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Idle air bypass Ford: F2PZ-9F939-A

9K views 20 replies 3 participants last post by  145566 
#1 ·
What do y’all think of these? Originally they were designed to stop “crud” from forming on the throttle body but people use them to try and solve surging idle and other idle related issues. It looks like it works for some but not others. Right now I have my TB blade opened enough to where it will stay idling with the fan running. It works but the idle will hang and then surge a few times before it settles down when coming to a stop. Prior to raising the idle it would die when the fan came on. I think it surges because I have the idle set too high and the ecu is trying to correct it, but I’m not 100% on that. With this device supposedly one can close the TB blade and “open the IAC” enough to where it’ll idle.
Anyone ever tried one? I know about the resrrditor plates that people make that reduce the amount of air coming in through the IAC, but an adjustable one seems like it’d be more user friendly if it works. Anyone with a lopey cam that has had idle problems ever tried the adjustable one and it worked? It’s kind of an expensive gamble at $60-$70.

https://www.cjponyparts.com/ford-idle-air-control-adjuster-5-0l-1986-1993/p/HW2451/

https://www.google.com/amp/www.full...air-pass-spacer-plate-idleing-saga.html?amp=1

https://www.google.com/search?q=Ford:+F2PZ-9F939-A&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari
 
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#2 ·
Nothing really new, I made one up for the EGR valve on my F150 1990 SWB 5speed truck.... to address the part throttle hesitation...… very well known issue back then. Are you sure you don't have a tiny/partial vacume leak?
 
#3 ·
Not 100% sure, but I don’t believe so. Prior to raising the idle the motor would die when the IAC was disconnected. So I raised the idle to where it would stay running with it disconnected and I plugged it back in. So now the idle surges some when it’s trying to settle after the motor has been revved. It’ll also surge a little once at a complete stop. It’ll surge a few times and then even out and idle steady.
Also prior to raising the idle It would idle well for a good 30 minutes or more. But when the fan came on the idle would surge iratically and often times it would die. If you revved it up it would usually “straighten out” and idle for a bit longer, but sometimes you had to keep it revved up to keep it going. It did, and does run down the road well. It just wouldn’t idle after the motor was warm, and turning on the accrssories exacterbated the problem. Sounds like it could be a vacuum leak but I think it’s really an IAC issue. I think there’s probably a short in the wiring actually. But it’s staying running via opening up the TB. I might just have the idle set too high though. I believe if it’s set over 750 rpm that the ecu will try to take over to get it to where it wants it. I’m not sure where it is exactly because my tach reads high. That 750 (if that’s the right number) might not apply to me though because it might have been changed via tuning. I can’t remember where it used to idle exactly. I just need to play with it some more, and possibly take a gamble wasting money on one of those adjustable rigs.
Sounds kinda like a vac leak but it would idle forever until it started having problems and it wouldn’t run or start with the IAC unplugged and I believe it’s supposed to be able too. If it won’t rumor has it that the TB isn’t open enough and or not enough air is going through the IAC.
Did the plate work on your egr problem?
 
#7 ·
If you crank the idle up to compensate for load (ac,fan,etc) & it puts the mechanical idle speed out of the range the ecu needs it to be in,in order to control idle via the iac valve,surging can definitely begin.Other than being used for a cold start,the next most important reason for an iac valve is load compensation.If you have to increase the idle by a couple hundred rpm to help with that load,thats definitely gonna work against the ecu for idle control.


