Idle issues at startup

[Croneybones]

Sir, I just read through your story and it mimics my own very, very well. The high initial idle, then the stalling out.

When I first noticed this, I thought it was nothing, was fall, not too cold. After the stall, it would fire up after a long crank, and giving it a little gas. The first real concern I had was in December when NW PA got its first big snowfall. I wanted to play in the snow, and the truck fired right up, then stalled as I put in in reverse and started to back up into the street. It wouldn't start back up, and I was stuck trying to manually push it back into the driveway. Eventually, I got it started by holding the gas pedal down all the way while turning it over.

Since that day, whenever it starts, it will idle high (1.8k-2k). If I touch the gas in the slightest while it idles this high, it will drop the rpms way low and willl try and stall. I can save it from stalling with the gas pedal, and like Sir, it will level out if I release the gas pedal very slowly. After this, it will surge and fluctuate in idle between roughly 500-1k erradically.

Once the truck is warmed up, it's fine. Slight surging on the rpm, but nothing concerning.

I moved to Virginia at the beginning of the year, and the ave. temp is a LOT warmer than PA, but it still has the issue. Coincidentally, my fuel pump died on me 2 weeks ago. I say coincidentally because after it was replaced, the problem still remains.

I went to Advance auto and priced out an IAC. $75.00. I have been thinking this is the problem. I will have $$ for a new one on friday, but until then, I'm going outside right now to beat it with a wrench to see if that helps.

Sir, please keep us posted on your progress, as I'm sure there are many more broncos with this same issue. I will keep posting on how my quest is going.

EDIT:

I was outside fiddling with it. I tapped the IAC with a wrench-- no noticable difference.

I took it down the road to warm it up until it idled at "normal" speed, which is about 800-900 rpm.

I unplugged the IAC while idling, and the truck stalled.

Plugged the IAC back in and it fired right up.

Unplugged IAC again, and it idled down to around 400rpm and remained there steadily without stalling or surging.

I plugged it back in and the rpm went up to about 600rpm and was surging a bit (+/-50rpm)

I turned the truck off, then started it again, it idled around 800-900 rpm.

Unplugged IAC and it stalled.

I think this may be my issue. I'm buying a new IAC Friday and will keep everyone posted on wether that worked or not.

 

[SirAltitude]

Yea yea, let me us know your progress as well. I've not had a chance to remove and clean the IAC yet so....

It will be done over the course of the next day or two.

 

[Croneybones]

Just to update/bump

After about 5 minutes of me holding the gas pedal in to keep it from stalling, the truck will begin to warm up. When it does warm up, it will resume idling on its own. Once warm, there are no problems that I notice, it does not want to stall.

I also noticed that when it first starts up, the exhaust smells very rich.

Its been nonstop rain here for the last 2 days, so I haven't had a chance to pull the IAC. I did check over my vacuum lines, and they all look good/fairly new. I saw only one tiny tube with a little bit of dryrot. (its on the passenger side of the throttle assemble toward the top.)

 

[VICTORKC]

I THINK YOU SHOULD TRY THE THROTTLE POSITION CENSOR . OR THE MASTER AIR FLOW CENSOR . OR THE O2 CENSOR .

ITS GOTTA BE ONE OF THEM . .

 

[BroncoJoe19]

Read through this

http://www.fordfuelinjection.com/?p=39

If I remember correctly it states that if one pulls the IAC connection while the engine is running and it makes a difference, the IAC is probably good.

Still it makes sense to clean it, check for vacuum leaks, and pull codes.

I left instructions on how to pull codes, and check for vacuum leaks above.

 

[Croneybones]

Got my "Innova" code reader in the mail today from Amazon.

I pulled the codes first with the engine cold, got the following:

136- Not in book.

114- ACT outside test limits

116- ECT outside test limits

636 TOT sensor voltage outside test lmits.

111- System Pass.

THEN I read the manual, and warmed the truck up (which as always is a P.I.T.A.)

After warming, I pulled codes again and got:

111- system pass.

I looked over my vacuum lines again and they are fine.

What could be causing the problem that isn't throwing codes???

 

[SirAltitude]

I know some of these things can still cause problems and not throw codes....

 

[Croneybones]

so it looks like process of elimination. we`ll team up... i`ll start by replacing the cheap stuff, you start on the other end and we`ll meet in the middle. lol

 

[BroncoJoe19]

What could be causing the problem that isn't throwing codes???

A sticking IAC

 

[S2LEGEND]

Just to update/bump
After about 5 minutes of me holding the gas pedal in to keep it from stalling, the truck will begin to warm up. When it does warm up, it will resume idling on its own. Once warm, there are no problems that I notice, it does not want to stall.

I also noticed that when it first starts up, the exhaust smells very rich.

Its been nonstop rain here for the last 2 days, so I haven't had a chance to pull the IAC. I did check over my vacuum lines, and they all look good/fairly new. I saw only one tiny tube with a little bit of dryrot. (its on the passenger side of the throttle assemble toward the top.)

