Hard start inconsistent afr
12-12-2021, 08:37 AM
#1
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Hard start inconsistent afr
Been trying at this for a minute and figured I'd try some outside input. Truck is an 03 5.3 with btr stage 3 cam, ported heads, Gen 4 intake w/90mm, and longtubes. Rn truck is run open loop on 91 without maf as I am trying to tune ve table. Recently I've had to double key the truck to start bc on first crank it either will not start or starts backfiring out the exhaust, 2nd attempt fires right up. Also my air/fuel seems to vary for example I'll get it to 14.7 at idle then after a short drive it drops to 14. I have replaced fuel pump and filter, stark plugs, cam sensor, crank sensor, and injectors. The intake holds pressure using a boost leak tester so i suspect no vacuum leaks. I have also checked and cleaned the 3 engine grounds. The throttle body is a remanufactured unit and the intake and x link were purchased new 1 month ago. I did notice with the engine off my scanner shows 98kpa instead of 100 but I wouldn't think that would cause a hard start? Any help is appreciated.
12-12-2021, 10:11 AM
#2
Can you post you tune?
try to throw some startup air at it and see if it helps. Then throw a little more cranking fuel at it.
Is the ECT and IAT consistent when tuning fuel at idle?
What injectors and you have the correct data in the tune?
try to throw some startup air at it and see if it helps. Then throw a little more cranking fuel at it.
Is the ECT and IAT consistent when tuning fuel at idle?
What injectors and you have the correct data in the tune?
12-12-2021, 10:49 AM
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I'm currently out of town for work but I can post tune in a few days. I did readjust base idle airflow and the etc area scalar for the 90mm. The injectors are 12613411 36lb that are set at 58psi static. I did update injector data with data from a post on here that said it was for those injectors with the exception of leaving the flow rate at 36lb. I don't believe I've ever had to mess with cranking fuel, any tips on how much to add? Engine is always at 190°f and 70-90°f iat while tuning
12-13-2021, 09:46 PM
#6
100% Redneck
Progressive Flow Rate
Static Flow Rate
12-13-2021, 11:00 PM
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Ok I should be home Wednesday and I will definitely try that. The injector data that I found for those injectors has that info but I thought the pressure being static would make the flow static. Just for clarification, my system is return style but w/o vacuum reference so my tables still need to be progressive?
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12-13-2021, 11:18 PM
#8
100% Redneck
Ok I should be home Wednesday and I will definitely try that. The injector data that I found for those injectors has that info but I thought the pressure being static would make the flow static. Just for clarification, my system is return style but w/o vacuum reference so my tables still need to be progressive?
When I had the old gen 3 truck intake with the vacuum regulator my 50lb/hr injectors were 50.4 across the table (shown in pic). Swapping to the TBSS intake and Corvette regulator I changed the flow rate to progressive 50.4 - 55.2 across the table (also shown in pic) My system is also return style