(Idle Air Adjust Spacer)copy/pasted
Allow me to elaborate on the Idle Air Spacer for a moment. Coking on Ford EFI Throttle Blades has been a problem for many years. If the PCV or vent filter clogs, oil tends to back up and accumulate in the Throttle Bore and plate. This is also caused by blow-by from worn piston rings in older engines. The oil becomes a sludgy residue which eventually hardens reducing the expected amount of air that can pass by the closed Throttle Plate. As less air passes by the closed Throttle Plate, the EEC commands the IAC to increase air flow around the Throttle Plate to maintain a good idle. Eventually, the IAC will approach edge of it's operating range. This is the point where the symptoms of poor idle are experienced and Throttle Body/IAC cleaning are indicated.
To alleviate this problem, Ford developed the Idle Air By-pass Service Kit (F2PZ-9F939-A) for EFI Broncos prior to MY1991. The kit includes an Idle Air Adjust Spacer that corrects sludge contamination concerns on the Throttle Blades to the point that Ford no longer covered Throttle Body Cleaning under the 5/50 Emissions Warranty. A secondary benefit is the ability to fine tune closed throttle plate idle air flow without altering the TPS, which has been very popular with Mustang performance builders having idle problems. The Idle Air Bypass Kit was installed by Ford Dealerships under warranty per TSB 91-25-07 and is still available from Ford as well as aftermarket versions from Tomco and eBay.
Beginning in 1991, Ford began using a Sludge Tolerant Throttle Body design which includes a special slick Teflon coating inside the throttle bore. This coating minimizes deposit formation and does not require cleaning or the service kit. The issue is harsh cleaning can remove the sensitive Teflon coating eliminating the protective qualities. These Throttle Bodies can be identified by a black/yellow sticker on the Throttle Body warning against cleaning or adjusting. Please note that this Sludge Tolerant Design does not include the IAC which may still require servicing or replacement.
 
#8 ·
What do y’all think of these? Originally they were designed to stop “crud” from forming on the throttle body but people use them to try and solve surging idle and other idle related issues. It looks like it works for some but not others. Right now I have my TB blade opened enough to where it will stay idling with the fan running. It works but the idle will hang and then surge a few times before it settles down when coming to a stop. Prior to raising the idle it would die when the fan came on. I think it surges because I have the idle set too high and the ecu is trying to correct it, but I’m not 100% on that. With this device supposedly one can close the TB blade and “open the IAC” enough to where it’ll idle.
Anyone ever tried one? I know about the resrrditor plates that people make that reduce the amount of air coming in through the IAC, but an adjustable one seems like it’d be more user friendly if it works. Anyone with a lopey cam that has had idle problems ever tried the adjustable one and it worked? It’s kind of an expensive gamble at $60-$70.

https://www.cjponyparts.com/ford-idle-air-control-adjuster-5-0l-1986-1993/p/HW2451/

https://www.google.com/amp/www.full...air-pass-spacer-plate-idleing-saga.html?amp=1

https://www.google.com/search?q=Ford:+F2PZ-9F939-A&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari

If you crank the idle up to compensate for load (ac,fan,etc) & it puts the mechanical idle speed out of the range the ecu needs it to be in,in order to control idle via the iac valve,surging can definitely begin.Other than being used for a cold start,the next most important reason for an iac valve is load compensation.If you have to increase the idle by a couple hundred rpm to help with that load,thats definitely gonna work against the ecu for idle control.


