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efi idle problems

jagbucket

Full Member
Joined
Aug 9, 2013
Messages
251
finally have my efi conversion running but i dont like the way it slowly idles down . the tps is set to 9 , base idle speed adjusted, iac is cleaned and timing is at 10. so i dont know what else to check the only non mustang part i am running is the explorer iac for better connector plug angle .
the way it is now i would have to wait 30-40 seconds for rpms to slow down in order to shift from drive to reverse Any help on this or is that the way it should run?
 

needsmoarturbo

Full Member
Joined
May 13, 2015
Messages
278
What happens if you blip the throttle does it idle down Sooner? Is this every start or only the first of the day? My 94 F-150 is kind of this way on the first start sometimes. My efi converted bronco seems like does it too but if I blip throttle seems to idle down quicker most of the time. I guess I just thought that's the way they all were

Sent from my Moto G (5) Plus using Tapatalk
 
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jagbucket

Full Member
Joined
Aug 9, 2013
Messages
251
acts the same hot or cold . starts up idles fast at first then slows down to a lumpy idle almost dies and slowly will some what smooth out but not completely. always slow to idle down if blipped
 

Sporto

Sr. Member
Joined
Oct 10, 2005
Messages
904
Do you have a vacuum gauge? It may be a slight vacuum leak causing the iAC to try and "chase" it. Also did you do the base idle reset with the TPS?

These are two things that can make your idle act funny.

Also note that mine does what yours does...Starts up, runs up to about 1500 RPM or so, and then settles down to about 900 RPM within the first 30 seconds. Runs fine afterwards...

Good luck,

Rich
 

PaveBronco

Sr. Member
Joined
Oct 30, 2012
Messages
912
I broke down and did the IAC Spacer adjuster plate for my surging idle that I've been plagued with ,no matter what I changed. lots of info out there on this Ford designed part, and its hit or miss...mine was a Hit, I only just opened one of the bleed screws and no more surge.. IDLE AIR CONTROL ADJUSTER - Ford (F2PZ-9F939-A)
For the RPM's slow to return to idle I first went with a sheet metal spacer that went between the intake and IAC, had 2 holes, one big one little. Also lots of info online for this. fixed the return to idle problem but I couldn't get the RPM's under 1500 no matter what I did...so SH!T canned that..EFI guy has talked about some sort of electronic dashpot in the ECU that he can change, but think that was on the explorer ECU's. Hope he chimes in on this..he knows a lot about these EFI issues...
 

Timmy390

Bronco Guru
Joined
Jan 1, 2011
Messages
5,609
Loc.
Conway, AR
I'm running the IDLE AIR CONTROL ADJUSTER - Ford (F2PZ-9F939-A) on my 95 Mustang EFI and it was a godsend. I had several issues.....return to idle, high idle, surging idle and would not idle after getting to N.O.T.

My issue was the cam I installed. My rig (351w) ran great with the stock explorer cam. I had a cracked head and upgraded the cam while I had the engine apart and all my troubles began.

I installed Comp 35-349-8/XE264HR and that cam just don't play well with stock EFI. You really need to have data logged and tuned specifically. I've read mustang after mustang thread on this subject and 99% of the time it's an aftermarket cam causing the issues. Most fix this by custom tune or the IACA.

After adding The Idle Air Control Adjuster, resetting TPS and adjusting the T-body, my idle settles quickly and my idle when warm ranges from 700-900 depending on conditions.

Tim
 
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jagbucket

Full Member
Joined
Aug 9, 2013
Messages
251
thanks for all the response ive had a few other fires to put out but i did read about the spacer plate mod and might go with that for a better tune. What im playing with right now is to install a different iac, i think is off a 90s 351, and remove the explorer iac difference is that the action on the 351 piece is much easier than the exp. but the connector is either into the intake tube or hitting the throttle bracket if i rotate it, so ive started it with the throttle removed and it is definitely starting at normal idle speed now once warm. had to play with the do not touch screw to get it to drop a bit without the iac and is the best idle ive had to this point . might be the explorer cam or i need to get new ignition parts. Hopeful that the ecu will adapt further in the right direction ..

On the iac orientation ive thought to make a washer that will go over the flange on the solenoid drill the two screw holes and then be able to turn the connector up or down to clear . is there a different iac or what have others done with this?
 
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jagbucket

Full Member
Joined
Aug 9, 2013
Messages
251
latest, found a new iac on a 1989 351 in the jy and a iac off a 3.8 taurus which has a straight connection on the coil . I swapped the shiny new valve body onto the 3.8 coil and installed. without touching the throttle It now starts with a much lower rpm after which will slow to a slightly rough idle which smooths out after a few minutes. in real driving i will not be starting and just idling as i am now . will likely get the spacer plate to see what happens,
Just wanted to point out that changing out the explorer iac completely changed the starting rpms .
 
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