any tips for the hunting idle?

[brownsvo]

any tips or links?
facts:
Ive set my tps (new) to .9~v closed throttle, all the way to 4.v~
I just set my base idle, ill admit my IAC is used, from a 95ish 4.6 but still the same plug as ours so not original.
I can get it to idle at 900 without a/c,


my issue is when letting the idle fall from over 3000 rpms when coming to a stop it will dip below 500 and correct itself, sometimes it doesnt and stalls. (new IAC would probably fix this)

It also does the up 300rpms down 600rpms, and does this for a min until i tap the gas and sometimes corrects itself.

[carversvo]

One thing to try before getting too technical is to take the iac off and soak it in carb cleaner for a bit to make sure it's all nice and clean. Unfortunately the idle thing is a common nuisance without a common solution, other than installing a standalone ecu.

What brand is the new tps? In many cases new electronics that aren't motorcraft can do strange things. No idea if that theory applies to the tps though...

[brownsvo]

i did swish some gas in the iac as i didnt have any other cleaner lol.. it helped the diving idle a little. the tps is autozone brand but still reads .9~4v. the wiring is damaged so i may take that part of the harness apart and fix it.

[KevinK]

I found my problem to be a cracked exhaust pipe in front of the muffler. I guess it does not like variable back pressure.

[brownsvo]

I found my problem to be a cracked exhaust pipe in front of the muffler. I guess it does not like variable back pressure.

well thats easy, my exhaust consists of a 4inch turbo elbow.

It likes to stick as well at say 1500 rpms.. i need to start from scratch lol.

[caroth]

Is your IAC the black plastic unit? I have never had any luck with those, replace with correct IAC. The few times I have experienced hunting idle was from a vacuum leak. Pressure test your system in front of the turbo and fix leaks. I had a bypass valve leaking which caused the idle issues.

[brownsvo]

it was all metal, black, and it has an accordian type valve on the inside. I do have a eclipse/talon/Mitsubishi bypass valve currently being used as a bov.

[brownsvo]

This Thread is now about what sensors i should actually replace vs replacing everything as im not made of money. :)

After having little issues like my fan not coming on (fixed it once), rough idle, rich tasting exhaust, and ok gas milage i figure tax return time is the time to update the sensors.
I know everyone will have a different opinion on what to do with each sensor so let me hear it. i get 18mpg with under 55mph driving.

List i have so far...

-Engine Coolant sensor (below upper intake by fuel injectors, i broke the plastic off trying to get to it..might as well replace it)
-EGR valve//Posistion sensor? Does it hurt to take it off, thus minimizing the engine clutter, or replace the egr stuff? if it helps MPG im all for it..
-Air Charge Temp. sensor? this is a LA3 sensor correct? I want to convert to the square intake eventually.
-o2 sensor is fairly new..ill replace it with the rest of it.
-Idle air control is eexpensive! @75$ should i pull some from the Junkyard and just try them out or what..
-tps is new and at .9v

am i missing any?

[caroth]

Do you have the 1G DSM valve with a check valve installed? I tried to run one of those and had problems like you are describing. Remove the DSM valve and see if your idle issues go away. I think I have a check valve for the DSM setup, let me know if you want to see pictures.


This Thread is now about what sensors i should actually replace vs replacing everything as im not made of money. :)

After having little issues like my fan not coming on (fixed it once), rough idle, rich tasting exhaust, and ok gas milage i figure tax return time is the time to update the sensors.
I know everyone will have a different opinion on what to do with each sensor so let me hear it. i get 18mpg with under 55mph driving.

List i have so far...

-Engine Coolant sensor (below upper intake by fuel injectors, i broke the plastic off trying to get to it..might as well replace it)
-EGR valve//Posistion sensor? Does it hurt to take it off, thus minimizing the engine clutter, or replace the egr stuff? if it helps MPG im all for it..
-Air Charge Temp. sensor? this is a LA3 sensor correct? I want to convert to the square intake eventually.
-o2 sensor is fairly new..ill replace it with the rest of it.
-Idle air control is eexpensive! @75$ should i pull some from the Junkyard and just try them out or what..
-tps is new and at .9v

am i missing any?

