TBI help?

[Nutro]

I recently rebuilt my throttle body and added a new Fuel pressure regulator spring. I got it all buttoned up and changed the plugs out. I fired it up and it's been idling a little bad. I let it idle yesterday and noticed a real strong smell of raw fuel at the tailpipe. I turned it off. Today I went to move it and when I ease into the throttle It is popping (Backfiring) a little. I realized I had bought a TBI fuel pressure regulator spring that bumps the FP to around 14 PSI. I ordered it thinking it was a 10 PSI spring.

My stock spring was pretty rusty so I am paranoid about yanking the TB and replacing it with the stock again. Is there anyone that sells a stock replacement spring? I Googled and can't find anything.

Also, I still feel like I had a miss and the exhaust stinks. I can't figure it out. It's not rotten egg like the converter is bad and it appears the cat was replaced in the last few years. I'm hoping it isn't burning coolant. No smoke so far.

I pulled the old Autolite plugs and installed some NGK plugs. Maybe that was a mistake as well.

The previous owner removed the emissions stuff from this 88. They left the EGR valve and the EGR solenoid with a vaccum line gong to the solenoid. That's it. No smog pump or tubes etc. The tubed were cut at the manifold and crimped. I'm betting he didn't pull the ECM and have it tuned, either.

 

[6872xtc]

My guess is that the computer had self tuned to the lower fuel pressure, as well as the other changes. Now it is having to deal with the higher fuel pressure, which will take some time. It may have bumped the injector on time up before, and now that's too much.

If it is really rich, it can cause a miss, but you would want to try and check if there is a bad spark plug or one that got fouled out from the extra fuel. (assuming that it is over-fueling)

 

[dyeager535]

Was it running ok before you did the work?

I believe you can google "TBI minimum air", and you will find the procedure. Anytime messing with the throttle body in depth, it doesnt hurt to make sure minimum air is set. Adding fuel (increased pressure) can be particularly problematic at idle, as at least some of these setups go open loop for idle, meaning the O2 sensor is not used to fine tune fueling. So I can see a need for resetting minimum air. It doesnt hurt anything when done properly, even if it turns out to not be needed.

All the TBI bolts/screws are tight? No vacuum leaks?

GM fuel spec is 9-13 PSI, but it is somewhat generally assumed anything less than 10 can cause issues. Conversely, adding fuel without tuning (such as increased pressure, larger injectors, etc) can cause issues as well.