HELP! Explorer rough idle, can't figure it out!

Please help if you can. I have a 1997 Explorer Sport 4.0 SOHC, 110,000 miles. When I start it in the morning or after sitting for a few hours, the idle is very rough. Most of the time it wont even stay running. My first thought was a vacuum leak. I found four leaks and repaired them, including the EGR valve control and the EGR solenoid. One stem on each was broken off. I bought these parts from the dealer and then tested the vacuum, which I now have vacuum pressure. The check engine light is on and doesnt read the "system evap emission control pressure sensor low" (vacuum leak) anymore, but it now reads "system too lean (bank 1) and system too lean (bank 2). I cleaned the IAC valve and have ran several bottles of injector cleaner through. My mechanic thinks it is the IAC, but when you disconnect the plug on it, the car will barely idle, so it must be working at least a little. I have seen suggestions for a fuel filter, which I am going to replace, but I am really lost here. Please help!

Cleaning the iac valve might not work.
The valve might be shot.
$50 at NAPA.

po171/174 usually indicates another vacuum leak on the explorers. The black plastic intake on those has o-rings which are real bad about leaking. They're not hard to replace if you know what you're doing and they make all the difference in the world.

Bank 1 and bank 2 are your O2 sensors. You will not get an engine light for the IAC valve. The PCM has no way of knowing whether or not the IAC is working. I can't remember which O2 sensors are which. I've changed one so far. My vehicle has 5 O2's. I'm not sure about yours. Auto Zone will usually hook up and get error codes and tell you which ones you need to change. I've been told you can clean them but I never had oppurtunity to try that yet.

I think that mine has 3 o2 sensors, 1 downstream and 2 upstream. Would this be a good place to start, by replacing them? I have also heard about the intake gaskets leaking too. Can o2 sensors cause a rough idle? Thanks for all of your responses.

I have a 99, and have the same prob. Idles rough until it reaches operating temp. I replaced the fuel filter, and the MAF ($$$$), but my check engine light still keeps coming on. I rented and OBD II from Auto Zone and the codes say Bank 1 and 2 too lean, and random multiple misfire detected. Have you tried the spark plugs or wires yet? I was thinking about that next.

Another mechanic looked at my X and said that it was running too hot because it was actually lean, not just a sensor bad. He said that he was 95% sure that the fuel injectors were clogged. That is my next step. I will let you know how it goes. If anyone has any other ideas, let me know. Thanks.

I have a 2000 explorer 4.0 SOHC w/ 61,000 miles on it. I have the exact same problem in the morning only without the check engine light. Once the vehicle warms up to operating temps its fine. I took it to a shop twice now and i had the IAC replaced. I still have the same problem i did before. When i turn it on it revs high for a second like its warming itself up and then dies almost immediatly, or it putters for 5 - 10 seconds and dies right after. I can not understand what the problem is with this, i have to take it back to the shop thursday 2/3 for them to look at again. If anyone hears any new info on this i would gladly appreciate if they could post it or better yet email me (Newzze913@hotmail.com) and if i find out what the problem is i will def post it.

Please, let me know! I havent checked my injectors yet, but I find it hard to believe that we all have clogged injectors. I need to figure this out soon. Any help is appreciated.

as a tech myself, i would have to check for vacuum leaks especially considering the trouble codes you have (Banks 1 and 2 lean), you can do this by spraying 2+2(gum cutter) around the intake manifold and everywhere vacuum is present, you will have to do this when the concern is present(on cold engine) since the leak sounds as though its going away when warm, you will notice a difference in engine speed if a leak is present, i would have to suspect intake manifold gaskets(always replace upper and lower on sohc engine)

I used starter fluid to check for vacuum leaks. That's how I found 4 of them. I used a computer to test for vacuum and it showed that I had vacuum pressure. Is it possible that I still have vacuum leaks?

