Hello, so recently had codes for a 2, 3,4 cylinder misfires and bank 1 too lean. Replaced spark plugs, coil wires, pack, rewired using Haynes manual for 3.0 engine. After fixing the misfire, received an IAC malfunction code.

A day later, the engine idles at/around 900-1000 rpm, but as soon as the a/c clutch engages it'll drop to around 3-400 but doesn't stall. Decided to check alternator, full load drops to 13.5. 14.0 no load and the engine sounds like it wants to die.

So after thinking I figured air flow as an issue. Replaced the IAC with negative terminal disconnected, applied new gaskets provided with valve. Started engine, shortly after starting, the engine revved to 2500-3000 rpms, steady, would eventually drop to 1500 then stay then drop to 800 with ac clicking on. It'll then Rev back up to 3000 rpms, drop to 700 then stall.

I have sprayed down all vacuum hoses visible even along the IAC valve, no changes. When driving, the truck will keep speed or gradually increase without touching the accelerator around 40 mph. At a stop, it'll feel as though the truck wants to lurch forward even pressing the brake heavily.

Not sure what to check next, replaced pcv hose recently due to a vacuum leak but no issues from there since.

Any suggestions or tips would be greatly appreciated

 

Fords need Motorcraft or Hitachi IAC Valves, other brands won't work well

After engine is warmed up and idling, unplug the IAC Valve
RPMs should drop to 500 or so, or engine can even stall, either is GOOD
If RPMs do not drop you have a vacuum leak, possible in the new IAC Valve

 

I will be able to check that issue this evening and will update the results

 

So, the engine did stall when I unplugged the iac. But it takes a while for it to finally reach 900 rpms to idle. It seems it has to stall before it settles at 900. It feels as though the engine is taking off when the ac kicks on and the rpms goes up. As if I am pressing the gas. Not sure what to do as of now

 

Well the RPMs should go up 50+ RPMs when AC comes on, not down

It shouldn't stall, ever
The computer and IAC Valve react too fast for that

Is this a manual or automatic?
Automatics need to idle higher

And what year?
idle RPMs are set for emissions standards for the model year they are made

 

2003 3.0 flex fuel. Automatic. It seems the only time it really feels it wants to stall is when the compressor kicks on.

I meant, when I unplugged the IAC it stalled, which earlier you said was good. Which means there's no vacuum leak.

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not sure if you tried this yet OP but did you try cleaning and dialing in your throttle body? I'm not sure if your 03 is like my 93 but take your intake tube off. Clean the mass air flow sensor with the appropriate mass air flow sensor cleaner. Do not use throttle body cleaner. Do not use brake cleaner.

Go to your butterfly valve and spray in a lot of throttle body cleaner. Open and close the plate and spray all in there. If you have an air compressor try to air dry that area out, if not just let it sit for a short bit to evaporate the fumes so it's not so hard on the motor when you start. Its not the end of the world if you don't.
Now, on my truck the throttle has a throttle stop screw. Sometimes you get morons that have a bad idle and try to fix it by using the throttle stop screw like an old school carb idle screw, and they crack the throttle open to make the engine idle when cold. This actually happened to me on my truck, I spent a couple weeks trying to find the problem. If you're still following along here, I need you to reconnect your air intake tube back up to the throttle body, start the engine and rev it up a few times to burn out the throttle body cleaner. If the motor isn't hot yet (middle of the coolant gauge, 190 degrees) you need to get it there. Once it's full hot, shut it off and go back under the hood. pull the IACV plug. Go inside your truck and shut off all your electricals. no blower, no radio, no headlights, etc. restart motor. let it limp along if need be, but then you need to go to your throttle stop screw and turn it until your engine is idling at approximately 500 rpm. This is setting the "base" idle. It's gonna sound rough but just go check your tach and adjust it to 500. Now go ahead and shut the truck off, go back and reconnect your IACV plug. You have now set your base idle correctly. This works for the early 90s obd1 trucks but I am not sure if it works with an 03, but I figured I'd try to help

 

Yes it's still open, still having an issue with it running like it does. The one time I disconnected the iacv while it was running it killed instantly. So will it actually start without it connected? I will try that this weekend. Not sure exactly which screw you're referring to or where it's located on the throttle body itself, but I'll try to find it.

 

This is my 99 ranger 3.0. its probably gonna more closely resemble your 03 than my 93 will. I circled the throttle stop screw for you. The throttle rests against it when closed. back it out (counterclockwise) to lower idle. Turn it in (clockwise) to raise idle. It is ABSOLUTELY CRUCIAL your engine is up to full operating temp. Hit the highway if you need to beforehand, or do it right after a drive.

 

Ah okay so it's more along the side of the throttle wire bracket? I'll have to look more when I get home, currently at work, but I definitely will take a look and let you know what I end up with.

 

Dont take this personally but as long as you aren't a complete dumbass you'll be able to figure it out once you see under your hood now that you see what my 99 looks like. Should be damn near identical. And you can't be a dumbass because they take the truck straight to the dealer instead of try to trouble shoot so you're ahead of the pack already.

 

Lol. Well I work at Infiniti so my car knowledge is pretty higher than most. But with the older vehicles, I'm still newer on. I had a 95 s10 which ic pretty much rebuilt, so any issues werent existent because of an older engine, mostly was fuel pump and starter issues. But never had to play around with the throttle Position on an older vehicle yet. Nah dealers are too expensive. 😂 Only reason I would bring it if it needed an ecm relearn for the idle

 

I'm not sure what sort of ECM relearn you speak of. This is done automatically after you unplug the battery and put it back in. The base maps in the ECU are programmed by ford and never need changing. The ecu will learn your driving conditions and atmosphere when you reset it by pulling the ECU fuse or pulling the battery and make small adjustments to the base maps. At least thats' what I've been told, and I know honda ECUs do the same thing.

 

Ah I understand. I know I was talking to one of our techs here and he said the throttle Position sensor is a Ford specific and is programmed within the ecm but can only be reprogrammed by Ford. Which I did replace the throttle Position sensor with an after market one for diag reasons but still ran into the same issue with the OEM one installed. Not too familiar with Ford, considering I've only had 2 cars since I began driving 10 years ago. A 95 s10 and an 07 honda civic which I've put over 120k miles on and haven't had any running issues engine wise.

 

So what's the deal here, did you do what I said?

 

I had not yet. Working on it tomorrow.