Random RPMs drop, engine seems want to stall

[Explorer75]

Recently I´ve been noticing a random drop in rpms, below 500. At first I noticed it on D on stop and go traffic, the engine seems to want to stall briefly, then the rpms got back up to 600+. Then today it happened at Parking. I turned the A/C on and off and the rpms seem unchanged, So I don´t think it has to do with the A/C.
All maintenance is up to date (almost 60K miles on the truckl: new motorcraft spark plugs 5k miles ago, new air filter 2k miles ago, new oil a month ago, cleaned throttle body couple of months ago, check engine codes, no pending codes. The only thing I can think of is a failing TPS within the throttle body.

What do you guys think?

,

 

[peterk9]

Does it do this as well when you are doing steady driving? If it was some sort of fuel delivery/starvation issue I would think it would do it at all times.
Found this on the Throttle Body Position sensor; What happens when throttle position sensor is bad? - Google Search

Peter

 

[Explorer75]

Does it do this as well when you are doing steady driving? If it was some sort of fuel delivery/starvation issue I would think it would do it at all times.
Found this on the Throttle Body Position sensor; What happens when throttle position sensor is bad? - Google Search

Peter

It only does it as stated. I haven´t noticed any flat spots when accelerating. This is the most difficult problems to pin point, I know. No CEL makes it very difficult to find the problem. Since it´s not that bad I can just wait to get worse before start throwing parts hoping I nail it. I´ve done that in the past without positive results only lighter pockets.

 

[Explorer75]

Update: I checked the price on the throttle body for the 3.5 NA 2011-2019, I was surprised that is about $70, including the gasket. So I ordered and replaced the TB, so far the problem is gone. Also, engine runs smoother now.

 

[Toddman41]

Where did you find a TB for 70.00?

 

[peterk9]

Where did you find a TB for 70.00?

Here's one for $48.74. Throttle Body for 2013 Ford Explorer | Auto Nation Ford White Bear Lake

Peter

 

[Explorer75]

Where did you find a TB for 70.00?

AutoNation Ford White Bear Lake | Parts & Accessories | Auto Nation Ford White Bear Lake

I got the TB and gasket.

 

[JWKberlin]

It appears I have a very similar issue with my 2011 limited. But it appears to be less severe in terms of the random drop - goes down to only ~500 not (far) below that. Thus I wonder whether there is a sort of "nominal" transient behavior with a "normal" drop and when does it start to become suspicious? Any ideas?

Second question for me is - when it comes to a TB replacement: what manufacturer would you recommend. Background to this is that I am here in Germany and need to import every part with associated shipment and custom cost - thus I would prefer to fix it once for longer than to order one every other year. Your choice?

 

[peterk9]

Welcome to the Forum.
I would recommend sticking with the OEM parts.

Peter

 

[Explorer75]

It appears I have a very similar issue with my 2011 limited. But it appears to be less severe in terms of the random drop - goes down to only ~500 not (far) below that. Thus I wonder whether there is a sort of "nominal" transient behavior with a "normal" drop and when does it start to become suspicious? Any ideas?

Second question for me is - when it comes to a TB replacement: what manufacturer would you recommend. Background to this is that I am here in Germany and need to import every part with associated shipment and custom cost - thus I would prefer to fix it once for longer than to order one every other year. Your choice?

As Peter said, OEM is the best choice. With OEM you buy once and it wont cost you a lot more, sometimes its cheaper, i know its weird.

You could try and clean the Tb first



Then do the relearn

 

[JWKberlin]

Thanks for your responses - Cleaning TB has been done. First no severe finding in terms of contamination, cf. photograph attached - state before cleaning. Second, cleaning did not help to fix/change the transient.
OEM Part (should be Hitachi, isn't it?) would mean $190 (including customs and shipment) - as compared to an alternate one for $90 (including customs and shipment) - that is far consistent with the above mentioned TBs at ~$70.

I am not doing a lot of miles thus I wonder whether that should be considered in the calculation. And also - my RPM transient is not as bad, just down to 500 rpms. Maybe somebody has a "good reference sample" captured on RPM in FORscan for the following condition:
- Engine in warm condition
- In Neutral, speed up the engine to about 2 - 3 k rpms for a few secs
- remove pedal at once
How should that look like?
Sorry about that, but you can't imagine what it means to drive this car to a Ford Garage in Germany - 99% probably won't recognize the model, let alone provide helpful information. Thus I am pretty much on my own and simply want to avoid the sort of random replacement of possibly "not optimal" parts ... if you know, where I am coming from.

