4.6 Mustang, idle problems

**X-Runner** · 08-12-2008, 02:32 AM

Ive got a 98 GT 4.6, auto. 146,000 miles, new plugs, wires, coils, K&N air filer, fuel filter, and harmonic balancer.

It had 3 codes when I got it home, first two were bank 1 & 2 lean. Other was an emissions code, cleared and havent come back on in 30 miles. I got the codes wrote down in the car.

Now its got an idle issue, when its cold it idles high. About 2000 RPM and sometimes it will idle like its got a bad IAC. Up and down slowy, from about 500 to 1600 RPM then smooth out at 2000 for while and finally drop down to like 700. Runs good otherwise with only a slight timing chain rattle at high RPM in second gear. IAC is good, any ideas?

Another issue, it vibrates bad. Kinda feel it at idle but more so when acclerating. Almost feels like something in the trans, it was replaced with a reman unit a year ago. Feels like its slipping slightly at WOT shifts also. I thought the balancer was the issue so it was replaced but no change. It was coming apart/cutting into the timing cover so it WAS bad. Motor mounts seem fine, engine doesnt move around more than normal. The vibration is also there if you just rev it in park, so its not a drive shaft/rear end issuse. Bad torque converter or cracked flywheel maybe?

**X-Runner** · 08-12-2008, 10:52 AM

Morning bump. More worried about the vibration.

**Nemesis** · 08-12-2008, 10:55 AM

Sounds like an IACV to me.

**Tech5** · 08-12-2008, 10:59 AM

Vibration an idle problem sounds to be a vaccum leak!..Also the bank 1 an 2 system to lean is due that your mass air flow sensor needs to be cleaned, Dont do it yourself unless you done it before you can damage the filament inside the sensor...Its like a light bulb that little spring for the bulb it has one of those in the mass air flow sensor,you take brake cleaner an lighty spray the little spring until its clean , But make sure the engine is cold, if that sensor is any what warm it will damage it, once you clean it install it back an clear the code an your good, I know you said you cleared the light an its not back on, but it will come back give it about 2 days, Those motors are bad about the PCV hose causing a leak, an on the throttle body there is a hose that goes to the intake , Make sure the INTAKE tube is tight no cracks, an doesnt have any holes....Best of luck hope this helped!

**X-Runner** · 08-12-2008, 11:01 AM

Your the one I was kinda waiting on, thanks. I cleaned the MAF last night but have even started the car since. Ill scope for vaccum leaks in a few minutes.

**Init2winit** · 08-12-2008, 11:20 AM

Just like stated above, sounds like some sort of vaccum leak. If you don't find any, I'll bet money that it is fuel delivery related. When was the last time you put a fuel filter on it?

**Tech5** · 08-12-2008, 11:22 AM

Well lets see MAF has to do with air an fuel mixture! So DUHH!, But not fuel filter that was wrong answer there !

Originally Posted by Init2winit

I'll bet money that it is fuel delivery related. When was the last time you put a fuel filter on it?

**X-Runner** · 08-12-2008, 11:22 AM

Originally Posted by Init2winit

I'll bet money that it is fuel delivery related. When was the last time you put a fuel filter on it?

**Tech5** · 08-12-2008, 11:22 AM

Originally Posted by JoshuaASE

Vibration an idle problem sounds to be a vaccum leak!..Also the bank 1 an 2 system to lean is due that your mass air flow sensor needs to be cleaned, Dont do it yourself unless you done it before you can damage the filament inside the sensor...Its like a light bulb that little spring for the bulb it has one of those in the mass air flow sensor,you take brake cleaner an lighty spray the little spring until its clean , But make sure the engine is cold, if that sensor is any what warm it will damage it, once you clean it install it back an clear the code an your good, I know you said you cleared the light an its not back on, but it will come back give it about 2 days, Those motors are bad about the PCV hose causing a leak, an on the throttle body there is a hose that goes to the intake , Make sure the INTAKE tube is tight no cracks, an doesnt have any holes....Best of luck hope this helped!

**X-Runner** · 08-12-2008, 02:45 PM

Its running better now that the MAF is clean, idles good now. Still has the vibration, no vaccum leaks found either. Checked over everything.

