Engine/Transmission (1998.5 - 2002) Anatomy of an APPS

[KarlC]

Does anyone have a source for the OEM APPS connector, both male and female ends? I'm thinking more about a high-idle module to insert between the APPS and the cable.

 

[Gary - K7GLD]

Yes, I think it would be that easy. The challenge is mostly one of mechanical fit. Don't get just any 'ol pot, though. Running thousands of hours, hundreds of thousands of wiper movements past the operating point at temperature with vibration is nothing to scoff at.

Perhaps - but we've both seen what is currently being used inside the APPS, and THAT is HARDLY what anyone would call an "engineering miracle"! :-laf:-laf



I would suspect that any of a number of better quality $5-$10 potentiometers would be up to the task - and then easy to swap out FAR cheaper than the OEM POS! :-laf:-laf

 

[KarlC]

Perhaps - but we've both seen what is currently being used inside the APPS, and THAT is HARDLY what anyone would call an "engineering miracle"! :-laf:-laf

You're right about that.

I would suspect that any of a number of better quality $5-$10 potentiometers would be up to the task - and then easy to swap out FAR cheaper than the OEM POS! :-laf:-laf

Something I forgot to mention is that the rotation angle of the bell crank is only maybe 90°, perhaps a bit less. This could make the task a bit more of a challenge. The APPS runs off the 5V supply, and goes from approx 0. 6V to maybe 4. 4V. This means running from 12% to 88% of total rotation angle. The calibration procedure probably will make up for some of this, but I don't know how much. Many single-turn pots are really 270° rotation. A small cogged belt could provide the 1:3 ratio, and might help with the mechanical fit.



Another thing to consider is backlash. That would get really annoying in a hurry. The APPS is spring loaded to eliminate this.

 

[Gary - K7GLD]

Yeah - the degrees of rotation was one thing that caught my attention too - several good ways to deal with that, might even be some special applications potentiometes out there - will check Mouser...



One thing I'll need before getting involved with a substitute for the OEM APPS, is another APPS bracket - I sent the only spare I had to Bob for his experiments - I might check with a Dodge dealership, and see if they might have a pull-off I can talk them out of...

 

[timbo]

Been following this one pretty close for awile now and i gotta say THANKS for all the effort and research you guys are putting into this!!! I just went out and tested resistence on my 86 mustang TPS,560- 3400 end to end. I'm seriously considering the microswitch on the linkage and Ford TPS as the pot. The Ford TPS might even be the same hole pattern, and bolt in place,it looks very close to our TPS!The ford TPS is reliable and very cheap if needed to replace it. Microswitch's are also reliable and very inexpensive to replace,if needed. I'm thinking about making up a small test fixture so the TPS and IVS microswitch occur at the right timing vs resistence values. Then plug it in and just operate the TPS with a screwdriver and see if it will rev up,hold constant(smooth) RPM, just to try it and see how it works. Right now my trucks at my work, I just got all the parts today to fix my busted NV4500 so that takes priority at the moment. But thats my idea,when i can get the time!

 

[rweis]

I'll go measure the Wilson APPS. The hole fit was perfect, the screw fit was perfect.



DTT uses a microswitch linked to a long spring pin to use a a gear selector indicator. Something like that would work fine as a out of idle switch. It is pretty heavy duty and functions in a dirty oily weather environment for years and years.



BRB on the ohms of the WIlson.



Bob Weis

 

[rweis]

The Wilson APPS is 2. 09K ohms to . 262 k ohms. The . 262 k is at zero throttle, the 2. 09 k ohms is at full throttle.



The throttle active measures 10 M ohms at idle then slightly out of idle the ohms drop to 13 ohms and hold at about 13 - 14 ohms all the way to full throttle.



The idle active is 10 - 13 ohms at idle and then goes to 10 m ohms slightly out of idle.



Does that help?



Bob Weis



As mentioned before the Wilson APPS is an exact fittment to the DC APPS mounting plate. As mentioned above, MAYBE there are several APPS that have the same mounting?

 

[SWC]

I have been following this thread with interest as well. I just put a new APPS on my truck. Does anybody want a part or all of it with the bellcrank? I am in Canada shipping might be a little more interesting.

Stan

 

[timbo]

I have been following this thread with interest as well. I just put a new APPS on my truck. Does anybody want a part or all of it with the bellcrank? I am in Canada shipping might be a little more interesting.

Stan

I could use it for some experimenting. (bellcrank also) I do not have a donor APPS and mine is fine at the time being,and don't want to disturb the delicate thing. I do want to have a solution for this before mine goes south! Would shipping be difficult?

 

[SWC]

timbo, the cost would be the biggest issue. I see York, PA is your address. I live on a farm. The next time I get into town I will check what the postage would be. I believe the postal service would be the most reasonable for price and the least hassle for customs.

Stan

 

[Gary - K7GLD]

For those interested, here's a pic of a section of ECM diagram as provided on a TDR thread related specifically to the ECM. That larger diagram included the various peripheral sensors, IAT, CPS, etc. , including this of the APPS equivalent circuit:

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You can see the APPS pinouts, as well as, on the extreme right, the corresponding ECM pins the APPS connects to. Interesting to note, that this diagram displays a simple switch to perform IVS operation, rather than complicated solid state electronic circuitry... - I'll also include this diagram on the APPS schematic further above for easier reference.



