rough idle

[murrajm5]

I had posted this before but I want to start anew. I have replaced the FPR, spark plugs and wires, cleaned the MAS, IAC, used GM top engine cleaner, and just last evening tightened the intake manifold bolts. After all of this, I still have a rough idle. I also have checked the vacuum lines and they seem fine. Anyone have any other ideas? Thanks.

 

[Alec]

I had a rough idle too, after I installed my throttle body. It turns out I didn't give the computer enough time to reset.

Try Disconnecting the negative battery lead for about 20 minutes. Then reconnect it and let the truck idle for 5-10 minutes (to be safe), with ALL accessories OFF!! <This is important. This should help after you did that maintenance.

Good luck!

 

[murrajm5]

I forgot to mention that I had done that also. I bought a code scanner from Walmart and nothing showed. I also removed the ignition module behind the passenger headlight and took it to Autozone because they said they could check it but they didn't have a connector for it. I also replaced the air charge temperature and coolant temperature sensors. It seems to run okay except at stoplights, in park, etc. The throttle position sensor was checked by a Ford mechanic with a voltmeter and no jumps. Maybe I should just forget about it and accept the fact that it does it but it irritates me.

 

[akchuck]

I own a 93 Explorer with the same problem. I recently bought it and right away noticed the rough idle. I changed the plugs, plug wires, cleaned the MAF sensor (wasn't dirty), have run two cans of injector cleaner through the engine, had a computer diagnostic run and they found no codes (my check engine light is NOT on), tightened the intake manifold bolts, changed the air filter. A mechanic recommended I have the injectors professionally cleaned. The idle is pretty rough but not at first when the engine is first started and idleing a little higher. It is fairly smooth then. But when the engine is good and warm the engine shakes and you can definitely hear the roughness at the tailpipe. I have also noticed recently that while acclerating the engine rpm will surge a little then decrease then surge then decrease etc.... The surging isn't much but is noticable. If anyone has any experience with this please give us rough idlers an idea!! Thinking maybe the Fuel Pressure Regulator????

 

[Chav]

Same exact problem. I have a 93 4 door XLT OHV with 75,000 miles. This is what I have done to my engine so far and I didnt do these things just becauses of the rough Idle usually there was another reason such as bad gas mileage or check engine light. All this has been done within the last 20,000 miles.

Resurfaced heads
Replaced Head Gaskets, Intake gaskets, + valve cover gaskets
Replaced lower intake gasket again with an updated version
Replaced all Injectors and FPR
New Fuel filter
New Idle air control valve
New 02s
Checked all Vacumm Lines (its not a vacum problem)
Compression checked and all read within 190-205psi
New Bosh +4s with premium Bosh Wires
New k&n air filter
New Belt

There is probably more that I'm forgetting, but this is really starting to piss me off that this rough idle hasnt been solved with all this stuff being replaced. I pretty much give up and live with it. It is an inconsistent shake though. Like it will be smooth for one sec then shake a couple times then steady. If it was a clogged Injector or a bad cylinder ring I would think that it would shake consistantly when ever that piston fired. U know? OK u know what to hell with this engine! It has gotta be cursed it is time to find a 5.0 outta a new explorer and make it mine.

Later,
Chav

 

[DrewP]

Try Fuel Pressure Regulator

Yes, definitely check out your fuel pressure by either hooking up a pressure gauge or just by replacing the regulator. They do fail and when they do the pressure gets too high and will cause your idle to vary and run rough.

Good Luck!

 

[murrajm5]

I tightened the intake manifold bolts this last weekend and it did not seem to help any. I do notice that it seems worse when I am parked or stopped facing downhill. Could it be the fuel pump even though the pressure checked out okay?

 

[Matt193]

akchuck,


I am having the same exact problem as you- rough idle and surging under acceleration. So, at least now I know I'm not alone. Let me know if you find out the problem.

Thanks!

Matt

 

[MikeP]

What about the PCM or "Powertrain Control Module" which has the computer that takes the sensor data and controls various engine functions? My 91 XLT 4x4 has similar "sickly" symptoms develop while I was working with a group of engine mechanic types and they first suggested clogged fuel filter, sick fuel pump, and went through a long list of possibilities. It turned out to be a "fried" computer module and I do not recall if this showed up on the code scanner (this was about 6 years ago). Had a new PCM installed and this fixed the rough idle, etc. Lastly, you might consider looking at the Ford Technical Service Bulletins for your model year at Dead Link Removed
Many problems and Ford's recommended fixes are presented in these TSBs. Good luck! Mike in Seattle

 

[Josh Adams]

I had a similar problem and it ended up being the MAS. It
didn't show up on the computer, so the mechanic said the only thing he couldn't check and he assured me that it was
the MAS. It was making it run lean and over heat a little. I went straight to the parts store and changed it in for a brand new. Didn't clean, because the little computer chip or whatever that plug is on the top of it, was probably bad. So off with the old and on with the new, and it ran like a new truck, and it seemed to pick up the power I had lost.