**mmmmpsi** · 08-12-2008, 03:01 PM

I second Fuel Filter.. if you've already checked your IAC... Could also be a IAT or Intake Air Temp sensor bad..

Just read your post about the codes.. if you're getting a fuel lean it's usually caused by a bad O2 sensor. Have you ever had those replaced?? are you still running cats?

**X-Runner** · 08-12-2008, 03:11 PM

Read the first post, IT HAS A NEW FUEL FILTER! I swear to god why did I waste my time putting that in the first post. o2 sensors are good, about 2 year old OEM ones. Stock exhaust.

**Tech5** · 08-12-2008, 04:52 PM

WRONG FUEL LEAN ISNT A 02 SENSOR!!! GOOD TRY!

Originally Posted by mmmmpsi

I second Fuel Filter.. if you've already checked your IAC... Could also be a IAT or Intake Air Temp sensor bad..

Just read your post about the codes.. if you're getting a fuel lean it's usually caused by a bad O2 sensor. Have you ever had those replaced?? are you still running cats?

**Tech5** · 08-12-2008, 04:54 PM

FILTER FILTER WILL NOT CAUSE A SYSTEM TO LEAN ON BOTH OR EITHER BANKS!

ALSO IF THE O2 SENSOR IS BAD IT WILL KICK A BANK 1 OR 2 O2 SENSOR CODE, NOT A LEAN! I LOVE PEOPLE THAT DOESNT KNOW ANYTHING, I BET IF YOU HAVE THIS PROBLEM YOU WOULD BUY A O2 SENSOR FROM AUTOZONE AN RETURN IT OVER AN OVER AGAIN SWEARING THAT THE O2 SENSOR IS BAD, AFTER ABOUT 20 O2 SENSOR REPLACED YOU WOULD BRING IT TO MY SHOP WHERE I CHARGE YOU 70 TO CLEAN AN DIAG YOUR MAF SENSOR ...NOOB

Originally Posted by mmmmpsi

I second Fuel Filter.. if you've already checked your IAC... Could also be a IAT or Intake Air Temp sensor bad..

Just read your post about the codes.. if you're getting a fuel lean it's usually caused by a bad O2 sensor. Have you ever had those replaced?? are you still running cats?

**Tech5** · 08-12-2008, 04:55 PM

THE VIBRATION IS EITHER YOUR CRANK PULLEY WHICH WOULD MAKE IT START TO RIDE ROUGH OR MOTOR MOUNT.... CHECK THOSE OUT AN LET ME KNOW

FORD IS KNOWN FOR THE KEY WAY TO WALLO OUT!!

**Init2winit** · 08-12-2008, 06:16 PM

Originally Posted by JoshuaASE

FILTER FILTER WILL NOT CAUSE A SYSTEM TO LEAN ON BOTH OR EITHER BANKS!

Since when? Stopped up filter = less fuel = lean condition = running rough = possible vibration........
I can't count the number of times I've found a clogged fuel filter on a ford, and has corrected a lean condition. And lots of those times, the clogged filter burned up the pump.

**jew_boy** · 08-12-2008, 06:22 PM

if your still having a problem i would ask BUGMAN, from what ive heard hes knows his stuff when it comes to mustangs

**Tech5** · 08-12-2008, 06:50 PM

A fuel filter isnt going to make a check engine light come on , unless its complete stopped in which it will kick misfire, manfacture codes, etc...I have fixed 1,230,00 fords with this same code all but a few was the MAF never ever being a fuel filter..... Not to mention if you read his post he has already replaced the filter so everything your saying isnt making any since good day mate!

Originally Posted by Init2winit

Since when? Stopped up filter = less fuel = lean condition = running rough = possible vibration........
I can't count the number of times I've found a clogged fuel filter on a ford, and has corrected a lean condition. And lots of those times, the clogged filter burned up the pump.

**Tech5** · 08-12-2008, 06:51 PM

I have fixed more mustangs in my day then ford its self! lol! I owned many, an worked at a shop an my boss an friends raced an drove many mustangs, not to mention I worked for a mustang shop!

