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I'm at a loss - IDLE!

B

Big Daddy Kane

Hard-core CEG'er
Joined
Jul 22, 2003
Messages
1,952
Location
Rockenhausen Germany
I seriously want to give up on this and just sell the car as-is since it's kicking my ass so bad!

Now, my problem started maybe about a year ago before I did the UIM/LIM cleaning. Finally have some time to work on it (well, this week at least!).

I should mention it has a MAC 70mm throttle body for a 4.6 Mustang. Something the original owner did when he had the supercharger on. Used a gasket for an SVT TB, and it worked upside down! Right side up, the IAC passages were able to suck air straight through (since the Mustang TB doesn't cover the IAC passages).

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Problem:
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Car doesn't want to idle for the life of it! Have to 2 foot it to keep running when stopped.

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Diagnostics:
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Slight vacuum leak on hose connected to UIM; unmetered air entering from poor seal on IAC tube. A/F guage showing LEAN almost 90% of the time. Assumed UIM/LIM gaskets could also be leaking.

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'Solution':
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Performed UIM/LIM cleaning (Berryman's) with new gaskets installed and everything torqued to spec with calibrated torque wrench. Also cleaned the IAC and TB for good measure, since they were pretty black.

Also installed W-R headers at the same time.

Lots of issues with disconnected sensors (mostly causing misfires), but now everything is hooked up properly again and no more misfires.

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New Problem:
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SUPER high idle. We're talking about it will hold 3,000 RPM for about 5 minutes. Only way to get it to drop during that time to around 1,200 RPM is to apply load via the clutch, but as soon as you tap the gas, it's back up to 3K.

After 5 minutes or so, seems the computer tells whatever is causing the high idle to change state, and idle is normal UNTIL you hit the gas again, and it goes back to 3K.

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Diagnostics:
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Unplugging IAC causes idle to drop around normal, but at a random time it seems to just die, which seems to coorelate with the above statement about the computer.

Unplugging TPS causes no change in the 3K idle, but when you plug it back in, it drops a few hundred RPM for about 1 second and then goes back to 3K.

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'Solution':
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My symptoms seemed to be the IAC not working properly (opening fully instead of a small amount). I purchased a new IAC from Bill J and installed it.

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No go! Exactly the same problems as with old IAC. So it seems that the computer is telling the IAC to go wide open for whatever reason.

I used carb cleaner and sprayed all around the engine to find any leaks. Never noticed a change in idle speed, so I have to assume I have no leaks. Sealed up any suspect unmetered air spots with RTV.

I need to get the car to pass inspection, and a stalling car or 3K idle doesn't help very much.

I made a video tonight showing what it does with the IAC/TPS are disconnected and when the gas is tapped. Also showing the car is still off the scale on the lean side! However, this is only random, seems the computer 'switches' the mode and the A/F guage will read like normal, then it'll switch again and be off the scale on the lean side.

Video - WMV 18.53MB! (might wanna save as if you have less than 3Mbps connection)

So... anyone have any ideas? I'm stumped. Will check back tomorrow and answer any other questions you may have (it's 10:30pm!).
 
What would happen if I were to get your car in my service bay when I was a tech would be that I would put the car back the way it was from the factory as a starting place. So, that Mustang TB would have to go before I could even start to test anything else out. I know that's not what you want to hear but that's what would happen if you took it to Ford, at least when I worked for them.
Karl
 
I had the high idle issue in the winter. It it was really cold outside and I started my car and moved it before it automatically idles down, the rpm's would sit at 3K and sometimes slowly rise up to 5K. If I let my car idle down before moving it, it was fine - no problems since I started doing that.
 
98SVTC said:
What would happen if I were to get your car in my service bay when I was a tech would be that I would put the car back the way it was from the factory as a starting place. So, that Mustang TB would have to go before I could even start to test anything else out. I know that's not what you want to hear but that's what would happen if you took it to Ford, at least when I worked for them.
Karl
Click to expand...

I'm thinking of doing that, but I'm not sure if the ECU has been reprogrammed for the stuff on it, which might make it worse with the 'incorrect' parts on it (according to the ECU at least). In fact, I bet if the ECU was reprogrammed, it probly still has the settings from when the supercharger was on...
 
Idle never gets better, it just stays at 3K with IAC plugged in, even after driving it for 30 mins. W/O IAC, it pretty much has no idle, so it's semi-driveable.

