2001 Explorer V6 SOHC rough idle driving me crazy!

[mattcc88]

Hey guys,

I have a 2001 Explorer Sport (V6 4L SOHC) that has a rough idle that has been driving me insane.

Problem: When stated after sitting all night, the car starts and runs fine whether it is hot or cold outside (same winter or summer). After the choke comes off, the engine immediately begins missing/ rough idle and will miss under a load. Once the temp makes it up to running temp (never overheats) the engine has a slight miss at idle and possibly a lack of power, but no where near as bad as the the transition from turning the choke off until it makes it to running temp.

Engine Codes: The local part store engine codes that turn up from the engine light are P0135 (O2 sensor heater bank 1 sensor 1) and P1131 (lack of bank 1 02/ bank 1 O2 at lean limit).
-I replaced the bad O2 about 2 years ago, after 1 day, the codes showed up again, never affected the engine miss.

Thieving Ford dealership diagnosis: says I have low compression on cylinder 1, 2, and 3, with cylinders 1 and 2 being "completely dead." Suggested that I get a brand new Ford Explorer to fix the problem.
-The car doesn't burn too much oil (5L in and about 4.5L out, i'm assuming most of the missing .5L is in the filter)
-The antifreeze is bright green, and never over heats, no "white smoke" exhaust and I never have to add antifreeze (no leaks)
-Oil always changed regularly and never looks milky
-Tail pipe is clean, no soot/black burnt oil deposits
-Spark plugs look clean and normal (no gunk, no green)
-I pulled the plug wire on a "dead" cylinder and the engine ran considerably worse
-I have replaced the upper/lower intake gasket/o-rings that are infamous on this engine
-plugs and wires are about 3-4 years old
-she's got about 170,000 miles on her and I'm hoping to get ~40k more, but the Ford diagnosis has got me worried. Aside from the slight mystery miss, the car runs great.

I really appreciate any help!!!

 

[2000StreetRod]

ECT sensor?

I suggest that you test the engine coolant temperature (ECT) sensor. It notifies the PCM of the engine temperature. If it "tells" the PCM the engine is still cold when it has actually warmed up the air/fuel ratio will be too rich.

 

[swshawaii]

What's a choke? As in carburetor? LOL
Check this commonly failed PCV elbow:

http://www.explorerforum.com/forums/showthread.php?t=314670

 

[mattcc88]

Thanks for the advice guys,

Well as an update, I took it to a mechanic who said it was the passenger side O2 sensor. I reluctantly had it changed and the CEL went off and the car ran great. After 2 days or so, it is back to its same old ways of missing/rough idle. This time there is no check engine light.

My model doesn't have the PCV elbow that was mentioned above

Thanks for any suggestions!

 

[RickOTR]

With that many miles on the engine, it makes me wonder if dirty fuel injectors may be the issue. Also, take out the IAT sensor and liberally clean it with MAF cleaner. It's amazing how this sensor can affect engine performance.

 

[mattcc88]

Thanks guys!
I know its been a while, but I still haven't figured this out.

I cleaned the IAT, which was really dirty, and the MAF, which I clean regularly. I also cleaned the throttle body which was disgusting. These helped only slightly if at all.

As for the temp sensor, this is my next step although I'm reluctant to try it. From what I've read, it is very hard to start a car with a bad temp sensor, and this is not the case with mine.

Fuel injectors: I run b12 chemtool or sea foam every 3 months or so. Should I try something different? Professional on car cleaning? off car cleaning? I don't have any gas smell in the engine compartment or poor acceleration, just an annoying rough idle at running temp. Its also weird that the rough idle is worse when the temp outside is above 45 degrees F. Around 30F outside, the rough idle goes away, even at running temp...

Thanks again for all the advice!

 

[2000StreetRod]

ECT & Techron

. . . As for the temp sensor, this is my next step although I'm reluctant to try it. From what I've read, it is very hard to start a car with a bad temp sensor, and this is not the case with mine.

If the ECT sensor sends a cold temperature to the PCM and the engine is cold it will start fine. However, when the engine warms up if the ECT is still sending a cold temperature then the PCM continues to richen the air/fuel mixture. An excessively rich mixture will result in an uneven idle. If you can get access to a scanner it is easy to read the ECT value and also look at the fuel trims. It's too bad your mechanic didn't do that before telling you to replace the O2 sensor. If you disconnect the battery long enough the fuel trims stored in the PCM get reset. It takes a while for them to get restored.

Fuel injectors: I run b12 chemtool or sea foam every 3 months or so. Should I try something different?

I have only used Techron fuel injector cleaner since I purchased a 1973 Volvo 142 about 35 years ago. Some less expensive cleaners cause a build up on the valves.

. . . Its also weird that the rough idle is worse when the temp outside is above 45 degrees F. Around 30F outside, the rough idle goes away, even at running temp. . .

The above could be due to a faulty IAT sensor. I agree with RickOTR that you should clean your IAT sensor. Your IAT sensor should be integrated (in the same housing) with your MAF sensor. Another thing that is easily checked with a scanner.

 

[Keno Biebrich]

cuando falla el sensor de temperatura, no le envía información correcta a la computadora y se acelera el vehiculo, cambia el ECT

 

[csa00]

hi i wanted to know if you guys had a diagram of the motor i to have a 2001 ford explorer sport and just bought it and trying to try to fix this rattling it has in idle not sure if its the IAT or the o2 sensor or spark plugs or wire

with what did you clean the IAT?

by the way for a better fuel efficency besides the tires and the quality of gas what other thing should i check on my explorer sport? spark plugs?

 

[Dadams410]

2001 ford explorer sport and just bought it and trying to try to fix this rattling

When mine was rattling it ended up being the timing chain tensionors, I would remove the driver's side valve cover and check the plastic piece that s against the timing chain and the metal piece thats keeping pressure on it.