2003 Explorer Rough Idle

[plasticseng]

This is what I have at idle. Not much different than yours except my intake air temp is much lower. It's about 70 deg here right now.

 

[Cashcrazy]

Thank you. My MAF reading is inline with yours. It was probably close to 90 degrees when I took the intake temp screen shot. I tried to test the MAF some this evening. I unplugged it while running to see if there was any change and the RPM's started going up and down. It ran rougher after the MAF was reconnected. So I disconnected the battery and the idle did smooth out but it would have times of roughness. The RPM is fairly steady. The new sensor should be here Wednesday and I can eliminate that. It has the symptoms of a MAF not functioning properly, but the data is good. I should have the fuel below 1/4 tank also by Wednesday to try a better(according to the net) fuel injector cleaner. I guess I will proceed changing the intake gaskets if there is no change with either of these.

 

[Autolabs]

What is your baro? I have a 2005 230,000mi headgaskets/timing chains 1 year ago and idles smooth
temp 190
outside temp 35
iat 43 (depending how long you sit and idle)
baro 97kpa
map 37kpa
rpm 615-640
MAF 4.5 - 4.7 gm/sec
Since mine is throttle by wire, I don't have an IAC valve, but I have had nothing but issues with aftermarket IAC valves on rangers and other ford vehicles. Motorcraft only! I have the luxury of bi-directional controls and a labscope. I am able to increase IAC duty cycle in 10% increments and for some reason aftermarket would not change the rpm smoothly. each 10% increase only gave about a 50 to 100rpm increase, until around 50% then the rpm would jump almost 1000 rpm. ???? I checked the duty cycle from the pcm and it was flawless. So after 2 different aftermarket IAC valves, I put on the motorcraft and no more problems. Although the A/M made the idle better, it made me think I had other issues. I'm thinking the reverse engineered plans were sold to a few of the AM manufacturers, either way i was pretty happy and pissed off all at the same time.

Your fuel trim numbers are telling a different story than a possible vacuum leak or intake gasket. Try giving it a little more air when the rough idle is happening to see what happens.

 

[Autolabs]

Oh and I forgot to ask, where did you get the replacement IAC?

 

[Cashcrazy]

IAC came from Advance Auto. I still have the original but is pretty dirty. The idle did not change with the IAC just the stalling out in reverse.

 

[Cashcrazy]

What is the baro? I'll check the app and happily get a shot of that also.

 

[Fordman999]

Tell you what happened to my Explorer. It was running a bit rich and not throwing a code because a code is only thrown if it gets to -25 difference on lean or rich condition and I was -8%. After changing my MAF and coolant sensor and oxygen sensor and catalytic converter and sparkplugs it ended up being a bad fuel pump pressure regulator which is located at the pump. It was not relieving the additional fuel back in the tank like it was supposed to and continued spraying it into the fuel rail and injectors since it had nowhere else to go since the regulator was bad. I was losing a lot of gas. The mechanical thing on the fuel rail if you have a 2002 or 2003 is not a pressure regulator it is simply a mechanical pulse damper. Those rarely go bad only the new electronic versions go bad on the 04-present explorers.

Are you losing considerable amounts of gas all of the sudden? Is your gas guage not acting right? Just a thought that is what happened to me.

 

[Cashcrazy]

The gas gauge is acting fine. I get 16mpg like clock work on it. I hope that increases with the new plugs and wires. I'll be posting the info Auolabs requested this evening. Please have a look if you are savvy on all the data.

 

[Cashcrazy]

Running 60mph

And idling for several minutes:

Any help is greatly appreciated. Thing thing has me stumped and about ready to give up.

 

[Autolabs]

Don't give up, you're too invested at this point to never know whats causing the rough idle. So an occasional miss or stutter at idle in park after it is warmed up. Is it only when the ac compressor kicks on?

50k on a 2003 is very low mileage. Did it sit in a barn for years, or has it had a lot of short trips? A bottle of seafoam through the intake can only help, unless you hydro-lock it of course. Do you ever drive it like you stole it? That is good to do once in a while to burn off excess carbon.

What is your altitude. Your vacuum is barometric pressure minus MAP. So 29.92 in baro with 10 in MAP = 19.92in of vacuum. I don't believe your rig has a map or baro sensor, it is just a calculation from MAF. I could very well be wrong. I am close enough to sea level here in west MI. and a normal map reading is usually 8-10 in. at idle, so 6.8in is a little on the low side depending on your actual barometric pressure. So maybe your MAF is causing a miscalculation by the PCM or maybe you are at a higher elevation, but if you do indeed have higher than normal vacuum readings look for an air inlet restriction since that can act like a second closed throttle plate starving it of air.

A couple of mechanical things to check with gauges;1. vacuum, 2. fuel pressure. I believe Autozone might have these in their loaner tool program. You might have to pay a deposit but you get it back. You could also probably check these readings while still in their parking lot to save the hassle of bringing them back. It is critical that you record the readings while the vehicle is stuttering and while smooth, and keep those numbers separated and titled with conditions. Does the vacuum gauge flutter or is it steady?

It still could be the MAF sensor since fuel trims sometimes tend to be a little erratic. You have negative at idle and positive at cruise.

