1971 Mustang
I have the FiTech EFI 4 600HP unit with a RobBMC PowerSurge pump. My engine is a 351 Cleveland, which is now stroked to 408. last year I first used the EFI with the 351 and recently with the 408. My engine setup is a 285/291 0.558" roller cam, Blue Thunder intake (dual plane) and Hooker headers. My cam setup now is #3. My idle is set at 890. Vacuum fluctuates between 10 and 12, but I have a know issue with a fluctuating idle due a distributor problem.
My installation is pretty hidden with the air filter on unless you have a trained eye. I purposely left the fuses exposed for quick check. I used Earl hoses and fittings throughout the installation. The pump works great and I insulated it very well since it sits relatively close to the header. The headers are ceramic coated and even went the extra mile to add insulation to the tube that nears the pump.
There is fine tuning that I have to do but now the car is away for the winter. It drove well but with a few nagging issues. I even drove it when it was 32 out and no major problem.
Nagging issues (both with the 351 and 408):
-Acceleration bug: I was able to tone this down by fine tuning the accelerator pump parameters. Now with the 408 the files were resetted so I need to work on fine tuning. However, I didn't find this process easy.
-Hanging idle: this one is annoying and dangerous. Even though my idle setting is 890, when I let the gas pedal go the idle hangs high. Sometimes as high as 2,000 and 2,500 rpm for a long while until I tap the gas pedal at which point it goes down to the 900 rpm target. The actual RPMs match the target RPMs. The hanging idle happens even when the TPS reads zero. I have my IACs in idle adjusted so that shouldn't be the issue. This happened less with the 351 and now more with the 408. I even changed the throttle cable spring to be tighter just in case, but since TPS is zero, I don't believe it is a throttle cable problem. The tighter spring creates another issue because the gas becomes hard to control when driving in town.
PS: I upgraded the firmware just before starting the 408
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Looks like a great build and thanks for all the info.
I can help you with the "hanging idle". Watch your handheld, monitor your IAC steps while idle is hanging. You will notice a high number that slowly reduces. This can be adjusted by raising the value on the IAC loop down setting. Sorry, I am tired. It is labeled something like that. Look in your Idle Control menu. Raising this number will increase the speed of the IAC closing, thus bringing it to idle much quicker.
Fyi. At that vacuum, setting 2 would be my choice. Would be interested to see a datalog.
Thanks for your reply. I have increased the value of Decel RPM Decay to the max of 15 to no avail. I also tried slightly increasing the Decel IAC Decay with no success. The RPM decay is maxed out, maybe I have to continue increasing the IAC decay but I am very close to the high limit. I could try setting the CAM at 2 but I don't think that will be changing my hanging idle issue too much. When I was running with the 351 I had the CAM setting at 2 and still had a similar problem.
I didn't mention your cam setting for that reason.
I have seen IAC motors go bad. Not common, but just saw one the other day.
I have not posted in a while because I had the car parked over the winter. I also replaced the differential and axles. The engine has not changed but this hanging idle issue seems to be getting worse.
Driving this weekend after cruising for a few minutes I will press the clutch pedal and the revs will stay up at 2,000 and sometimes 3,000 rpms. If above 2,000 rpms they will slowly come down to about 1,800-1,900 rpms and they will stay at the level indefinitely. If you tap the gas pedal hard it will then come down to the present idle of 900rpm. It is not the throttle because when this hanging idle happens the TPS is at 0%. It is an annoying issue. You can feel it all the time when you change gears, as I press the clutch the RPMs stay in the 2,000 rpm range.
Check your primary and secondary butterflies. Make sure they are closing fully. Also what does your IAC steps say when it is hanging.
I think there is a way to adjust the secondary butterfly, right? I will guess the primary is where the TPS is. It may be interesting checking the butterflies when "idle" is stuck in high and compared to "normal" idle. I am calling idle when the TPS is at 0%.
I will check once the rain stops around here. It may not be until the weekend.
Austin. I was finally able to play with the system. The secondaries were not closing all the way so I readjusted them so they are all the way close when in idle. It now takes a little bit of throttle movement to starting moving the secondaries. The idle issue has significantly improved, but it is not there yet. Now it is is settling at around 1,300-1,400 rpms. When at these rpms the TPS is zero and the IAC is at zero. If I tap the pedal it will go down to the set idle of 900 rpms. If I don't tap the pedal it will just stay at the higher RPMs. The weird thing is that the Target RPM value is also at 1,200-1,300 rpm. I would have thought that the target rpm should be at the idle setting value of 900 rpm.
This is a huge improvement but there is still something wrong that I can't figure out.
If you start it with the butterflies slightly open, that will be zero TPS. Check to make sure nothing is hanging.