I've read every write up I can google on base idle set procedures, and any time I can get my idle to stabilize, it's still wrong. I'm down to this: TSB# 91-25-7 (http://"https://docs.google.com/file/d/0B4pi2v_E11qaOTFwbHF4eVZvanc/edit?usp=sharing"). Has anybody else had to install the IABP air bleed spacer kit?
No codes right?
When is the rolling idle occurring? Start up, coming to a stop, or at some other time? I've done the base idle reset on mine several times with part swaps and it's been fine. I've got mine set to idle at 775 rpm hot in park and 700 rpm in drive hot, both of which are on the high end of the scale on the emissions decal (550-700rpms hot in drive is the factory idle speed). I will say this: use a tach/dwell meter to set the base idle not the factory digital cluster. Using the factory cluster a 775 rpm idle bounces between 5 and 6 bars illuminated on the factory tach. If the idle speed is set too low or two high the computer will open and close the IAC rapidly, causing the dreaded idle surge.
Mine is not perfect. Once in awhile it will surge a bit on a cold start. Other than that it's fine.
When I've got it to idle steady in park, idle (per a tach/dwell meter) is about 980, with about 800 in gear. At stops the push is almost intolerable. Any time it's NOT steady, I get surging at idle both in gear and in park. I've been beating my head against this since last summer when I put the Explorer engine together. I'm running a 96 Explorer engine with an 88 Mustang PCM and a 90 Mark VII cam. If this service kit doesn't help me, I'm going to assume that the problem is the extra 10 degrees of exhaust duration that the 90 HO cam has versus what the 88 HO cam has and what the PCM expects to be dealing with.
I would try to get the base idle lower, to somewhere around 800 rpm in park and 700 in drive. Try to get it as low as possible where the engine won't stall and the car will start with just a turn of the key and no other help (ie you having to hold the throttle open). Make sure that the IAC is disconnected when you reset the idle. If the idle is set to high it will cause surging as the computer tries to lower the idle speed down to factory specs.
The computer you have should be fine with your mods. I was running with a 89 Mark VII computer with the same cam I have now (Comp Magnum roller #35-308-8) and it idled fine with no surging.
All the bypass plate does is allow a higher base idle without disturbing the TPS setting, can do same by setting idle where you want it and then resetting TPS if necessary... It's original purpose was for correcting issues without cleaning the TB, but the Mustang crowd latched on to it as a cure all for a lumpy cam...
I've seen a PCV that was flowing too much air cause a surge...
As far as surging because the base idle is too high, I'm having a problem with that... If it's high, the IAC isn't going to respond to commands to lower as it's already at minimum and idle is still above specs... With the TFS-1 cam, I'd set mine to Idle at 900 in drive...
Min idle should be set along with the TPS at 1V. This is accomplished with the IAC disconnected. I am sure you know this as a ford tech. But some of the early ECM'S do not fare to good with big cams. Specks on the cam would be nice to know and you most likely need to have a tune dun to correct this. A stand alone would be the best bet. I have totally figured out that a stand alone system is superior to the older OBD1 ECM systems. Just my .02
Also try and make a restrictor plate and start out with 1/4" HOLES
Tom, I'm running a 1990 stock HO cam.
I had it all set before I left the shop last night, but by the time I drove 15 miles home, it was back to idling too high and rolling in park but not in drive. The service kit will be in this morning, so I'll beat my head against it some more on my lunch today.
The whole setting the TPS as close to 1V at idle is an old wives tale with any reference to tip in on the throttle (Tom, not picking on you here as you are most likley using the 1.0V as a reference point to set a TPS to and knowing your abilities I will assume that is the case). The EEC will adjust to the base setting of the TPS as long as it is within a range of 0.5V to 1.19V according to several sources. I quit setting mine as close to 1.0V many moon ago. This is what I would reference in trying to adjust base idle and the TPS setting:
http://sbftech.com/index.php/topic,1031.0.html
I have the IAC bypass on my Coupe and it was the only way we could get the car to idle without surging but its not a stock 5.0 or one with your basic bolt-ons. The Mustang crowd jumped on it to solve surging issues for right and wrong reasons. Right would be those of us who have more than mildly modified engines and wrong would be those that just used it as a band aid due to piss poor diagnostic abilities.
Darren
Thanks for that, I actually have the .pdf for the TSB linked in my first post above that the writer of that thread refers to, and I discovered after reading the TSB that when you set the idle as instructed, you're meant to set it while idling in drive (not mentioned in the write-up). I set my idle last night before leaving the shop, and it was perfect. By the time I got home, it was back to rolling and surging. After having the plate in my hand today, and reading the sheets that came in the kit, I understand better what it does. It takes the throttle trim screw out of the game, instead using the air bleed screws to set base idle.