(Idle Air Adjust Spacer)copy/pasted
Allow me to elaborate on the Idle Air Spacer for a moment. Coking on Ford EFI Throttle Blades has been a problem for many years. If the PCV or vent filter clogs, oil tends to back up and accumulate in the Throttle Bore and plate. This is also caused by blow-by from worn piston rings in older engines. The oil becomes a sludgy residue which eventually hardens reducing the expected amount of air that can pass by the closed Throttle Plate. As less air passes by the closed Throttle Plate, the EEC commands the IAC to increase air flow around the Throttle Plate to maintain a good idle. Eventually, the IAC will approach edge of it's operating range. This is the point where the symptoms of poor idle are experienced and Throttle Body/IAC cleaning are indicated.
To alleviate this problem, Ford developed the Idle Air By-pass Service Kit (F2PZ-9F939-A) for EFI Broncos prior to MY1991. The kit includes an Idle Air Adjust Spacer that corrects sludge contamination concerns on the Throttle Blades to the point that Ford no longer covered Throttle Body Cleaning under the 5/50 Emissions Warranty. A secondary benefit is the ability to fine tune closed throttle plate idle air flow without altering the TPS, which has been very popular with Mustang performance builders having idle problems. The Idle Air Bypass Kit was installed by Ford Dealerships under warranty per TSB 91-25-07 and is still available from Ford as well as aftermarket versions from Tomco and eBay.
Beginning in 1991, Ford began using a Sludge Tolerant Throttle Body design which includes a special slick Teflon coating inside the throttle bore. This coating minimizes deposit formation and does not require cleaning or the service kit. The issue is harsh cleaning can remove the sensitive Teflon coating eliminating the protective qualities. These Throttle Bodies can be identified by a black/yellow sticker on the Throttle Body warning against cleaning or adjusting. Please note that this Sludge Tolerant Design does not include the IAC which may still require servicing or replacement.
Yeah the theory/hope with using one I think is that I’d be able to close the throttle more with that thing in there and it would still idle. You know, maybe I can lower the idle to where it wouldn’t surge but also stay running with the fan on.
I dunno. Maybe I’ll play with the idle this weekend and go from there. If the plate was say $30-$40 I’d be more willing to take a gamble on one. But at $60-$70 that’s kind of an expensive crap shoot.
 
#9 ·
I'd make a trip to pull-a-part if youve got one and look around the Ford isle before I'd spend that kinda money on one.Heck that part may be considered a pocket item,but I try not to walk out the door with anything until I have asked to make sure.Generally if the counter person doesn't even know what the part is called,they'll just wave you thru anyways since they dont know what price to charge anyway.The plate works for some and it doesn't work for others,so youre right in your thought process about being reluctant to spend that kinda cash.It worked for my lx when I had a Ecam,but there was likely something else wrong that the plate was just acting as a bandaid for.I'd go check all of the late 80's-90 Broncos and other 5.0/5.8 Fords near that year range and see if you can locate one.Its only $1 entrance fee with vip card or $2 otherwise,to get in pull-a-part to look around.If I knew where to look in my disorganized garage,I'd send you the one I bought years ago,but finding it would be the ???.I may have some time tomorrow to search for it though and if I locate it,I'll drop a note here or thru a pm.
 
#10 ·
Thanks bother. This weekend if the weather holds out maybe I’ll get some time to play cars and that’s a good idea about browsing the pull-a-parts. $70 would be ok I guess if I knew it’d work. But if it didn’t that’d be fairly bunk.
 
#16 ·
The part came and I got it on, but I hadn’t made any adjustments yet. I started it and the idle is considerably higher than it was/is with out the spacer. Which I believe is a good thing, because I believe I’ll be able to back the throttle stop screw enough to where it idles close to stock.
 
#17 · (Edited)
Good deal.Im glad you didn't waste that hard earned cash.I found some decent info about adjustment @ LMR,if you feel like using it. One of the paragraphs lists the following and it may be the reason why your idle is notably higher.
**The Idle Air Adjuster Spacer comes preset at maximum air flow for engine applications of 5.0L displacement and smaller**

One thing I did notice in the instructions though (which was never mentioned in the instructions that came with my plate) is something called a cup plug.I cant tell from the wording in the instructions whether this plug is supposed to be removed for all 5.0's & up or just the 5.8 & strokers?? So see if your plate has this plug and give your thoughts on the wording.The wording almost sounds like theyre saying a 5.8 & stroker motor requires more bypass air to keep the engine running,than a 5.0 motor does.If thats the case,the plug would only need removal for 5.8 & up.



https://lmr.com/products/how-to-install-mustang-idle-air-control-adjuster-86-93
 
#19 ·
What do y’all think of these? Originally they were designed to stop “crud” from forming on the throttle body but people use them to try and solve surging idle and other idle related issues. It looks like it works for some but not others. Right now I have my TB blade opened enough to where it will stay idling with the fan running. It works but the idle will hang and then surge a few times before it settles down when coming to a stop. Prior to raising the idle it would die when the fan came on. I think it surges because I have the idle set too high and the ecu is trying to correct it, but I’m not 100% on that. With this device supposedly one can close the TB blade and “open the IAC” enough to where it’ll idle.
Anyone ever tried one? I know about the resrrditor plates that people make that reduce the amount of air coming in through the IAC, but an adjustable one seems like it’d be more user friendly if it works. Anyone with a lopey cam that has had idle problems ever tried the adjustable one and it worked? It’s kind of an expensive gamble at $60-$70.