I believe he did check for vacuum leaks this first time i took it up there, i know he said he cleaned the throttle body, there was a good amount of gunk in there. I would assume he checked for leaks when he did this? Maybe he did not. I'll find out friday some more information as i have to leave it overnight thurs into friday bc it has to be a cold start for the problem to occur. It really is becoming a pain the but, i have looked all over the internet and everyone seems to be hooked on the IAC theory. That is not the problem as i had it replaced last friday, and it still continues to give me problems in the morning

I have a 01 sport and I have a rough idle...Its caused by a old & minorly clogged fuel filter.
You said you have 110,000 miles Brian,
Its time for a new fuel filter as well as mine. I have 120,000 on my 01.

also you said you have a vacuum leak. a vacuum leak will cause a lean mix. also check your pcv valve I beleive there cheap but I've never bought one before,. check for any loose ground wires and electical wires. gl

Changed my fuel filter today and I still have the same problem. So much for the cheap fix. Next is the injectors and maybe the intake gaskets. Any more suggestions would be helpful.

Changed my fuel filter today and I still have the same problem. So much for the cheap fix. Next is the injectors and maybe the intake gaskets. Any more suggestions would be helpful.
as i stated before, i would replace upper and lower intake gaskets, a cheap and relatively easy repair, much cheaper than replacing all injectors, and ive never seen an injector problem that would only show its face when cold and go away, most of the time they also cause other concerns such as misfiring and running rough all the time, but its your money not mine

down at the shop they changed my fuel filter, and cleaned the injectors. I started it today and it still idled somewhat roughly but it didnt stall or come nearly as close to stalling as it was before. Im going to take it back AGAIN (cause its warrentied thank god) and see what else can be done ill post my findings when i find out

Will bad gaskets cause an MIL code "system too lean, bank 1 and 2?" If thats what it takes, I'll do it. What do I need to know? You say that its easy. Do you have some instructions? I'm not a mechanic, but I'm not scared to try it myself. Thanks for your help.

Will bad gaskets cause an MIL code "system too lean, bank 1 and 2?" If thats what it takes, I'll do it. What do I need to know? You say that its easy. Do you have some instructions? I'm not a mechanic, but I'm not scared to try it myself. Thanks for your help.
yes, it will cause both banks to be lean, and theres nothing special to know about pulling it apart, just try to do it in the same day so you can remember where everything goes back in

I had my o-rings and intake gaskets replaced and my Explorer has never run or idled better than it is now. If you have a cold rough idle, this may be your problem. I Should have done this first. But now after 3 days, my check engine light is back on. I haven't run the codes yet, but that's not what bothered me in the first place. I just wanted it to stay running in the morning. Thanks for all of your help.

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INTAKE GASKETS WILL FIX THIS PROBLEM
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I have spent three (three) months attempting to cure this same problem. Trusted and competent mechanics couldn't until I (yeah, I'm laughing too) called a local radio show and asked for help.

IAC replacement, EGR was tested, Injector Cleaner out the ying yang, fuel and PCV filters...and it was the UPPER AND LOWER INTAKE GASEKTS that needed replacement. $12.99 at O'Reillys, heh.

The cost of what it took to replace them in my garage? Two years off my life and half my hair...but worth it. It was the only problem with an otherwise amazing truck.

Oh...and my gas mileage went up 2 MPG since the fix.


Email one and all with this, for those with 2001's with crappy morning idle's and otherwise smooth warm-engine running.

I had the opposite problem: rough idle when the engine got warm. No check engine light. I cleaned the IAC and the MAF, checked for leaks etc, but no success. I read somewhere on the net that if you disconnect the battery over night the computer will loose all reference values from various sensors and needs to be re-trained.
I tried that and it works after that!
Might be worth a try for your problems as well?

Martin/

Re-trainingis preformed simply by driving it for a while, by the way. Martin/

i have the damn problem on my 99 explorer v6 sohc. everytime i start it in the morning and if its been sitting for hours. its starts fine but then it starts to shake like its about to stall and if i dont rev the gas it sometimes stalls. is this a cold start idle problem? iac or intake gaskets?????

