Still Another EFI Idle Problem - Could still use help!

70_Steve · Sep 24, 2010

Sorry to bother you guys with this, but I'm running out of ideas...

Freshly rebuilt 351, .004 over, high torque cam. GT40 lower w/Explorer upper and throttle body. A9P EEC w/reworked Mustang harness (Kolibar Kustoms). Stock Ford 5.0 MAF, rebuilt distributor and new TFI.

Warm/hot idle, it will idle well for a minute or so, then quickly loose a couple hundred RPM and generally idle like crap, misfiring, etc. It might idle like that for a couple minutes, then the idle will pick back up and idle normally. This will happen with the IAB connected or disconnected. It has idled well long enough for me to get through the base idle reset. Base timing is set to 10° and when idling normally, timing is running 18° or so. I notice that when the idle goes to crap, the timing increases to 30° or more and is very erattic. I'm begining to suspect this is more an effect than a cause.

KOEO codes are the standard 81, 82, 85, 84. CM code is 11 (Pass!) Fuel pressure is 39 psi with the vacuum line disconnected, and ~34 psi when idling normally. When idling badly, FP is ~35 psi, but again I think that's an effect, since I can move the throttle to get the engine speed back up to idle rpm, and the FP goes back to 34 psi. I've checked for vacuum leaks and found none, but can't think of a vacuum leak that would come and go...

Any ideas????:? I would like to get the idle straightened out so I can get it through emissions before the end of the month...

ransil · Sep 24, 2010

Air blowing over the intake air filter..
firing order wrong..
what are the code definitions?? I'm too lazy to look up...
you pay all that money for a harness and they don't terminate the connections so the thing does not throw code.

ransil · Sep 24, 2010

with it warn/hot the motor is in closed loop operation and looking at sensors for input.

Viperwolf1 · Sep 24, 2010

The timing increase is interesting. I have read that at some point during the KOER test the timing is bumped up 20 degrees. I'm sure you don't have the STI grounded though.

70_Steve · Sep 24, 2010

ransil said:
Air blowing over the intake air filter..
firing order wrong..
what are the code definitions?? I'm too lazy to look up...
you pay all that money for a harness and they don't terminate the connections so the thing does not throw code.

It happens with the hood up or down, so not sure about that air blowing over the air filter as a cause. Plus when it happens, it's a pretty immediate change.

I've checked the firing order, but I'm running the same cap and Motorsport wires as with the Duraspark setup. Never removed the wires from the cap, and the Motorsport wires are numbered!!! Not saying that I've never made that mistake, but I really have checked it several times.

Codes are TAB, TAD, CanP and EGR.

ransil said:
with it warn/hot the motor is in closed loop operation and looking at sensors for input.

Per the Probst book, idle can either be closed loop or open loop, depending on the input from the O2 sensors. Also, EEC will want to change idle speed depending on ACT and ECT inputs. But again, this is a pretty immediate change.

70_Steve · Sep 24, 2010

Viperwolf1 said:
The timing increase is interesting. I have read that at some point during the KOER test the timing is bumped up 20 degrees. I'm sure you don't have the STI grounded though.

I've read that the EEC will control idle speed both with the IAB and by changing timing. I was thinking that, when the idle goes to crap, the EEC was increasing timing in an attempt to increase idle speed. But, it may well be the cause...

I don't have the STI grounded, at least at the connector!! And I wouldn't think there's an issue in the harness because I have to ground the STI to start the KOEO codes.

I mentioned that the idle will go to crap with or without the IAB connected. Kinda wierd that, if the EEC is reacting to the low idle by changing timing, why wouldn't it also try to move the IAB to compensate? The IAB seems to be working (at least somewhat) since I can get a definate drop in idle (when it's idling OK) when I disconnect the IAB.

needabronco · Sep 24, 2010

What you need is a good long drive up to Payson tommorow morning, a little light wheeling to see how the new efi changed your off camber and low speed torque, then a nice lesiurly stroll back home;D

SWFLABRONCO · Sep 24, 2010

Do a quick test and unplug the MAF sensor. Mine was doing the same and when I unplugged the MAF, the computer went into a default setting and things improved (slightly). I replaced the sensor and things are good.

70_Steve · Sep 24, 2010

needabronco said:
What you need is a good long drive up to Payson tommorow morning, a little light wheeling to see how the new efi changed your off camber and low speed torque, then a nice lesiurly stroll back home;D

I was trying real hard to get there..

