View Full Version : Idle hangs a bit
Now that I've had a chance to resurrect the car. I've noticed that the idle seems to hang a bit. It idles around 850 when in gear but when cruising you almost have to ride the brakes a bit. If I give it a quick rev it seems to hang at about 1,500 for a few seconds until it settles back down.
There seems to be a brand new IAC on it, looks like it just came out of the box. I'll start by cleaning the mass air flow sensor, the car has a 90 mm unit, the IAC and TPS.
I don't think there are any vacuum leaks but I'll check again.
Am I missing anything? I tired the search function but my tablet doesn't seem to like the feature, won't let me type in the box.
Thanks!
MOTOWN
11-05-2015, 09:13 PM
What brand throttle body is on the car?
I believe it's stock. I will double check tomorrow and get back to you. I had the procharger off yesterday and went through all the connections after changing the belt.
I had noticed the delay in the idle coming back down prior to this and I figured it was due to the supercharger.
What brand throttle body is on the car?
Just had a quick peak, it's pouring rain here today.
Throttle body appears to be stock, seems to have a new IAC and gasket.
MOTOWN
11-06-2015, 12:25 PM
Just had a quick peak, it's pouring rain here today.
Throttle body appears to be stock, seems to have a new IAC and gasket.
The fact that it has a new IAC seems to suggest the high/hanging idle has been an issue in the past, unplug the IAC connector, the engine should stumble, and die immediately, if it does the IAC is good, if it continues to run with no change in the idle the IAC is bad , my guess is you more than likely have a vacuum leak.
Marauderjack
11-06-2015, 03:18 PM
^^^+10^^^:beer:
Check and report back!!;)
The fact that it has a new IAC seems to suggest the high/hanging idle has been an issue in the past, unplug the IAC connector, the engine should stumble, and die immediately, if it does the IAC is good, if it continues to run with no change in the idle the IAC is bad , my guess is you more than likely have a vacuum leak.
It finally stopped raining so I went for a short drive and got the car warmed up. When cruising and it gets into third / fourth gear it hangs around 1300 rpm.
Once I stop at a light and it shifts into first it seems to idle fine at around 850-900 rpm. Start driving and once in third or fourth the same thing, it seems worse once the car has warmed up.
When I got back home I unplugged the IAC and the car still idled, it didn't stumble at all.
So it looks like it's a bad IAC, it looks new (I know the car sat for a long long time).
As for vacuum leaks, I checked every hose, nothing seems loose or cracked but there is a hose under the intake which has been blocked off.
MOTOWN
11-06-2015, 09:37 PM
It finally stopped raining so I went for a short drive and got the car warmed up. When cruising and it gets into third / fourth gear it hangs around 1300 rpm.
Once I stop at a light and it shifts into first it seems to idle fine at around 850-900 rpm. Start driving and once in third or fourth the same thing, it seems worse once the car has warmed up.
When I got back home I unplugged the IAC and the car still idled, it didn't stumble at all.
So it looks like it's a bad IAC, it looks new (I know the car sat for a long long time).
As for vacuum leaks, I checked every hose, nothing seems loose or cracked but there is a hose under the intake which has been blocked off.
Ok at this point i would grab a test light, and check for voltage at the IAC plug, then remove the IAC and give it a good cleaning with some brake cleaner, you want to get any carbon build up of the plunger/rod assembly, the IAC may be bad , and need replacement all together , but try cleaning it first before dropping $65-75 for a new Motorcraft unit, and last check your bosst/vacuum gauge at idle you should see 18-20 inches/hg of vacuum (assuming the car isn't running radical cams), anything less than 18 to 20 inches/hg of vacuum, and you have a leak some where.
Marauderjack
11-07-2015, 03:28 AM
Mine had these exact symptoms recently and it was a vacuum leak......took awhile to find it but I finally did!!!:(
I was encouraged to add a catch can and it ended up having a BAD GASKET.....BAD LEAK......fixed it and all is well!!:beer:
Spray staring fluid or WD-40 around any suspicious spots with the engine idling.....it will rev up when ya spray the vacuum leak!!:eek:
Good Luck!!
Thanks guys, I will clean it and check again for vacuum leaks. I do see between 18-22 on the boost / vac gauge . The idle issue only occurs after the car has reached operating temperature. As for the IAC it looks as if it just came out of the box. I have a small propane torch which I can use to locate any vacuum leaks .
