idle hunting... any ideas?

[jeanrw2000]

My engine idle is hunting all the time while on neutral or normal idling some times the whole car shuts down because it. the harder you rev the engine the more chances to stall on you. Now once i unplug that hose near the throttle body(see picture below inside red circle) i really don't know what that hose is for but like i was saying if unplug that hose the car runs normal, i do loose about a 1Hg of boost or so but a least the car runs better, now i know that hose is normally there for a reason.



So far i have trace that hose all the way out took the and replace the purge canister solenoid and all hosing on it and clamp and sipped tie all other vacuum lines replaced all damage vacuum lines as well took intakes back out and cleaned them, also took the EGR valve and cleaned the **** out of it. NOTE: intakes and egr valve very fairly clean before i took'em apart. replace intake gaskets for new ones recheck for leaks around the intakes,installed gasket in between blow off valve and supercharger intake to make sure no leaks in there,installed fuel pressure regulator, installed a Boost gage and read about 11 Hg on idle driving around while shifting i will increase as much as 20/25 Hg. I was told car is suppose to have about 18/20 Hg of boost while on normal idling so i automatically suspect of vacuum leak but i can't find any...



Any help or ideas will definitely make my life a little easier and, all comments are gladly appreciated it.

Jean. :cry:

 

[TT SHO PROJECT]

My engine idle is hunting all the time while on neutral or normal idling some times the whole car shuts down because it. the harder you rev the engine the more chances to stall on you. Now once i unplug that hose near the throttle body(see picture below inside red circle) i really don't know what that hose is for but like i was saying if unplug that hose the car runs normal, i do loose about a 1Hg of boost or so but a least the car runs better, now i know that hose is normally there for a reason.



So far i have trace that hose all the way out took the and replace the purge canister solenoid and all hosing on it and clamp and sipped tie all other vacuum lines replaced all damage vacuum lines as well took intakes back out and cleaned them, also took the EGR valve and cleaned the **** out of it. NOTE: intakes and egr valve very fairly clean before i took'em apart. replace intake gaskets for new ones recheck for leaks around the intakes,installed gasket in between blow off valve and supercharger intake to make sure no leaks in there,installed fuel pressure regulator, installed a Boost gage and read about 11 Hg on idle driving around while shifting i will increase as much as 20/25 Hg. I was told car is suppose to have about 18/20 Hg while on normal idling so i automatically suspect of vacuum leak but i can't find any...



Any help or ideas will definitely make my life a little easier and, all comments are gladly appreciated it.

Jean. :cry:

lol ok so most ppl wouldnt say to do this... but this has worked for me in the past on all of my fords... if you unhook that line and teh car runs fine... then just plug the whole... like get a cap for the ****** on the tb(or is that on teh intake?) and put a sscrew in the vac line and if you dont get a check engine light and the car runs/drives fine then problem fixed... thats just my $0.02

or if you dont want to do that try resetting your idle... have your car off.... unplug the wires to the IAC (idle air) start your car it may or may not idle.... if it stalls just turn the idle screw to the right a turn or 2 and try again... try setting your idle at 750rpm if the car idles ther then with it running plug the wires back in and you idle should jump up a couple 100 rpm if it still surges try to set it up a lil higher... if you have to have the car ideling over 1k rpm then give up hehe theres something more wrong with it.

-Bob..

 

[jeanrw2000]

lol ok so most ppl wouldnt say to do this... but this has worked for me in the past on all of my fords... if you unhook that line and teh car runs fine... then just plug the whole... like get a cap for the ****** on the tb(or is that on teh intake?) and put a sscrew in the vac line and if you dont get a check engine light and the car runs/drives fine then problem fixed... thats just my $0.02

or if you dont want to do that try resetting your idle... have your car off.... unplug the wires to the IAC (idle air) start your car it may or may not idle.... if it stalls just turn the idle screw to the right a turn or 2 and try again... try setting your idle at 750rpm if the car idles ther then with it running plug the wires back in and you idle should jump up a couple 100 rpm if it still surges try to set it up a lil higher... if you have to have the car ideling over 1k rpm then give up hehe theres something more wrong with it.

