Still having idle issues...only when car is warm..

bigcletus94

Registered User
I was asking about this a little while ago and it is still a problem I am having. I recently put in the stock 97 degree Tstat and cleaned my MAF sensor with electric cleaner and a Q-tip.

It will idle fine until it gets warmed up, then it will idle at 500 rpm and the low batt indicator will light up very dimly. If I turn on my heater, it will bring up the idle enough to make the light go out. It gets really bad like it will die if I am turning the wheel when the rpms drop. I don’t think I have a vacuum leak because it is only a problem after I have been driving for a while. Any idea what could cause this? Thanks.
 
i would say that it's a vacuum leak....just like you said it's only when the engine heats up. I would guess that a hose or something is heating up and getting loose?
 
The motor mounts are solid ones from MN12 Performance. I replaced them a couple months before I put my new motor in.
 
Sounds like your IAC is getting lazy to me. When you turn the steering wheel like that it of course puts a load on the engine and the IAC is supposed to keep the idle up, from what you say it is'nt. A vac leak would make the engine idle at a higher RPM not lower.:)
 
bigcletus94 said:
The motor mounts are solid ones from MN12 Performance. I replaced them a couple months before I put my new motor in.
Check BobGpzs thread about engine mounts. If, when you installed the new mounts, the limiter arm on the driver's side touches the upper part of the mount bracket, bare metal to bare metal, there's your problem.
 
I replaced the IAC a little over a year ago with a brand new one from Ford.

I am confused on how the motor mounts could effect the idle after it has warmed up. What is the limiter arm? Are you implying that it is an electrical grounding issue? I don't understand.

To top it off, my F'ing radiator hose started spewing coolant out this morning and forced me to park the bucket bird once again and resort to the Mustang for means of transportation. I am pretty sure Autozone sold me the wrong hose too. Those guys are the biggest monkeys. I hate this car!!!!.:mad:
 
The limiter arm is the "finger" part of of the top mount bracket. It fits through the opening which is part of the bottom mount bracket. Normally, the engine is isolated from the frame of the car by the good mounts. However, when the limiter arm comes in contact with the opening (metal to metal), the vibrations can be picked up by the knock sensor and falsely interpreted by the EEC which then retards the timing to correct for it. As a result, the idle drops.

If you look as how the engine twists, you'll see that the driver side arm moves up, and the pass side moves down. This is why Ford put the rubber bumper on the driver side bracket and not the pass side.

As for why it drops when the engine warms up, its due to the EEC using a differnet idle speed when its cold.

It may or may not be your problem, but its easy to check. Another thing is I've heard that the solid mounts are taller than the original hydraulic. This means that the arms are likely to sit much higher.. shoot, might not be a bad idea to check both sides. ;)
 
TbirdSCFan said:

It may or may not be your problem, but its easy to check.

How can I check the mount for this? I am assuming a visual inspection of the "finger" of the mount to see if there is a rubber bumper on it still? Is this a common problem others have experienced? I haven't looked yet, but I'm not sure that the mounts are even visible from the top of the motor. It’s been a couple of years since I replaced my motor, I don't know why that would become a problem now. The only recent changes I have made were the addition of my ZR intake and the removal of my Apten chip. Thanks for all your help.
 
Easiest way is to turn the wheel all the way to the right, jack up the car, securely supported of course, and crawl underneath on the driver side and look/feel with a flashlight. You might be able to see the pass side from the top or from under the front. A hand mirror might work also. If the limiter arms are not touching the bracket, you can rule that out as the cause.
 
I just checked the mounts, the driver side has rubber on the top part of the opening where the finger goes through and the finger sits dead center in the square. On the passenger side, there is no rubber (like you said) and the finger sits dead center on that side too. So I guess I can rule out the mounts as a possible problem for the idle?
 
