smelly 454

[sparky]

after pulling my truck out of winter storage and running two tanks of premium fuel threw it it is getting smelly after sitting at idle in drive thru,s and traffic lights no codes coming up motor has 3 summers on it less than 20 thousand kls anyone have this happen it is a 1994 bravo stock bore 454 boat motor with 1999 279 casting heads tbi edelbrock intake manifold lunati efi camshaft installed staight up the mild one stock 1991 ecm 1999 gm dual exhaust with two cats i believe the timing is 5 degrees btdc

 

[andy396]

Could it simply be that the cats are dead? If you have an IR temperature gun, you could see what temp they're getting up to at around 2k rpm. I don't know the number off the top of my head, but it should be much hotter than the incoming exhaust pipe temp.

 

[sparky]

i hope not the y pipe with cats was 700 plus and they have less than 10 thousand kls on them

 

[sparky]

i just checked the timing it was at 6 degrees btdc the garage that did the etest may have moved it and did not tell me i have it at 4 now no stink yet but it pings on low acceleration im running 92 octane ill try moving it back a half degree and try again tomorrow

 

[Schurkey]

after pulling my truck out of winter storage and running two tanks of premium fuel threw it it is getting smelly after sitting at idle in drive thru,s and traffic lights no codes coming up motor has 3 summers on it less than 20 thousand kls anyone have this happen it is a 1994 bravo stock bore 454 boat motor with 1999 279 casting heads tbi edelbrock intake manifold lunati efi camshaft installed staight up the mild one stock 1991 ecm 1999 gm dual exhaust with two cats i believe the timing is 5 degrees btdc

i hope not the y pipe with cats was 700 plus and they have less than 10 thousand kls on them

1. Proper punctuation and sentence structure would be appreciated. That would be taught in our schools starting about third grade.

2. "Stink" in relation to exhaust gas is almost always a result of excess hydrocarbons. The other components of exhaust gas--water vapor, CO and CO2 are colorless and odorless. NOx has some color, and some odor, but isn't much of a problem at idle.

3. Excess hydrocarbon in exhaust is usually the result of MISFIRE, including misfire from too-lean fuel mixture. ANY cause of misfire will throw lots of hydrocarbon in the exhaust (except a non-firing fuel injector.)

4. Excess misfire can kill a catalyst in a few days.

5. I would connect a scan tool to read the data stream looking for clues.

6. A cylinder-balance test is good for finding weak or dead cylinders (misfiring cylinders)

Good luck!

 

[sparky]

sorry about the punctuation im happy i spelled it all correct for you the timing was the only thing that had changed like i said because of the etest i have not driven it far enough yet but it pings so we will reset the timing after i mark tdc again on the balancer