2003 Explorer Rough Idle

[Cashcrazy]

03 XLS, 45k, 4.0 flex fuel, new motorcraft fuel filter, and clean MAF sensor. I have a rough idle after its warmed up and not getting codes. I have googled and found similar complaints, but the others were getting a check engine light. Has anyone else had a similar problem? I am not sure what to test next. Thanks in advance.

 

[Cashcrazy]

I am now at 46,500 miles and I still have a rough idle while idling in Park. The idle seems smoother while in Drive. The other day it acted like it was going to stall and then surged backwards when I put it in reverse from a cold start. A few days later it tried to stall when I put in drive. I started the explorer and let it idle a few minutes to warm up before backing out of the driveway and putting in drive. After this I replaced the IAC, air filter, cleaned MAF(again), and replaced a vacuum hose that runs from the intake manifold on the passenger side to some switch under the brake master cylinder. The hose was badly deteriorating is why I replaced. Does anyone know what this part is that the hose connects into?

I have not had an improvement in idle quality after replacing the mentioned parts. Does anyone have any input on this?

 

[ScaryWoody]

You may want to try this. Simple clean. https://www.explorerforum.com/forums...d.php?t=339793

 

[Cashcrazy]

Thanks for the response. The link says the page is no longer there.

 

[Autolabs]

No check engine light doesnt mean there isn't any pending codes hiding under the surface. Maybe I didn't read your post right and you did have it scanned anyway. What would be helpful is some datastream info at idle such as fuel trims, MAP OR MAF. There are some pretty inexpensive bluetooth adapters that work with smart phone apps to get you that info.

 

[Cashcrazy]

No check engine light doesnt mean there isn't any pending codes hiding under the surface. Maybe I didn't read your post right and you did have it scanned anyway. What would be helpful is some datastream info at idle such as fuel trims, MAP OR MAF. There are some pretty inexpensive bluetooth adapters that work with smart phone apps to get you that info.

I ordered a Bluetooth model only to find out that it doesn't work with an iPhone. I ordered a wifi model this weekend that should work. Any app suggestions for it?

 

[ScaryWoody]

https://www.explorerforum.com/forums/showthread.php?t=339793

Sorry about that link. There is a How to on cleaning the MAF, throttle body and IAC valve. I have a 2003 and it had a bit of a rough idle but after clening it was much improved. I don't think mine had ever been cleaned.

 

[Autolabs]

I heard dash command was pretty good. Just do a little research and make sure it can read and record live data.

 

[Cashcrazy]

Will do. Ill post more when the reader arrives

 

[Cashcrazy]

Still waiting on the obd reader to arrive apparently there were delays shipping. I have put about 250 miles on it and I have been trying to replicate the problem to make it easier to diagnose. This morning I started it and let it idle to warm up for about 3-5 minutes. I backed it out of the driveway very slow, came to a complete stop, and waited a couple seconds to see if it would stall. Everything was fine, then I shifted into drive. It stumbled a couple of times and then died. It did restart without an issue.

Whatever is going on might be related to the rough idle. I have googled this and most threads suggest cleaning the MAF and IAC. I cleaned the MAF twice and replaced the IAC. Still no check engine light. Are there any other sensors that could cause this issue? I would like to diagnose the issue before it leaves me stranded.

 

[dla]

Still waiting on the obd reader to arrive apparently there were delays shipping. I have put about 250 miles on it and I have been trying to replicate the problem to make it easier to diagnose. This morning I started it and let it idle to warm up for about 3-5 minutes. I backed it out of the driveway very slow, came to a complete stop, and waited a couple seconds to see if it would stall. Everything was fine, then I shifted into drive. It stumbled a couple of times and then died. It did restart without an issue.

Whatever is going on might be related to the rough idle. I have googled this and most threads suggest cleaning the MAF and IAC. I cleaned the MAF twice and replaced the IAC. Still no check engine light. Are there any other sensors that could cause this issue? I would like to diagnose the issue before it leaves me stranded.

I'd consider checking the Torque Converter Clutch and related system. If the TCC doesn't disengage when coming to a stop the engine will stumble. Check the stickies as I think I remember one on this.

 

[Cashcrazy]

Thank you. I will look for the sticky and check this out.

 

[Cashcrazy]

dla- I didn't see a sticky on the TCC, but there is a good sticky on flashing the PCM with the latest update. The people who had the flash reported their rough idle corrected and smoother shifting. I am going to call the dealer and see what they would charge me for the PCM update

 

[Cashcrazy]

It's been awhile since I have updated this. I am not at 50,400 an my only complaint is the rough idle. I got so tired of feeling it that I finally sent it to the dealer. They hooked up their computer, found no codes, and said I had the latest update. The dealer told me that they "can't find anything wrong with it and these models idle rough." Not sure what's next, I may try different spark plugs.

How bad would a vacuum leak need to be before I get a code?

 

[Cashcrazy]

I had a detour on this issue to resolve a horrid popping noise. Now that that is done I'm back on the rough idle. The stalling in reverse has ended. I'm assuming the new IAC corrected the issue. I just installed new Autolite double platinum plugs and Autolite wires. The idle is better while idling in drive but still rough in park. It couldn't have been this rough when new so I am going to keep working on this. I guess my next move will be to remove the throttle body for a thorough cleaning. It now has 56,800 miles on it and the original plugs were surprisingly worn. I had one worn to a .070 gap! I'll drive around more with the new plugs and wire to get a better idea how much better it really is.

 

[Cashcrazy]

I read that a leaky gas cap will act as a vacuum leak and cause a rough idle so I just replaced my 13 year old cap. It made another noticeable improvement in idle quality. It idles great at red lights in gear but is still a little rough in Park with the AC compressor running. I'm going to consider minor stumbling in the idle normal since I have been told these weren't the smoothest idling machines when new. It's close, but not quite there yet.

 

[plasticseng]

I don't know how long it has been since you unhooked the battery, but it takes a week or two of normal driving for the idle to smooth out on mine after I unhook the battery. I guess the factory default parameters just aren't quite right after 260,000 miles.

 

[Cashcrazy]

I haven't unhooked in awhile. I'll unhook it after I clean the throttle body to see if there is any change

 

[Cashcrazy]

I just cleaned throttle body and I believe this is as good as it's going to get. It's still a little rough when comparing to a 3.5 explorer, but not too bad. One thing I did notice after cleaning the throttle body is the RPM adjusting at idle when the AC compressors kicks in. Before the RPM's would just drop. I have read that some air is supposed to pass the butterfly valve when closed and mine was more than likely sealed with soot. Case closed for now. I hope this info helps someone down the road.

 

[plasticseng]

I haven't unhooked in awhile. I'll unhook it after I clean the throttle body to see if there is any change

I was getting at the opposite point. Unhooking it may give you a low or high idle, or even cause it to 'hunt', until it adapts to your current engine condition. You should unhook it if you change out a defective part or fix a big vacuum leak; it will learn faster that way. And of course you need to unhook it for certain jobs. But just understand that unhooking it puts it back to factory defaults that may not be just right for your engine age, atmospheric conditions, etc., and it will take time (sometimes several days) for it to adapt and give you a really steady idle.

The above is mostly referring to idle speed. If is obviously skipping, you probably still have some troubleshooting to do.