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Rough Idle and Engine Surge Under Load

you need to find someone with a good scanner and look at the live datastream. So you can see you fuel trims, misfires, and maf. data to get a decent idea of what is going on.
where are you located?

http://obd-2.com/

Get pwm+iso module, cost about $150. Will even read ABS and GEM codes, which alone is worth the price. Reads all Mode 6, which has all the misfire data and stuff. Lots of the scanners at twice and 3x this price are garbage.

DOUBLE COMBO - contains any two of the above networks $142 (pick that option).

This scanner is as close to one costing a few grand as you will ever get.
 



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Here's another thought:

About a week before I had all this trouble, my CEL came on and gave me a P0442 "EVAP small leak detected" code. I figured I didn't tighten my gas cap all the way, so I tightened it, reset the code, and forgot about it. That code has not come on since.

I wonder if a vacuum line somewhere in this system is leaking. Would this cause the EVAP code AND possibly the P0171 and P0174 codes as well? I don't smell fuel in the engine compartment, but I'm not sure if its leaking somewhere else...

I won't have time to work on the car until the weekend, so don't expect a follow up until maybe saturday or sunday; however, I'm online periodically and am free to brainstorm.

What do you all think?
 






Ok.

I checked the EGR system. I blocked EGR flow using a piece of a beer can. The EGR valve holds a vacuum. The EVR selenoid doesn't leak. Unplugging the DPFE didn't yield any changes.

I'm kinda frustrated with all this... I'm going to my mechanic soon to borrow his scanner and see WTF is up with my car. Sorry. I'm pretty frustrated; however, on the plus side, I've driven about 150 miles after resetting the CEL and the lean codes haven't come up yet. I'll see what my gas mileage is like next time i fill up since its been pretty crappy lately (~14 mpg hwy as opposed to between 20-22 mpg hwy).
 






Here's another thought:

About a week before I had all this trouble, my CEL came on and gave me a P0442 "EVAP small leak detected" code. I figured I didn't tighten my gas cap all the way, so I tightened it, reset the code, and forgot about it. That code has not come on since.

I wonder if a vacuum line somewhere in this system is leaking. Would this cause the EVAP code AND possibly the P0171 and P0174 codes as well? I don't smell fuel in the engine compartment, but I'm not sure if its leaking somewhere else...

I won't have time to work on the car until the weekend, so don't expect a follow up until maybe saturday or sunday; however, I'm online periodically and am free to brainstorm.

What do you all think?

Not impossible for an evap line to have a small leak due to corrosion.
 






Ok. You all have me convinced to purchase a nice scanner. But I'm not sure which one. 96eb96, you mentioned one in your above link. How does this one compare to an ELMScan or others?
 






Just an update...

Ok everyone, here's what I have done thus far to try and correct my idle problem:

1. Cleaned the MAF and IAC. Replaced the air cleaner.
2. Replaced the TB and IAC gaskets. Also cleaned the TB while I had it off.
3. Checked for vacuum leaks both with a gauge and starting fluid. Vacuum stays steady at 20-in.Hg during smooth idle and drops to 19-in.Hg during lopey idle. The lopes occur erratically, varying from every second to every five seconds.
4. Several doses of HEET and fresh gasoline from various stations don't seem effective, although it did take care of my driveability issues earlier.
5. Changed fuel filter and checked fuel pressure. Fuel pressure is adequate according to my Haynes book.
6. Checked EGR system thoroughly (or at least I think) by unplugging the DPFE, blocking EGR flow with a piece of a beer can, and testing the EGR valve and EVR selenoid. Everything seems to be functioning normally.
7. Seafoamed the intake through the brake booster hose. It idled much worse for a few highway drives, bit it soon cleared up to the normal lopey idle.
8. Visually inspected the sparkplugs and wires. No abnormalities seen.
9. Visually inspected the ignition coils for corrosion, charring, etc. None present.

Also, I've driven roughly 250 miles and no codes have come up, nor are any pending. Maybe one of the above remedies fixed my 171 and 174 lean problems. Since I've been working on it a lot lately, my gas mileage is probably horrible due to idling while checking vacuum.

I think a good scan is needed to see what's going on electronically. I have a slight suspicion its a faulty MAF, even though it has proper input voltage and resistance. I'll probably have it done soon, unless someone has any other ideas???

Thanks A TON for all the input from everyone. Once I get it scanned, I'll post the results.