70_Steve · Sep 24, 2010

SWFLABRONCO said:
Do a quick test and unplug the MAF sensor. Mine was doing the same and when I unplugged the MAF, the computer went into a default setting and things improved (slightly). I replaced the sensor and things are good.

I did actually try unplugging the MAF, and the idle changed (increased slightly) but didn't improve. Plus, if the MAF was hosed up I would have expected a CM code (maybe..) However, I do have another MAF sensor around here somewhere that I was planning on trying, as one step in my "throw parts at it" repair stratigy.

needabronco · Sep 24, 2010

Get some mass air sensor cleaner and hose it and the throttle body out, also do the bypass valve while your there. It's a quick and easy, plus it may very well improve your general driveability.

What are the chances your fuel is bad/dirty? It did sit for what 6 months;D while you swapped engines? There could be enough gummed up junk in the filter to cause an intermittent issue at idle but not enough to hamper flow at higher rates?

73azbronco · Sep 24, 2010

If it stays running, go drive it for an hour, vary speeds below 45 to above 60, include some idle to 45mph and above cycles. Any way to check air fuel ratio? I'll be home Monday/Tuesday if you need another set of eyes.

70_Steve · Sep 24, 2010

needabronco said:
Get some mass air sensor cleaner and hose it and the throttle body out, also do the bypass valve while your there. It's a quick and easy, plus it may very well improve your general driveability.

What are the chances your fuel is bad/dirty? It did sit for what 6 months;D while you swapped engines? There could be enough gummed up junk in the filter to cause an intermittent issue at idle but not enough to hamper flow at higher rates?

Cleaned the sensor, throttle body and IAB as I was putting it together. I thought about the bad gas thing, so I drained the tank, and am running on 20 gal of fresh gas. And I put the gas I drained from the Bronco into my Camaro, and it ran fine.

I also pulled each injector and tested each one. I rebuilt them 6 months ago, before pulling the engine for a rebuild. I have a little test box with a 9V battery and a push-button switch. Each injector clicks nice and solid, and will pulse carb cleaner just fine. I don't think the injectors are an issue as it runs pretty well on the street, no misses or anything.

70_Steve · Sep 24, 2010

73azbronco said:
If it stays running, go drive it for an hour, vary speeds below 45 to above 60, include some idle to 45mph and above cycles. Any way to check air fuel ratio? I'll be home Monday/Tuesday if you need another set of eyes.

Driving it is my plan for this afternoon, if only in an attempt to generate some codes. No practical way for now to check A/F ratio. I'll let you know about coming over Monday/Tuesday. I feel like I'm just missing something simple...

73azbronco · Sep 24, 2010

No, my guess it just needs to learn it's managing a 351 vice 302.

gddyap · Sep 24, 2010

Check some of the things suggested here:

http://www.muscularmustangs.com/iac.php

jw0747 · Sep 24, 2010

just a suggestion but maybe your ECC needs to be reset. part 3 on the above website. my EB sat in a body shop for awhile w/ battery disconnected. after picking it up it was doing about same as yours, wouldn't idle right. went thru the steps listed in part 3 and that fixed it.

70_Steve · Sep 24, 2010

gddyap said:
Check some of the things suggested here:

http://www.muscularmustangs.com/iac.php

jw0747 said:
just a suggestion but maybe your ECC needs to be reset. part 3 on the above website. my EB sat in a body shop for awhile w/ battery disconnected. after picking it up it was doing about same as yours, wouldn't idle right. went thru the steps listed in part 3 and that fixed it.

I actually have done all those steps listed, and done them off of that web site!! Cleaned the IAB, throttle body and MAF wires. Done the idle reset and checked the TPS voltage.

Gonna take it for a bit of a ride here in a few minutes to see if that makes a difference.

ransil · Sep 24, 2010

What is pin 30 connected to in the harness?
Does the harness include a plug for auto or manual?

70_Steve · Sep 24, 2010

ransil said:
What is pin 30 connected to in the harness?
Does the harness include a plug for auto or manual?

Right now pin 30 isn't connected to anything. Yeah, I know. It's supposed to be connected to the Start wire. But, after the engine starts (key is ON), that wire doesn't connect to anything, it's open. So, I may not have the "start" performance I want, but I have the same wiring that I would have once the engine is running. (I think...

)

Still Another EFI Idle Problem - Could still use help!

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