Good deal. Hopefully between setting it in drive and the adjuster you can get the problem fixed.
Darren
Almost there, she still hunts for about 5 seconds, and then settles down.
Mine does that when its cold but once it warms up there are no issues.
Darren
Mine does the same thing. When fired cold (sitting a day or more) it surges a bit for 5-10 seconds then it's fine the rest of the day.
I've heard that setting the base idle too high can cause an issue. I've never experienced it myself though.
the air bleed screws in the trottle plate?
I know the parameters of the TPS as being .5-1.19 i just use 1V as a base setting because it simplifies the reading for the NOVICE. Some guys do not have a digital METER. Actually to be exact it makes NO DIFFERENCE as long as the setting falls between those numbers. I also do not spend any time getting exact voltage numbers from the TPS. It makes no difference as you so truly point out. The ECM is mapped to run that way as to indicate a TPS out of range. And that in turn sets a TPS code. But FORDS have had issues with UN STABLE IDLES FOR YEARS. What i do is look at the TPS with a scope and also set it with a scope. This way you can see the NOISE. Basically the other thing i do is use a restrictor ( that is a given) that i make from a piece of sheet metal. I have found that 1/4 inch holes are BALL PARK. If the cam is stock you do not have an issue with that. But surging at idle can be many things and a SCOPE is the only way to look at it in my view. Eliminating the IAC is what i do and you can substitute it with a BOSCH controlled bleed IAC from an early BMW. I know i will get tuns of feed back from this but it works perfectly. Or you can use a solenoid controlled by a thermal switch to introduce a metered vacuum leak that does the same thing. Basically what you are trying to do is introduce a bypass air feed that is controlled by the heat of the engine. I have dun this on many a ford. Ford OBD 1 systems are far from being a good system. You can also use an OLDS EFE control valve to institute this MOD. But i have found that a GM purge valve controlled by a thermal switch works real good and the BOSCH valve works the best. If the idle surges slightly FORD says that is ok. But they have a nasty habit of getting out of range with either age of transient signals. The idle system basically SUCKS!!!
Also is your IAC tuned up. I have a thread about tuning the IAC that you might be interested in. Basically what you have to do is see if the IAC when off the car does not pass any air through it. If you can pass air through the valve the valve is no good. You must tune the valve to not do this. Or just use one of my MODS.
DARREN than how does your engine go to high cold idle??? Just asking!!
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Bellow is an IAC that i have modified for a stable idle. This also makes it easy to clean it out and polish the valve in the unit. This valve is fully adjustable and can be cleaned properly for service intervals. If you are not tuning your IAC you are missing out on a tuning operation of the IAC that in my view is a must. Good luck
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YES because the TPS gets out of range. ABOVE 1.19V
And another trick you can do is drill an extra hole in the throttle plate!!! I do this for BIG cam instillation. But that is a little tricky and if you are not familiar as how to set this up do not do it!!!
My IAC is new, and does not leak. I checked this before I opened the thread. I'm concerned about the idle targets, so today I'm going to check the functioning of the ECT, just to make sure the PCM knows the difference between a hot engine and a cold one.
Mine has always done that too. I just thought it was normal:hick:
It doeshiznit a high cold idle for a few seconds then drops down and idle hunts for a bit but only when the engine is cold. I reread what Joel wrote up on setting the base idle and I think I am going to do that again but I want to talk to my tuner first to see if he wants me to set it before it gets retuned. I am still running on the 306 tune with the 331 and the heads and lower intake are ported now so I am pretty sure its lean. I want some miles on the motor before we make a bunch of WOT pulls on the dyno.
Darren
Swapped the IAC, idles 775 free, 680 loaded. shag. I'll have to play with the trim a little, but generally 100% improved. As a side note, I've found through the use of the gauge tester to simulate ACT signal, that #5 intake runner really is where the ACT should be; not in my intake tube. My tailpipe smells way worse than with a higher ACT temp AND I idle lower without hunting. I actually have to trim the idle higher to not hunt when the ACT is in the tube. Guess I'm going to be drilling my GT40 intake soon.
Ah the ACT wasn't in the intake's #5 runner. That will screw with the computer and idle settings as the EEC-IV is expecting the ACT reading to be in a range that is similar to the ECT reading. With the ACT in the intake tube the intake charge readings are lower (the air is cooler) which throws the computer off. You can leave the ACT in the intake tube but the computer would need a tune to run properly.
I'm going to move it next week. The internet is split about 50-50 on ACT relocation, apparently this is why I don't go to Vegas. Anybody know what drill and tap sizes I'll need?