I kind of suspect the procharger bypass valve, it's an internal bypass valve and the shafts that the bypass valve rides on may be allowing air in. I'm heading out to get a real good look. I'll do everything suggested above and will report back. I store the car next week and want to have any issues taken care of.
martyo
11-07-2015, 08:43 AM
Ask the prior owner whether the idle started to hang after he had it tuned. Hanging idle can be a tune issue as well.
chief455
11-07-2015, 10:43 AM
Ask the prior owner whether the idle started to hang after he had it tuned. Hanging idle can be a tune issue as well.
His issue there, is the car was covered in dust from sitting and they knew pretty much nothing about it.
I'm guessing it had the idle issue, thus the 'new' IAC already, probably attempting to correct it.
I ran the car got it up to operating temp, unplugged the IAC and the rpm's dropped by maybe 100 or so (there was a brief stumble) but it did not stall. (Does this mean IAC is bad).
I then checked voltage at IAC with a test light and measured resitance. I had voltage and there wasn't an open circuit, I don't recall the reading for resistence.
Then I removed the IAC and cleaned it, it wasn't really dirty to begin with, I suspect it was changed not too long ago as it looks fairly new.
Vac gauge is showing 20 when idling. I could not find any obvious vacuum leaks anywhere. I zip tied every single hose and inspected them for cuts or cracks and there are none from what I can see.
I'm suspecting a tune since when I drive the car and come to a stop light it settles right back to about 800-850 rpm as soon as it goes into first gear, either rolling, or stopped. As long as it's in first the idle is 800-850. The issue seems to appear once in any other gear other than first.
When driving along at low speeds 60 kph / 40 mph the tach stays at about 1300 rpm car just rolls along as soon as I slow down enough and transmission down shifts into first the idle returns to normal.
Unfortunately the previous owner had $$$ and knows nothing about the car, he would have regular service, oil chages, procharger oil changed, and a tune up (plugs were gapped at 60 thou, replaced with ngk tr6 gapped at .028 now).
They had it for 6 years and used it for two or three summers, he was 67 years old. He couldn't answer any of my questions regrading the tune etc.... he had given me a stack of service records, nothing about the IAC there, oil changes, battery, tires, brakes, etc etc....
I doubt that any tune would purposely do this but.... , any other thoughts or suggestions?
Thank You!
MOTOWN
11-07-2015, 04:03 PM
If you don't have the Xcal tuner your going to need one , you may want to contact MartyO , and see about an Xcal4 with a remote tune , as he stated it could be a tune issue, it should have died when you unplugged the IAC.
justbob
11-07-2015, 04:45 PM
If you don't have the Xcal tuner your going to need one , you may want to contact MartyO , and see about an Xcal4 with a remote tune , as he stated it could be a tune issue, it should have died when you unplugged the IAC.
I agree with this^. Only other thing to rule out is the TB is in fact closing completely.
My idle hangs when coming to a stop but only about a hundred or so. The second it's fully stopped it comes down almost like its a MPH thing and not a gear as mine is a manual.
Hell, mine idles at 1,100 so another hundo isn't even noticed. I've all but given up on my high idle as everything is brand new top shelf, readjusted TB stop & TPS, and the tune is set far lower. I've actually started to like it as I can just release the clutch in traffic. I never had any issue at speed but I can imagine it would really get old..
Builder Of Badassery
MOTOWN
11-07-2015, 05:00 PM
I agree with this^. Only other thing to rule out is the TB is in fact closing completely.
My idle hangs when coming to a stop but only about a hundred or so. The second it's fully stopped it comes down almost like its a MPH thing and not a gear as mine is a manual.
Hell, mine idles at 1,100 so another hundo isn't even noticed. I've all but given up on my high idle as everything is brand new top shelf, readjusted TB stop & TPS, and the tune is set far lower. I've actually started to like it as I can just release the clutch in traffic. I never had any issue at speed but I can imagine it would really get old..
Builder Of Badassery
Funny you mention the throttle body, my used mamouth throttle body isn't closing completely, Jeff turned the iac value down very low until I get a new throttle body, mines would idle around 2K which drove me crazy! I'll either get a new mamouth dual, or single blade , or maybe a Kenne Bell "Bigun" lol
I smoked it twice, and couldn't find any leaks, come to find out the throttle blade is slightly flexing when the engine is started , and closes back when the engine is off , took a while to find that gremlin.