Here is what I've gathered over the last couple of days:

It hesitates right before the secondaries open, but is probably unrelated to the idle issue.

Sometimes when the engine is warm and the IAC is unplugged, it will idle at 2K RPM after hitting the gas. Goes back down after a little while.

When it was doing the no IAC 2K RPM thing, I went in and unplugged the MAF. Instantly the idle dropped to around normal (didn't look at the tach). So I plugged it back in, then plugged the IAC in, which after a dip in the throttle went up to 3K RPM... unplugged the MAF and instantly dropped to around normal idle.

Seemed like that was the ticket, UNTIL I started driving it. Didn't even make it down the block since it bucked so bad. The RPMs were constantly going up and down, like I was mashing the gas, then letting off, mashing again, etc... The entire time, which made the car nearly undriveable in the less than 1 block I went.

HOWEVER, I didn't clear the computer after doing so. I will go out and do that either later this evening or when I drive to work tomorrow morning.

Will keep you guys posted of further updates!
 
Big Daddy Kane said:
Sometimes when the engine is warm and the IAC is unplugged, it will idle at 2K RPM after hitting the gas. Goes back down after a little while.
Click to expand...

You do realize that the engine should not be able to run at all with the IAC unplugged, right?

Cap off the large UIM vacuum nipple to the PCV valve. See if it runs with the IAC unplugged. If it does, remove the TB and see if air can bypass the plate. There has to be air getting in somewhere.
 
I've had a similar issue, hung at ~1800 instead of the 3k, but none the less. Did you replace the EGR or IAC gaskets? Could your throttle linkage be sticking?
 
Rogerm60 said:
You do realize that the engine should not be able to run at all with the IAC unplugged, right?

Cap off the large UIM vacuum nipple to the PCV valve. See if it runs with the IAC unplugged. If it does, remove the TB and see if air can bypass the plate. There has to be air getting in somewhere.
Click to expand...

I do... so it seems like the car is getting air from somewhere (and unmetered would explain the lean, which isn't happening as frequent anymore, btw), however, I sprayed the carb cleaner all around and never heard a change.

My guess is maybe the Mustang TB is allowing some air to pass by?

juspifool said:
I've had a similar issue, hung at ~1800 instead of the 3k, but none the less. Did you replace the EGR or IAC gaskets? Could your throttle linkage be sticking?
Click to expand...

Yes, both were changed when I did the UIM/LIM cleaning, and they were torqued down to spec with a calibrated torque wrench.

Due to the Mustang TB, the linkage cage thing doesn't fit correctly anyway, so it's not that. Also, I've tried to pull the TB closed, and it's already fully closed.

==========

Do you guys think the Berryman's may have screwed up the MAC throttle body?
 
I'm dumb... I totally forgot I bought an OBDII code scanner while I was deployed. My wife stuffed it with all my other electronic junk, so I forgot about it.

However, I am going on vaction real soon like. I will check codes when I get back and let y'all know!
 
Big Daddy Kane said:
... and be off the scale on the lean side.
Click to expand...

There's your CEL.

First the obvious (Sorry if this seems simplistic. I'm just trying to help, I don't mean to be insulting or nuttin'). Check for splits in the rigid tubes on top of the UIM and cracks/breaks in the elbows - the end at the brake booster & vac coupling too. Check the tubing to/from the PCV valve. I've seen more than one come loose from the UIM. Check the blue intake coupling for cracks & tears. I had one just tear appart while I was moving the intake out of the way in another project.

Once the car is running. Try manipulating the UIM just a bit. Press down a little - front, back, then each side in turn. See if your idle changes. One idiot cougar guy down here got an SVT UIM/LIM & TB and just cranked down his TB one nut at a time. Didn't seat the thing properly before tightening the bolts evenly and he got a MASSIVE air leak at the TB. You could easily hear it at idle. Same thing can easily happing if the UIM or LIM are not tightened evenly in the proper sequence.
 
Last edited:
Yea even that little rubber hose to the PCV can cause some wack issues if it has a tiny crack. I'd get that big TB off of it though.
 
Back on this!

Got a chance to check out the car today... bought myself some carb cleaner with the spray tube (as opposed to the non-spray tube stuff I had before).

NOW, I've pinpointed some vacuum leaks.

First is a given... the 4.6L throttle body with SVTC gasket.

Second is understandable... main vacuum fitting on UIM.

Third hurts pretty bad... UIM and/or LIM gaskets :blackeye:

SO

I may have a source of an SVT throttle body, gasket is still like-new. A bolt is broken off on the bottom, so I guess I over torqued it and it broke?