 

[akchuck]

Chav,

I forgot to mention that I have the same symptom of running smooth for a second or two then sputtering a couple of seconds. No real pattern to it but it does seem to be intermittent. Will replace the fuel filter this week and check the fuel pressure.

 

[Chav]

Yeah it seems that the inconsitent sputter is common. I hooked up a vacuum gauge today and it swayed about 1 inch and that is ok i guess. So I will live with it. I'm wondering if maybe it is the MAS because that is about the only thing I havent checked or replaced.

-Chav

 

[roadkill]

ruff idol!

Well, I went around with this prob last year; $60 @ mobil garage, $60 @ ford mech.... Frod thru in a thermostat, engine READ low temp. Temp read same. Turns out my sensor was out. The idle runs better, but I've found out from nay mechanics that the 4.0 V6 is a ruff rider, no if, ands or butts!

Let me know if the secret is ever found out!

Will a super chip idle better?

 

[Stephen S]

I've got a 95 and I am trying to diagnose a rough idle problem. It just started a few days ago. Cold or hot, if it sits idling, in gear or in park, the engine will run rough. I changed the plugs and wires about a year ago, put in a K&N air filter and cleaned the MAS about 2 months ago. I read this thread and searched but couldn't find any vacuum leaks, and the intake bolts are tight. I also tried disconnecting the battery to reset the computer; no help. The truck was running great, then just a few days ago, I crank it up and it idled really low, much lower than normal. When I rev it, it smooths out and goes, no problem. I also notice that if I'm in park and I rev the engine to any RPM (say 2500 for example) and hold it there the engine will hunt. It'll hunt between about 2400 and 2600, in a regular pattern. UP/DOWN/UP/DOWN steadily. No check engine light and no codes from my scanner. I figure it has to be a sensor or something that has gone bad, but how do you diagnose it when no codes come up and no check engine light??? Maybe O2 sensor, fuel pressure reg, idle air control valve or sensor...etc.
Have any of you fixed your problems??

 

[MikeP]

As it idles rough when cold and when the engine is cold the air/fuel mixture is rich, this implies the engine should be receiving plenty of fuel - "in theory" when cold. When was the last time you had the fuel injectors cleaned? One partially plugged fuel injector will screw up that cylinder. I use fuel injector cleaner (Red Line) additive to gasoline and have the injectors cleaned by that flush method (while still installed) maybe every 1.5 years. Keep us informed on what you find! Good luck.
Mike in Seattle 91 XLT 4x4

 

[HUNTERS]

rough idle corrected

I just had that problem fixed after it was at the Ford dealer for the third time. Originally they thought it needed new plugs and wires, which it did. But, that didn't correct the problem. I found out that the person who installed my new shocks didn't reconnect the line going to the charcoal filter in the back, which collects the fumes from the gas tank. After they spent a couple of hours cleaning out the charcoal filter and reattaching the line, it now runs like a charm. So, I would have the charcoal filter checked out. ( Sorry, I don't know the real name for the filter.)

 

[dpodborn]

idle problem 1994 ford explorer

i have the same problem as everyone else. Bad idle. Sometimes enough to almost kill the engine. I have read somewher else the it could be the MAF(Mass Air Flow Sensor).
You dont really need to replace it, just clean it. With your engine cool, You need to remove the interior sensor wire, you will need a security star(Size T15 or T20). Remove the 2 screws and carefully remove the sensor. You will see 2 sensor filaments(Like in a light bulb). Carefully clean them with an O2 carb cleaner, like gumout. Let it gry thoroughly. While it is drying carefully wipe any dust off the aluminum mount surface of the MAF body.(do not get dust in the mount hole). Then put back together
Hope this helps some of you!!

 

[kb5zcs1]

OK i have had this problem also,i have a 1991 and found that the O2 sensor was dirty take it off and clean the itp of it,the part that go's in side the pipe if its black it's pretty bad put back in and try it out, if that don't work go and buy a new one,it helped me don't rub it to hard on tip,a dirty O2 sensor will also cause bad gas mileage,it makes the motor burn rich.also check your fuel Reg.if this is bad it will also cause the motor to burn rich to,at the same time this will also make the 02 bad and cause the hole thing to burn rich.Hope this will help...................

 

[Duke727]

Check this out
I had a simmilar rough idle with my explorer. I had a shop run it for codes. The the coolant temp. sensor and o2 sensors came up bad. I went and changed the sender. The plugs were fouled and the fuel filter was cloged, I changed them as well. Now in the process of doing these repaires I also noticed that the air duct from the MAS to the trottle body was cracked. This ment that the singnal that the MAS was sending to the computer was way off in comarison to to the air the trottle body was actually getting. I have it taped up right now in the truck is running better than ever. I had the shop run it for codes again and it came up clear. This may be something to look into. good luck!

 

[bentley]

I had the same problem this past summer with my 98 sport. First i took it to a corner garage and they told me the oil from the K&N filter clogged up the mas air flow sensor. After replacing it the problem was still there. I then took it to the dealer and they replaced the lower and upper intake manifold gaskets. Cost me 300 bucks and the problem was fixed. 2 weeks later i got my money back after ford announced the extended warranty on them. hope this helps