High Idle after Cleaning

[1-MEAN-X]

I've done a great deal of searching and can't quite find the answer I'm looking for per say. I decided to clean the MAFS and throttle body today and after doing so my engine revs around 1750-1800 in park and 1100-1200 while driving. Now I was hoping for a little higher RPM from what I had but nothing like this. I also popped up a p1506 code after putting everything back together. I used STP throttle body cleaner on the throttle body and electrical contact cleaner on the MAFS. I checked for vacuum leaks, but can't seem to find any. I unplugged the IAC while it was running to see if that changed anything which it didn't. Does this mean that it went bad? It was fine before I cleaned everything. It's a 2001 sport with the 4.0 SOHC. I appreciate any ideas that anyone may have.

If this has been discussed just point me in the right direction.

 

[2000StreetRod]

Did you remove and then reinstall the throttle body? If so, is there any slack in the throttle cable?

 

[1-MEAN-X]

There is still slack in the throttle cable as well as the cruise control cable. I checked behind the gas pedal and at the TB and their is still enough slack.

 

[jlsparky7]

Did you unhook the battery and let it sit for a bit then reconnect? Computer needs to be reset after a major cleaning like that.

If that doesnt work sounds like your IAC is shot.

 

[2000StreetRod]

. . . I also popped up a p1506 code after putting everything back together. I used STP throttle body cleaner on the throttle body and electrical contact cleaner on the MAFS. I checked for vacuum leaks, but can't seem to find any. I unplugged the IAC while it was running to see if that changed anything which it didn't. . .

I agree with jlsparky7 about disconnecting and reconnecting the battery to reset the PCM's TPS voltage range after making sure the TPS connector is on tight.

You can rotate the throttle body plate without disconnecting the cable. Make sure when released it returns to the fully closed stop.

P1506 = Idle Air Control Over Speed Error
Did you happen to clean the IAC when you cleaned the MAFS and TPS? If so, did you put the gasket back?

 

[1-MEAN-X]

No I didn't clean the IAC, just took it off to take a look.

I'll try leaving the battery cable off for a bit and see what happens.

When the TB is fully closed it has a very small opening between the inner cylinder and the butterfly. I'm talking just enough to see day light through. Is this normal?

 

[2000StreetRod]

When the TB is fully closed it has a very small opening between the inner cylinder and the butterfly. I'm talking just enough to see day light through. Is this normal?

That sounds about right. If it closes completely then it will stick and you'll feel it resist when you depress the throttle pedal.

 

[1-MEAN-X]

Well I took the negative cable off the battery for about 45 minutes and turned on the lights to reset the computer and got no change, so I guess its off to the parts store and pick up a new IAC and see if that does the trick.

 

[1-MEAN-X]

Alright, I reset the computer AND replaced the IAC with no change. Any other ideas before I take it in and have it professionally looked at? I'm stumped.

 

[2000StreetRod]

When you cleaned the MAF did you just spray it and then let it air dry? Did you touch either of the fine wires with anything? Make sure the electrical connector to the MAF is on tight.

In order to idle that fast, there has to be air flowing to the intake manifold. Either it is getting there thru the throttle body, the IAC or a vacuum leak. It sounds like the throttle plate is closing adequately. With a new IAC, it would only be open enough to idle that fast if the PCM were directing it to. Your OBD-II code indicates that the PCM knows the idle is too high so I doubt that's the problem.

Check all of the vacuum lines in the vicinity of where you were working to make sure you didn't knock one loose or break it. They get brittle after several years.

 

[1-MEAN-X]

Thanks for the input streetrod. I think I'm going to go back and retrace everything one more time. I'm sure it will be something little and stupid making all this fuss.

 

[jlsparky7]

Make sure the gaskets are all sealing. Could be an intake leak.

 

[1-MEAN-X]

Ok, I took everything back apart this morning and put it all back together double checking gaskets, plugs, etc were all in place and functioning. Still nothing.

So what I did for the time being is just backed off on the idle screw to make it run normal and now it runs fine. I read somewhere that the idle screw should never be adjusted because of the calibration or something along those lines. Should I have not messed with the idle screw even though it runs better?

 

[2000StreetRod]

Good News!

So what I did for the time being is just backed off on the idle screw to make it run normal and now it runs fine. I read somewhere that the idle screw should never be adjusted because of the calibration or something along those lines. Should I have not messed with the idle screw even though it runs better?

As long as the throttle plate doesn't stick you should be OK. The only thing you need to do now is disconnect the battery again for about 5 minutes and then reconnect. That forces the PCM to adjust the new lower limit for the throttle position sensor. I'm glad that it's running right now!

 

[1-MEAN-X]

You and me both, thanks for all the help.

 

[1-MEAN-X]

Well, it's over a month later, and while the idle issue is under control the Explorer is getting shatty gas mileage.

I went from 21-23 mpg between highway and city down to 12-14 mpg.

Any ideas what could start out as a high idle and also affect the gas mileage?
IAC is brand new. Could it be the TPS or maybe bad MAFS?

I played with my scanner and got 10.115 lb/min from the MAFS and TPS readings of:

02s11 = under 1 v and between 0- (-3) %
02s12 = 0 and N/A%
02s13 = under 1 v and between (-2) - 1.5%

Any ideas?

 

[ThePhoenix]

you used to get 21-23 highway miles?

I havent even gotten close to that

 

[2000StreetRod]

scanner results?

. . . I went from 21-23 mpg between highway and city down to 12-14 mpg.
Any ideas what could start out as a high idle and also affect the gas mileage?
IAC is brand new. Could it be the TPS or maybe bad MAFS?
I played with my scanner and got 10.115 lb/min from the MAFS and TPS readings of:
02s11 = under 1 v and between 0- (-3) %
02s12 = 0 and N/A%
02s13 = under 1 v and between (-2) - 1.5%
Any ideas?

I don't see any TPS data. My scanner only provides absolute throttle position in percent. Mine reads 18.8% at closed throttle and 92.9% at WOT. My voltmeter readings are 1.03 volts at closed throttle and 4.7 volts at WOT. OBD-II does a comparison of MAF sensor and TPS for reasonable correlation and sets a DTC if they don't track. It seems unlikely that a TPS would degrade mpg at cruise.

I don't understand your O2 readings. I have 2 cats and 4 O2 sensors. Each bank downpipe has an O2 sensor followed by a catalytic converter and then another O2 sensor. There's a cross pipe (equalizer) after the cats. My O2 sensors are numbered B1S1 (bank 1 precat), B1S2 (bank 2 post cat), B2S1 (bank 2 precat) and B2S2 (bank 2 post cat). What is your O2 sensor configuration?

A bad (reads low) engine coolant sensor can adversely affect mpg. The PCM enriches the mixture when the engine is cold. That could also cause an idle speed increase. Does the scanner read a reasonable Engine Coolant Temp?