Trouble setting idle on 408 build

[Glaser67]

Hey all,

Finally reached the point in my project where it's time to get her running. Build detail listed below. I have limited experience with Quarterhorse and Binary Editor, but had success with both on a mild 302 project, but this is a different animal...

Issue:
Unable to achieve a stable idle, or get RPM's over ~450

Symptoms:
Very low idle, won't rev, bucking, choking out, backfiring at times, no vacuum/low MAF voltage @ ~300-450 RPM

The build:
408w
Promax 205cc heads
FRP X303
1.7 RR
10.7:1 static compression
~0.035 quench
Stock 351 EFI upper/lower
MAF conversion
C&L 73? mm TB w/stock MAF sensor
A9L, GUFB, BE

The Tune:
Attached
Displacement set to 408
Injectors set to 30#/hr, no slop changes
Turn off emissions, VSS
Mono HEGO
set idle to 800 RPM
C&L 73mm MAF transfer

What's right:
managed to set base timing to 10 BDC w/spout unplugged
Fuel pressure set to 40 PSI W/O vacuum
Power/ground, and signal voltage to MAF sensor
<1.0 volt at idle for TPS

What I've done:
Set timing last night, verified power/Ref voltage to MAF
Fuel pressure gauge shows 40 PSI, no vacuum, but doesnt pull vacuum anyway at this rpm
Idles poorly with spout at at 10 degrees, bucks and backfires with spout in.
Almost no change with IAC plugged/unplugged
No change in backing down idle set screw with or without IAC
Side note; lots of water coming out of the pipes, no smell of gas whatsoever

Next:
Plug every vacuum line and PCV line to eliminate or find any vacuum leaks. IDK if the X303 wont pull vacuum or not at such a low RPM.
Missing my WB sensor, I'll install before I fire it up again and see where my AFR's are at.
Suggestion from another community was to increase fueling to see if it raises idle or RPM's, so I'll go there.

As I was just informed about this site, I see the GUFX and A9L2 calibration/strategies and am considering starting with those...

Any insight or pointer would be greatly appreciated.

[decipha]

backfiring out the exhaust means you have a misfire

popping through the intake means its lean

[dleach1407]

The tunes on the site are for TunerPro RT, not BE. I would suggest installing a wideband so you can see what the exhaust is seeing. If you changed your injectors to 30s, you need to adjust high slope, low slope, voltage offsets and break point. You can find injector data on the home page in the reference section. IF they are ford injectors, the data should be on the site.

[Glaser67]

Post by glaser67 » Sun Jan 02, 2022 5:51 pm

Hey all,

After making some fuel/air adjustments and still pulling zero vacuum, I believe I may have a mechanical issue or a more fundamental EFI issue (wiring, ect.)

After verifying the plug wires, setting up my wideband O2, and fiddling with the fueling, there was no change and figure I need to take a step back. Called Ford Performance and the gentlemen advised that the X303 should pull around 12"hg, at a very minimum of 10". He though it could be the gasket between the head and lower manifold that could be the issue. The guy at Promax heads had the same idea.

So this morning I did a cold leak down test across all 8 cylinders, and all held about 26 of 30 PSI, so at this point I believe the valve lash is not the issue.

Pulled the upper and lower off, and swapped in the stock 302/351 lower intake gaskets.

Afterwards decided to test my injector pulse, so I grounded the dizzy that I pulled in order to remove the intake, plugged it into the harness, and with the fuel pump relay (green) removed, turned on the ignition and spun the dizzy by hand, hoping to get an injector pulse 180 degrees from the firing position (within the rotor). When I had my spare injectors hooked up, while rotating the dizzy by hand, all 8 injectors are firing at the same time, 8 times per rotation of the dizzy. I cannot imagine how this is not a serious problem, UNLESS there is a cranking-specific strategy that is controlling the injector pulses. I used a stethoscope to verify every injector does have power/ground (verify they fire), but cannot verify the injector wiring is in the correct order while they all fire in unison.

Any idea on this behavior?

Thanks,
​​​​​​​Glaser67

[Glaser67]

A member from another forum (CGrey8) recalls that the injectors batch fire until ignition to #1 cylinder, so I moved forward putting it all back together with the stock 302/351 EFI gaskets, and it fired right up, idles, and pulls vacuum. Apparently the gaskets called for by the head manufacturer are too large of openings to seal with at least the 351 EFI lower.

Now on to tuning...

[decipha]

yeah it has to batch fire on crank until it sync's otherwise it wouldn't know which cylinder to fire

[dleach1407]

I always thought it turned over without firing the injectors until it found#1. Good info

[red5.0fogger]

The Buick GN engine has a long cranking time compared to the 5.0. It has sfi with a crank sensor and cam sensor and it waits till it sees #1. Smart using batch fire to light it on ours.