Lean spike at idle and tip in on Warm Engine
Hello,
I have the Go EFI 600HP on a stock 350 SBC. I have a Tanks in-tank pump. It has been installed for about a month or so and I keep on having this odd lean spike after the engine warms up. It does not happen every time the engine gets warm, but does only seems to do it while driving. If I let the engine warm up in my driveway, I cannot reproduce the problem. What it boils down to is while driving it seems fine, but then it will die at a traffic light after get off the freeway, or just struggle and almost die before it catches itself. If I watch on the handheld, the AFR will go up to 20 at this time. I can start it right back up, but if I give it much gas, the AFR goes right back up to 20 and will almost die again. If I give it gas real slow, I can get the car to move. I have to baby it this way to get it home and while in my driveway I can watch it do this lean spike and then swing rich and it never seems to improve until I shut it down, let it cool, and start it the next day, when it is fine. I installed a fuel pressure gauge and it reads 50 at idle and this lean spike will continue but the pressure does not vary. I tried removing the vacuum line from the regulator and the pressure goes up to 58, but the lean spike is still there. So it does not appear to be the pump causing the lean out. (I also have the PMW set to 100%.) My IAC counts are difficult to keep steady, but right now are between 5 and 10. Idle AFR is set at 13.90.
Thoughts on what is causing this?
How is the fuel pump wired? I'm having a similar issue but have isolated the issue to my Mallory "inline" pump. It overheats above 90F and causes the exact same condition. I'm switching to an in-tank pump.
Not sure how the "Tanks" pump is configured/installed. Perhaps fill the tank & see if the condition goes away - if so, then your pump may be overheating when not emerged in fuel.
What is your AFR trim and AFR Learn when this issue is happening?
Quote from 69_R-Code on March 9, 2020, 11:50 amHow is the fuel pump wired? I'm having a similar issue but have isolated the issue to my Mallory "inline" pump. It overheats above 90F and causes the exact same condition. I'm switching to an in-tank pump.
Not sure how the "Tanks" pump is configured/installed. Perhaps fill the tank & see if the condition goes away - if so, then your pump may be overheating when not emerged in fuel.
Hi 69,
The Tanks pump is an in-tank pump. I do not have an in-line pump.
Quote from Austin DeHaas on March 9, 2020, 9:44 pmWhat is your AFR trim and AFR Learn when this issue is happening?
Austin,
I will check that next.
Quote from jbart on March 10, 2020, 9:30 amQuote from Austin DeHaas on March 9, 2020, 9:44 pmWhat is your AFR trim and AFR Learn when this issue is happening?
Austin,
I will check that next.
I made some changes since I last posted. I added a 2 gauge ground cable from the battery to the frame and then ran a 10 gauge cable from the throttle body directly to the battery. There is already a 4 gauge cable from the frame to the block. (The body is fiberglass, so no ground wires to the body.) Since I could not keep my IAC counts steady, I also replaced the IAC valve. I also reflashed the ECM by deleting the original settings and learning and started fresh with a new set up.
(BTW, FiTech uses two different IAC valves, one from a 1996 Camaro (AC Delco #19333273) and one from a 1996 Astro Van (Standard Motor Products # AC147). Mine is the Astro van style. You can tell which one you have by looking at the pintle and comparing the pictures of the part on Rock Auto).
It is now easier to keep my IAC counts steady. With the original one, every time I revved the engine and waited about 15 seconds for the idle to settle, I would get a different IAC number by about 30, without touching the idle screws. I'd have it set at 5, rev it, then get 35, then rev it and get 15, then rev it and get 30, then rev it and get 0. And so on. The new IAC seems to have fixed this. It is pretty stable now between about 10 and 15.
Since making these changes, it has not died on me when coasting to a traffic light or stop sign (the problem I identified above in my original post), but it is getting close. I can watch the idle, which is set for 750, sometimes drop to 500 before it catches and comes back up. I can watch it lean out as well.
(Austin, while it is doing this, the AFR Trim goes up to about 12 or 13 and AFR Learn stays about between 2 and 5.)
In an effort to totally eliminate this weird idle drop, I have turned off DFCO by raising the enable temp to max, no improvement. I then increased loop rate up from 25 to 55, no improvement. I then increased loop rate down from about 20 to 36, no improvement. I also tried dropping my idle AFR from 13.90 to 13.80, which might have improved it slightly, but it tough to say for sure. I still experience a weird idle drop and lean out when coasting to a light or stop sign.
So I am out of ideas at this point. Does anyone have any other ideas?
Jbart were u able to figure out what was the cause of your idle drop? Having the same issue.
Quote from Slick76tb on March 28, 2020, 12:26 amJbart were u able to figure out what was the cause of your idle drop? Having the same issue.
Which issue? I'm dealing with a couple. It has stopped dying, and I think the new ground cables, the computer reset, and the new IAC either fixed this or at least made it better. As far as the idle drop, but not dying, I think I may have fixed it, but it is too soon to know for sure.
After my last post, I called the FiTech tech line. After talking about the idle drop, the tech was convinced I was doing the opposite of what the engine wanted. He said to turn DFCO back on and restore the loop rate up and loop rate down settings back to default. I think loop rate up default is about 20, and loop rate down is about 10. After I did this, the odd drop at idle (down to 500 RPM at times even though it is set for 750) did seem about the same. I then reduced loop rate down to 5 and the idle drop seems to have totally gone away. The return to idle speed seems much more controlled now. I was unable to do any more test drives over the weekend, but plan to do so in the next day or two. I'll post up when I have more information.