Rough Idle on 97 Limited 5.0L

[97ExplorerAWD]

ok here I go I just got a 97 Explorer Limited AWD had it for a few days everything was good. one day I'm driving and it throws a check engine light I didn't really pay to much attention to it few days later I go to start it and it starts then stalls so I start it again it starts but runs a really rough idle sometimes feeling like it's going to stall so I talked to a few people and they told me it might be the MAF sensor so I unplug the MAF and it starts up fine no rough idle it just idles at a higher RPM dumping more fuel so I plug back in the MAF runs bad again I wanted to make sure it was the MAF so I went out and bought an OBDII Reader but when I scan the codes nothing about the MAF sensor comes up here are the codes I got (Generic Code) P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control (Ford Code) P1137 Lack of Heated Oxygen Sensor Switch - Sensor Indicates Lean (Ford Code) P1151 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean Bank 2 but here's the weird part I cleared the codes unpluged the MAF sensor and did alot of driving the check engine light came back on so I scanned it again but the only code that came up was (Generic Code) P0102 Mass or Volume Air Flow Circuit Low Input so why is it when I unplug the MAF it runs fine and the only code that comes up is for the MAF but when I leave it pluged in those other codes come up and it runs like crap but nothing about the MAF comes up???

 

[Turdle]

Hi
When you unplug the Maf sensor it will throw the PCM into "open loop" or "limp" mode. This makes it run smooth, although the fuel mixture is rich. Basically in open loop the PCM ignores all the sensors so the vehicle will get you to a shop.

edit

There is a vacuum leak somewhere-check the PCV valve and hoses-

 

[jah81592]

Or try cleaning the MAF meter.

 

[97ExplorerAWD]

Iac

well I took the MAF off cleaned it still the same thing so today I took off IAC Valve what is the best thing to clean it in it looks really dirty?????

 

[alohamonte]

Yeah clean the IAC... if you dont you'll have to replace it eventually... like I did

question... did you have any issue removing the MAF? Mine is secured by two torx screws, which i have the security bit for, but one of the screws is sealed over in hard plastic... anyone experience this? do I have to melt the plastic off? it doesnt scratch off that's for sure.

i can post a picture if that will help.

 

[97ExplorerAWD]

well I didn't completly take the whole sensor off I just took a q-tip and some alcohol and lightly keyword lightly stuck it down the hole and tried to clean it best I could the MAF sensor did look pretty dirty but it's clean now yeah so what would be the best for cleaning out the IAC brake cleaner??? and some WD40 maybe the spring does seem alittle sticky and it's really dirty in their so I'll clean it out and if that does nothing I'll just go to a junk yard and pull one off a vehicle cheap

 

[Firestorm]

Use electrical parts cleaner on the MAF and IAC. Take a Q-tip and clean both, and use a toothpick to poke the spring up and down. WD-40 can't be used on this valve, that I know of.

 

[97ExplorerAWD]

ok so I went to the autoparts store and bought some electrical cleaner cleaned it out real good put it back on and all and all it runs alittle better when I first started it fired right up no stalling no rough idle then after a couple seconds it would start to idle rough again then go back to a normal idle do you think I should replace the IAC altogether??? ohhh and yeah it does run alittle better since I cleaned it out

 

[Firestorm]

Do you have a voltmeter?

If you have a voltmeter, I would suggest testing to see what kind of voltage you are getting.

Also, have you tried to find any vacuum leaks?

 

[97ExplorerAWD]

No I havn't and how should I go about it??? thats like finding a needle in a hay stack

 

[Turdle]

There is a grommet for the pvc valve which may leak-it is at the very center and rear of the lower intake manifold-
The large vacuum hoses under the driver side upper intake plennum go to it, and the brake booster.
Another common leak area is the vaccum resevoir globe in the passeneger side wheel well area-behind the park lamps-the hoses can break-

spray something like wd40, or even an unlit propane torch in these areas and listen for the idle to rise-if it does you have found a leak.

Definitely clean the maf sensor first-

 

[Firestorm]

I had actually noticed my vacuum reservoir line was broken when I changed my spark plugs. I didn't notice any huge difference though. All I did was taped it back together.

I was going to tell you to test your MAF sensor, and IAC valve.

JT is onto it though, you should check for vacuum leaks.

 

[99SportX]

Just out of curiosity Jon, how would you seal up a leak in the back near the PCV valve? From my experience, the PCV doesn't really fit too tightly in the large black grommet in the intake. I am wondering if this may cause me a slight problem.

 

[Turdle]

You have to find a grommet and valve which fit tightly. It's best to start over with a new hose and all. It seems to me the old hose doesn't flex, and it will itself pull the valve loose also. I remeber it took a few grommets to find the right one.

http://www.explorerforum.com/forums/showthread.php?t=157568&highlight=pcv+grommet

 

[97ExplorerAWD]

ok here's something I just noticed maybe I wasn't paying attention when I start it up it will fire up idle fine for a few seconds then start dying then the rpm's will rise to 2,000 by it's self then back down to 1,000 then rough idle sometimes it stalls and other times it just repeats that process

 

[Turdle]

How is the coolant level-check the radiator?
There was an insufficient coolant logged.

You know--
The ect (engine coolant temperature) sensor-does play a role in the fuel mixture also. hmmm. Since there is a code present it might not hurt to check it out. I think there is a way to verify it is working properly measuring it's resistance

 

[97ExplorerAWD]

I have no clue where to start the EGR the MAF the IAC the PCV check for a vaccum leak check the coolant level I reset the check engine light from the last code I got which was about the MAF which was just from me unpluging it I have to drive it around for a while for it to throw the check engine light again and see what codes come up altho everytime I want to drive it it wants to stall on me at stop lights either that or I have to quickly throw it into park and keep the rpm's pegged at 2k for it not to stall

 

[97ExplorerAWD]

well I was checking the hoses and such for a vaccum leak and guess what I find the PCV Vavle is completely unplugged here's the problem I have big butchers hands and the vavle is all the way in the back along the fire wall tonight I will really try getting in their and getting it plugged back in I'm pretty sure I found the problem somebody tell me what they think would this cause a rough idle???

 

[Turdle]

well I was checking the hoses and such for a vaccum leak and guess what I find the PCV Vavle is completely unplugged here's the problem I have big butchers hands and the vavle is all the way in the back along the fire wall tonight I will really try getting in their and getting it plugged back in I'm pretty sure I found the problem somebody tell me what they think would this cause a rough idle???

Unplug the pcv and it will idle like it had a radical cam--

you have found the problem.

or at least one of them. Id get a new grommet and valve which fit tightly if possible.

 

[99SportX]

Oh yes, plug the PCV back in and you are golden.

Has anyone tried to seal the PCV in place with a little RTV instead of trying a bunch of grommets? I would think that would work fine and it is free if you have RTV laying around?

I am lucky in that I have skinny hands. It is a tight squeeze. You may be able to guide it in using screwdrivers or something.

Also, having my 1" upper intake spacer helps give me more room to get my hand back there and check things out.