Idle Problem!!

[97cobrachris]

hey guys as you can see im pretty new here-- just bought my 97 cobra convertible a few weeks ago, although im not all that new to mustangs since ive owned a 96 mystic cobra and an 06 gt before...

with that being said today i was driving my car down to the muffler shop to get my off road x pipe and turn downs welded on to my flowmasters, and i began to notice that my idle was really uneven- surging up and down in some type of cycle. all of a sudden as i was stopped at a light watching my idle surge between 200 and 1000 the car just died. it started back up when i turned the ignition, and it proceeded to go through this exact same process at every light on the way to the shop.

so far my mods are just a k&n filter and flowmasters, and within a few hours hopefully my bbk off road x will be on there as well. my check engine light has been once since the purchase and it is throwing codes for a cylinder 6 misfire (ford racing plugs and wires are on their way from 50resto), heater ckt failure (ive been told this is a faulty o2 sensor and i am putting MIL's right now), and a code for my EGR valve-- which happened to go away along with the heater ckt code at least momentarily when i plugged the MIL eliminator in up front.

im looking for some help from the community here since i have no idea what my problem could be right now. the muffler guys said they would give it a once over when they were all done and see if they could identify any problems, but im not even really sure where to start with this. any suggestions would be much appriciated. thanks guys!

 

[GR40Snake]

Idle Air Control Valve :shrug:

 

[bvysochin]

Sounds like you've got quite a few problems.. and that's what's resulting in a bad idle.

Post up the exact codes so we can give you more accurate advise.. Another thing, you don't plug the mil eliminators up front.. You should change your plugs, change your wires.. then run codes and report back..

At this point, it could be a million different things.. If that heater circuit malfunction is for your front O2's, your car will run like shit. If it's for your back, it won't run as bad. I hope that misfire codes goes away after plugs and wires, if it doesn't.. you could have other major problems..

 

[97cobrachris]

Sounds like you've got quite a few problems.. and that's what's resulting in a bad idle.

Post up the exact codes so we can give you more accurate advise.. Another thing, you don't plug the mil eliminators up front.. You should change your plugs, change your wires.. then run codes and report back..

At this point, it could be a million different things.. If that heater circuit malfunction is for your front O2's, your car will run like shit. If it's for your back, it won't run as bad. I hope that misfire codes goes away after plugs and wires, if it doesn't.. you could have other major problems..

hmm ok.. just curious- why do you say the MIL eliminators shoudlnt be plugged in up front??

anyhow ill check that stuff out, and when i get home tonight i should be able to find out what all my codes are im sure theyre written down somewhere...

i was thinking while changing the plugs and wires i could try cleaning out the mass air and filter-- maybe that would help.

after getting the car back from the muffler shop a few minutes ago i took it around town for about 10 miles and the idle was still surging somewhat, although less severe, and luckily i couldnt get it to die again.

anyone else have any suggestions?

 

[STAMPEDE3]

Mils go on the rear to change the signal to the ECM since the O2s will read out of spec with no cats. You rears are only there to tell if the cats are working or not, they do nothing for the way the car runs.

The fronts adjust A/F ratio, Mils on the front=Bad.

The surging while coasting is part of a normal thing but yours is acting up.

These cars have what is called dashpot mode.

If the car is at idle and the TPS is reading the ~.99 ford spec and the VSS tells the ECM that the car is coasting over 3MPH it is designed to raise the idle for steering and braking.

Yours is surging. It is searching for the correct RPMs

Clean or change the IAC first as it may be sticking.
Next probe the middle wire of the TPS with a volt meter at idle. See if it around .99 volts.


You can somewhat get around dashpot mode by lowering the TPS to ~.97 volts.

Misfire is probably the wires, Change tham and install some Autolite 764s in the process.

After all this, disconnect the battery and let the ECM reset and see if any codes come back.

 

[STAMPEDE3]

.
lol

 

[STAMPEDE3]

Thie server screwed this one.
It wasn't me.

 

[97cobrachris]

Thie server screwed this one.
It wasn't me.

its cool, thanks for all that advice. also PM'd...

 

[F8tlByte]

Not to Hi-jack the post, but...
STAMPEDE3... you said MIL eliminators do not go in place of the front two cats... What do you put there if you have an O/R H or X?

 

[STAMPEDE3]

Mils go on the Rear set of O2 sensors.

 

[bvysochin]

As far as the front O2 sensors go, nothing changes between an offroad pipe, and a regular catted one..

Mils have absolutely nothing to do with front O2's.. Nada.. zip.. zilch..

 

[97cobrachris]

cleaned out the IAC this afternoon-- probably the easiest thing ive ever done on my car, only took me about 5 minutes, and after disconnecting the battery and re-starting the idle seems to be a lot better (but still not quite up to par).

im thinking about cleaning my K&N filter out as well as cleaning the mass air flow sensor tommorow to see if that will help me out some more, and things should be a whole lot smoother in general when i get those autolites and ford racing wires in.

im definitely going to try to get under the car and switch those MIL eliminators to the back before the end of the day, and i was also considering picking up a new fuel pump since im assuming after almost 70k miles i still have the original in there, so that probably needs to be replaced as well.

do you guys think that's worth a shot, or would my time and effort be better spent somewhere else??

 

[sighwest]

I'm not as experienced as the others, but I would switch those mil eliminators from the front to the back asap. That may fix your entire prob.

 

[STAMPEDE3]

Check fuel pressure for problems and change fuel filter first.
No need to change pump just due to 70K.

And yes, as I said in the PM, switch the Mils ASAP.

 

[sighwest]

You're in great hands with Stampede...he's the best in the business!:bowdown:

 

[97cobrachris]

Check fuel pressure for problems and change fuel filter first.
No need to change pump just due to 70K.

And yes, as I said in the PM, switch the Mils ASAP.

yes sir tommorow in the morning the MIL's are being switched to the rear, and again like the poster said above-- thanks for all the advice, its been a great help!

 

[97cobrachris]

hey guys, i have an update on my idle problems... sort of.

i cleaned out the IAC, the throttle body, the MAF, as well as my K&N.

my idle is a lot better now, and the car revs much more smoothly, but ive still been noticing some problems persisting with the idle.

first, when i stop the car on a steep incline the idle goes up and down and is very unstable, whether the car is facing up or down on the hill.

also, when i turn the steering wheel completely to the right or left the idle dips down immeadiately and begins to fluctuate strangely until i straighten it out a bit.

anyone have any idea what could be causing this? is it normal??

thanks guys!

:beer:

 

[Stavesacre21]

cleaned out the IAC, the throttle body, the MAF, as well as my K&N.

those were actaully all the things I was gonna suggest after reading your first post :shrug:

sure hope you figure it out. let us know if you find something new!

 

[97cobrachris]

those were actaully all the things I was gonna suggest after reading your first post :shrug:

sure hope you figure it out. let us know if you find something new!

yeah, its running a whole lot better, i reccomend everybody does this on their cars every so often-- after cleaning all of that, its really a night and day difference! :banana:

im going to seafoam the car next, and the last couple of problems i can deal with, just thought they might be easy fixes...

 

[STAMPEDE3]

There is a pressure switch system on the power steering. When you turn fully you hear the motor load up from the increased pressure load on the P/S. The computer then raises idle to compensate.

This is normal however if it fluctuates bad then the IAC is searching for where it needs to be or sticking.

Cleaning may not have been good enough changing it may solve it.
But IMO if turning to full lock is the only time your having trouble then I'd leave well enough alone and not worry about it. lol