Another idea completely different to TB is the Thesis that the engine sucks in some - dunno how to call it in english, direct translation is "false air". So any kind of leakage behind MAF. But most likely, this would also reveal a problem in "steady state" idle, or what do you think about it?

 

[JWKberlin]

and yes, I did relearn the TB - but avoided the procedure linked in the video above. Reason is, that I don't like the idea of pulling the entire engine electronics return hard up to +12 V - instead I removed the return line only from the bat and left it floating for some hours - same effect but much less stressful to the electric, at least in my opinion.

 

[Explorer75]

and yes, I did relearn the TB - but avoided the procedure linked in the video above. Reason is, that I don't like the idea of pulling the entire engine electronics return hard up to +12 V - instead I removed the return line only from the bat and left it floating for some hours - same effect but much less stressful to the electric, at least in my opinion.

I´ve done the +/- procedure, no harm there, what it does is shorts the capacitors and discharge them. What you can´t do is short the battery. Also you can disconnect both terminals from the battery and short them (without any battery connection).

 

[JWKberlin]

what it does is shorts the capacitors and discharge them

This is of course the goal, such that relearning can start. All I am saying is that in the way to achieve this there are different possibilities obviously. As I am more on the safe side, I like it better to avoid the very dynamic way to do so, at least without knowing all the details of the circuitry. But sure obviously the system is robust enough to cope with it, nonetheless, if you have time (e.g. overnight) I would rather tend to do it conservatively.

@Explorer75 You would not mind help me with some data after you replaced the TB in the following as described above?

I am not doing a lot of miles thus I wonder whether that should be considered in the calculation. And also - my RPM transient is not as bad, just down to 500 rpms. Maybe somebody has a "good reference sample" captured on RPM in FORscan for the following condition:
- Engine in warm condition
- In Neutral, speed up the engine to about 2 - 3 k rpms for a few secs
- remove pedal at once
How should that look like?

An associated curve captured on mine with FORscan is denoted in this Thread:
A favor - bitte - I need a "reference RPM FORScan" Oscilloscope capture

That would be more than helpful!

 

[Explorer75]

This is of course the goal, such that relearning can start. All I am saying is that in the way to achieve this there are different possibilities obviously. As I am more on the safe side, I like it better to avoid the very dynamic way to do so, at least without knowing all the details of the circuitry. But sure obviously the system is robust enough to cope with it, nonetheless, if you have time (e.g. overnight) I would rather tend to do it conservatively.

@Explorer75 You would not mind help me with some data after you replaced the TB in the following as described above?

An associated curve captured on mine with FORscan is denoted in this Thread:
A favor - bitte - I need a "reference RPM FORScan" Oscilloscope capture

That would be more than helpful!

Ok, I will record that with the Forscan and get back to you.

 

[JWKberlin]

Ok, I will record that with the Forscan and get back to you.

Great, that would really help me.
Thx so much.

 

[Explorer75]

Great, that would really help me.
Thx so much.

I´ll be checking that in the next couple of days, sorry for the delay

 

[JWKberlin]

Don't worry - enjoy Thanksgiving first - as much as possible.

 

[Explorer75]

Don't worry - enjoy Thanksgiving first - as much as possible.

Which sensors do you want to display in the oscilloscope?
Edit: I read only RPMs, I'll throw one or two more...

 

[Explorer75]

This is of course the goal, such that relearning can start. All I am saying is that in the way to achieve this there are different possibilities obviously. As I am more on the safe side, I like it better to avoid the very dynamic way to do so, at least without knowing all the details of the circuitry. But sure obviously the system is robust enough to cope with it, nonetheless, if you have time (e.g. overnight) I would rather tend to do it conservatively.

@Explorer75 You would not mind help me with some data after you replaced the TB in the following as described above?

An associated curve captured on mine with FORscan is denoted in this Thread:
A favor - bitte - I need a "reference RPM FORScan" Oscilloscope capture

That would be more than helpful!

Did several screen shots of the oscilloscope, I hope they help you. I did all with a/c on. Let me know if you need anything else.