1999 Ford Ranger Idle Problem
 

I have the 4.0L v6. When I start the truck and it is cold, it idles terrible. Put it in gear and its even worse. If I let the truck warm up, it will run fine as long as the engine is warm. Even after I shut it off and run an errand or something it will start and run just fine. Any Ideas?

When was the last time a Tune up was performed?? Plugs,wires and filters.

IAC, clean or replace

What is the IAC??

I changed the plugs at 68000 approx. It now has 97833 on it. I have never changed the plug wires.

Input Air Controller, Found on the throttle body, small cylindrical, 2x 10mm bolts and a wire connection. Signal from the CPM, opens and closes the control valve to modify engine RPM

Clean with brake cleaner, if it works OK, if not replace.. $45.00

Welcome to FTE.

With the clue about it starting & running poorly when cold, but starting, ideling & running ok After it fully warms up, you may have more than one problem.

Do you have a CEL lit???? If so, run this puppy by your favorite autoparts store for a no cost computer trouble code scan & post All of the code Numbers found, as they can offer up good trouble shooting clues, if you have more than one problem.

As has been mentioned the Idle Air Control (IAC) is a frequent problem part for idle issues & cleaning it often doesn't last & thats what I found with mine & as such Ford recommends replacement, rather than cleaning.
So, if you decide to clean yours & it clears the problem, if/when it returns at least you'll know what to replace.

If you clean it with a strong solvent, Don't let that solvent get into the IAC's little black caps air filter, or into the cylindrical end where the electrical connector attaches, as strong solvents can damage the air filter, or dissolve the formvar insulation on the solenoids windings & short them out.

So maybe consider using something more benign, like WD-40 or the like & a wire brush type pipe cleaner, for removing any deposits.
Here is a link to the Tech Info thread atop this forum about the 4.0L IAC, what it looks like & where it is on your engine.
https://www.ford-trucks.com/forums/1...formation.html

Has the PCV valve been replaced???? What I'm thinking here is that it may be gummed/sludged up such that it's hanging open when cold & causing an uncalculated for vacuum leak, that the IAC can't compensate for, but frees up & works after the engine warms up.

Or maybe you have a Vapor Recovery or EGR system vacuum leak, or lazy O2 sensors or even fuel pressure troubles, that's figuring in on the cold idle problem, so any trouble codes for those systems would tattle on them.

Are you up to date on all past & present due scheduled maintenance items????

A bunch more thoughts for consideration, let us know how it goes.

Check for upper and lower intake manifold gaskets leaking. They are O-ring style, and can get compressed and stay that way until warmed up, thus allowing extra air intake. You can also use WD-40 if you want to check. Spritz around the meeting surfaces while the truck is running rough.
A better method is to use a propane tank (bernz-o-matic style) along with a piece of rubber tubing. Crack the valve and move the end of the hose around the gasket area. If the idle smooths out, you have found your problem.
A sticky IAC would also likely cause stumble when the A/C is engaged or the steering wheel is turned while the truck is standing still.
tom

Here are the error codes that came up when scanned.
1. P0171 Fuel Trim one bank Condition
2. P0303 Cylinder 3 Misfire Condition
3. P0133 A/F Sensor response Malfunction
4. P1131 Lack Of bank 1 O2 Transitions - Lean

I did change the IAC about 2 months ago because of the humming noise while at an idle. The rough idle was there before I changed the IAC and is still there. I am going to change the plugs and wires tonight and clean the intake.

I think also I will reset the computer codes after I do the plug and wire change and see what new codes pop up.

Thanks for the help so far. Seems like there are defiantly a bunch of talented people on here.

Cylinder 3 is on bank #1, the miss fire could either originate due to lean mixture, or the lean adjustment on bank 1 could be in response to the fuel load caused by the #3 miss fire.

Without a FF or live data we wont know, the correction is the same either way,
First plugs and wires, clean the MAF & new filter.
Reset the CPM and Run the required drive cycles to set the monitors.

If the MIL illuminates again it would be useful to jot down the FF data when you get it scanned..

Plugs and wires did the trick! When I pulled the #3 plug out it was damp. Must have been a bad plug wire. After I replaced everything it runs great no cel. I will drive it to work tonight to confirm. Hard to believe something so simple would trip it.

Thanks for the help!

Happy that got you going, would not be surprised if the O2 sets a code, if it has been in this operating condition for a long period it may have coked up, hence lack of switching or it could just have just pegged @ lean trying to cut the fuel.

Anyway, Welcome aboard.. P

I just drove it for about 6 miles. abd the cel came on. I have to go back to autozone to get a part i ordered tomorrow so I will have it checked then. Still runs good, but like you said might set off the O2 sensor. Will I have to replace it?

Also The ABS light stays on as well. Does that reset with disconnecting the battery? I just replaced the rear ABS Sensor and the light is still on.

EFI systems are complex.

a lean condition (any cycle) will cause misfire.
misfire does 2 things.
1 : adds extra oxygen, making O2 sensor go lean and ecu to rich.
2: misfire , dumps raw gas to exhause, rich. #1 makes ECU pyshoctic. HUNTS.