New to FiTech - Failed Emissions...BADLY
Hey all,
So, I have a FiTech GoStreet 30003 system on a 350 SBC. Nothing radical...sits in a 1984 GMC Jimmy. Pump is an Aeromotive 340 on a painless relay with appropriate wiring all the way back. Have taken it on a few short trips around town (as I do not have current tags on the vehicle and purchased this system as part of my rebuild to ensure I could breeze through emissions). Maybe a total of 50 miles of drive time?
Took it to emissions today. Hydrocarbons were within range. Carbon Monoxide was more than double the acceptable range. Very frustrating. Vehicle runs. Starts up and idles down after a second or 6...but to see 107.6 grams of MO per mile leads me to believe my trust that this system would be a good long-term investment was misplaced.
Before I remove it carefully off the truck and break it into 1000 pieces with a sledgehammer (sorry, my frustration level at the entire project is pretty close to ready to burn it to the ground, LOL) ...does anyone have any ideas on places I can start? Things to check as to why my AFRs all show relatively within target but I failed so badly?
Sorry, I should follow this up with the info that I followed the suggestions regarding shielding the blue cable and swapping out the temp sender unit to the appropriate Delco one. Did all this during the initial install. MSD ProBillet HEI was checked to ensure timing was correct prior to leaving to the emissions station. Plugs and MSD plug wires are all relatively new (maybe 1.5 hours of run time, total).
Grounds are as follows: Single 0ga cable battery->block, 2-6ga cables battery->framerails, 2-10ga cables (1 to battery->firewall and 1 to battery->radiator support), 1-8ga block->firewall, 1-8ga block->framerail. Painless wiring advised more grounds are better when I rewired...so I tried to go overkill. Make sure there were plenty of grounds to go around.
Used the O2 sensor they included in the kit. Have a dedicated O2 bung welded into the system 4 inches behind the header collector.
Did not make any adjustments to target AFR or anything like that. Figured a stock setting should be adequate to drive with.
So what is your AFR setting at idle?
What type of fuel and octane are you using?
What is your spark plug gap?
What is your IAC at at idle?
Sounds like you are running rich and to much unburned gas.
“High CO means too much fuel. Fuel can only come from three sources: the crankcase vapor control system, the evaporative control system, or the actual fuel delivery system”
-Joe
Hey Jripp58,
AFR setting at idle says it is right at 13.6. In AZ, they do a dyno-based test where they take the truck through a sample 'test drive' so you don't just get idle AFR, they do gradual acceleration, moderate acceleration, decel, holding speed at 20mph for 4-5 sec, holding 55 mph for 4-5 sec...the whole works. I was rich the whole way, but ESPECIALLY under acceleration.
Use QT fuel, premium unleaded. Engine is 9.3:1 iron vortec headed SBC, 198-206@ .050 duration and .515-.525 lift. Timed straight up. MSD Pro-Billet HEI set at 8* idle, 32 total at 3700.
Gap is .050 on autolite mid-range heat plugs
I do have a PCV valve running from the valve cover to the passenger rear unported vacuum line. Breather cap on the other side...shows no real signs of puking oil anywhere. No oil blow-by through the exhaust (better not be, engine is brand new and we file/fit all our own ring packages to meet the bore...no guesswork).
IAC WAS 77...yes, I know way too high. I just found some additional instructions to make some adjustments and I was able to successfully set it to between 4-8. Reset the learn per the suggestions for IAC. Maybe this was part of my issue? Dunno. New to FI. Just knew that when it was cold, I needed more throttle to keep it running. When warm, it seems good.
So if it was me, I would dial in the IAC, Getting the correct amount of air in will help burn the fuel better, if you are running rich. This adjust could fix your problem.
The other thing I would check is your base timing seems like it should be more advanced (unless your engine builder said different) with the size cam you have I would think you would be between 10 and 12 deg advance at idle. If you are firing to late it will leave a lot of unburned fuel. Might want to check into that.
You can always turn on logging, drive it through the same paces as the testing and have FiTech give you more feed back.
-Joe
Depending on your cylinder heads, compression ratio, camshaft, and centrifugal advance curve in the distributor, "normal" base timing for a street high-perf small-block Chevy is somewhere in the 12- to 18-degree before top dead center (BTDC) range, with total timing at full centrifugal advance about 34 to 36 degrees ...Jan 11, 2019
Having trouble dialing in the IAC. When I start the engine and bring it up to temp, I can set to 4-7. When I drive around for a bit (I do have the electric fan assist engaged) and then let it idle, the IAC sits between 28 and 35...depending upon variables I haven't narrowed down yet. I would have thought the IAC would have come back to 4-7...but it did not. Frustrating...for sure. Is this expected? Also, it takes 20 sec or so for it to come down from 70-s to 30-s IAC steps when I stop the truck and put it into idle. I will say that the transmission does pull the idle down substantially when I go into gear. More than any other I've ever owned. Not sure why, but it does.
I also decided to set my Target AFRs up by .5 across the board. Will drive it around and watch the temps to see how the engine reacts. I SHOULD be able to run 89 octane with the lower compression, but have been running 92 just to be safe as I go to dial everything in. Maybe I should add some 89 to see if I get a more complete burn next time I try to do emissions?
As for the timing, I am the engine builder. I did a bowl job that was specifically designed to enhance the Vortec's great flame travel characteristics, already. We put the engine on our dyno and found that 8-9 initial (which went to 32-33.5 total) actually had better EGTs and power than 12-36.5. You are very correct that a normal SBC would need more timing, specifically for a cam of that size, but I widened the LSA on the cam for reduced overlap (read, more useable compression) and worked the heads to need less timing. Since I wasn't squeezing 10+ to 1 compression...I had plenty of room at the piston to alter the lobe timing and still have happy valves.
You could also possibly have a vacuum leak that is adding more O2 to the system and throwing off the IAC. Might want to check around the throttle body base and any vacuum hoses or accessories pulling vacuum from the vacuum connections on the throttle body.
-Joe
I suggest you follow the IAC setting procedure that involves moving the front and rear blades. Sometimes the rear blades can be off and not touching the set screw so they will fluctuate and mess up the IAC. I just copied these procedure in another thread:
Are you running a catalytic converter?