Warm Engine Start Up Idle

Nightstang00 · Jun 17, 2017

I have been experiencing a rough idle when engine is warm. If I would park, go to the store, then start the car up to leave I get about a 500-800 rpm surge and almost stalls. If I give the car gas up to 3k when I first start it, it levels out much faster to a normal idle around 900 rpm. I replaced the iac/ cleaned throttle body, check tps sensor (1.00). Its stock 5.0 gt40p heads and intake 1.7 rockers , trick flow 499-510 cam. I use 93 octane, recently chanced fuel pump and full tuneup. Any ideas?

mikestang63 · Jun 17, 2017

run the codes- it could be a number of things- ECT, vacuum leak, TPS, etc.

Nightstang00 · Jun 17, 2017

mikestang63 said:
run the codes- it could be a number of things- ECT, vacuum leak, TPS, etc.

That was my next step, just feeling out people's ideas.

jrichker · Jun 17, 2017

Rich Carotenuto said:
That was my next step, just feeling out people's ideas.

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 200,000 hits, which indicates it does help fix idle problems quickly and inexpensively.

Nightstang00 · Jul 9, 2017

So I scanned the codes today, I don't have Ac /egr/smog/ and have the coolant plug disconnect to have an autometer gauge connected.

Codes
84 o egr vacuum regulator circuit failure

81o air diverter solenoid fault , intake air control circuit fault / air injection diverter

82o integrated relay control module

85o canister purge solenoid circuit failure

Engine on
21r cooling temperature sensor out of spec range or ect out of range

94r air diverter solenoid circuit fault

44r thermactor air system fault

33r egr valve not opening
-----
Do any of these cause my idle issue?

Nutty 5.o · Jul 9, 2017

Which cooling sensor did you pull for your Autometer gauge? Assuming you know this but if not: The computer engine coolant sensor needs to stay connected so the computer knows what temp the engine is at. Dash gauge sensor removed wouldn't matter.

Nightstang00 · Jul 9, 2017

So I scanned the codes today, I don't have Ac /egr/smog/ and have the coolant plug disconnect to have an autometer gauge connected.

Codes
84 o egr vacuum regulator circuit failure

81o air diverter solenoid fault , intake air control circuit fault / air injection diverter

82o integrated relay control module

85o canister purge solenoid circuit failure

Engine on
21r cooling temperature sensor out of spec range or ect out of range

94r air diverter solenoid circuit fault

44r thermactor air system fault

33r egr valve not opening
-----
Do any of these cause my idle issue?

Nutty 5.o said:
Which cooling sensor did you pull for your Autometer gauge? Assuming you know this but if not: The computer engine coolant sensor needs to stay connected so the computer knows what temp the engine is at. Dash gauge sensor removed wouldn't matter.

in got the car like this. It was unplugged on the manifold, and the gauge is connected to it.

Nutty 5.o · Jul 9, 2017

Can you snap a picture of which one is disconnected? It very well could if it's the computer coolant temp sensor unplugged.

Nightstang00 · Jul 9, 2017

This is what it looks like

Nutty 5.o · Jul 9, 2017

Ok Rich thanks. I believe that is the dash sensor (hoping someone will confirm) so it shouldn't affect idle.

Nightstang00 · Jul 9, 2017

Nutty 5.o said:
Ok Rich thanks. I believe that is the dash sensor (hoping someone will confirm) so it shouldn't affect idle.

the connector runs right into the gauge , in not sure where any other sensor would be. I'm new to this

Nutty 5.o · Jul 9, 2017

No problem. I'm out of town but the engine coolant sensor I believe is on the other side.

Follow the surging idle checklist above one thing at a time will get you there. As far as the codes you listed, several of them seem to be potential issues. Hoping one of the others can provide more help.

Nightstang00 · Jul 9, 2017

Nutty 5.o said:
No problem. I'm out of town but the engine coolant sensor I believe is on the other side.

Follow the surging idle checklist above one thing at a time will get you there. As far as the codes you listed, several of them seem to be potential issues. Hoping one of the others can provide more help.

I appreciate your help man. Thanks.

Nightstang00 · Jul 16, 2017

So I changed the temp sensor. Didn't change. I checked for vacuum leaks , started the idle check list, reset idle and tps, cleaned throttle body , and mass air sensor. Still having the issues. I unplugged the mass air and it didn't jump in rpm's but it turned the check engine light on and was a tight rough idle. It didn't go up and down like it typically did. I am just trying to avoid brining it to a performance shop and paying someone to do it. The only thing I noticed was that when I moved the salt and pepper connectors when the car was running it seemed to rev up for a second. And stayed there. Any ideas ?

90sickfox · Jul 16, 2017

Take the salt and pepper shakers apart and clean them with electrical contact spray. Spread dielectric grease in them.

Over time the contacts get a layer of corrosion on them or the factory grease becomes waxy and makes a bad connection causing all types of issues.

Parts stores carry the cleaner and the grease. In a worse case scenario ( like mine ) I had to take the connector apart and remove each pin one by one. I tightened the connections by using pliers to gently close them up...just a tad.

General karthief · Jul 16, 2017

Along with the above post I will add that you should check your vacuum lines behind the intake and just for fun there is a ground wire that is under that same area too.
You did clear the computer codes by disconnecting the battery for 20 minutes or so after the sensor change and adjustments

Nightstang00 · Jul 16, 2017

Yeah, I unplugged everything. I'll try to clean the connectors. Thanks for your advice !

General karthief · Jul 16, 2017

Our advice, it's a team effort, but I think they keep me around because they feel sorry for me, I likely have the ugliest car on this site.

Nightstang00 · Jul 16, 2017

Mine is in need of paint. Half primer gray and half factory black (got it this way) that is my last worry. I am almost finished redoing everything inside.

03mustangv6wh · Apr 10, 2019

Nightstang00 said:
Mine is in need of paint. Half primer gray and half factory black (got it this way) that is my last worry. I am almost finished redoing everything inside.

Ever figure out what it was. Got a warm idle issue with my 03 v6 mustang

Warm Engine Start Up Idle

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Wasn't a pretty sight...and I've got big hands

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wonder how much it would cost to ship you a pair

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