The ACT takes a 3/8 NPT thread. The required drill bit for a 3/8 NPT tap is 37/64 but a 9/16 is just 1/64 smaller so you might be able to use it if you are careful tapping the hole i.e. lots of cutting fluid and don't get too aggressive.
Again, Fastenal is a great source for taps as most places don't carry a good selection any more. You would think I work there or something but I just buy a lot of tools & fasteners there as they usually have what I need, the quality is great, and the price is right.
Darren
Just for the record this idle procedure is not BRAIN SURGERY. Once it is DUN that's IT. Of course the sensors have to be in the proper place to do there job correctly. Also how does the cold idle increase without an IAC . Just curious how that happens???????????
FOE i thought you had a brand new one??? So swapping it out corrected the issue??? Just curious . Guess you did not like my fully adjustable IAC mod. OH WELL i will let you ponder on !!!!!!!!!
You need to check for NOISE. Here is a clean noise free sensor . The scope is necessary to check for that. just saying!!
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I did have a new one, newish as in several months old. I swapped it with the one off the SO engine I've got laying on the floor waiting for a buyer. Since I messed with the idle trim, it's really close and only surges now in gear, which is why I say it needs a little fine adjustment yet.
I'm certain you're right about a scope, but I don't have one. Also, I don't remember anyone saying anything about cold idle, with no IAC. Somebody may have suggested eliminating it and replacing it with a thermostatically controlled bump solenoid, but I don't recall.
I do that and it fixes the issue permanently. using a BOSCH unit is the best as it works flawlessly and is void of TPS and is not connected to the ECM. Just saying,
Tom,
I am not sure if your last question in Post #25 was directed my way or not but I still have a functioning IAC on my car. The idle air bypass is just doing the same thing as drilling a hole in the TB blade but its adjustable so I don't have to drill the hole and I was able to fine tune it with the adjuster screws.
I am pretty sure Tom knows what the idle air bypass is but for those of you that do not Late Model carries them as well as other vendors and the Ford P/N is F2PZ-9F939-A:
http://www.latemodelrestoration.com/item/LRS-9939A/1986-93-Mustang-50L-58L-Idle-Air-Control-Iac-Adjuster
I could not find the instructions posted up on the net so I scanned mine and posted them:
(http://i786.photobucket.com/albums/yy142/dbrune_83/IdleAirAdjustSpacerInstallationInstructionsPage01_zps82c1c7b3.jpg)
(http://i786.photobucket.com/albums/yy142/dbrune_83/IdleAirAdjustSpacerInstallationInstructionsPage02_zps3a8aa9e8.jpg)
(http://i786.photobucket.com/albums/yy142/dbrune_83/IdleAirAdjustSpacerInstallationInstructionsPage03_zps90f038a6.jpg)
You can read on the instructions that this was a band aid for a sludge issue. The nice thing is they also made a part that works to correct idle issues on cars with alot of mods and/or additional cubic inches.
Darren
i saved this thread because i always suspected i could do better in the idle department.
My 20th did not sway up and down, it was a nice steady 650rpm with nothing on.
today i reviewed this thread, did a little thinking about how my car feels with lights on, ac on or other stuff on and seem to notice that the idle is lower sounding *especially* as soon as i put it in drive.
i went out and started the car,
observed my car revs up to about 1100rpm till warm up then it rolls down to about 650-700 (ish)
like normal, the rpms go lower with added loads.
with all the loads added or turned on, i adjusted my idle to about 800.
i turned off my loads and the idle went up to about 1k then i observed the car attempting to drop the base idle down
i shut off the car thinking i will do a couple restarts to see if the EEC starts to learn something.
i shut down and restarted 5 times, during each restart i added and removed loads.
after a couple trips up front to back off or add on a smidge of a turn on the idle screw this way and that... i now have a car that will hold 750rpm with a lot of loads or not.
I dont experience that annoying audible drop in engine rpm or struggle i use to get when i turned on my headlamps or turned on the AC.
seems a lot more correct now.
so the two things i used to guage my idle setting where hi beams on and AC running on hi
i noticed that there is a large period of adjustment within the idle screw which will still allow the eec to control the idel/fuel delivery ect.
if you stay in this goldielocks zone and adjust more on the high side , the cars EEC is able to tolerate your adjustment and still back down the idle to a nominal rpm.
if you go over the goldilocks zone, the eec cant roll the rpms down, so you want to be on the upper edge.
To be honest, now when i add loads, i dont feel like my alternator is struggling as much either. Im sure this probably reduces current draws on various gear in the car as well.
just my added info to this great topic!!!
thanks guys