Fast EZ EFI Driveability Problems ? - Chevy Nova Forum
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Old 13th-December-2011, 10:33 PM   #1
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Fast EZ EFI Driveability Problems ?

My first EFI install. Went on a new crate 383, broken in on the dyno by the builder with all the parts from the same FAST kit.
Cam is flat tappet with .490/.490 lift, 230/236 duration at .050.
Fuel system is the FAST kit with their pump and regulator coming off the stock pickup with pump mounted slightly lower than tank.
Went through the normal setup wizard and was having a lot of trouble with the engine stalling at every stop.
I spent several sessions on the phone with FAST tech rep and after his suggested adjustments, mainly getting the IAC adjusted to the high teens, low 20's at idle, it is better, but still dies on about 1 out of 5 stops while driving. I thought it might be a fuel slosh problem uncovering the pickup and losing fuel pressure, so I added about half a tank of gas and still have the same problem.The FAST rep that I have been dealing with seems to out of answers. During the stops when the engine dies, it seems to dip way below the set idle speed and doesn't recover. Starts right back up.
Anyone here have simalar issues? Any help would be greatly appreciated.
Thanks
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Old 13th-December-2011, 11:02 PM   #2
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Poor electrical connection??Vacuum leak at booster when braking?RF interference from other components?have you tried watching various sensor readings when the idle dips? Does the IAC count go up or down? meaning is it trying to correct or is it actually closing down?Chucks had issues but not what your describing.
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Old 13th-December-2011, 11:10 PM   #3
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Thanks for the suggestions Bryan. It does have power brakes. I will check that first.
It does the same thing at times while it is parked and idling when you blip the throttle, but not every time.
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Old 14th-December-2011, 10:43 AM   #4
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As Brian said (& probably the tech), they are real critical for clean power and interference. Only done two with a third waiting in the shop, but haven't had that, or a problem with the ones I've done.
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Old 14th-December-2011, 09:29 PM   #5
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Thanks Walt, I am using their RPM module which they kind of advise against. I am going to block the brake booster tomorrow and try again. Power wires to ECM are #12 direct to battery, so I don't think that is the problem. If I had an MSD laying around I would try that because it is the prefered source for the RPM signal.
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Old 14th-December-2011, 09:37 PM   #6
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Remove any un-used wires in the FAST harness. meaning pull them out and cut them off at the computer. They act like antennas and cause interference within the harness and cause erratic signals to be interpreted. I've been through it before with FAST XFI, I work at a speed/restoration shop. Also disconnect the IAC, set your TPS to the recommended voltage (somewhere around .5) at idle and drive it. See if that helps. Holley has a similar problem with their Avenger system and we've had to eliminate the IAC. I might wait to cut your harness but i'd pull out any un-used circuits for sure. also, according to a couple of our local tuners the further you stray away from stock engines the IAC usually gets deleted, it's not uncommon.
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Old 14th-December-2011, 09:40 PM   #7
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hey Ken, Dave had a FAST unit on his '67 before switching to the LS... he went through a few diagnostic sessions with his, if you holler at him to look at this thread he might have something for ya... hopefully/maybe
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Old 14th-December-2011, 09:41 PM   #8
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And all that IAC, harness stuff doesn't mean anything if you're losing fuel psi. If you can monitor psi on your stops with a guage taped to the winshield that would help
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Old 14th-December-2011, 09:49 PM   #9
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you need to see what the IAC count is when this is happening. it is real easy to miss adjust the IAC and have this problem.
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Old 14th-December-2011, 10:24 PM   #10
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Quote:
Originally Posted by Rantnrave1969 View Post
And all that IAC, harness stuff doesn't mean anything if you're losing fuel psi. If you can monitor psi on your stops with a guage taped to the winshield that would help
That was the techs suggestion. I may have to try that.
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Old 14th-December-2011, 10:28 PM   #11
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Originally Posted by David_H View Post
you need to see what the IAC count is when this is happening. it is real easy to miss adjust the IAC and have this problem.
IAC has been all over the place. I have it where the tech suggested, about 20 at idle but will have to see where it is going during the problem occurances.
Is it normal for it to increase as you open the throttle? This stuff is all new to me.
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Old 14th-December-2011, 10:49 PM   #12
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to simplify, think of the IAC like this... its job is to control the engine rpm in small increments. when you put a lil load on the engine at idle like a/c or when the fans kick on, in order to keep the rpm up and have a "seamless" operation of those accessories, the IAC lets air in. the counts should go up on a scan tool.
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Old 14th-December-2011, 11:39 PM   #13
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Quote:
Originally Posted by plumrat View Post
IAC has been all over the place. I have it where the tech suggested, about 20 at idle but will have to see where it is going during the problem occurances.
Is it normal for it to increase as you open the throttle? This stuff is all new to me.
An IAC is like an idle circuit on a carburetor. Once you are firmly in the throttle it should be closed.
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Old 2nd-January-2012, 12:15 AM   #14
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I have a ls2 with ezi efi very similar size cam and had the same problems the first thing i suggest is reset to a new tune, stick with the 13.5 idle 14 cruise and 12.8 wot and accell on 00 , then when the engine is running ckeck your load percentage in the live data, with a large cam and low vacumm signal your load percentage at low idle will be very close to 50% and thats when the ECU changes from the idle map to cruise map and the ECU has problems staying in the idle section of the tune, the best way to fix this and get it down near 40% is to lift the idle a little higher, you will notice the load percentage will come down lower as idle goes higher and this will keep it away from that 50%. What happens is when you sit ther idling its all fine but when you drive the car and you deaccellerate the load percentage drops into and out of the 50% load range and has trouble coming back to the idle map, this is why ezi efi doesnt work that well with camshafts that have low vacum as they dont recommend anything under 8 inchs of vacum, my camshaft runs between 5 and 6 inchs at idle. Another thing that helps is timing i have the msd 6010 and can map the timing map via lap top if the timing is very erratic at idle it wont help keep a steady idle i have kept mine at around 17 to 20 degrees at idle and set the vacum advance map to keep a far bit of advance when you deaccelerate and helps the idle from dipping right down when your back off the throttle. My idle is set at 850 a little high than i would like but the only way to keep around 42% load at idle. after you drive for a while you will probably find that you accell works best at -2 or -3. I hope this helps and makes sense i have spent a massive amount of time with this ezi efi as i feel its a great product and was determined to make it work.ecub
Quote:
Originally Posted by plumrat View Post
My first EFI install. Went on a new crate 383, broken in on the dyno by the builder with all the parts from the same FAST kit.
Cam is flat tappet with .490/.490 lift, 230/236 duration at .050.
Fuel system is the FAST kit with their pump and regulator coming off the stock pickup with pump mounted slightly lower than tank.
Went through the normal setup wizard and was having a lot of trouble with the engine stalling at every stop.
I spent several sessions on the phone with FAST tech rep and after his suggested adjustments, mainly getting the IAC adjusted to the high teens, low 20's at idle, it is better, but still dies on about 1 out of 5 stops while driving. I thought it might be a fuel slosh problem uncovering the pickup and losing fuel pressure, so I added about half a tank of gas and still have the same problem.The FAST rep that I have been dealing with seems to out of answers. During the stops when the engine dies, it seems to dip way below the set idle speed and doesn't recover. Starts right back up.
Anyone here have simalar issues? Any help would be greatly appreciated.
Thanks
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