ERUSH
 






Ok. You all have me convinced to purchase a nice scanner. But I'm not sure which one. 96eb96, you mentioned one in your above link. How does this one compare to an ELMScan or others?

Many "scanners" just read OBD-2 parameters. I'm not saying that is useless, but its only o2 sensors, fuel trims, coolant temp, and a few other params. Its like asking someones height, weight, age and interests on a dating site. There are so many other pieces of info..

For example, you cannot read DPFE for the EGR, so the scanner is essentially useless if you want to check that. My first scanner was the CarChip, don't get me wrong its excellent but it is limited to those 8 or so OBD params. Sometimes it comes in very useful, but other times I need more functionality.

You are going to have to buy the elmscan ford enhanced package for $80, in addition to the hardware and other software. Otherwise it is just a regular OBD-2 scanner.

The software in my link is very comprehensive and will also work with extended data many other vehicles. I also know it reads GEM and ABS and misfire counts (4 ways!). If you want to buy the CAN (its a bit more$$) version it will work with 2008 cars. It is also pretty well supported, he updates every few months. I had a problem with a car and he fixed it in the next version.

They both have return policies so you can try both if you want.

Honestly, in my research nothing even comes close in functionality at that price to obd-2.com. I'm not saying its a Ford scan tool, but remember its $150. Its not fancy or pretty, very no nonsense and utilitarian. The interface does take a bit of getting used to, but it works very well.

I know some techs who use it in their service bay on a daily basis, even to supplement more expensive ones.

The other option is to search eBay for an older snap on MT-2500 with as many cartridges as you can find. Probably looking at 250-300 bucks there.

Make sure you get at least PWM + ISO. Then you can read ABS codes.
 






Thanks 96! I'll probably get the one from obd-2.com

Thanks for the reply!

ERUSH
 






Merry Christmas and Sorry about the wait

Hey everyone!

I finally had a chance to use the scanner from obd-2.com. It works great! Here are some results:

1. Pending P0174 lean (Bank 2) code.

2. The MAF is ok. The scanner didn't find any faults. The voltage and BARO are working correctly.

3. Both the long and short term fuel trims are both pinned at -100%.

4. The Misfire counter detected A TON of misfires in cylinder 4 (The low counter. I assume this counter is used at low RPMs?) and a few among cylinder 1 and 6.

Is this misfiring the culprit? I assume the oxygen sensors are detecting the unused oxygen and interpreting this as a lean condition.

What should be the next course of action? Should the plugs and wires be replaced? Is there anything else I need to look at?

Thanks again for all your input!

ERUSH
 






Some Thoughts

Ok. After a bit of thought and reading of my haynes manual, I'm going to test the following to isolate the misfiring of cylinders #1, #6, and #4:

1. Re-inspect the sparkplugs for cracks, burns, corrosion, etc. I'll try switching sparkplugs around to determine if these plugs have failed.

2. Check for continuity and proper resistance in the plug wires. I will also clean inside the boot in case corrosion is an issue.

3. Check the coil for proper resistance not only at its input connection, but also between coil pairs (1-4, 2-5, 3-6).

I'll do this tomorrow and get back to you.

Any suggestions are greatly appreciated! Thanks again!

ERUSH
 






sounds like a good list. Go ahead and check the resistance of all the plugs, maybe #4 will show tons of resistance or an open.
 






Ok. After a bit of thought and reading of my haynes manual, I'm going to test the following to isolate the misfiring of cylinders #1, #6, and #4:

1. Re-inspect the sparkplugs for cracks, burns, corrosion, etc. I'll try switching sparkplugs around to determine if these plugs have failed.

2. Check for continuity and proper resistance in the plug wires. I will also clean inside the boot in case corrosion is an issue.

3. Check the coil for proper resistance not only at its input connection, but also between coil pairs (1-4, 2-5, 3-6).

I'll do this tomorrow and get back to you.

Any suggestions are greatly appreciated! Thanks again!

ERUSH

Run a ford KOER test with your scanner. May give a clue too. I believe it is in the enhanced menu.

move around your fuel injectors too. Maybe there are issues with some.
 






Ok:

I've discovered the fault in cylinder #4: Broken Sparkplug. This is very frustrating; I didn't see any visible cracks or imperfections when I inspected them earlier, but it came out in pieces. I went ahead and replaced all the sparkplugs for good measure.

