Idle question (i know diff. variation of this q have been asked)

[KZGUNS]

Here's my specific issue. When cold it starts with fast idle then settles down to ~800 or so which is fine perhaps a bit high. Now once its warm and restarted the idle dips to -500 then back up a few times or more before settling out back to ~800. If i blip the thorottle a few time during this it will settle quicker. I do have the adjustable IAC plate and have adjust the idle via the plate once warmed up. I have reset the base idle and i've also checked the TPS Voltage and its at .68v Any other places i can look to for a solution to this issue?

Thanks!

 

[Mustang5L5]

Have you cleaned the IAC lately? It could be sticking once warm and causing the delayed response.

 

[KZGUNS]

It has a new tb but it did this prior to that as well. The iac is newer as well but I’ll check that out.

 

[General karthief]

Did you reset the computer after installing the new parts? If not try that, also check out the surging idle checklist in the 5.0 technical/how to thread, it shows you how to properly adjust and diagnose idle/stalling issues, do it step by step, don't skip around.

 

[jrichker]

You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 250,000 hits, which indicates it does help fix idle problems quickly and inexpensively.

 

[KZGUNS]

You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 250,000 hits, which indicates it does help fix idle problems quickly and inexpensively.

Thanks read through the post whew, didnt see my specific issue and i've done the checklist with the exception of testing the O2 sensors. will do it again with a clear head since i got more knowledge about everything. I will post up on there, maybe i missed something. Thanks again!

 

[General karthief]

Keep to this post, the checklist thread is mostly for reference

 

[KZGUNS]

Keep to this post, the checklist thread is mostly for reference

Oh ok.. I must have read wrong...

 

[General karthief]

No worries, let us know what you find

 

[jrichker]

Thanks read through the post whew, didnt see my specific issue and i've done the checklist with the exception of testing the O2 sensors. will do it again with a clear head since i got more knowledge about everything. I will post up on there, maybe i missed something. Thanks again!

Ditch the idle air plate adjuster, it is a band aid to cover other problems.

What year is the car and what are the aftermarket add on parts? Is it Speed Density or Mass Air? If Mass air do you have a filter located in the engine compartment?
What codes did you get when you dumped them?
What has been done to the engine besides the idle air plate adjuster?
Has the ignition timing been checked with a timing light? Yes/No

 

[KZGUNS]

Ok getting a code 92 now while running. My book says HO2s sensor. That is the o2 sensors correct?

 

[KZGUNS]

Ditch the idle air plate adjuster, it is a band aid to cover other problems.

What year is the car and what are the aftermarket add on parts? Is it Speed Density or Mass Air? If Mass air do you have a filter located in the engine compartment?
What codes did you get when you dumped them?
What has been done to the engine besides the idle air plate adjuster?
Has the ignition timing been checked with a timing light? Yes/No

87 timing at 14 deg.
Previous owner removed smog pump, egr and cats. Plug in egr to “fool” computer. Edelbrock intake, tb and cold air intake in the fender not compartment. This issue was present before the intake change.

 

[jrichker]

87 timing at 14 deg.
Previous owner removed smog pump, egr and cats. Plug in egr to “fool” computer. Edelbrock intake, tb and cold air intake in the fender not compartment. This issue was present before the intake change.

What codes did you get?
No code 11 (two flashes when the computer dumps the codes)? A perfectly functioning system will always get a code 11, it is the everything is OK code. The 11 code is computer passed its internal self test.

If you don't get an 11, you have computer or wiring problems.

Please check and repost.

 

[General karthief]

code 92
O2s say the system is running rich
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter. You can expect to see the voltage switch from .2 volt to .6 volt on the average O2 sensor. More voltage swing is good, less voltage swing is bad.
thanks to jrichker for that little tidbit.

 

[KZGUNS]

What codes did you get?
No code 11 (two flashes when the computer dumps the codes)? A perfectly functioning system will always get a code 11, it is the everything is OK code. The 11 code is computer passed its internal self test.

If you don't get an 11, you have computer or wiring problems.

Please check and repost.

Yes I did get 11

 

[RangerJoe]

Aside from your original question, 14 degrees and 87 octane is a little much. Probably could get away with it on 93, but I would try turning the timing down a little. Probably not related your your idle issue, but who knows.

Joe

 

[KZGUNS]

Aside from your original question, 14 degrees and 87 octane is a little much. Probably could get away with it on 93, but I would try turning the timing down a little. Probably not related your your idle issue, but who knows.

Joe

Oh I’m aware of timing and octane. I run 94 and have no pinging. Now my 66 t-bird with 10.5:1 compression is really touchy about timing and octane level. Thanks though, kinda figured someone say something about that.

 

[Mustang5L5]

Swap the O2 sensors. See if that code 92 turns into a code 42. If it does, the o2 sensor is bad and you should replace it. If it doesn't, they you have an exhaust leak or a vacuum leak that is leaking into that bank of cylinders. That could cause your surging.

I also second ditching the idle plate. It's a bandaid that covers up issues rather than fixing them. I'd investigate the O2's first but after that issue is solved, I would try to remove the plate and establish a new idle baseline.

 

[KZGUNS]

Swap the O2 sensors. See if that code 92 turns into a code 42. If it does, the o2 sensor is bad and you should replace it. If it doesn't, they you have an exhaust leak or a vacuum leak that is leaking into that bank of cylinders. That could cause your surging.

I also second ditching the idle plate. It's a bandaid that covers up issues rather than fixing them. I'd investigate the O2's first but after that issue is solved, I would try to remove the plate and establish a new idle baseline.

I actually already have new o2 sensors on the shelf since I planned to replace them as a maintenance thing since I had no idea when or if the previous owner had done so. I think I’ll swap them though just to see if it switches to 42 before putting in the new ones. Thanks the info!

 

[RangerJoe]

I actually already have new o2 sensors on the shelf since I planned to replace them as a maintenance thing since I had no idea when or if the previous owner had done so. I think I’ll swap them though just to see if it switches to 42 before putting in the new ones. Thanks the info!

Sorry, looked back and saw that you were referring to year model and not octane, carry on!

Joe