Not so EZ-EFI Question

[TnBlkC230WZ]

I installed an EZ-EFI system on my Nova about six - eight weeks ago. I had two issues, one with the idle and cold driving and the other with fuel pressure. several weeks ago, I resolved the fuel pressure issue which was a filter problem.

I'm still stuck with the inconsistant idle. I've talked to FAST a couple of times but they only want to blame my car. Vacuum leaks and faulty charging system to name two. The car ran perfectly with the carb and was dyno'd by Dyno Speed Racing to get a bench march of power curve and A/F ratios the week before I started the install. I've had it back to Dyno Speed who says there is an issue with the EZ-EFI and I took it to another shop to confirm there isn't a vacuum leak. I'm hoping someone has a suggestion for my problem listed below?

Engine (nothing fancy): ZZ4 with:
Weiand Air Strike intake
1.6 rockers
Comp Cams 26955 springs and matching retainers
Manley Street flow valves (stock size).
Valve job in April.
No porting and the short block is stock.

6 speed transmission.

The symptoms are inconsistent, but this is the trend.

Warm idle, fan and AC off.

If I set the IAC at 15 as recommended by FAST, the idle will fluctuate. It may start as a 100 -200 RPM swing from my idle of 800 RPM. and eventually fluctuate up and down enough for the engine to die. If I blip the throttle to 1200 RPM, it will start to idle correctly for a while again. At this setting, my vacuum will fluctuate.

If I plug the IAC hole or set the IAC to 5 (its lowest setting), it will idle near perfectly. the Idle will sometimes drop to 500 RPM when I let off the gas but recover and idle fine. At this setting, my vacuum is a steady 16 lbs.

Warm Idle, fan and/or AC on or cold.

Anything that causes the IAC count to increase will make the problem worse. With the IAC set at 15, the RPM fluctuation can be 500+ RPM. It does sound like a massive vacuum leak but I don't have a leak. I have to constantly blip the throttle to keep it idleing. if I have to stop quick and can't hit the gas, it will die.

With the IAC at 5, it idles much better. The fluctuations are a consistant 100 - 200 RPM and occassionally higher. It rarely stalls with the IAC at 5.

Cold and AC on:

IAC at recommended setting, it is a battle to keep it running. With it set at 5, It will stall once or twice until it warms up a little.

The most frustrating part:

Once the engine stalls, you have to turn the key off and wait at least 5 seconds to restart. If you wait 4 seconds and try, You will have to wait 5 more seconds. This can seem like an eternity when stalled at a green light.

Other than Idle, the system seems to be working pretty good. My MPG is down about 20%, but I think it is getting better now that the computer is learning. It does take a couple of weeks of daily driving for the computer to learn the engine

[4mul8ion]

Just a SWAG, but is the idle stepper motor bad? I'm making up numbers here but if the idle motor is looking for say 1 volt to open 20%, 2 volts to open 40% or whatever and yours is actually opening up 30% with 1V and 50% with 2V, that overshoot seems to fit what you are describing. Does FAST have a bench test to measure voltage demand from the ECU versus actual idle motor opening?

[avewhtboy]

It could be alternator, what is your voltage at idle? Older alternators were not made to put out voltage at idle, I had to replace the alternator on my 81 Trans am after I put an amp in for the stereo, the radio would cut off at idle.

good luck

[BonzoHansen]

Just a SWAG...

I had to look that up. Scientific Wild Ass Guess

[Mr.VENGEANCE]

[TnBlkC230WZ]

I'll have to research the stepper motor. Is that the same as the IAC?

The Altenator is a Powermaster CS130. I installed it a little over a year ago when I put the AC in. It puts out 14 - 14.2 at idle depending on the load at the fuse panel. The FI probably sees a little less since it is conncted to the battery. It is a custom wiring harness and everything goes to the fuse panel first; except the FI.

[4mul8ion]

I'll have to research the stepper motor. Is that the same as the IAC?

Yes. My understanding is that either there is a bypass port that is opened up or, for the old TBI systems, it opened up the throttle plates. Not sure how FAST does it with their EZ system.

