Cracked Air Box

[old-tech-guy]

I've been chasing a problem for 6 months: my engine stalls frequently, usually at highway speeds, and usually under hard acceleration about 4000 RPM. And it bucks at 3 - 4,000 RPM. Based on great advice on this forum, I've done a lot of testing and inspection of fuses, relays, sensors, vacuum lines. I've replaced the DME Relay, I replaced the fuel filter. I added injector cleaner and water remover to the gasoline. I ordered new CHT and oxygen sensors from our host (they are not installed yet). Today I discovered the air box is cracked (see photo).

My question is: can this cause stalling and bucking? It's worse in hot weather and after the engine is warmed up.

[slodave]

I can only say this.... I have one (maybe two cracks) on the inside, like yours, but not to the edge. I don't have any of the problems that you are having. I really should epoxy the cracks, but have been super lazy!

Dave

[schnellmann]

Any air leaking in through there would still be metered by the AFM barn door, so this can't be the source of your problem. It's basically just letting in unfiltered air. You might need to clean the AFM contact track, or move the wiper arm itself to another arc path arc. If you search, you will find the info you need to do it. Lots of people have the same issue.

Or else you may have a leak on the other side of the AFM - like a cracked or disconnected hose...

[Racerbvd]

If you need a lower box, I have one

[stlrj]

You have a cracked air filter housing. The cracked air box problem is limited to CIS engines only.

Running a cracked housing, as you have, is no different than running without an air filter and has no effect on mixture.

Cheers,

Joe

[Zef]

Time to pass to an adapter and a cone filter...

[slodave]

Originally Posted by Zef

Time to pass to an adapter and a cone filter...

Yes, this would be a good time, but I know that in California, we need to have the OEM unit on for smog checks. As well, you could switch it back before the test...

Dave

[old-tech-guy]

That's great. Thanks for all the responses.

[stlrj]

JB Weld or even duct tape should take care of the cracks ( air tight is all that's needed here ) and since it's hidden in the back, nobody would ever know unless you told them.

Cheers,

Jose'
74 w/86 3.2

[88911coupe]

I just tried JB Weld on this same problem and have noticed the JB Weld seems to not be sticking particularly well. Is there some type of epoxy that would work? I know some epoxies don't work on some plastics but I have no idea what type of plastic is used on the Carrera air box...anyone know?
TIA

[HarryD]

Originally Posted by 88911coupe

I just tried JB Weld on this same problem and have noticed the JB Weld seems to not be sticking particularly well. Is there some type of epoxy that would work? I know some epoxies don't work on some plastics but I have no idea what type of plastic is used on the Carrera air box...anyone know?
TIA

JB Weld should work.

Clean the area very well with Carb Cleaner, scuff the surface with fine sandpaper to give a rough surface for the JB Weld to bind, wipe it down with more Carb Cleaner to remove the dust and after the solvent is gone, apply JB Weld.

[old-tech-guy]

I used LOCTITE 2-part epoxy. I glued a small piece of aluminum about 3/32" thick) to the outside of the box to reinforce it. Seems to be holding up well.

[Paulporsche]

CIS guys have used 3M 5200 Marine sealant on their boxes w/ good results. Someone reported he made a backer piece from pop bottle plastic, which is a type of polyethlene, to place behind the split.

[john walker's workshop]

the glue should have HDPE or PP on the bottle. 3M DP8005 is one type. not many glues melt into and bond with polyethylene/polypropylene.

[88911coupe]

Good information, thanks.