MIKE 38sc said:
Sounds like your IAC is getting lazy to me. When you turn the steering wheel like that it of course puts a load on the engine and the IAC is supposed to keep the idle up, from what you say it is'nt.:)

Those pesky IAC's:rolleyes: Need a FORD only unit. About $80.00 and gasket $3.00. Any funky sounds (Dying goose honk) coming from intake filter area when: you shut off the car or when driving in cold weather???
 
I've had this problem also. It would drop rpm below 500 and occasionally stall while sitting at a stop light. It only happen while under load but would go up to 750 if I put it in neutral or park. It was because of vacuum leaks, 1 was the hose from the PCV valve, the small rubber one had a hole on the bottom right after the metal tree. I just used rubber hose to replace it, and will check to make sue it doesn't melt. I had checked PCV itself and it did still suck. The other was the end of the hard plastic tube under the SC nose and ends behind the DIS, it had pulled out of the rubber hose that goes to the bottom of the intake tube. I took it apart and added a clamp.
I noticed my vacuum got closer to 20- as opposed to the 18+- that I was getting before and I think my mpg has improved. Good luck
 
BobGPz said:
Those pesky IAC's:rolleyes: Need a FORD only unit. About $80.00 and gasket $3.00. Any funky sounds (Dying goose honk) coming from intake filter area when: you shut off the car or when driving in cold weather???

No funky goose honks. I replaced the IAC a little over a year ago with a brand new one from Ford.


vancouverBC said:
I've had this problem also. It would drop rpm below 500 and occasionally stall while sitting at a stop light. It only happen while under load but would go up to 750 if I put it in neutral or park. It was because of vacuum leaks, 1 was the hose from the PCV valve, the small rubber one had a hole on the bottom right after the metal tree. I just used rubber hose to replace it, and will check to make sue it doesn't melt. I had checked PCV itself and it did still suck. The other was the end of the hard plastic tube under the SC nose and ends behind the DIS, it had pulled out of the rubber hose that goes to the bottom of the intake tube. I took it apart and added a clamp.
I noticed my vacuum got closer to 20- as opposed to the 18+- that I was getting before and I think my mpg has improved. Good luck

This sounds exactly like what mine is doing. I am off to a Euro car show today and then Portland, OR tonight, but I am definitely going to check out those vacuum hoses like you suggested. Thanks for the input!!
 
These leaks don't show up when you do the propane test to seal the intake because air is being pushed out of the engine and not sucked in like the SC tubes. I hope you fix yours because stalling in traffic is no fun at all. Good luck
 
I just finished swapping out most of the previously mentioned vacuum hoses and added clamps to some that didn't already have them. I replaced the same small hose you were talking about that connects the PCV to the metal tree like tube that connects to the back of the inlet plenum. That metal tube that plugs into the inlet plenum was pretty soiled with oil and grime. Not sure if that is normal. It doesn't make a very tight connection into the inlet plenum. So I added a little high-temp silicon around the connection. I replaced the PCV valve too.

But unfortunately, there hasn't been any improvement in the idle. Still idles very low (500 or lower) when in Drive or Reverse. Moving into P or N brings the idle up. So does the electric fan running but only about 100-200 rpm. Just enough to make the “low batt” indicator light turn off. I am running out of things I can think of. I am pretty sure I have an exhaust leak on the driver side of the motor (clicking sputtering noise from the driver side of motor) but I don't think that could cause this problem. The other problem I have is that the motor cranks over for along time before it starts sometimes. Mostly when it has been driven. It has always done this, at least since I have owned it. I think that is my stock fuel pump going out though. Not sure if any of these things can be related or not. Any other ideas? Or are there any other common places that could cause a vacuum leak? Thanks for the help.
 
get a can of carb cleaner and spray around intake gasket and maybe some vacuum lines and see if car speeds up.i found couple of my top intake bolts backed out alil and had a lil air intake leak.i replaced the whole intake gasket though rather than just tighten them up cuz i didn't really know if the air leaking past might have screwed the gasket up.so anyways get a cheap can of carb cleaner and put that lil fine hose they come with on and spray around those bolts and anywhere else u can get to and see if car idles up and if it does there is ur leak!
 
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