Still having rolling idle/idle surge problems. Reply #15 – April 04, 2013, 05:58:22 AM 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!!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 Quote Selected
Still having rolling idle/idle surge problems. Reply #16 – April 04, 2013, 06:02:44 AM Quote from: thunderjet302;412538I've heard that setting the base idle too high can cause an issue. I've never experienced it myself though. YES because the TPS gets out of range. ABOVE 1.19VAnd 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!!! Quote Selected
Still having rolling idle/idle surge problems. Reply #17 – April 04, 2013, 07:07:59 AM 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. Quote Selected
Still having rolling idle/idle surge problems. Reply #18 – April 04, 2013, 07:45:37 AM Quote from: thunderjet302;412537Mine 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. Mine has always done that too. I just thought it was normal:hick: Quote Selected
Still having rolling idle/idle surge problems. Reply #19 – April 04, 2013, 10:43:57 AM 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 Quote Selected
Still having rolling idle/idle surge problems. Reply #20 – April 04, 2013, 01:18:26 PM 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. Quote Selected
Still having rolling idle/idle surge problems. Reply #21 – April 04, 2013, 04:52:05 PM Quote from: TheFoeYouKnow;412584Swapped 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. Quote Selected
Still having rolling idle/idle surge problems. Reply #22 – April 04, 2013, 05:03:23 PM 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? Quote Selected
Still having rolling idle/idle surge problems. Reply #23 – April 04, 2013, 05:30:12 PM 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 Quote Selected
Still having rolling idle/idle surge problems. Reply #24 – April 04, 2013, 06:42:19 PM 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??????????? Quote Selected
Still having rolling idle/idle surge problems. Reply #25 – April 04, 2013, 06:44:32 PM 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 !!!!!!!!! Quote Selected
Still having rolling idle/idle surge problems. Reply #26 – April 04, 2013, 06:50:12 PM You need to check for NOISE. Here is a clean noise free sensor . The scope is necessary to check for that. just saying!! Quote Selected
Still having rolling idle/idle surge problems. Reply #27 – April 04, 2013, 08:47:47 PM 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. Quote Selected
Still having rolling idle/idle surge problems. Reply #28 – April 04, 2013, 09:16:22 PM 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, Quote Selected
Still having rolling idle/idle surge problems. Reply #29 – April 04, 2013, 09:27:14 PM 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-AdjusterI could not find the instructions posted up on the net so I scanned mine and posted them: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 Quote Selected
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