When it comes down to the top ten things that can go wrong on a sock (I'm sure FordTech4U would agree with me on this!) intake O-rings are right up there with the apalling cam-drive cassete issues! While I put in my time as a FoMoCo tech I lost count of how many manifolds I've resealed before the TSBs reccommending them joined the many camdrive recalls already on my plate! (Just wait till I find the nerd that thought it looked good on paper :chair: :nutkick: :twak: ) (Getting back on the subject of vaccuum leaks.) The EGR transition bell O-ring on the Sohc and OHV 4.0s with plastic intakes also have a nasty tendency to leak the "suck"! :2cents: :grinno:

And yes, I was surprised to see it was 'plastic'. And the condition of the inside of that plastic manifold? Angels Cried. That's all I'm saying...but check the first date of posts by me to this one--it's still running tip-top.

-CWJ
Chattanooga, TN

I've got a 98 sport that has a bit of a rough idle. No stalling yet but its all the time, not just cold start. I'm about to change the plugs and wires and possibly the fuel filter since it needs it anyway probably. My question is the gas addetive you can buy to stop rough idleing and such, are they worth it? Does anyone use a particular one that they found really works?

Rough Idle at Start Up - Recall Repair 0012MC
My dealer did the recall repair for 0012MC which calls for replacing tensioners and low intake manifold gasket. This fixed the problem (the rough idle was caused by a leaking gasket...the tensioner was a side item to replaced under the same recall).

Was getting a lean engine code and after replacing the O2 sensors it still didn't fix it The recall is over now, but replacing the lower intake gasket fixed this problem for me.
-b

Fordtech4U is right - maybe his handle has something to do with it..... justa thought.

For those that have a 98 4.0 SOHC there are 2 upstream and 2 down stream O2 sensors.

I have a 1998 Sport 4.0 SOHC I purchased at an auction for $2400.00, the CEL was on when I bought it. $2400.00 no body damage or major issues, I can deal with the CEL...

I have experienced all of the issues listed in this thread. Now at 147,000 miles I have a constant CEL on situation and am comfortabler in knowing what the issue is, and probably was all along.

The first time I had it checked out the right side downstream O2 sensor was replaced. CEL came on with in 100 miles. Next time I had it checked I was told that the left side may have gone out due to the right side being replaced. Um, yeah...a good one took out another? Doubtful, but, ok replaced the right side. CEL on within 100 miles. Solution-found a new shop.

I took the Ex to a Ford stealership against all previous experience. Had them do diag on it. O2's all good, possible manifold o-ring leaks. $15.00 in parts and 3 hours in the driveway at home, I have new intake o-rings and no CEL. Good to go for about 8 months.

Three weeks ago CEL comes on. I also notice that gas mileage went from about 280-300 miles a tank full down to about 240-260 miles. I took the Ex back to the dealer and had the codes read. My cats are bad. While I do not wish to deplete the ozone layer and all, $2400.00 for the vehicle and $1390.00 for cats.....I think I'll drive less and leave it parked on ozone action days.......A test pipe might be an option, but I don't want people to think I an an environment hater, you know?

So all in all, my experience tells me, get the car diag'ed at a dealership, they know it better than anyone else does. Diag is an hour's worth of labor in most cases, say $65.00 - $125.00 in some places, for me, here in the motorcity it cost me $95.00.

Something tells me that Fordtech4U knows what he is talking about and if he reccomends you look at something in particular...well, that might be a really good place to start...

out...

Take a look at the rubber hose connected to the PCV and the rubber grommet that the PCV sits in. If the hose is old and soft, it will collapse under load, which won't allow the valve to work. If the hose is cracked, it will leak. A friend of mine with a '95 Navigator (150,000 miles) had a problem with a rough idle, typically at stop lights, and had all of the things you have described replaced/repaired before a mechanic found that the hose to the PCV was collapsing.

I know this is an old topic but I have the same problem. Rough idle,Stalling and won't stay running when cold. I installed a new IAC valve cleaned the mass air flow and put new plugs and wires plus a fuel filter a while back. Check engine light is on and came up with bank1 and bank2 on the test. Just wondering if i have the problem with my intake gaskets? To the ones who did do the Intake gaskets did this fix the problem and was it a hard project to do? Thanks for any input.