Ask the prior owner whether the idle started to hang after he had it tuned. Hanging idle can be a tune issue as well.
I'm beginning to think it's a tune / speed issue. As long as I'm in first or below 15mph idle is rock steady at about 850 rpm. Once in second third or fourth gear and I let off the gas and coast it settles at about 1300 rpm., at slow enough speeds you almost have to ride the brakes in traffic.
I even shifted into neutral coasting at about 25 mph and the idle went to about 1500 rpm. I kept letting it coast almost to a stop and the idle settled back down to 850 when it got to about 10 mph.
I've established that unplugging the IAC, the car still idles.
I've checked the throttle body and the throttle blades close fully.
I don't think there are any vacuum leaks, if there were in think the idle would always he high, ill double and triple check all lines on the methanol kit as well as a possible source of unmetered air.
From my understanding the IAC should come out of the equation once the throttle is depressed, let go of the throttle the IAC then comes back into play.
I'll put it on a diagnostic scanner which runs real time data and see what the IAC is doing, I would have done that today but my b-law who owns the scanner tool is off hunting.
I'll also get in touch with Marty for sure. I agree I need an xcal4.
If I'm missing anything or there are any other ideas with what I mentioned above, keep the advice coming.
Thanks.
Jim
justbob
11-07-2015, 09:26 PM
Funny you mention the throttle body, my used mamouth throttle body isn't closing completely, Jeff turned the iac value down very low until I get a new throttle body, mines would idle around 2K which drove me crazy! I'll either get a new mamouth dual, or single blade , or maybe a Kenne Bell "Bigun" lol
I smoked it twice, and couldn't find any leaks, come to find out the throttle blade is slightly flexing when the engine is started , and closes back when the engine is off , took a while to find that gremlin.
Good catch! My single blade was ever so slightly rubbing against itself but only when the engine warmed up. That was extremely annoying as it was only when I'd need to take off or coast.
I just centered the blade better and all is good. I still don't understand why they make such a big deal out of adjusting the stop? It's not rocket science adjusting it and dialing in the TPS!
Builder Of Badassery
hotford
11-07-2015, 10:14 PM
where is your by-pass valve located.....before the inner cooler core or after......
where is your by-pass valve located.....before the inner cooler core or after......
It's an internal bypass valve, intercooler core is behind the bumper cover below the grill. Here are a couple of pictures which I just took. It looks to be mounted after the intercooler one side is in the up-pipe into the throttle body, and the other is in the fresh air / filter side. Are the valves directional?
It's located on the thinner of the blue silicone hoses.
It seems to have a small bolt on which I think can be used to make adjustments but I haven't touched it.
chief455
11-08-2015, 05:43 PM
that outlet from your intercooler to tb up-pipe (to the first small blue hose), looks like a good place to mount a blow off valve to atmosphere. Then clean out that stuff feeding hot air back to the head unit intake. Good project for after winter ;)
hotford
11-08-2015, 05:44 PM
Ive seen it with vortech ones when they are install wrong and or installed in the wrong location can cause driveability issues......
Ive always ran the by-pass valve before the innercooler core back into the inlet air of the supercharger, not after....maybe other here can chime in as to where theres are locted that similar set up as your self....
all my vortech cars were before the core recycled back into the inlet..
my fox bodies had issue when doing the after the core......
hotford
11-08-2015, 05:48 PM
that outlet from your intercooler to tb up-pipe (to the first small blue hose), looks like a good place to mount a blow off valve to atmosphere. Then clean out that stuff feeding hot air back to the head unit intake. Good project for after winter ;)
He cant atomsphere it from there as the Maff has already sampled the incoming air, that forsure will cause driveability problems, if he want to atomsphere the by-pass the Maff will need to be relocated up stream near the TB this way it wouldnt matter.
MOTOWN
11-08-2015, 06:01 PM
You definitely want to mount the blowoff valve after the s/c , and before the intercooler, no sense in cooling boost only to discharge it at the blowoff valve, and tax the intercooler unecessarily , where the mass air meter is placed is the difference between a blow thru setup and a draw thru setup.
From what I gather, the SC kit was installed by Forced Induction Technologies F.I.T and it's kit #5. As to where the best place to mount the bypass valve, this has started to confuse me.