Going to RTV the crap out of the vacuum fitting since the stupid brass piece never fit in properly in the first place (mallet deformed it). Should have left the old one in and put the new o-ring in there.

Guess I'm gonna get some gaskets from the dealer and attempt the UIM/LIM rebuild again :nonono:

After that, I'm crossing my fingers that it's cleared up!
 
TourDeForce said:
Once the car is running. Try manipulating the UIM just a bit. Press down a little - front, back, then each side in turn. See if your idle changes...

...Same thing can easily happing if the UIM or LIM are not tightened evenly in the proper sequence.
Click to expand...

I never thought about pushing down on parts of the UIM... I'll try that tomorrow!

I followed the UIM/LIM FAQ to the T, and I do remember following the torque order/specs perfectly, guess I had a gasket misaligned?
 
Check to see if the wiring to TPS is correct. I see you had to make the wires longer on the connector. Check the grey 11 or 12 pin connector by the firewall bank valve cover .
The white wire wasn't properly seated when I had my wire harness recall done and after a few months had worked itself loose. I was getting a P0122 code though. I had a high idle like yours.
 
Ok, I've had it up to here with this car! Here being above 6'3"!!!

Today, I went to see about getting some exhaust work done. As I'm leaving, I'm stuck a broken stop light where the Polizei are directing traffic. In the 10 minute wait, I noticed the temp guage was right on the line between Normal and overheating. I shut off the engine immediately to wait for my turn.

When it was my turn, I kicked on the heater (mind you, it's 85+ outside) to check if the water pump is bad. Was like a furnace in my face (almost as bad as getting off the plane in the middle of summer in the desert the first time!), and a mile or so down the road the guage had gone back to the A in NORMAL, so I assumed the fan must have died.

Due to my car previously having a supercharger installed, it has a slim Flex-A-Lite fan installed with none of the original parts left. It has a control box which allows me to adjust the temperature when the fan kicks on.

Well, I could freely move the fan by hand, so it's not obstructed (which caused a fusebox meltdown in my brother-in-laws [soon to be my!] German spec Scirocco... still working on that one!). The fuse isn't blown, so I bring out the control box and adjust the temperature.

Nothing at all! When I set it to the hottest setting (where the fan won't come on at all), I can hear a relay clicking inside, so it must have power.

Guess I'm in the market for all the related fan components off another SVT :nonono:

Sorry, is unrelated to my idle issue... Carry on!
 
Same is a V6 car. Sounds like your issue are related to poor repair and all aroung ghetto rigging. Can't blame the car.
 
todras said:
Same is a V6 car. Sounds like your issue are related to poor repair and all aroung ghetto rigging. Can't blame the car.
Click to expand...

Thanks, I'll look around later for some fans. Hopefully the stock connector is still in place on the car.

Nope, can't blame the car itself, but instead the parts on it... Just about every aftermarket part on the car has had problems from either a shoddy install or just plain failing.

I am taking this car as a lesson to never buy a modified car again, unless I know the person who modified it.

I definitely screwed up the UIM/LIM cleaning, but I followed the FAQ step by step, so I have no idea why it leaks. Torqued everything down in order. Guess I should have left 'good enough' alone.
 
Sweetness!

Sweetness!

So now I have another problem...

Car was cutting out at low RPMs like it wasn't getting any fuel. However, fuel pressure guage is reading a steady 50psi, and after about 2000 RPM, it seems normal. Kinda funny, since the car chirps the tires a few times before it smooths out. Everyone looks at me like I don't know how to drive a stick.

Well, except for a whistling/squealing type noise (kind of like a serpentine belt slipping or something rubbing).

Get to work and pop the hood. Noise is coming from rear of engine, but the water pump belt looks ok. Then I see that it's leaking fuel out of where the rubber hose meets the quick release. Noise is definitely coming from the fuel pressure regulator.

Now, on the way home from work, noise is still there, but the cutting out is gone. However, now it's revving to a bit over 2000RPM and holding no matter what. A/F guage is reading mostly on the rich side.

Looked around, but can't find the same symptoms I'm having (unless the ECT is at fault). You guys think the vacuum leak could cause the regulator to not supply fuel at low RPM? Or is the regulator toast?
 
Fuel pressure should be 35 not 50 at idle.

You have to get vacuum to the FPR or you will run rich, not lean.
 
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