 level which they said was thru the roof at 130. I believe part of the ECU reflash is to make the air/fuel leaner than stock as stock is too rich. Can anyone confirm this? The dealer never mentioned the ECU so maybe they saw the lean mixture from the ECU reflash and blamed it on the spacer?

 

Can you say RTV?

Remove the plenum spacer, clean with solvent, apply RTV silicon, replace spacer... If done correctly, this will stop the leaking...
The plenum was not properly installed the first time; who installed it?