Strange Idle problems!

Topic: Strange Idle problems! (Read 3351 times) previous topic - next topic

Strange Idle problems!

September 01, 2011, 11:39:22 PM

SO my car randomly has a funky idle. I was trying to find out why my throttle screw had to be screwed in so much for the car to idle properly and discovered why. When I first purchased the car it would randomly idle up to 3k after it warmed up. I went back to the dealership I purchased the car from and their mechanic "fixed it." I had replaced the IAC and that didn't solve the problem so when I asked him what he did he said he cleaned the throttle body.

:mad:Well, today, when I was looking around, I noticed that all the s.o.b. did was cut the red wire to the IAC, tuck the ends in the wire cluster and tighten up the throttle screw so it would compensate. This has probably been a large chunk of performance loss. If it was supposed to be like that they would have manufactured the vehicle like that.

Now, I reconnected the wire with a butt connector, lowered the throttle screw down to 500 rpms, put a new TPS on it set to .899 V closed and 4.565 V WOT. Now the car responds much better, but here is my problem. When I first start the car the idle jerks from 1k to 500 rpms and back to 1k and back down to 500. If I rev it up hard and drop the throttle it dies. If I rev to 2k and slowly lower it back down to 1k it will still flutter from 900 to 1100 rpms for a few minutes. Once the car is warm I no longer have this problem. So we can rule out the IAC and the TPS. It was stable when it was s.o.b. mechanic :beatyoass:engineered aside from low idle at first start. I'm pretty sure it's not a vacuum leak so I'm stumped. Any one have any idea?

Also, where and what adjustable FPR do you guys recommend?

Strange Idle problems!

Reply #1 – September 03, 2011, 02:15:14 PM

I will be reading this thread intently because my car does the same thing.

Also http://www.kirbanperformance.com/product/776/Mustang+BILLET+ALUMINUM+ADJUSTABLE+FUEL+PRESSURE+REGULATOR+%235005.html

by far the best you can get

Strange Idle problems!

Reply #2 – September 03, 2011, 05:22:30 PM

THanks for the info man. Could it be a problem with the 2g electrical ? THe 3g upgrade is on the long list of things to do so I'll let you know if that helps if you haven't done it already.

Strange Idle problems!

Reply #3 – September 03, 2011, 08:48:19 PM

Well

Strange Idle problems!

Reply #4 – September 03, 2011, 10:33:15 PM

A std 5.0 idles around 625 RPMs, why would you set the base idle at 750-800??? With a long duration cam it's common to "jack up" the idle, I have mine set to around 900 but if it's necessary in a std 5.0 something is wrong... I would raise the base idle to 600 and go from there...

Some years back I had a Turbo Coupe that idled all over the place when cold, running a bottle of the professional fuel injector cleaner(one that connects to fuel rail)fixed it...

Strange Idle problems!

Reply #5 – September 06, 2011, 10:33:04 AM

I set it according to the faq on Forced4. Well, with it set the way it is now, it does something strange. When I shift gears up if I close the throttle and push the clutch in it idles up 200 rpms or so between the gears for about half a second. It's kind of strange, it sounds like I'm not reducing throttle at all. It's like the IAC is wide open I guess. Also, the TPS is perfectly adjusted for the 500rpm base idle, should I tighten the idle screw up to 750rpms - 800 and adjust the TPS to it? THis is where I found the FAQ for adjusting my base Idle and TPS.

http://galatea.meccahosting.com/~a00015a5/gfaq.html

Strange Idle problems!

Reply #6 – September 06, 2011, 02:08:30 PM

In a manual transmission application it's common for the idle to hold at approx same RPMs then reduce, it's to prevent possible stalling(this is why some vehicles have stall issues after a HO conversion, speed sensor not connected)... In my Bird with automatic, I can put it in neutral at say 35mph and idle will hold near what it was till the vehicle slows to around 5-10mph, only then Idle will come down... It's due to the EEC seeing input from the speed sensor...

Strange Idle problems!

Reply #7 – September 06, 2011, 10:48:18 PM

No matter how fast I'm going if I hold the clutch in it goes back down to normal idle after about half a second. It seems to have worked itself out for the most part. It still does it when the car is cold. I don't know, I'm going to tinker with it when I get the time and try different idle settings to keep it where it should be. I'll see how this pans out, I think you guys may be on to something with the 750 base idle. I think it being so low is not allowing the IAC enough time to open so it's making the ecm flip out a bit not knowing what to do.

Strange Idle problems!

Reply #8 – September 10, 2011, 05:08:45 PM

I disconnected my IAC again and adjusted my idle manually. It idles better than it ever has before with the IAC connected. It even feels more powerful. I don't think I am ever going to plug that piece of in again.

2 separate cleaned IACs both had crazy idles (1500 all the way up to 2800 rpm) I was killing my clutch at stoplights trying to hold the idle back down to 1100 or so.

Strange Idle problems!

Reply #9 – September 10, 2011, 08:53:07 PM

After about a day of research, I found that you don't need the IAC especially if you have deleted A/C

I just bought this.

Case Closed!

http://www.jegs.com/i/Holley/510/112-560/10002/-1