Originally Posted by jew_boy

if your still having a problem i would ask BUGMAN, from what ive heard hes knows his stuff when it comes to mustangs

**X-Runner** · 08-12-2008, 07:14 PM

Originally Posted by JoshuaASE

THE VIBRATION IS EITHER YOUR CRANK PULLEY WHICH WOULD MAKE IT START TO RIDE ROUGH OR MOTOR MOUNT.... CHECK THOSE OUT AN LET ME KNOW

FORD IS KNOWN FOR THE KEY WAY TO WALLO OUT!!

Crank pulley/balancer is new, so Im thinking motor mounts. Going to check them out tomorrow.

**OTG Signs** · 08-12-2008, 07:42 PM

I had the high idle issue on my first GT. Ultimately, cleaning the plenum and all it's connections fixed the issue.

And vibrations are most definitely motor mounts.

**X-Runner** · 08-12-2008, 07:43 PM

Originally Posted by OTG Signs

I had the high idle issue on my first GT. Ultimately, cleaning the plenum and all it's connections fixed the issue.

And vibrations are most definitely motor mounts.

The intake was replaced last year due to a leak, so all thats clean. The MAF was nasty though.

**OTG Signs** · 08-12-2008, 07:48 PM

Originally Posted by X-Runner

The intake was replaced last year due to a leak, so all thats clean. The MAF was nasty though.

Good!

**Slomaro Z28** · 08-12-2008, 07:58 PM

If you look closely enough you'll find the problem......

They circled it for a reason.....

J/K, Good luck getting it figured out.

**Atlblkz06** · 08-13-2008, 05:08 PM

Originally Posted by Slomaro Z28

If you look closely enough you'll find the problem......

They circled it for a reason.....

J/K, Good luck getting it figured out.

ROFL

Let us know if the mounts were the issue. Good call on the MAF!
b

**X-Runner** · 08-13-2008, 05:17 PM

Replacing the drivers side today. Finally got a chance to get someone in the car to rev it for me, its busted

**Tech5** · 08-13-2008, 08:45 PM

all you have to do is pop the hood get in an look threw the crack an you can see the motor, an you can see which side is moving...BTW glad I diag it for ya...that will be $50.00!

Originally Posted by X-Runner

Replacing the drivers side today. Finally got a chance to get someone in the car to rev it for me, its busted

**Tech5** · 08-13-2008, 08:47 PM

I know I am Good !

Originally Posted by Atlblkz06

ROFL

Let us know if the mounts were the issue. Good call on the MAF!
b

**X-Runner** · 08-13-2008, 08:50 PM

I couldnt see it

You want to put this damn mount on for me? What a b!tch, I dont even want to screw with this. Ill pay someone $50 to do it before 2:00 tomorrow

**Slomaro Z28** · 08-13-2008, 09:49 PM

I know this is off topic, but did you paint your wheels yourself? Parked across from you at the V and they looked good...well 3 out of 4 anyways. j/k

**X-Runner** · 08-13-2008, 09:53 PM

Yes sir, I did. One has a run in it but Ill fix it soon. Its just been to hot for me to want to mess with it and paint the remaining two wheels. It has a matching spare, so Im going to paint it also.

**Slomaro Z28** · 08-13-2008, 09:56 PM

Been wanting to do mine but looks like a nightmare. And I only saw one silver/gunmetal or w/e....but anyways looks good and good luck with that motor mount.

**Tech5** · 08-13-2008, 11:39 PM

Its easy if you Grind some of the steel off the new mount, an install it!Sorry But at my shop we get 130 to do that!

Originally Posted by X-Runner

I couldnt see it

You want to put this damn mount on for me? What a b!tch, I dont even want to screw with this. Ill pay someone $50 to do it before 2:00 tomorrow

**X-Runner** · 08-13-2008, 11:40 PM

Originally Posted by JoshuaASE

Sorry But at my shop we get 130 to do that!

I gotta make some profit off this deal too.

**BUGMAN** · 08-14-2008, 06:00 PM

Originally Posted by JoshuaASE

I have fixed more mustangs in my day then ford its self! lol! I owned many, an worked at a shop an my boss an friends raced an drove many mustangs, not to mention I worked for a mustang shop!

Off topic but what Mustang shop did you work for?

How many Mustangs have you owned?

Oh and no reason to get so defensive, he was just making a suggestion. More than one opinion is always good when troubleshooting anything.

Don't take this the wrong way, I am in no way trying to be a smartazz. Just inquiring with a Mustang brotha!

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