Ford has a TSB that deals with a rough Idle condition which involves reflashing the PCM.

OK, guys. My 1997 Sport has 174K miles on it and has been running a bit rough for the last 30K miles, But a few weeks ago during a road trip he started running noticeably rougher. It progressively got worse and now its not drivable. In the last year I have replaced the crankshaft and throttle positions sensors, the thermostat, starter and solenoid. I took it to a shop where he mechanic said no codes came up on the reader . After reading this blog I ran it for a while and sprayed carb cleaner around the vac lines with no change in idle. When I removed various vac hoses there was no change in the motor. I'm guessing that means there is a vacuum leak I couldn't detect with the first test. I decided i should clean the throttle body and it was such a mess that I continued on to at least get the upper manifold gasket replaced. Wow, what a trip! So many devices, each with its different connectors and quirks.

I finally got almost everything off the upper manifold, but I cant get the EGR tube out of the manifold. How does it come apart? Is the voltage regulator supposed to come off with the upper manifold? Should I drain the coolant before I get to the lower manifold? There is much talk about o-rings. Where are those located and should I replace them all? My manual doesn't bother telling me how to disconnect the various connectors! :confused: I dint want to quit before I replace the lower gasket. Are there any other obstacles I'll be running up against that your experience and wisdom can foresee? Any guidance would be greatly appreciated.

hi
1-check the ignition coil(distributer).if o.k
2-your engine vaulves stucked,you should open engine check core and change the vaulves.
good luck
omar,ford lover

I certainly wouldn't jump to stuck/bad valves based on the symptoms. Definitely before tearing in to the engine, check the compression on the cylinders to see if there is on that is noticeably lower. If there is a problem with the valves it would shop up as a compression issue.

-Rod

i have done the following:

1. cleaned IAC
2. new plugs and wire
3. replaced 4 o2 sensors..chek engine lite was on
4. injector flush
5. cheked fuel pressure

and in the process of this my mechanic says that engine' runs cool' and wants to replace thermostat

thing is the problem i took it to him for was not resolved. it still idles rough before warmup and sometimes idles down to stall. it also sometimes has to be started twice.

is the 'cool' running engine the culprit?

i don't know...but he didn't fix it. and i am talking about a grand here.

is there something fundamental to this ford 4 l OHC engine that we don't know about?

Welcome to the forum!

What model year is your V6 Explorer? What diagnostic codes did it have that lead to the replacement of the 4 oxygen sensors? Did that cause the CEL to go out?

Depending on the particular 4.0L engine and model year, intake manifold gaskets and PCV elbow are known sources of vacuum leaks that can cause rough idle. Likewise, DPFE sensors have been known to cause issues as well.

-Rod

gents ...bear with as i describe my problem...if we solve mine i think we solve everyone's

99 ford x 4l -6cyl SOHC with 164k miles

over past year the problem of starting and rough idle developed. i would occaisonally have to start the car twice as it wouldn't catch first try. this was intermitent. as time progressed it got to where this was the case every time. in addition once it started it surged at idle and died out. other than that it never ran poorly. about 6 months ago, recognizing a problem i did the IAC/MAF cleaning . it did nothing. over the the last 6 months problem progressed to nearly never starting first crank, surging at idle and dying. if i applied gas on cranking this would not happen. aslo in last 3 months CEL came on and stayed on.

so this last week i took it in and had the mechanic guy do the following:

chek any exhaust leak...none detected
chek fuel pump pressure......fine
complete tune up.......
new fuel filter
all new 02 sensors. there are 4.
fuel injector flush.
cheked vacum leaks....he didn't say

he said the engine ran 'cool' and wanted to replace thermostat. i held off on that


results
CEL off
starting....while regularity of problem has abated, that is, mostly it starts first time, about 15% of time it does not. it still surges but doesn't die after surge. nearly but not all the way to stalling.

in other words all the repairs seemed to only have only partially fixed the problem.

i have had these problems last week when temps around here were in 7-0's and 80's , for those of you thinking about the gasket warm up/seating issue. i love the idea but would ambient temps render moot that problem? or maybe ambient temperture not significant influence on gasket performance.

so i tried all the fixes described in this thread except gaskets.
where do we go from here?