The idle is a dream and the car seems as if it finally woke up! It hasn't run this good since we bought it :D

I drove around for a while with the scanner on and monitored the fuel trims and misfire data. NO MISFIRES COUNTED ON ANY CYLINDERS!! :D On the other hand, all the fuel trim values are pinned at -100%; however, the lambda values stayed between 0.85 and 1.00, which I think is normal for city driving conditions (right?). I didn't find any faults in the injectors and the pulses were equal between both banks. The O2 sensors "seem" ok, but I'm not sure how they should behave. Any tips??

Thanks again for all your input. At least I've solved my rough idle problem, but I might have a fuel problem now since the trims haven't changed, I dunno.

Any ideas??

ERUSH
 






Here's another thought

I reset the KAM by pulling the fuse in hopes that the fuel trims would be reset. When I scanned again, all the fuel trim info was pinned at -100%. Could this mean that the computer doesn't output this particular information? There are two extended vaules that I believe imply fuel trims:

1. LERFT: Lambda Equivalence Ratio FT (Fuel Trim?)
2. AFCFT: Adaptive Fuel Corection FT (Fuel Trim?)

Are THESE the values that indicate fuel trim? The other ones don't seem to be useful, since they were pinned at -100% AFTER I reset the KAM. I'm suspicious because these values should be zeroed if the KAM was reset. Since they weren't, I assume these values are useless. Am I right?

ERUSH
 






Ok:

I've discovered the fault in cylinder #4: Broken Sparkplug. This is very frustrating; I didn't see any visible cracks or imperfections when I inspected them earlier, but it came out in pieces. I went ahead and replaced all the sparkplugs for good measure.

The idle is a dream and the car seems as if it finally woke up! It hasn't run this good since we bought it :D

I drove around for a while with the scanner on and monitored the fuel trims and misfire data. NO MISFIRES COUNTED ON ANY CYLINDERS!! :D On the other hand, all the fuel trim values are pinned at -100%; however, the lambda values stayed between 0.85 and 1.00, which I think is normal for city driving conditions (right?). I didn't find any faults in the injectors and the pulses were equal between both banks. The O2 sensors "seem" ok, but I'm not sure how they should behave. Any tips??

Thanks again for all your input. At least I've solved my rough idle problem, but I might have a fuel problem now since the trims haven't changed, I dunno.

Any ideas??

ERUSH

Reset your computer now by unplugging the battery for a few minutes. Let it forget about that bad plug :)

-100% almost seems like the scanner is reading something wrong. Are you reading this off the main OBD screen with the few parameters?

Try to plot your front 02 sensors. Give the car some gas, you should get a nice up and down waveform there (.2 to .8 V) I believe. You can search the web too for a proper 02 sensor waveform.

This is something also in the back of my head...I remember vaguely that my car chip had a comment about the 97 explorer, something with the computer having issues. I did a search and came up with this. (he had a similar problem to you too!)

http://www.explorerforum.com/forums/showthread.php?t=154736

You may have to contact the obd guy, but its seems there is no real solution.

Try reading the fuel trims from the enhanced screen where you see the misfires. I think your problem is solved, however.
 






Reset your computer now by unplugging the battery for a few minutes. Let it forget about that bad plug :)

-100% almost seems like the scanner is reading something wrong. Are you reading this off the main OBD screen with the few parameters?

Try to plot your front 02 sensors. Give the car some gas, you should get a nice up and down waveform there (.2 to .8 V) I believe. You can search the web too for a proper 02 sensor waveform.

This is something also in the back of my head...I remember vaguely that my car chip had a comment about the 97 explorer, something with the computer having issues. I did a search and came up with this. (he had a similar problem to you too!)

http://www.explorerforum.com/forums/showthread.php?t=154736

You may have to contact the obd guy, but its seems there is no real solution.

Try reading the fuel trims from the enhanced screen where you see the misfires. I think your problem is solved, however.

I can't graph any O2 sensor data. I believe its a software issue in my vehicle, based on your link. I'll monitor my fuel economy and see if it changes.

Thanks again for everyone's input. I can't believe the ultimate issue was a dumb sparkplug. There must have been a hairline crack or something in the #4 plug that went unnoticed until it finally came apart. I'll let you all know if my fuel economy improves or stays the same (~13-14 mpg highway).

Again, THANKS!! :salute:

Best,

ERUSH
 






I can't graph any O2 sensor data. I believe its a software issue in my vehicle, based on your link. I'll monitor my fuel economy and see if it changes.

