Rough Idle/poor power

[samsfiveo]

This is the first thing that has ever happened to my '02 ExplorerSport. I ran it at WOT for a while on an unoccupied section of interstate to see where it topped out at, everything was fine until I let off and coasted to the legal speed limit then the CEL came on and it was down on power and idled rough. I parked it and switched over to my Ranger for a few months and the battery went dead taking the code with it, I tried to drive it to bring back the code but it just won't give it up again. I have checked for broken/disconnected vacuume lines/wires, cleaned the K&N filter, I changed the sparkplugs, wires and fuel filter. Did a compression check (all above 150) and there is no steam from exhaust pipes. My fuel is fine because my Ranger has the same fuel from the same station and bought on the same day (price kept going up so I filled up both). I have no oil in the water nor is there any water in the oil, the radiator or engine oil never lost a drop. It runs like it has an injector not working, but I tried all the easy stuff first. I was told by a Ford mechanic that it could have melted a cat or fouled an O2 sensor, does that sound plausable? I would appreciate any and all suggestions and help you can offer. Thanks in advance.

 

[samsfiveo]

Stumped everone ehh?

 

[FIND]

What cel is it displaying.

We'd be a lot less stumped if we had that information.

Any other information you can provide? Smells, sounds.....

 

[samsfiveo]

When that happened I just parked it and started driving my Ranger, after a couple of months the battery went dead, taking the code with it. Not to sound smart but I gave that info in my first post, otherwise I would have noted the code....thats why Im in the dark. I tried to drive it around some to get the code back but it won't come back......no CEL now, but still poor power and rough idle. Thanks.

 

[backfrmcolorado]

just courious.. what did you top out at?

 

[samsfiveo]

Right at 104-105 mph. It doesn't hit the rev limiter, the computer just cuts power to the engine somehow, because it doesn't go up and down rapidly like when you hit the rev limit, just a smooth power loss until it kicks back in.

 

[backfrmcolorado]

not bad.i tried toppin my '94 x out but the speedo stops at 85. had no ideaa how fast i was going but the needel was going striaght down. i know my truck has a rev limitor in park but nothing happened at top speed. just ran out of clear freeway.

use a radar detector too. learned that lesson the hard way last year in my '04 f-150

 

[bigman4921]

I am no expert but did you check you ground wire or fuses sounds like electrical to me

 

[aldive]

Have you checkedthe O2 sensors for function?

 

[FIND]

When that happened I just parked it and started driving my Ranger, after a couple of months the battery went dead, taking the code with it. Not to sound smart but I gave that info in my first post, otherwise I would have noted the code....thats why Im in the dark. I tried to drive it around some to get the code back but it won't come back......no CEL now, but still poor power and rough idle. Thanks.

For some reason, I missed that.

02 sensor or cat sound plausible. Run it for a while and look at your plugs, they will probably give you the most information.

I cannot remember the configuration of the engine in an 02, but if you can reach, you can take a LONG screwdriver and touch it to an injector, put your ear to the other end, and you will be able to hear if the injector is functioning. Though, if the injector wasn't, it should throw a code. 02 sensor or bad cat should throw a code as well. How long are you running the vehicle at a time? Does it reach operating temperature?

Try seafoaming your intake, might have plugged an injector with carbon.

 

[moosejaw]

You may have got a lean condition code from the long coast down. The ECU will do a fuel cutoff when coasting in gear (if you are coasting long enough). You may have been coasting for long enough that you timed out one of the lean cel timers.

Another cause would be oil (from the K+N) getting on the maf from your long high throttle run. This would cause a rough idle for sure.

I doubt you would have melted anything at that speed. Not only does Ford go a little rich on the tune at the top end they also add fuel enrichment at high speeds.

 

[samsfiveo]

Didn't check the O2s yet, but I have a whole spare set of cats/sensors from a donar Ex. that I am going to swap in. (I am disabled with a fused back and it is hard for me to get under there!) I just wanted to get an ideal in the right direction before I just start throwing parts at it. The coastdown was very brief, in fact hard braking to make an exit. I checked the fuses in and underhood. The K&N is factory oiled, been in there since '05 (clean), I made roughly a 10 mile cruise to try to set the CEL again, so I would think I got to operating temps. Gonna swap in the O2s today and the cats if nessary. Thanks again Guys.

 

[Turdle]

And clean your maf sensor.

How can your K&N filter be factory oiled if you cleaned it?

 

[2000StreetRod]

Speed limiter

I believe the stock PCM program limits the revs to 6250 rpm and the vehicle speed to about 105 mph in any gear. When you hit the max speed I think the ignition fires on alternate compression strokes. The speed limiting or the after effects may have triggered the CEL.

If an injector is clogged causing repeated misfires it is sometimes detected and reported by the PCM. There may be a more general degradation that can not be isolated by the PCM.

I suggest that you add a bottle of fuel injector cleaner to the tank if you haven't already done so.

 

[samsfiveo]

I believe the stock PCM program limits the revs to 6250 rpm and the vehicle speed to about 105 mph in any gear. When you hit the max speed I think the ignition fires on alternate compression strokes. The speed limiting or the after effects may have triggered the CEL.

If an injector is clogged causing repeated misfires it is sometimes detected and reported by the PCM. There may be a more general degradation that can not be isolated by the PCM.

I suggest that you add a bottle of fuel injector cleaner to the tank if you haven't already done so.

Literally everything you said, EXACTLY!! StreetRod, I just read your post and we were on the same wave, I fixed it this morning!! I had it scanned yesterday at AutoShaft and it threw P0306 (injector failure/low fp) and P0316 (crank sensor/coil) codes. I started with the crank sensor (for $13 it was first/easiest to do and it was 8 years old), that wasn't it. I decided checking the injectors was harder than a coil swap, but cheaper (free)! They all Ohmed out fine and the Orings were intact. All six of them were filthy, one (#6) was totally clogged! I cleaned them with carb spray, blew them out and silicone sprayed the O rings (makes easy install) and I have my power back! I just got home from a 2 hour cruise and many glorious smokey powerbrake burn outs! I was blasting SkidRow and Metallica on my screen and thinking about doing a total detail job on it tomorrow. Now that the 'Sploder is running, I can start the 5.0 swap for my Ranger and move on to totally new problems! Thanks to everyone who tried to help me, I genuinely appreciate your time.