I know an old topic, but I think I have figured out my problem after literally MONTHS of monkeying around.

There were two holes, yes holes about the size of dimes in the intake manifold.

Truck died and lots of stuff looked at, and it was finally found. Replaced that and she is running pretty good now. Maybe check that... maybe you are just at the 'crack' phase now... you don't want to get to where I was at. :nono:

We think it started off as a small 'crack' and after a cat converter went bad, replacement, and then another cat going bad and car losing total power, this was found out... previous to this replaced vac hoses, egr's, O2 sensors, on and on....

I have 2003 Explorer XLT, 97,500 miles 4.0 V6
Good luck

After reading through these posts I figured my problem is similar. Rough idle when cold and gets better as it warms up, first start rpms up high then back down to stalling. Using starter fluid found a subtle vacuum leak in lower manifold gasket area. All the orings were pretty flattened out. Replaced and BAM problem gone completely!

I've had the same problem with my 97 4.0 L V6 EFI that's grown worse and worse over the last year. Now just this afternoon my truck won't start. It turns over idles rough and dies. Same codes P0171/P0174. It seems like the most consistent fix is the o-rings on the plastic intake or the upper and lower gaskets on the intake manifold. Any suggestions? Can this be fixed at home?

I've had the same problem with my 97 4.0 L V6 EFI that's grown worse and worse over the last year. Now just this afternoon my truck won't start. It turns over idles rough and dies. Same codes P0171/P0174. It seems like the most consistent fix is the o-rings on the plastic intake or the upper and lower gaskets on the intake manifold. Any suggestions? Can this be fixed at home?


During idle, spray the manifold area with starter fluid or some other really volatile spray. If the idle changes (better or worse) consistently if you spray in one spot, there's a vacuum leak. The intake manifold gaskets, both upper and lower, get flat over time. I paid about 5$ for the starter fluid and $10 for a gasket (upper and lower)set. Fixed my idle problem right away. Easy garage job took about an hour.

my 97 5.0 has rough idle; changed plugs; wires; cleaned throttle body; cleaned mass air flow sensor........Code said EGR Valve but there isn't any vacuum at EGR Valve so i was told it was ok........ help

What was the specific code number?

-Rod

they didn't give me a code # just said also number 7 cylinder

Did changing the spark plugs and spark plug wires improve the way the engine runs? Do you have a parts store in your area? If so, many of them offer a service to connect the diagnostic tool to your vehicle and read active diagnostic codes as no charge. You want to get the actual code number though versus the salesperson's interpretation of the diagnostic code. There's no such thing as a code that says the EGR sensor is bad, only codes that indicate an issue has been identified in that system. The EGR may be the issue, but not necessarily.

On many older Fords issues with the Differential Pressure Feedback EGR (DPFE) sensor would cause rough idle, lack of power, and even stalling.

-Rod

i don't believe it is the DPFE because i have no stalling at all; just rough idle; kick it down and power is there.... and i cleaned the MAF Sensor but no different; i un-plugged the MAF Sensor while idling and there was no change in idle at all; i think there should have been if that Sensor worked correct? i un plugged the IAC Valve while idling and it stalled so i know it's working.......... :runaround:

Your best bet would be to find a scan tool with a datastream mode, check the diagnostic code and monitor the related parameters to see if some sensor is not providing appropriate information to the PCM, then diagnose from there.

Not noticing a change when unplugging the MAF doesn't necessarily mean that sensor is not working. It might just mean you have a big enough vacuum leak that taking that sensor open circuit doesn't effect the way the engine idles.

-Rod

Usually if the MAF is bad the vehicle will run better with it unplugged.

ok the code # that came up on my 97 explorer 5.0 is PO 401 and a 307? any help?