https://www.cjponyparts.com/ford-idle-air-control-adjuster-5-0l-1986-1993/p/HW2451/

https://www.google.com/amp/www.full...air-pass-spacer-plate-idleing-saga.html?amp=1

https://www.google.com/search?q=Ford:+F2PZ-9F939-A&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari

If you crank the idle up to compensate for load (ac,fan,etc) & it puts the mechanical idle speed out of the range the ecu needs it to be in,in order to control idle via the iac valve,surging can definitely begin.Other than being used for a cold start,the next most important reason for an iac valve is load compensation.If you have to increase the idle by a couple hundred rpm to help with that load,thats definitely gonna work against the ecu for idle control.


(Idle Air Adjust Spacer)copy/pasted
Allow me to elaborate on the Idle Air Spacer for a moment. Coking on Ford EFI Throttle Blades has been a problem for many years. If the PCV or vent filter clogs, oil tends to back up and accumulate in the Throttle Bore and plate. This is also caused by blow-by from worn piston rings in older engines. The oil becomes a sludgy residue which eventually hardens reducing the expected amount of air that can pass by the closed Throttle Plate. As less air passes by the closed Throttle Plate, the EEC commands the IAC to increase air flow around the Throttle Plate to maintain a good idle. Eventually, the IAC will approach edge of it's operating range. This is the point where the symptoms of poor idle are experienced and Throttle Body/IAC cleaning are indicated.
To alleviate this problem, Ford developed the Idle Air By-pass Service Kit (F2PZ-9F939-A) for EFI Broncos prior to MY1991. The kit includes an Idle Air Adjust Spacer that corrects sludge contamination concerns on the Throttle Blades to the point that Ford no longer covered Throttle Body Cleaning under the 5/50 Emissions Warranty. A secondary benefit is the ability to fine tune closed throttle plate idle air flow without altering the TPS, which has been very popular with Mustang performance builders having idle problems. The Idle Air Bypass Kit was installed by Ford Dealerships under warranty per TSB 91-25-07 and is still available from Ford as well as aftermarket versions from Tomco and eBay.
Beginning in 1991, Ford began using a Sludge Tolerant Throttle Body design which includes a special slick Teflon coating inside the throttle bore. This coating minimizes deposit formation and does not require cleaning or the service kit. The issue is harsh cleaning can remove the sensitive Teflon coating eliminating the protective qualities. These Throttle Bodies can be identified by a black/yellow sticker on the Throttle Body warning against cleaning or adjusting. Please note that this Sludge Tolerant Design does not include the IAC which may still require servicing or replacement.
Do you think the Allen screws will ever bottom out and stop if tightened all the way, or will they fall out of the hole? I think the one I’m able to access is the fresh air side and not the vacuum side, down the street from Zach Morris at bayside.
 
#20 ·
The good, the bad, the weird.

What do y’all think of these? Originally they were designed to stop “crud” from forming on the throttle body but people use them to try and solve surging idle and other idle related issues. It looks like it works for some but not others. Right now I have my TB blade opened enough to where it will stay idling with the fan running. It works but the idle will hang and then surge a few times before it settles down when coming to a stop. Prior to raising the idle it would die when the fan came on. I think it surges because I have the idle set too high and the ecu is trying to correct it, but I’m not 100% on that. With this device supposedly one can close the TB blade and “open the IAC” enough to where it’ll idle.
Anyone ever tried one? I know about the resrrditor plates that people make that reduce the amount of air coming in through the IAC, but an adjustable one seems like it’d be more user friendly if it works. Anyone with a lopey cam that has had idle problems ever tried the adjustable one and it worked? It’s kind of an expensive gamble at $60-$70.

