studying the service manual... wondering if since it is a refurbished TB, if I should try blocking one or both of the throttle plate orifices... thought being that the bore/plate is not as tight a fit as it should be.

Easy enough to play with a bit of tape.

 

I doubt that is a problem since you were able to get the idle down to 500-600 rpm. Does the stop screw look like it is still in a close to factory setting? I would still lean more toward the butterflies binding up in the bore.

I wonder what they actually do to “refurbish” the throttle body?

 

Not sure if this will help, but..Back in the early 90's my father had a '90 Bronco with 5.0/auto, had high idle issue and we tried a few things, found the gasket between the upper/lower EFI manifold was bad. Installed new gasket and idled again at 6-700 rpm. Hope this helps.

 

So, I gave it a whirl... had to readjust the stop screw to open the butterflies quite a bit... and no more hanging up but it was idle hunting between 1200 and 800 rpm. When I backed it back off, it hung up again. I think the relationship between how much air is being let in compared to the TPS position is off, because of something wrong with the reman TB.

I will put the BBK unit back on and see if there are any problems with it. other than the ones I know about.

As far as the refurbishment goes... it looks very clean, maybe new shaft bearings. Other than that IDK, it looks like a clean stock unit. No apparent machining.

 

Was that idle with 1, or both holes taped, like you were going to try?

 

I started with one hole covered... didn't seem to make any difference. Covered both and I had to open the butterflies significantly. I could try again with just one covered... if that is my problem I would have to improvise a permanent solution as the plug kits from Ford are long gone.

I have installed and adjusted throttle bodies several times over the years and never had so much trouble.

 

BBK unit is installed on the truck. One drive cycle went fine. I still hate the BBK. I will clear codes in the morning and go from there. IDK if I should just return the Autoline unit or ask for a replacement and try again...

 

According to RockAuto you either send your throttle body to be rebuilt or there was a large ($50) core charge. I don’t know how you would return the part and not end up eating the core charge. If the BBK throttle body is performing as it is supposed to then I would give Autoline a second chance. The pedal is far too stiff to continue using the BBK unit which is why I am using a junkyard throttle body.

 

On the BBK throttle body, I loosened the top spring with needle nose pliers. I took 2 turns out of the spring. It helped tremendously.

Definitely check with Autoline about your problem. I was thinking of sending in my old one, but gonna wait after your issue.

 

I’ll have to give that a shot. I have a twin 61mm throttle body on another truck that I bought back in 2009 and it does not have these problems.

 

Apparently I bought the last throttle body Rockauto had in stock, so I will have to use the R&R service and see what happens. I will report back...

Took the truck for a longer drive, with some interstate miles, and the shift points seem to be off... 70mph on a flat road was 3000 rpm, normally it is around 2200ish rpm... unlocked the torque converter and it bounced even higher... didn't notice anything out of the ordinary until I got on the highway. Not sure what to think about that... I know the TPS has influence over the shift points as well as the MAP sensor the two critters I have had trouble with. No codes at present. I do have the TPS 180 degrees from where I had installed before, now the pigtail is pointed toward the passenger side. This was a ****s and giggles move and I can turn it back around and see what happens. The voltage signal seems fine.

I also tried the Ford spec procedure to adjust the base idle speed and found no success with that. Basically, some of the computers can be put in a testing state and will report whether the TPS is out of range, idle good, idle low, idle high based on the CEL frequency, and you proceed to make repairs/adjustments based on the computer feedback. I was able to get the computer in the right mode, but I could not make it happy.

The alternate method if your computer doesn't have that feature is to pull the spout, pull the IAC, plug the PCV at the manifold, pull the fuel vapor line off the TB and plug the port, and then set the idle speed based on rpm. This is what I did.

 

Okay, with some help from RLA, I have the tachometer problem remedied. The new harness was meant for a 94 Lightning, which grounds the tach module on a different circuit than the standard 5.8 trucks. No, ground meant the display was calibrated for a 4.9 engine. Added an appropriate wire to the harness and problem solved.

With that worked out, I gave the Autoline throttle body another go... and got it dialed in. I got the engine to normal operating temperature, and set the mechanical idle fairly low. Acted like it did before with hanging idle once the throttle moved. Best I can figure is that it was hanging up, if ever so slightly, and the computer was under the impression the throttle was open, if ever so slightly. So, I would shut it down, cracked it open a touch, and retested until I got it right, which didn't take too many tries. I drove it all over town today without issue. Idle in park sitting around 750rpm or so and idle in drive sitting a little lower, 650rpm or so.

Pleased with the results, just wish it had been a shorter road getting there.

Thank you to everyone who contributed to the thread.

 

Looks like you got this under control! Let's hope it stays that way

 

Good to hear the rebuild wasn’t the problem. I have a few old throttle bodies in a bin. I’ve been thinking of trying the rebuild service. Glad you have it sorted out.

 

So the plot actually thickened and I thought I would report back...

My AC started coming out of of the defroster vents... vacuum leak! Got that resolved and then the truck was wanting to stall when backing out of the driveway in the mornings.

I figured that the TB calibration was off a bit because of the vacuum leak, so I turned the stop screw just less than a 1/4 further open, and cured the stall with not other apparent problems.

When I had some time on my hands I checked the spark plugs, and sure enough they were pretty dirty with carbon, so I think on top of everything else the truck has been running quite rich which can cause idle problems on its own. New plugs, and it is purring like a kitten, and much better mileage. It is amazing to me that it would run that rich in response to a lean condition and not throw a CEL, or even a code.

I am thinking of re-checking the base idle or having another stab at the Ford procedure to reset the stop screw, but it seems to be just fine as it is.