From the factory service manual:

Diagnostic Trouble Code (DTC) P0401 indicates that self-test has detected insufficient EGR flow.
Possible causes:


Disconnected or damaged vacuum hoses.
Damaged EGR valve.
Damaged EGR Valve Position sensor.
Damaged EGR Vacuum Regulator solenoid.

P0401 is a pretty common code. I'd suggest you search this forum for P0401 (note those are both 'zeros') to see what typical issues others have found.

P0307 is a misfire code for cylinder #7. There's a good chance that this is the code causing the engine to run roughly. I'd suggest you try swapping the spark plug with one cylinder and the plug wire with another to see if the misfire follows the plug, the wire, or remains on cylinder #7. Depending on what you find there should help lead you down the path to getting the misfire solved.

-Rod

wires and plugs are all new; took plugs out and made sure they were properly gapped and had no cracks............ thinking it mat be the coil packs.

Are you absolutely certain that the plug wires are fully seated? Did you install the least expensive plug wires available? I've no kidding seen cheap plug wires that were never even stripped before the terminals were installed. It really won't be too difficult to swap a couple of spark plugs and wires around to help you determine if the plug or wire is the issue. Since one coil pack feeds two cylinders it would be unusual for a bad coil to cause a misfire on only one cylinder.

-Rod

wires were checked numerous times and they are all seated; wires are regular Ford Motorcraft wires; Coil packs are the original from 97; have no choice their already ordered........

How can 1 coil pack feed 2 cylinders? i have a 5.0 V-8 each coil pack has 4 plug ins i have 2 coil packs; each plug in represents 1 cylinder.......:runaround:

Each "plug" on the coil pack represents 1 cylinder, but there is 1 coil for every 2 cylinders. It's a waste spark system. You might check out this link (https://en.wikipedia.org/wiki/Wasted_spark) if you're interested in understanding how the system works.

-Rod

finally found out it was only 1 Bad plug; even tho they were new plugs; put an old plug in that i had and nooo rough idle............

Glad to hear you found the issue. Thank you for following up on your post!

-Rod

I have 2001 ford explorer sport trac. I had the rough idle problem. I replaced IAC,tps, o2 sensors, intake gaskets, and the hose in the back. So I had replaced the maf sensor. I bought an aftermarket one. The truck still ran like shit. I was baffled that wtf could it be. So I took unplugged the maf sensor and it didn't die. As soon as I plugged it back in it would automatically die. The maf sensor was reading to much air and not enough fuel. The MAF HAS TO Be OEM. That was the dreaming problem.

I know this is an old thread but I can't help but comment on this.

There seem to be two types of mechanics I am seeing here.

1 - Parts changer - Take everything said on any forum as the gospel and start changing parts, hoping that one will fix the issue. This is wasteful the and expensive route. Sure you may get lucky, but most likely you will spend needless time and money. I.E. (It's your valves = engine tear down).:banghead:

2 - Diagnostitian - This person listens to the forum members that make sense and explain what and why they think the issue is. Now they can be incorrect as they don't have the car in front of them, but this is a good place to begin your own diagnosis.

Did you get that, begin your own diagnosis. Spend some time studying the theory of modern vehicles and apply your knowledge. Just because one person had a problem and they fixed it with a part has nothing to do with your vehicle. Use a systematic approach and rule out the systems and parts that others just change based on a generic code. Lend more credence to those that obviously have experience (I.E. Ford techs) than you do to the 16 year old repeating what his sisters boyfriend told him.

Enough of a rant. It's your car, your time and your money so you choose how to spend it. Me I have been able to fix every problem that I have had on every vehicle I have owned. During that process I have learned a great many things and solved a great many issues at minimal cost.

In the end I just hope a few people heed my advice and avoid being a parts changer. Save your money and expand your mind, it's very satisfying to problem solve and correct any issue and save thousands.

TTFN

bank 1 and two codes on domestic vehicles usually calls for cleaning/replacement of MAF... Try using Mass air flow cleaner first.... Unplug the maf and see if the car runs better. Same with the IAC, If you unplug it and the car runs better that part needs to be replaced. The car should stall if unplugged.