https://www.cjponyparts.com/ford-idle-air-control-adjuster-5-0l-1986-1993/p/HW2451/

https://www.google.com/amp/www.full...air-pass-spacer-plate-idleing-saga.html?amp=1

https://www.google.com/search?q=Ford:+F2PZ-9F939-A&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari

If you crank the idle up to compensate for load (ac,fan,etc) & it puts the mechanical idle speed out of the range the ecu needs it to be in,in order to control idle via the iac valve,surging can definitely begin.Other than being used for a cold start,the next most important reason for an iac valve is load compensation.If you have to increase the idle by a couple hundred rpm to help with that load,thats definitely gonna work against the ecu for idle control.


(Idle Air Adjust Spacer)copy/pasted
Allow me to elaborate on the Idle Air Spacer for a moment. Coking on Ford EFI Throttle Blades has been a problem for many years. If the PCV or vent filter clogs, oil tends to back up and accumulate in the Throttle Bore and plate. This is also caused by blow-by from worn piston rings in older engines. The oil becomes a sludgy residue which eventually hardens reducing the expected amount of air that can pass by the closed Throttle Plate. As less air passes by the closed Throttle Plate, the EEC commands the IAC to increase air flow around the Throttle Plate to maintain a good idle. Eventually, the IAC will approach edge of it's operating range. This is the point where the symptoms of poor idle are experienced and Throttle Body/IAC cleaning are indicated.
To alleviate this problem, Ford developed the Idle Air By-pass Service Kit (F2PZ-9F939-A) for EFI Broncos prior to MY1991. The kit includes an Idle Air Adjust Spacer that corrects sludge contamination concerns on the Throttle Blades to the point that Ford no longer covered Throttle Body Cleaning under the 5/50 Emissions Warranty. A secondary benefit is the ability to fine tune closed throttle plate idle air flow without altering the TPS, which has been very popular with Mustang performance builders having idle problems. The Idle Air Bypass Kit was installed by Ford Dealerships under warranty per TSB 91-25-07 and is still available from Ford as well as aftermarket versions from Tomco and eBay.
Beginning in 1991, Ford began using a Sludge Tolerant Throttle Body design which includes a special slick Teflon coating inside the throttle bore. This coating minimizes deposit formation and does not require cleaning or the service kit. The issue is harsh cleaning can remove the sensitive Teflon coating eliminating the protective qualities. These Throttle Bodies can be identified by a black/yellow sticker on the Throttle Body warning against cleaning or adjusting. Please note that this Sludge Tolerant Design does not include the IAC which may still require servicing or replacement.
Do you think the Allen screws will ever bottom out and stop if tightened all the way, or will they fall out of the hole? I think the one I’m able to access is the fresh air side and not the vacuum side, down the street from Zach Morris at bayside.
Never mind the screws falling out. The weirdest thing, I had one of those IAC adjusters in my “spare parts bin.” I’m not sure where it came from exactly. I just can’t remember getting one. I found it when I was putting the stuff away from working on the car. That’s the weird. But anyway, I see that the Allen screws screw from one side of the spacer into the other, and no it won’t fall out.
The good- It idles pretty well at around 700 or so. It doesn’t die when turning the steering wheel from lock to lock with the engine fan running, the vent fan on high, and with the lights on. It pulls itself through the neighborhood better than it ever has, no more buck & chug. It’s a lot easier to drive around town as well, But...
The bad- the idle still hangs for a second when coming to a stop, and the ability to let off of the throttle and engine brake has diminished.
I’m going to call it a win for now though. It engine brakes in response to downshifts and it’ll slow down easy enough when the brakes are applied. I just need to be mindful of what gear I’m in and I need to go ahead and get on top of that brake job.
Another weird and crappy thing, my raptor shift light is on the fritz. It wasn’t coming on when revved. After feeling around on the wires it started blinking and it wouldn’t stop. So I disconnected the ground wire to make it quit and that’s how it sits. Argh it’s always something.
 
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