My truck is sick =(

[Raduque]

Having a fairly serious problem with my truck here. When it's sat for a long time and it's cold (or it's cold outside), it won't start. Cranks fine, but dies right off as soon as you let go of the key. If I give it gas while cranking it fires right up, but if I let off the pedal, it'll die. Once it's warmed up (either warm outside, or above 1/4 of the temp gauge) it'll fire right up.

It got really bad this morning leaving work, I couldn't get it to stay running without giving it gas. It would idle down below 500rpm and the lights dimmed, then I'd give it some gas and it would hesitate then jump up to about 1500rpm. It runs strong as ever when giving it gas, it just won't idle.

It's not lighting the CEL, and Autozone won't even plug in their OBDII reader without a CEL showing so I can't find out if it's throwing a code without lighting the CEL. They did test the battery and alt and both tested fine on their machine. All the battery wire connections are tight and clean.

It started this when it started to get rainy, and it started with just having to crank it twice to start and got progressively worse from there. All the signs point to the IAC, but when warmed up it's not idling wrong and doesn't hunt for an idle. I'd replace it today if I could afford to.

Anybody got any ideas what else I can look at that doesn't cost money right this second?

 

[LTC8K6]

IAC or the coolant temp sensor.

I'd bet IAC.

You can try cleaning it and it's passages.

Also clean your throttle body.

 

[Raduque]

Easy way to clean the TB without removing it? It looks like a giant PITA to pull it.

 

[LTC8K6]

Throttle body cleaner spray while opening and closing it a few times.

 

[LTC8K6]

When the truck won't start, get out and give the IAC a few good firm taps with a wrench and see if that helps. This may unstick it if it has gotten stuck.

It would be better to have another person do this while you are trying to start it.

 

[franksta]

Originally posted by: LTC8K6
Throttle body cleaner spray while opening and closing it a few times.

No need to remove it just do this.



Also, the IAC is 2 bolts and an electrical connector (at least on the 4.6s that I have). It's very easy to remove and clean, be careful with the gasket beneath it.

I had the exact same symptoms as yourself and it was the IAC. I was able to clean it and that helped but eventually I did replace it.

 

[exdeath]

If it's idling ok after you release the throttle it's prob not the IAC. How does the dashpot behave if you goose the throttle then slam it shut rapidly? That's a good way to test for a sticking or slow responding IAC; if it doesn't respond fast enough it will die down too quickly and overshoot idle and stall.

You could check both the IAC counts and the coolant temperature sensor for reasonable values with a decent scan tool.

Re-reading your post it does sound sound like the IAC. For some reason I thought I read that it idled fine once it started.

 

[kalrith]

Same problem in my '01 Mazda Tribute. I've had to clean the IAC 2-3 times, but it runs a good 15k miles between cleanings.

 

[BlahBlahYouToo]

Originally posted by: LTC8K6
Throttle body cleaner spray while opening and closing it a few times.

do you do this with the engine running or not?

 

[LTC8K6]

Originally posted by: BlahBlahYouToo

Originally posted by: LTC8K6
Throttle body cleaner spray while opening and closing it a few times.

do you do this with the engine running or not?

Not. You want the crud to run out.

 

[radioouman]

How about bad spark plug wires? Humidity will make them arc to anything metal that is nearby as they break down.

 

[BUTCH1]

Originally posted by: radioouman
How about bad spark plug wires? Humidity will make them arc to anything metal that is nearby as they break down.

This, I had a set that would arc to the head under load. I would also check the fuel filter, if it's the original might be causing low pressure to the injectors, the control module would be calling for a long pulse ( engine cold) but if the pressure at the rails is poor it could affect fuel delivery and you would notice it first in cold situations as this is where a engine needs a lot of fuel. OP. what's the mileage on this truck?

 

[Raduque]

I can pretty much guarantee it's not the plug wires. The 5.4 doesn't HAVE them (coil on plug). I'm going to try pulling the IAC and cleaning it.

butch1, it has about 108 thousand. I really do need to have the plugs and cops replaced, but I'm extremely scared of having the plug blow out and having to replace the head. I'll have to check the fuel filter, too. I'm betting it's in-tank. It's extremely hard to do any work on my truck though, because the garage is full of blown-up Dodge Stealth.

exdeath: When you goose the throttle, it's sluggish to respond. It seems to idle back down normally to idle. This is when warm. I haven't tried when cold.

 

[BUTCH1]

Originally posted by: Raduque
I can pretty much guarantee it's not the plug wires. The 5.4 doesn't HAVE them (coil on plug). I'm going to try pulling the IAC and cleaning it.

butch1, it has about 108 thousand. I really do need to have the plugs and cops replaced, but I'm extremely scared of having the plug blow out and having to replace the head. I'll have to check the fuel filter, too. I'm betting it's in-tank. It's extremely hard to do any work on my truck though, because the garage is full of blown-up Dodge Stealth.

exdeath: When you goose the throttle, it's sluggish to respond. It seems to idle back down normally to idle. This is when warm. I haven't tried when cold.