Thanks again for everyone's input. I can't believe the ultimate issue was a dumb sparkplug. There must have been a hairline crack or something in the #4 plug that went unnoticed until it finally came apart. I'll let you all know if my fuel economy improves or stays the same (~13-14 mpg highway).

Again, THANKS!! :salute:

Best,

ERUSH

What kind of plugs did you have before, and what did you replace with?
Also was the rough idle happening all the time or just when cold,hot?
I'm trying to track down an idle problem with my 99 SOHC when the truck is warm. I think the culprit might be the Autolite plugs I put in a year ago. From day one I noticed the idle "different" and it got progressively worse to the point that when sitting at a light the truck vibrates.
 






Hey, Mike!

I had Bosch plugs in before. As many of us around this forum have noticed, Bosch plugs do not play well with Ford ignition systems. I highly recommend not using their spark plugs in any Ford motor.

I replaced all of my sparkplugs and plugwires (for good measure) with Motorcraft products. This has solved my idle and poor mileage issues. Autolite plugs are essentially Motorcraft ones. If I remember correctly, Motorcraft and Autolite plugs are manufactured by the same company, but they are NOT identical. I haven't heard of any issues with Autolite plugs, but i wouldn't rule out your ignition system as a possible culprit to your idle issues. Do you have any other symptoms? Poor mileage, "skipping", no/low power? Codes?

As you have probably seen around this forum, rough idles are difficult to solve because of the array of essentials needed for proper combustion (i.e., air, fuel, spark, compression, etc.) If any of these components aren't working properly, your idle (among other symptoms) will be horrible.

Unless you have a scanner or have access to live PCM data, I would go through each combustion component category and narrow it down (for the "air" side, check your filter, MAF sensor, check for vaccum leaks, etc.; then for "fuel", check your rail pressure, filter, clean the injetors, etc.; etc.). As I've experienced, this "trial-and-error" process is long, slow, and can easily become frustrating. Unless your certain about the cause, cave in and pay for a proper diagnosis or buy a capable scanner. It is well worth the time and headache saved.

That's my two cents.

ERUSH
 






Hey, Mike!

I had Bosch plugs in before. As many of us around this forum have noticed, Bosch plugs do not play well with Ford ignition systems. I highly recommend not using their spark plugs in any Ford motor.

I replaced all of my sparkplugs and plugwires (for good measure) with Motorcraft products. This has solved my idle and poor mileage issues. Autolite plugs are essentially Motorcraft ones. If I remember correctly, Motorcraft and Autolite plugs are manufactured by the same company, but they are NOT identical. I haven't heard of any issues with Autolite plugs, but i wouldn't rule out your ignition system as a possible culprit to your idle issues. Do you have any other symptoms? Poor mileage, "skipping", no/low power? Codes?

As you have probably seen around this forum, rough idles are difficult to solve because of the array of essentials needed for proper combustion (i.e., air, fuel, spark, compression, etc.) If any of these components aren't working properly, your idle (among other symptoms) will be horrible.

Unless you have a scanner or have access to live PCM data, I would go through each combustion component category and narrow it down (for the "air" side, check your filter, MAF sensor, check for vaccum leaks, etc.; then for "fuel", check your rail pressure, filter, clean the injetors, etc.; etc.). As I've experienced, this "trial-and-error" process is long, slow, and can easily become frustrating. Unless your certain about the cause, cave in and pay for a proper diagnosis or buy a capable scanner. It is well worth the time and headache saved.

That's my two cents.

ERUSH

It's only when it's warm and at a light I get the "vibrating" idle. Other than that it's flawless. No CEL comes on. I am going to try the Motorcraft plugs when the weather gets warmer.
 



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Mike,

Just a word of caution: I wouldn't blindly replace things without being absolutely sure. Based on your description, I would first check the "air" side of things (air filter, MAF, IAC, vacuum leaks, etc.). These things are easy to get to and relatively cheap to clean/replace. In my experience, bad sparkplugs will cause driveability issues along with a rough idle, too (low/no power, skipping, etc.). I haven't heard of spark plugs only causing rough idles and nothing else (I could be wrong here, at least it hasn't happened to me).

A word on CELs: Even though the CEL is not lit, your PCM may have codes "pending" (that is, your computer isn't sure if the issue is a constant problem). If a code is "pending" for some time, your CEL will come on. I would stop by your local auto store and borrow their handheld scanner to see if anything is pending.

Good Luck!

ERUSH
 






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