18mpg is bad. I have been driving the SVO for the last few days and pretty much driving it like I stole it and still am managing 20mpg in town. I get 30mpg on the highway running 80mph.

Have you pulled codes from the computer? Do you have a wide band O2 sensor?

If the ECT is bad and triggering fuel enrichment then you could be loosing fuel economy. I guess the ECT could be bad, but I have never run across one. You can test the ECT, the procedure is in this document: http://rothfam.com/svo/reference/sensors.pdf

I have not been running an EGR for years so can't help there. I think I have disabled the code in the EEC, but I forget.

ACT is mounted in the intake. VAT is mounted in the VAF meter. If you don't have an ACT, the computer will default to 140°F. ACT only adds spark advance if the intake is cool. A missing ACT will not effect fuel economy.

IAC will not cause a fuel economy issue, but will mess with your idle. Look for an IAC off of a Tempo, they are mounted on the top of the throttle body with the ports facing down and tend to not be as dirty.

My guess is the VAF meter could be part of your fuel economy issue, test it too, including the VAT.

Chris

[brownsvo]

I have the 1g dsm bypass valve, not recirculated, no check valve. I have a front mount intercooler setup im piecing together and ill get a real dual-piston bov.

I drove it to austin (~250 miles) averaging 70mph, i think i got 24mpg. I actually got the same gas milage when my turbo elbow fell off (long story, 1 bolt holding it on) and drove it for another 2-3hours. My mods now are still a ghetto 3in Elbow and the k&N. i remember replacing the spark plugs before my trip this past thanksgiving.
around town 40-50mph stop and go for about 15 miles i get about 200 miles to a tank/11gal of gas=18mpg


I do not have a wideband, My mods are (at the time) 2.5 exhaust, new o2 sensor, new tps, and a K&N filter on the vam. I pulled KOEO codes awhile back and i believe i got 2 codes. ill run it again because i seem to of lost the paper i wrote them down on.

[Chalky]

Pull some codes but a bad ECT is guaranteed to cause bad mileage numbers. It's also far easier to remove if you take off the upper intake. I've got a couple of spare IAC's and VAM's in snohomish if you need one.

[brownsvo]

With tax return season apon us if the vam really is bad, i may take a little convincing to just upgrade to a PiMP. Im reading up on VAM testing on the Turboford now.
Later today ill get some codes posted. I realized 300+ hp is obtainable with la3/35s, but switching to newer tech. and eliminating other older tech is a good reason to switch IMO. I also understand fixing the broken stuff now will help sort stuff out later on when i upgrade other things. Does the haynes/chiltons manuals usually have Sensor testing procedures or is it mostly remove/replace/taadaa!?

[Chalky]

As much as upgrading is fun, get a good baseline in stock form first or you'll be forever chasing your tail!!! Chiltons is useless, too generic. Go Ford manuals or search caroth's site.

[brownsvo]

Yeah i understand that haha.. as far as i know it runs/ran "normal". I was getting 16mpg driving 2miles to work and other svo owners said that was normal considering my short 5 min. drive.


i should get out of here in about an hour and get some codes :)

[MikeFleming]

Does the haynes/chiltons manuals usually have Sensor testing procedures or is it mostly remove/replace/taadaa!? You need one of the technical manual reprints. All the sensors are detailed in it:

http://www.svocop.com/forum/showthread.php?841-Some-Things-For-Sale

[brownsvo]

oh imagine that! :) pm sent and paypal ready

[caroth]

I have the 1g dsm bypass valve, not recirculated, no check valve.

You just identified your idle issue. The DSM valve will leak at idle or close to idle. Get a check valve on it or remove it.

[brownsvo]

54 vam
82 air circuit, what the hell?
83 egr

I replaced the engine coolant sensor..not fun. Tightened a couple valve cover gasket bolts which led to oil spilling everywhere lol... loose as can be, no leaks. Over tighten them and they filled the lower intake cavities with oil. Love hate relationship svo..... mostly hate right now until she straightens out.