Do you think the location of the bypass valve is causing the hanging idle? Could it be the extra few r.p.m. once off idle causing the throttle valve to slightly open due to pressure in the inlet pushing past the throttle valve?
As I mentioned once I come to a stop again the idle will return to about 850, it's when I cruise that it hangs and at speeds around 25 mph or so I need to ride the brake a bit since with my foot off the throttle the car revs at about 1,300 and will travel down the road without me having to touch the gas.
While poking around the Internet and looking at bypass valves I came across a point which said "installing a bypass valve after the inter-cooler blows off more air and prevents run on after the blade is closed, more air will go threw the valve once it has been threw the inter-cooler, its cooler air and takes twice the valve area to blow off hot air"
Maybe I'll start a new thread asking what other F.I.T. procharger owners have done.
I have until Tuesday to sort this out or it will have to wait until spring, the car goes into storage.
Thanks for the responses I think I've confused myself even more. I think I need to sleep on it and then read this all over again.
Jim
Marauderjack
11-09-2015, 03:34 AM
If you are sure there are no vacuum leaks, I agree with Marty that it's all in the tune!!:beer:
I had severe stalling problems with the Diablo tune from F.I.T. and Scott Beer worked with it numerous times finally doing what you seem to have....."hanging idle"!!:cool:
Do you happen to know who tuned it and with what software??:confused:
chief455
11-09-2015, 10:19 AM
I don't think the blow off location has anything to do with your idle issue.
I feel it is likely tuning, and was never corrected before you got the car.
Any centri set up I've seen had the blow off to atmosphere before the intercooler, as to introduce less hot air to the system at all. But I have very limited experience in this area.
I believe the blow off returning to into the system must be a regulation or 'better idea' type thing??
I'd do as you said, study into that topic seperate from this thread.
good luck!
martyo
11-09-2015, 11:59 AM
I don't think the blow off location has anything to do with your idle issue.
I feel it is likely tuning, and was never corrected before you got the car.
Any centri set up I've seen had the blow off to atmosphere before the intercooler, as to introduce less hot air to the system at all. But I have very limited experience in this area.
I believe the blow off returning to into the system must be a regulation or 'better idea' type thing??
I'd do as you said, study into that topic seperate from this thread.
good luck!
The BOV location can definitately effect idle quality. Also we have noticed that a lot of the centri cars benefit from a slot style meter.
The best thing to do with diagnosing this issue is to look at mass air flow AD count and see if it is real jumpy.
We had a car with a similar set up come in with similar complaints so we have been down this path.
Hopefully I can get this looked at tomorrow morning because at noon I have to put the car into storage. I'll check the mass airflow and see how it looks.
If all else fails it will have to wait until spring and I will be contacting Marty for an Xcal4 and a remote turn based on the info I can provide him. I'll let you guys know if I'm able to get the scanner tomorrow and drive around with it a bit.
I also fired off a message to procharger with some pictures with a few questions about the bypass valve location. I'm on nights this week and it makes hard to get things done.
Here are a couple of videos of what it's doing, I had my son video it and post it up to youtube.
I'm definitely leaning towards the tune as regardless of when it's in gear or I shift it into neutral, the revs will stay up at about 1300-1400 and then return back down to about 900 once the car goes below about 10-15 mph.
I also monitored the IAT it never went over 60 degrees (about 15 Celsius and it was about 10 Celsius out so bypassing after the inter-cooler hasn't really affected the IAT) and when the methanol sprays I get much colder than ambient temps.
Still waiting to hear back from procharger as to where they recommend where the valve should be.
Throttle hanging in gear https://www.youtube.com/watch?v=0B_m1FM6vFs
Throttle hanging in neutral https://www.youtube.com/watch?v=OMX3DxnlAFU
Short little blast for the kid https://www.youtube.com/watch?v=u8l6PKWOQmM
Well I didn't have the opportunity to get it on the diagnostic scanner and the storage facility where it's currently siting was on my case to get it into my reserved spot. I'll l revisit the issue in the spring, contact Marty then for an xcal4 and will keep you posted. For now I'll visit the forums and hopefully be able to give someone else some asistance.
You have a 1.75" upper heater hose on 1.5" ends.
I'd fix that before anything else.
You have a 1.75" upper heater hose on 1.5" ends.
I'd fix that before anything else.
I've added it to the list.
Thanks!
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