TBI questions

bbaxter51

bbaxter51

Well-Known Member
Joined
Jun 21, 2010
Location
Stillwater, MN
I swapped in a TBI setup out of a 91 GMC onto my 86 block with a fresh rebuild with a mild cam. Bad part is I got the motor out of a truck and have no clue what cam is actually in it. It's not lumpy and runs smooth.

Questions:
1. It used to smoke pretty bad, but after I unplugged the brown wire and adjusted the timing again, it smokes really randomly. At the flats I wheeled all day with minimal smoke. I sat idle while I winched a guy back on his wheels, looked back and couldn't see the trail for all the smoke I was blowing. I reved the piss out of it, it cleared and ran smoke free again for a while.

It seems like it's almost loading up when I'm not on the gas. The power is there, throttle response is great, just smokes. I bought a ODB1 usb cable and quickly realized I have no clue how to make it work with the free software that's out there.

I dont want to just start throwing sensors at it unless I know they're bad. I replaced the O2 sensor and cleaned the TPS. Where does a newb start to troubleshoot a TBI setup?

I'm sure I'm missing some details, so let me know what else you need to know to make a e-guess to what my issue is.
 
Almost positive that the o2 sensor doesn't really matter on these. I'd pull the plug and clean/replace. The coolant temp sensor will make these run crazy rich. What color smoke btw?
 
If its a carb cam or not stock or 'mild' you may need to tune the chip.

With a carb or 'RV' cam usually the vacuum signal changes (lower) from what the computer is expecting, it sees this as load on the engine and is using fuel values in a different column of the fuel table(s). When I ran TBI on my last jeep w/ a chevy 307 I had to adjust those value for that RPM and that load and tune that out..

Use winaldl and your cable to log some data...
 
I'd go ahead and check that temp sensor, I had this problem after doing a swap in an 89 and it flodded it. When they are bad they default to -40 F. It could just not be hooked up all the way. Also which tbi unit are you using the injectors are different for each motor, that and it wouldn't hurt to rebuild the tbi unit. It pretty easy and cheap to do. The temp sensor is about 12 bucks and the tbi rebuilt kit is bout 25.
 
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