Just for giggles can you throw on your old IAC and take the same readings? (just two 8mm or 5/16 bolts and a plug right?)

What also could help is a snapshot of your datastream when problem occurs, vs when it is smooth.


Don't give up and sell it quite yet. There is still more data to gather.

Keep fighting the good fight my friend...

 

[Cashcrazy]

It was a daily driver before I bought it, but just to work and home with the occasional trip out of town. I have a vacuum gauge That I use for tuning carbs that I can hook up to check. Ill wait on the MAF so I am replacing one thing at a time in case it does correct the issue.

 

[Cashcrazy]

Don't give up, you're too invested at this point to never know whats causing the rough idle. So an occasional miss or stutter at idle in park after it is warmed up. Is it only when the ac compressor kicks on?

50k on a 2003 is very low mileage. Did it sit in a barn for years, or has it had a lot of short trips? A bottle of seafoam through the intake can only help, unless you hydro-lock it of course. Do you ever drive it like you stole it? That is good to do once in a while to burn off excess carbon.

What is your altitude. Your vacuum is barometric pressure minus MAP. So 29.92 in baro with 10 in MAP = 19.92in of vacuum. I don't believe your rig has a map or baro sensor, it is just a calculation from MAF. I could very well be wrong. I am close enough to sea level here in west MI. and a normal map reading is usually 8-10 in. at idle, so 6.8in is a little on the low side depending on your actual barometric pressure. So maybe your MAF is causing a miscalculation by the PCM or maybe you are at a higher elevation, but if you do indeed have higher than normal vacuum readings look for an air inlet restriction since that can act like a second closed throttle plate starving it of air.

A couple of mechanical things to check with gauges;1. vacuum, 2. fuel pressure. I believe Autozone might have these in their loaner tool program. You might have to pay a deposit but you get it back. You could also probably check these readings while still in their parking lot to save the hassle of bringing them back. It is critical that you record the readings while the vehicle is stuttering and while smooth, and keep those numbers separated and titled with conditions. Does the vacuum gauge flutter or is it steady?

It still could be the MAF sensor since fuel trims sometimes tend to be a little erratic. You have negative at idle and positive at cruise.

Just for giggles can you throw on your old IAC and take the same readings? (just two 8mm or 5/16 bolts and a plug right?)

What also could help is a snapshot of your datastream when problem occurs, vs when it is smooth.


Don't give up and sell it quite yet. There is still more data to gather.

Keep fighting the good fight my friend...

I just realized I didn't answer all your questions.

1. It's not just an occasional miss or stutter. I would be happy with that. It has a constant stutter or miss in park or neutral. Its rough an noticeable to everyone in the vehicle. It also happens when sitting at red light while in drive, but its not near as bad. It does it with or without the AC on, but the AC being on does amplify it. I am assuming the slight increase in idle from the compressor takes it to the sweet spot. 800-900rpm is the roughest.

2. It has been driven daily for short trips before I purchased. I cleaned the throttle body and have tried multiple injector cleaners in the fuel, but never used seafoam. I've never noticed an improvement with any of the cleaners.

3. Altitude is 550ft.Ill check the vacuum.

4. I'll see if I can find the IAC, but I don't think it was that. The IAC didn't change the idle quality.

The fight is coming to an end with defeat.....

 

[Cashcrazy]

One more thought to throw out there. Could the EGR valve cause this?

 

[plasticseng]

One more thought to throw out there. Could the EGR valve cause this?

If it is stuck open it could.

 

[Autolabs]

EGR valves can cause a rough idle if they are not sealing at an idle. I just looked at your screen shot again and your small numbers to the side show 50inhg of MAP under 100% load. Maybe just a calculation bug within the app, but that can't be right. Your fuel trims are in the positive 20's under load and negative 20s at idle,(long and short combined),... that is quite the swing. I'm anxious to see the same readings with your new MAF sensor when you get it.

If this has been a daily driver since new you have an average of about 10 miles a day for over 13 years. If this is true, there has got to be carbon caked on those valves

 

[Cashcrazy]

It had 44k when I purchased about a year ago so roughly 3,700 miles per year. I drove about 12,000 miles over the year that I have owned it. I originally started treating the fuel with ethanol treatment thinking I had water in the tank. I have also used supertech, STP, Lucas, Liqui Moly, and a few of the different GUMOUT fuel injector cleaners. They all claim to help clean valves so if it really works I should have cleaned them fairly well.

 

[Cashcrazy]

Also just for the record I am running the Liqui Moly in the tank now and it didn't cure my rough idle. It might be a little better in drive but actually feels worse in park or neutral.

Is the EGR valve something easily removed that can be cleaned with carb cleaner?

 

[plasticseng]

The EGR valve is easy to get to. The toughest part of removing is breaking the EGR tube loose without kinking it.

Can you get a reading on your DPFE sensor? It may show if you are getting EGR flow at idle, which you shouldn't be.

 

[Cashcrazy]

I looked through the options and I didn't see a DPFE option. This app seems to have everything monitored by the computer. Is the 03 equipped with this sensor?

 

[Cashcrazy]

I just made a two hour drive at highway speeds. Here is a little more data just for kicks.