-Bob..

if i cap that hole then the car stalls for sure,also i have SS race cams on it and the car is already preset to idle @ 1000 rpms

 

[Yamaha V6]

First thing's first... with a blower application you NEED to remove the ability to overpressurize the crankcase.

1) CAP where you have the circle.
2) CAP the intake side of the vac line that runs to the front cam cover.
3) Run the cam cover line to a breather / catch-can / exhaust neg. pressure valve, whatever.
4) CAP the underside of the throttle body, where the large dia. line runs to the crank case.
5) Run the crank case line to a breather / catch-can / exhaust neg. pressure valve, whatever.

If you do not have a method in-place to avoid over pressurizing the block, you WILL blow oil seals (or worse) out of the engine. BTDT.

Idle - what fuel injectors are you running - the SHO Shop modified 48 lb-hr ones? If so, consider switching to the Accel 48 lb-hr ones. You're more than likely out of tune, caused by fuel issues.

 

[SuperchargedSHOguy]

First thing's first... with a blower application you NEED to remove the ability to overpressurize the crankcase.

1) CAP where you have the circle.
2) CAP the intake side of the vac line that runs to the front cam cover.
3) Run the cam cover line to a breather / catch-can / exhaust neg. pressure valve, whatever.
4) CAP the underside of the throttle body, where the large dia. line runs to the crank case.
5) Run the crank case line to a breather / catch-can / exhaust neg. pressure valve, whatever.

If you do not have a method in-place to avoid over pressurizing the block, you WILL blow oil seals (or worse) out of the engine. BTDT.

Idle - what fuel injectors are you running - the SHO Shop modified 48 lb-hr ones? If so, consider switching to the Accel 48 lb-hr ones. You're more than likely out of tune, caused by fuel issues.

Fred, I had him and Mike Kelly bypass the crank system. That hose he is talking about on the throttle body is still hooked up on my 91 and I have no problems with idle or vacuum. We installed Josh's AFPR and it helped the idle hunt alot, but Jean said after his 40 mile trip home it was doing it again. He has the SHOSHOP firehose injectors as well. They were even playing with a TwEECer and couldn't make it better than the LPM.

I believe when we disconnected that line and then capped it with our finger, the car wanted to stall?!? We then left it disconnected and much better idle. Everything else looks fine under his hood. I am stumped again because I am 180 miles away and I can't physically touch the car.

 

[jeanrw2000]

thanks for the sugestions guys.
where there be any other reasons why the idle will surge like that?
what about my vacuum shouldn't i have about 18/20 Hg of boost i only get about 12/14 Hg on idle.
thanks

 

[TT SHO PROJECT]

thanks for the sugestions guys.
where there be any other reasons why the idle will surge like that?
what about my vacuum shouldn't i have about 18/20 Hg of boost i only get about 12/14 Hg on idle.
thanks

well when you have "Race Cams" you will always have less than stock vacuum so this hsould be normal... but then again iv never seen the vac on a sho with "Race Cams" before but thats pretty much what happens to all cars once you put in a wild cam... my blown 5.0 with a e303 cam and 1.72 RR's made 15hg at the most and my stocker pulled more than 20hg

 

[Yamaha V6]

Exactly the same setup as my 91's... S2 cams, 15 psi. Idle's crappy (jittery) with the cams, but the surging in my case was the fuel. There is essentially nothing much you can do with the firehoses - they STREAM, not SPRAY (as an over-exaggeration). It's very hard to atomize the stream accurately & consistently.

So, you're saying there are post-picture modifications to the vac lines, right?

 

[jeanrw2000]

Exactly the same setup as my 91's... S2 cams, 15 psi. Idle's crappy (jittery) with the cams, but the surging in my case was the fuel. There is essentially nothing much you can do with the firehoses - they STREAM, not SPRAY (as an over-exaggeration). It's very hard to atomize the stream accurately & consistently.

So, you're saying there are post-picture modifications to the vac lines, right?

this is kind of the best picture i could get today basicly the only hose is left is the one i can leave without it right now is plug but because i am afraid to run the car without it, also today i replaced the fuel filter and cleaned up the nostros not quite sure about the spelling? of the throtle body and it seems to be running a little better, stills hunts but not as bad i don't know what to do anymore. So i you guys thinks is ok to have 12/14 Hg of vacuumm?
thanks

 

[Lupo]

My idle hunting was due to fuel overpressure of the stock FPR.
Get a gauge, and make sure that your FP is correct at idle. It should be around 31psi at idle with 16inch VAC, and it should be 39psi with the FPR unplugged from the vacuum line.