Should be a canister-type on that year ford. Looks like plug change is going to be a project for that vehicle but after 8 years and 108K it's due.

 

[Raduque]

Yes, the plug change is a pain. I don't think I'm going to do it myself. I'm going to have a shop do it, that way, if it's done wrong and a plug blows, THEY have to replace the head(s), not me. I can't afford new heads.

 

[Pacfanweb]

It's the IAC. Very typical for them to do this in the A.M., especially after a weather change.

You can clean it while the engine's running, but it's not very efficient.

Take it off, and get some carb cleaner and clean it. It'll have two holes in a row...air goes in on, out the other. There's a slide valve in-between them. You can take a pocket screwdriver and work the valve back and forth to let the cleaner get past it. Fill them up, work the valve, dump it. Repeat a few times. That "should" fix it for quite awhile.
On the pre-MAF cars, you could just take the air inlet tube off the throttle body and keep spraying carb cleaner into the IAC port hole while the car was running. But they won't run without air flowing through the MAF.

Oh, and there's very likely not a code set, anyway, so don't bother getting it tested.

Plugs don't cause this problem, and I'd never try replacing them at home, anyway. You very often need a special tool to get them out of the head, because a lot of them break. A 5.4 doesn't have wires, either, so that's also not the problem.

 

[Raduque]

I think I'm just going to replace it. And yea, I'm not going to do the plugs at home. I just don't feel like fighting with them and worrying about installing the new ones wrong and blowing out the 3-thread plug hole, which is the LAST thing I need.

 

[Pacfanweb]

Originally posted by: Raduque
I think I'm just going to replace it. And yea, I'm not going to do the plugs at home. I just don't feel like fighting with them and worrying about installing the new ones wrong and blowing out the 3-thread plug hole, which is the LAST thing I need.

It's not installing the new plugs, it's getting the old ones out that's such a problem. They typically will have several break, and Ford has a special tool to get the remaining part out. (I'm sure the aftermarket has a tool, too)

 

[cardiac]

Originally posted by: Raduque
I think I'm just going to replace it. And yea, I'm not going to do the plugs at home. I just don't feel like fighting with them and worrying about installing the new ones wrong and blowing out the 3-thread plug hole, which is the LAST thing I need.

It really isn't that big of a job. Having done them on my V-10 Excursion (Same motor with 2 more cylinders), and 2 friends F-150's with the 5.4l, it is a lot cheaper than the $300-400 a dealer is gonna charge.

While the truck is warm, pull all of the COPS, then blow out the area around the plugs with a compressor. The plugs should break loose fairly easily if the head is pretty warm. Coat the plug threads with anti-seize and make sure you torque them properly (132 in/lbs). That is very important in your battle to keep plugs from blowing out. Make sure to use the Motocraft OEM plugs.

Here is a step by step outline for doing the plugs on a 6.8l: Ford modular plug change procedure.

Good luck, and if you have any other questions, I'll try and help.

Bob

 

[slag]

I have had more problems tearing the fuel rail o rings (injector o rings) than anything when replacing plugs or COPs on my 97 F150 with the 5.4. Those things should be greased or lubed or something because they tear easily.

 

[Raduque]

Well, cleaned the IAC. Will see what it does tonight and tomorrow morning. I'm going to replace it anyway though, so it's good that I figured out how to take it off. The IAC is a pretty big PITA to pull - it's behind the TB against the firewall inside the engine/trans tunnel. I was practically laying ON the engine to get at it.

Edit: Started and ran great both last night and this morning. Cleaning it worked wonders. I'm still going to replace it, and look at getting a spare one.

 

[franksta]

It must be in a different location on the 5.4 vs the 4.6 as when I did mine it was super easy.

 

[cardiac]

The IAC on my Excursion was a bitch to get at also. The IAC is about $50 at any local parts store. If you do the plugs, stick with the Motorcraft platinums. They are about $3.50 each.
I don't think I would worry about carrying a spare, as it may never go out again, nor will it leave you stranded if it does.

Bob

 

[Raduque]

Cleaning the IAC seems to have done the trick. Several days now and it's still starting great. My dad drove it to work the past couple days (60 miles/day) and said that it feels smoother and seems to be getting better gas mileage. If it starts acting up again, I'll replace it.

And cardiac, I wasn't actually going to carry the spare around, just get a spare and keep it in the garage for when it acts up again another hundred thousand miles down the road.

 

[cardiac]

Cool. Cleaning it may have gotten you another 25k out of it.....