I have thoroughly cogitated on this, and am convinced the easiest and most practical APPS substitution approach is not to reproduce the electronics section for installation away from the engine bay, but instead, to fully simplify the APPS with a simple quality potentiometer for accelerator sensing, and a switching setup for the IVS function - a simple mechanical 2-piece replacement that is essentially totally insensitive to ambient heat.



I still have a used pair of APPS units - the actual APPS itself, not the mechanical bracket and mechanism - and will see if I might be able to carefully use one as a base, including connector, to fabricate the complete potentiometer and IVS switch upon - in other words, a complete direct replacement unit that is fully compatible with the OEM wiring harness and APPS plug.



For this, I'll need to obtain another APPS bracket and mechanism - when that is obtained, I'll get started!

 

[KarlC]

I still have a used pair of APPS units - the actual APPS itself, not the mechanical bracket and mechanism - and will see if I might be able to carefully use one as a base, including connector, to fabricate the complete potentiometer and IVS switch upon - in other words, a complete direct replacement unit that is fully compatible with the OEM wiring harness and APPS plug.

Great idea to use the existing housing. I was able to get the flex circuit out in one piece including the resistance elements and connector tabs. What was left in the housing was the connector and the rotating mechanism with wiping fingers on one side. There is a dust seal on the rotating shaft where it enters the housing. It would be neat to use the shaft in the housing to actuate your pot.



The flex circuit is glued to both sides of the partition in the center of the housing. This partition isn't glued in to the housing, it's just a snug fit. I used a knife starting opposite the connector end to pull it up and out. In the process a right-angle piece broke off the partition. It holds the flex circuit against the zebra strips. With a fair amount of force, you can then pull the broken piece, the flex circuit, and the piece containing the zebra strips out of the housing.

 

[rweis]

DTT uses a microswitch linked to a long spring to use as a gear selector indicator (ie what gear set you have selected by the gear selector in the cab). Something like that would work fine as a out of idle switch. It is pretty heavy duty and functions in a dirty oily weather environment for years and years.

I think this would be the ideal IV switch. DTT simply bolts it to a bracket and bolts the bracket to an existing bolt on the auto transmission.



The switch could be held open with the bell crank at idle. As soon as the bell crank moves to a throttle position it closes the switch. (or vice versa)



I like the idea of getting rid of more electronics we really do not need.



Bob Weis

 

[mhenon]

HOLY HYSTERESIS BATMAN!! Can't believe the progress being made on this project. Just finished a 3 day road trip from LA to Texas and log on to find a complete schematic of the APPS. Great job everyone!

It looks like there will be at least two solutions to the APPS problem when this is all over; fix the exsisting APPS or adapt a replacement APPS/TPS. Very encouraging so far.

Mike

 

[mhenon]

HEY, GREAT JOB on that schematic!... Thanks from all us APPS experimenters!. .

I'll second that! Nice work Karl!

Mike

 

[timbo]

Alright here's the deal. I took a microswitch and the Ford TPS and wired exactly to the schematic (except). The way i'm reading the diagram it shows it in the accel mode (not idling), so with engine off i made #1 and #2 contacts closed and 1and 6 open. Then proceeded to turn the key on (nevously). The CEL came on with the key, then went out like normal,i thought thats a good sign. The tps voltage was . 56 idle pos. and 4. 7 WOT. That seemed pretty close! I then proceeded to start it. Fired right up and idled @ 1100 RPM. I then actuated the TPS (without pushing the M. S. ) It reved up. Oo. But without actuating the M. S,that connect #1 and #6, and open #1 and #2 it should only idle and also only @ 850 RPM . I then actuated the M. S. It still reved up just like normal. It reved up smoothly through the RPM band, so the TPS seems to do that part of the job alright, but idle validation did not work correctly. I rev checked it 4 times then the idle dropped to 850 and then TPS did not respond anymore,Just like dead petal. I then checked codes with the smarty, ( coded TPS but not idle validation). I then cleared codes hooked APPS back up and refired it, runs like normal. At this point, i'm scratching my head for a little while, and doing some more research. Do you guys have any input on this??

 

[Gary - K7GLD]

HMmmmm - I would suspect the ECM would expect to see a rise in TPS signal at the same time the IVS signal changes, or else sense an error, I don't think you could engage one without the other without setting a fault or code - and I agree, the diagram further above seems to display that pin #1 (ground) will contact/ground out #2 at idle, and #6 at off idle. Also, if/when I get into this, I think I will include the 470pf caps across #2 & 6, as well as the . 01 uf from 2 &6 to ground to provide filtering and eliminate MS contact "bounce" or arcing that might compromise the IVS signal.

 

[Gary - K7GLD]

MEANWHILE, I'm still in need of someone's old swapped out APPS and mounting bracket, if anyone has one around to donate and help the cause... :-laf



Naturally, glad to pay the transportaion expense...

 

[timbo]

The part that don't make sense (at this point), Why did it start immed. and go to 1100RPM. #1 and#2 contacts are closed, it should only idle.

 

[Gary - K7GLD]

The part that don't make sense (at this point), Why did it start immed. and go to 1100RPM. #1 and#2 contacts are closed, it should only idle.

Well, as far as I can see, Idle RPM - other than hi-idle in cold temps - is controlled entirely by the resistance of the potentiometer - so that would be the RPM control, not the IVS switch - in fact, if idle RPM is too high because of the (incorrect) potentiometer resistance, it might also trigger a fault in the ECM...