 

[SuperchargedSHOguy]

My idle hunting was due to fuel overpressure of the stock FPR.
Get a gauge, and make sure that your FP is correct at idle. It should be around 31psi at idle with 16inch VAC, and it should be 39psi with the FPR unplugged from the vacuum line.

We set the fuel pressure correctly when we installed the SHONUT adjustable fuel pressure regulater...I still think the LPM programing has alot to do with it inconjunction with your mods. I think your vacuum is low, but I have not installed my cams yet, so I am going off my stock cams and vacuum.

 

[Lupo]

Start the motor, and yank the vacuum line to the FPR (just for a few seconds) and make sure it's at a dead-on 39psi.

 

[SHO Dude]

...I still think the LPM programing has alot to do with it inconjunction with your mods.

Couldn't have said it better.

 

[jeanrw2000]

i reset the fuel pressure again this time i ground the fuel pump and set it to 39psi engine off key on and then turn the car on and took the vacumm line out and it read 40psi so rather than mess around with anymore i left it like that for now with that done i believe that the hunting is gone for the most part i still have a little bit which i am not to happy with it but i keep hearing i am going to get some kind of hunting with the supercharger regarless no sure about that. as far as the LPM i think is time to get rid off even if is just to make sure that in fact there it may be a problem with it so i think i am going to go for one of those superchips everybody is talking about it...

 

[bobreimer]

I have the same setup as you on a stock motor. I have 20 inches of vacuum at idle. The idle bounced slightly after the installation until I cleared the computer. Now it idles like a stock motor.

I suspect a vacuum leak which is consistent with the reading on your boost guage.

Bob

 

[NCTaurusSHO]

We had the same exact problem with our turbo sho knocking off. I replaced the engine coolant temperature sensor, not the gauge sensor... the temperature sensor.

In the ford fuel injecton and enginge control manual it states:
The engine coolant temperature sensor affects air-fuel ratio, spark timing, idle RPM and emissions control.

So we replaced it, and it completely took care of the idling and knocking off problems all together. We recommend that you try that ASAP, intead off just unplugging vacuume lines all willy nilly. It is not expensive to buy. TRY IT. NOW! haha.

 

[SuperchargedSHOguy]

Jean, lets give that SCT tuning a chance later this month at the dyno the 29th...

 

[jeanrw2000]

Jean, lets give that SCT tuning a chance later this month at the dyno the 29th...

i think i just going to way until i get back and then get me the clucth, catch up on some bills and then do the dyno and the SCT i need to take a brake from the credit cards

i think i finally nailed the idle problem i did so many replaced here and there and change here and there that its hard to say what fix what but a least the car is running the dyno is going to have to wait for now i guess

thanks for all the inputs.

 

[FAST4DR]

We had the same exact problem with our turbo sho knocking off. I replaced the engine coolant temperature sensor, not the gauge sensor... the temperature sensor.

In the ford fuel injecton and enginge control manual it states:
The engine coolant temperature sensor affects air-fuel ratio, spark timing, idle RPM and emissions control.

So we replaced it, and it completely took care of the idling and knocking off problems all together. We recommend that you try that ASAP, intead off just unplugging vacuume lines all willy nilly. It is not expensive to buy. TRY IT. NOW! haha.

I have had the same exact problem for a while now also. Most of the time it runs ok, but occasionally it will try and stall. I had the 255 pump(didn't know any better at the time) and changed that out for a 155 and it made it better, but it still happens. All the maintenance is up on my car and the motor is completely stock. I have changed the temp sensors and the IAB. I suspect that it is a small vacuum leak somewhere. I will eventually get around to replacing all hoses, etc. It mostly happens when I'm at heavy throttle and jump off the gas and push in the clutch. As the revs come down it will want to stall, unless I feather the gas a little. If I don't give it gas it will drop to about 500 rpm, stutter and then rebound to 1500, then down to 7-800 then idle normally. Weird

Will