I've had similar idle surge problems with an Eagle Talon and a Triumph motorcycle. Both referred to the IAC as a stepper motor but in googling that term, apparently that's not the norm.

[EFI69Cam]

Does the FAST system have a procedure for setting base idle? You set the IAC to full close then adjust the bypass air to a certain idle speed usually lower than set idle speed.

[GregWeld]

I have EZ EFI on an 8 stack injection (using their ECM and Multiport harness)... and had ZERO idle issues.

My thought would be that you didn't allow the ECM to LEARN the TPS (throttle position sensor) process... There is a "set low throttle -- wait - set WOT throttle" learning curve it goes through...

Then you're Idle RPMS input has to match what you've physically set it for.

After that -- I would ask about your vacuum line's -- NO T's? One line straight to the MAP sensor -- NO TEES...

And is your ECM getting a good CLEAN Tach signal?

Did you mount the ECM AWAY from any ignition box??

[Fuelie Nova]

Not to side track the thread but how did the EZ work with the 8 stack system? I run the XFI on an 8 stack.
Tom

[GregWeld]

Not to side track the thread but how did the EZ work with the 8 stack system? I run the XFI on an 8 stack.
Tom

You can read my posts about it on Lateral-G.net -- beginning with post #103

http://www.lateral-g.net/forums/show...275#post294275

[TnBlkC230WZ]

It does have a procedure for setting the base idle which I followed. It recommends setting the idle with the IAC count at 15. Doing this causes the problem to get worse, that's why I set it to 5. With it set at 5, it idles good until the AC and fan comes on, then it has problems as stated above. The more the IAC needs to open, the worse it gets.

The computer isn't recording any EMI issues, but I'm replacing my plug wires and rerouting them in hopes of finding a cure. Everying kees suggesting it is an EMI problem.

[4mul8ion]

What about the idle air / fuel target in the advanced options menu? What is that set at?

[68Formula]

Stock camshaft?

[TnBlkC230WZ]

I used my carb settings as my starting point. It was running pretty good with it.

I set the idle AF at 14.2. My carb was idling at 14 - 14.1. The cruise is at 14.4, the carb was at 14.2 and WOT is at 11.5 or 11.8. The carb was at 11.3.

I'm wondering if richening the idle would help.

The cam is a stock ZZ4 with 208 intake and 221 exhaust duration at .050. It is a ZZ4 with an intake and valve train upgrades. The cam and head ports are stock.

[4mul8ion]

I used my carb settings as my starting point. It was running pretty good with it.

I set the idle AF at 14.2. My carb was idling at 14 - 14.1. The cruise is at 14.4, the carb was at 14.2 and WOT is at 13.5 or 13.8. The carb was at 13.3.

I'm wondering if richening the idle would help.

...

From what I've read on FASTs instruction book for the EZ, it seems like the idle AF target can be adjusted while idling. Since your engine liked the carb's 14 - 14.1 it seems like an easy thing to try. Sure beats trying to trace an EMI problem.

[4mul8ion]

Something I found while I was searching for something else. See http://forums.corvetteforum.com/c3-t...is-yet-11.html about halfway down a posting from bluzman2004.

[TnBlkC230WZ]

That is something to check. He is describing my problem. My mechanical starts at 1500 RPM, but I need to check where the vacuum advance starts. When the AC comes on, it bumps the RPM up about 100 RPM. Maybe setting the idle at 700 RPM instead of 800 will help.

[TnBlkC230WZ]

Well, it's not the timing. My Vacuum kicks in around 1300 RPM. I reset the tune and bumped the idle to 850. It will still fluctuate, but hopefully it won't stall. Except for the idle, it is running really good. I may replace the IAC and see what happens.

[4mul8ion]

Hmmm.

The only information I can find about IAC valve operation is from http://www.megamanual.com/ms2/IAC.htm where coolant temp reading is part of the position calculation. I would assume FAST has a similar operation. Deep stretching here but how's the coolant temperature sensor readings? Could it be grounding out occasionally tricking the ECU into thinking the car is really cold or hot?