TBI running rich? (1 Viewer)

[theo]

I have about 250 miles on a new Chev 5.7 TBI. ('76 FJ40) Starts easy, idles pretty well, runs very strong. But I have what I think is too strong exhaust smell - like I've been sitting on an old tractor all day. More fumes than I believe a brand new "modern" engine should be putting out. And they funnel back into the cab and are giving me headaches. Happens at all speeds and rpm.

I kept the smog pump, air rail, charcoal canister, EGR, etc. I don't have a catalytic converter. I'm running 2 external electric fuel pumps with a surge tank, 3/8" fuel line, 5/16" return line, 13 psi.

I replaced the O2 sensor (without testing the old one) then decided to get WinALDL working. I was thinking it wasn't going into closed loop for some reason, but it is. Here are some graphs for your amusement. The only odd thing I notice as a novice is the rich flag constantly cycling ON/OFF. Is that normal?

 

[Wayneraintree]

is it possible the EPROM does not match the engine/tranny combo? I have a 93' TBI 350 in my 55 and when I had an auto EPROM (though I run an SM465) it ran richer than you would believe... something about the idle for an auto is higher than a manual due to the load the auto in D creates (also park/neutral switch is monitored by the ECM).. so some differences exist. I switched the EPROM to a basic 93' worktruck (TBI 350 SM 465, no A/C, etc...) and viola! idles great and no codes. I know suppliers make custom EPROMS as well for the application.. HTH.

 

[Mr. Toad]

... I don't have a catalytic converter.

Exhaust smells worse when an engine is out of tune (too rich, too lean, incomplete combustion, etc.), but it's never going to smell like a new engine's exhaust unless it has all of the new engine components, like the cat.

Of course, the catalytic converter can make it's own interesting smells . . .

 

[theo]

is it possible the EPROM does not match the engine/tranny combo? ... HTH.

Yup, I'm using an auto chip with a manual tranny (NV4500), but lots of folks have done this before. Are they running rich and just not admitting it? I'm not throwing any codes but maybe I should try a different chip. Is it just the BLM table that's different?

Also, are all the chips interchangeable? I mean, do the pinouts stay the same no matter which OBD I EPROM you put in? Seems risky. I'll look into this some more.

thanks for the thoughts Jeffrey.