I'm having similar issues. Temps are in the teens here, and def getting the rich smelling exhaust, a rev up, then almost stalls... erratic idle... any updates on your end? Watching with interest now. [-o<

 

[Croneybones]

I pulled the IAC today and cleaned it out. Used almost half a can of carb cleaner on it. There was a bit of carbon built up in there, but I got it all out.

Hooked it back up and fired the truck up... same story. IT WASN'T THE IAC.

The friendly guy at NAPA said there was a guy in there a couple years ago with the same problem and ended up replacing half his engine only to eventually find out that his problem was the coolant temperature sensor malfunctioning. Since this is a 15 dollar part, I'm heading to pick one up here shortly. I'll keep you all posted on the results.

 

[Elmo]

just a thought but I just had a 90 5.8 bronco that would not start with out a shot of starter fluid,after which it would idle rich with no power to take off. It would pop back through the intake and raise all sorts of **** and stall if I tried to work the gas and get it to take off. I have had this truck in my shop for several weeks waiting on lady to get me money for brake parts. Was not showing any codes at first then after several tries during the weeks i have had it I finally got a 41 o2 sensor temp low. I took the chance and replaced the O2 sensor and solved the starting and running problems.

 

[SirAltitude]

what did that coolant temperature sensor do for ya?

I took my IAC off and cleaned it, was'nt much to clean, i could spray off what was there....

did the butane trick and nothing in the vacuum lines...

no codes, nothing, ever...

 

[Croneybones]

Haven't had a chance to change it. its hard convincing wifey to let me spend 20 bucks on a 1 inch wrench ill only use once.

EDIT:

Changed out the coolant temperature sensor today. I now have a 1 inch wrench for sale- haha

It was a quick job, but without pulling the rubber hose above it, it's hard to get the wrench down there. You will also lose a bit of coolant, so have a fresh jug handy and keep the pets away.

SAFETY FIRST... I almost lost my finger. I was wearing my wedding band and it got snagged on the edge of a clamp for the antifreeze. Remove it if you have one.

At this point, I still have to wait for the engine to get back to cold before seeing what she does. When that happens, expect another update... within a few hours here...

 

[Croneybones]

Ladies and gentlemen.... boys and girls... I believe I have my fix.

I replaced the coolant temperature sensor and let the truck cool for a couple hours. I just went out and fired her up and she ran great. No weird idle, and no attempting to stall.

I'm going to let the truck sit overnight and try starting again in the morning. If it doesn't do it anymore, then I will be done.

 

[SirAltitude]

that's what i want to hear...

wait till morning after she's sit there all night and do it...

Mine wont do it hardly atall if i've run it any during the day, it's always the next morning, or if it's super f'n cold outside and she's sat for atleast a few hours.......

 

[Croneybones]

Fired her up this morning... stalled again. The problem is still there, though it does run differently after i replaced that part. smoother. less surging. looks like back to the drawing board. can we eliminate iac and coolant temp sensor as the issue?

 

[miesk5]

ok, try the butane/propane test inside too; under dash..do it 'round all da vac lines for HVAC system

Next is what I posted awhile ago in this thread...:

yeah ... my 96's IAC was gunky, but the Throttle Body port (where IAC meets) was cruddy too. The IAC tested good, so I saved some $ on replacing it (but it''s on my List for replacement in spring)

Also, be prepared in better temps to clean EGR valve (I don't use solvents, just a Dollar Store brass brush) and the "EGR passage under da throttle body...

So, pull the TB and clean it thoroughly.

Inlet (TBI) Description w/pic, Ford; "...A dirty throttle body (Especially worse on Ford products) can cause rough or erratic idle speeds and stalling at idle. This carbon build up at the inlet of the TBI unit can cause the throttle vane to stick thus producing the above problems..."

Source: by trustmymechanic.com

Follow these steps to service the throttle body:

1. Remove the throttle body.

2. Hold it up to a light. No light should be visible between the plate and bore with the throttle plate closed. The hole in the plate should be visible and unobstructed.

3. Rotate the throttle lever and allow it to return. It should not stick or bind. It should return to the closed plate (idle) position freely when released.

If the problem cannot be corrected (an obstruction cannot be removed, free sticking, etc.), the throttle body must be replaced.

 

[SirAltitude]

yea i ran butane all over the place on the truck, inside and out.... kinda liked the feeling after about 20 minutes... but that passed,

as well as determining what the issue is, so,

It's not IAC, CTS, or vacuum on my truck, that leaves the TB and inspections on the in'rds of it...

i've torn town TB's before and it's not exaclty difficult to do, just time consuming if you have to clean'er up....so..

start: plan E,

; pull throttle body and inspect for debri/damage

FYI: cts switch-out did nothing on my truck btw... bought one 20$ new and nothing changed....

 

[Croneybones]

ill look into tps and egr and update as i go.