High idle and sluggish shifts. Need help!

[Mounty99]

Hey guys.

Having issues fellas. 1999 Mounty 5.0 with 259,000 miles! She has always been quiet as a mouse at idle, but now having high RPMs at idle (1600). Also, has been shifting (late?)...revs up high (3000-3500) before going from 2nd to 3rd.

First thought was TPS...which I just went ahead and ordered. Has not arrived yet. But now wondering if perhaps something else (throttle body assembly, 4r70w on the way out, etc)?

Any thoughts on this is much appreciated!

*[Don't think it matters?, but did recently put on a new water pump & thermostat]

 

[C420sailor]

Did the high idle and shifting issues start at the same time?

My 4R70W was doing the same shifting business. I dropped the pan, cleaned out the valve body, replaced the check balls, installed new 1-2 and 2-3 accumulators and removed the accumulator springs per the J-Mod (but I didn’t drill the separator plate). Also replaced shift solenoid pack and TCC solenoid. New gaskets, obviously.

Shifts like a dream now.

 

[Mounty99]

Yes, both issues started with in a day or so of each other. Would tranny issue cause high RPMs in park?

Man, I've mostly done all my own repairs...but never touched a transmission. Your awesome work may be above my pay grade! About how much $$$ would I be looking at to have that done down at my local independent transmission shop? Thanks!

 

[fast_dave]

@Mounty99

Just a suggestion that costs $0.00 re: Out of the blue high idle

When your engine is cold, preferably in the morning, first, open the hood on your Monty and then cold start it.

Let it run for about one minute, and then let the hood drop and slam closed - emphasis on slam.

If suddenly your idle reduces to "normal you could either have gunk around the throttle body shaft and/or top/bottom of the butterfly, or you could have a throttle body bore that is getting oblong /distorted do to 259,000 miles of shaft opening and closing.

Report back

 

[C420sailor]

Honestly, I’m not a tranny guy either (wink wink)

I watched the official J-Mod how-to video on YouTube and simply did what he did...minus the plate drilling. And I replaced the accumulators, check balls, solenoids instead of re-using.

That said, I can’t think of a tranny issue that would cause a high idle. Maybe try disconnecting the battery to give the PCM a hard reset?

Coolant temp sensor didn’t disconnect during your thermostat work, did it?

If all that checks out, I’d take a good hard look at the IAC...

 

[Mounty99]

Report back

Thanks Dave. Tried it this morning...and no change. But then immediately after shifting from park to drive, RPMs drop from 1700 to 1000. On the throttle plate note, my plate does get sticky on longer interstate driving (esp if using cruise). So the throttle assembly still could be in play

 

[Mounty99]

Honestly, I’m not a tranny guy either (wink wink). Coolant temp sensor didn’t disconnect during your thermostat work, did it? If all that checks out, I’d take a good hard look at the IAC...

Haha. Think coolant temp sensor is ok, as my ScanGauge 2 still consistently showing 190. Was waiting to do a hard reset after I install the new TPS (Monday). Could bad IAC cause these late/stalled shifts?

 

[fast_dave]

@Mounty99

The Temp Sensor in conjunction with IAC Valve "talk" to the computer and between the two of them control the idle speed.

As far as your High Idle condition goes; I think the clue in all of this is your reply that your throttle body has been sticking.
Start cheap $$$$

Remove the rubber air intake from the throttle body.
Get an old CLEAN tube sock, turn it inside out so the high-nap side is now on the outside, and spray it down with carb cleaner.
Clean your Throttle Butterfly - especially the edges that contact the inside of the throttle body - that's where you will get sticking.

While you're in there, check the throttle butterfly shaft - look for excessive radial play which would indicate wear on the actual throttle body (body is made from aluminum, shaft is made from steel).

Use an aerosol spray that cleans/lubricates/protects such as Break-Free CLP or Rem-Oil, and spray the area where the shaft penetrates the body of the throttle body. This will ensure that your butterfly is easily opening and closing.

Then, disconnect the throttle cable where it connects to the throttle body butterfly linkage.
Clean out the interior of the ball & socket connect joint and lube with new grease.

Check the adjustment point of your throttle cable that goes from your cruise control box to the bracket near the connection point to the throttle linkage. The connection point is adjustable and you might have to take up the slack, tighten it.

Check the tension of your MAIN throttle return spring. It might have stretched and you might have to tighten it up by cutting off a coil.

 

[Mounty99]

Clean out the interior of the ball & socket connect joint and lube with new grease. Check the adjustment point of your throttle cable that goes from your cruise control box to the bracket near the connection point to the throttle linkage. The connection point is adjustable and you might have to take up the slack, tighten it. Check the tension of your MAIN throttle return spring. It might have stretched and you might have to tighten it up by cutting off a coil.

Thanks Dave, and sorry for late reply. Cleaned the throttle butterfly about six months ago...due to the interstate stickiness. But will get back in there and clean/check it all out again. Will report back when job complete!

 

[fast_dave]

Thanks Dave, and sorry for late reply. Cleaned the throttle butterfly about six months ago...due to the interstate stickiness. But will get back in there and clean/check it all out again. Will report back when job complete!

@Mounty99
Cleaning 360% around the edge of the butterfly where it comes in contact with the inside of the throttle body is very important.
The tolerance there is very tight, and pollution control oil fumes collect there, harden, and get taller, thus the butterfly eventually sticking.
As these vehicles age on their original engines, the maintenance schedule in areas such as this needs to be increased.

 

[Mounty99]

Cleaning....inside of the throttle body...very important.

Ok, followed Fast_Dave's cleaning instructions (thanks Dave), and installed a new Motorcraft TPS. Seems to be shifting better, but won't really know for sure until get a few miles on it. Will report back. Thanks again to everyone who took the time to reply!

 

[fast_dave]

Ok, followed Fast_Dave's cleaning instructions (thanks Dave), and installed a new Motorcraft TPS. Seems to be shifting better, but won't really know for sure until get a few miles on it. Will report back. Thanks again to everyone who took the time to reply!

@Mounty99

The following used to be a popular topic when after about 10 years Stock TPS' started burning out.

The subject is Absolute Throttle Position.

The TPS is essentially a rheostat, and different rheostats have different manufacturing tolerances, and guys on the forum found out early on that dialing-it-in to a sweet spot with some "pre-voltage" cured the condition of rolling idle and sluggish throttle response/tip in.

It was generally settled upon that right around and up to 1 Volt was "the sweet spot" (.96, .97, .98, .99 & 1.0)

There are those that claim that this is "unnecessary" or "that it doesn't do anything" ; BUT in my experience, when replacing a TPS, I try to get the voltage reading at the TPS to "the sweet spot" and the results worked for me when comparing to just "throwing on" a TPS Verses "tuning" a TPS. I not only noticed the difference I felt the difference.

Don't mess with any idle adjustment screws on your linkage. All you want to mess with is twisting the installed TPS as it comes from the factory to hit "the sweet spot" (sometimes there's enough manufacturing tolerances to allow this), OR if you need to oblong the mounting bolt holes on the TPS with a drill to allow you to twist it in the correct direction to obtain 1 Volt.

If you measure your TPS voltage now, and then adjust it to hit the "the sweet spot voltage" - I believe that you too will notice an improvement in your Ex's general idle characteristics and off the line/throttle tip in performance.

Hope that helps - and here's a link to an epic 23 page thread on the subject: adjust your TPS (another free hp mod)

 

[Mounty99]

Hope that helps