Efi do i need vss on an automatic? Will it affect idle. Still have hanging idle!

[70injectedbronc]

Still trying to get my hanging idle issue figured out and getting no where. In my past threads I've said everything I've done. New iac, tps, no vacuum leaks, egr is omitted, new pcv. Runs like a champ but the idle hangs up for a few seconds when you give it any gas. Was just wondering if it could be the temperature sensor (ect) or not having a vss hooked up? I'm lost. But I've been told the vss is mainly for manuals or electronic stuff like cruise control and stuff. Took it to a ford pro down the road and he unhooked the iac and it ran low idle like it should and he said he would just drive it without it. Well I drove off and everything was great and wasn't hanging up at all. But as soon as you kill it and let the engine cool it won't fire back up. Help please.

 

[Ranchtruck]

Do you have a neutral switch hooked to pin 30 of the ECU? It should be getting a signal from the transmission range switch telling it when it's in drive or neutral, and it can change the idle based on that.
According to this thread:http://www.my5oh.com/forum/viewtopic.php?p=225

As explained in case #2, regarding the VSS and the "dashpot" logic in the EEC-IV for idle control....the neutral switches circuit, also have an influence in the EEC-IV calculations for the operation of the IAC valve, by helping identifying engine conditions and selecting the proper Idle Speed Control (ISC) strategy. Their input, or state, is used in the VSS/ISC dashpot calculations to identify engine operation conditions (accelerating/decellerating/cruise mode/closed loop idle modes), and prevent idle problems (stalls and surging, hanging idle).

It could also be the missing VSS.

VSS input in the EEC-IV is also used to arrange and set idle strategy while shifting/deceleration/stopping via the "dashpot" control mode and prevent deceleration stalls. If you complain about stalling, hanging idle, surges when coming to a stop or between shifts....make sure you don't have a code 29: Insufficient input from vehicle speed sensor.

Or it could be a missadjusted throttle plate. You set the plate to hold 650-750 rpm with the IAC and SPOUT connectors unplugged, then readjust the TPS after setting the plate. This is only necessary if someone tried using the throttle plate stop screw to adjust the idle.

There's a bunch of info in this thread: http://www.stangnet.com/mustang-forums/threads/help-me-create-the-surging-idle-checklist.698148/

 

[gunnibronco]

I have the exact same problem as the OP (fresh EFI intake swap onto older 302, not 5.0 motor swap), and am following his other thread. But I have a manual trans & ECU. Does the manual ECU also use the VSS & neutral switch the same way?

I bought a bad reman'd ECU and am waiting on the warranty replacement, so I don't know how my truck will run with a good ECU, but I'm expecting the same symptoms with a new ECU.

 

[av bronco]

I have no vss on a auto(well I have it but not hooked up) with a slight delay in return to idle, I can tune it out with my moates Q/H but you need a little delay when returning to idle to prevent it from surging. how long is your delay? have you checked your tps voltage?

 

[70injectedbronc]

Yeah checked the voltage and its in good range. It hangs for like 4 or 5 seconds every time you touch the gas. In gear or not. Definitely not normal.

 

[gunnibronco]

Yeah checked the voltage and its in good range. It hangs for like 4 or 5 seconds every time you touch the gas. In gear or not. Definitely not normal.

Same for me. I played a bit with my TPS and it sat about .7-.95 depending on the position, but I didn't spend much time on this because I knew my ECU was going back.

 

[av bronco]

I think the idle control motor is energized for a sec. on decel, you might have a sticky iac motor.

 

[gunnibronco]

The PO has replaced his IAC w/new and I've cleaned mine, but the symptoms remain.

This is the other thread the PO started w/more of his info:
http://classicbroncos.com/forums/showthread.php?t=199146

I have a 2nd IAC & TPS but the pigtails don't match my harness, so I was waiting to swap them out till I had checked other things.

 

[av bronco]

There is a dashpot adjustment you can have a tuner adjust or if you have a moates or tweecer, but they do hang for a couple of seconds. my wifes 04gt does it a long time too, 5 speed car also.

 

[ilovemaui]

I have C4 with no VSS and no idle issues at all.

 

[itsabronco]

Mine does the same thing. The RPMs at the high idle is about 1100, after a few seconds , it drops to around 800. Thats after its warmed up. It stays hi alittle longer when its first started.

 

[70injectedbronc]

Yeah I'm still leaning toward a computer issue...going to hook up my vss just because now too.

 

[70injectedbronc]

Or maybe its doing it because it has aftermarket parts and hasn't been tuned accordingly. Aka headers, engine rebuild, etc....who knows.

 

[gunnibronco]

Just got my "new" reman'd ECU back. I hope to install it soon, but I'm also waiting on my alternator to get warrantied & returned. I don't know if its worth trying to run it & check it on just battery power. I think I'm going to wait for a functional alternator, so I can be sure the ECU is fully powered/functional.

 

[70injectedbronc]

Well let me know if that helps or what happens. Sounds like we are in kinda the same boat.

 

[gunnibronco]

I'll keep updating as I try things. I was going to go through the list of suggestions in the other thread, if the new ECU doesn't straighten things out.

 

[broncoitis]

Mine does the same thing. The RPMs at the high idle is about 1100, after a few seconds , it drops to around 800. Thats after its warmed up. It stays hi alittle longer when its first started.

Mine does the same thing while driving and can't seem to get the idle below 800-900 ELMS! Gonna keep a better eye on it but mostly all the EGO stuff is new.%)

 

[gunnibronco]

Bad news, I swapped ECUs and not only did the idle stay high, maybe even higher, but I didn't drive it around, but all the same codes reappeared. I've got some real work to do.

 

[70injectedbronc]

Damn! Sorry buddy. Who was working on your ecu? And what do they have to say about the swap and the problems its having? I bet I know how frustrated you are.

 

[gunnibronco]

I now have 2 reman ECUs I bought from Advance Auto. Cardone #78-4352, should be for a 91 Mustang 5.0, manual trans. Advance can barely process a warranty return, let alone give me advice. It took 5 phone calls, and over 1 hour to get my warranty processed.

The truck runs great (other than the hanging idle), but throws codes. Now both ECUs are throwing the same codes, and 2 new ones. I have my build thread here (end of thread w/code problems):
http://www.coloradoclassicbroncos.com/viewtopic.php?f=5&t=2795&p=31428#p31428

I just posed up here looking for help:
http://classicbroncos.com/forums/showthread.php?p=2003522#post2003522

So things seem to be getting worse, not better. The truck sat for a week in the cold and snow and developed an ACT & ECT self test problem. Yes, I'm frustrated.