My truck has three codes currently 212 (I believe I need to replace the grey icm with a black one), 311 (checked for vac leaks but haven't done much else), 411 code: unable to control low rpm in test. The symptoms it is displaying is high idle rpm 1,900 for 30 seconds then slowly lowering to 1,100. It also has a slight miss or stumble all the time.


Removed and cleaned the throttle body (was very dirty) with tb cleaner, replaced gaskets, replaced the tps (and set it to 1.0v it was not a motorcraft one, it is within spec for voltage tests but can't get it to have the correct resistance the book calls for), new delphi IAC, cleaned MAP sensor replaced most of the vacuum lines with rubber and tried to find leaks & ran some seafoam through the gas. It also recently had new plugs, wires, cap & rotor and delphi fuel pump put in & K&N air filter. I also replaced the plenum gasket since I was doing valve cover gaskets (oil leak) too. Checked with propane for leaks and found none.

I need some help on where to look next...

 

they're going to need more truck info, minimum closed TPS is 350 ohms
Fuel Injection Technical Library » Throttle Position Sensor (TPS)
Throttle Position Sensor Testing, Replacement and Adjustment - Ford Bronco Forum

 

1994 F-150 5.0 130,000 miles
I get a proper reference voltage of 5v. TPS signal is also good. But my resistance readings are .955 k closed & 3.6 k open. I'm not sure I understand the k value of omhs does 1k=1000omhs? Anyway pretty sure that closed value is way out of spec at least. Guess I better pick up another TPS motorcraft this time around.

I got the below info off of https://www.fullsizebronco.com/forum...djustment.html It seems to match with the Haynnes Manual.

KOEO TPS Values
KOEO TPS Reference Voltage - 5v
KOEO TPS Signal Voltage - <1v to <4.8v
Unplugged TPS Resistance - <4k ohms to >350 ohms


KOEO TPS Testing
KOEO TPS Reference Voltage - VREF and SIG RTN
KOEO TPS Signal Voltage - TP SIG and SIG RTN (while rotating Throttle)
Unplugged TPS Resistance - TP SIG and VREF (while rotating Throttle)

1988-1991 TPS Wire Colors
VREF - Orange/White
TP SIG - Dark Green/Light Green
SIG RTN - Black/White (My 1990 is actually Red/Gray)


1992-1996 TPS Wire Colors
VREF - Brown/White
TP SIG - Gray/White
SIG RTN -Gray/Red


Motorcraft TPS Wire Colors
VREF - Orange
TP SIG - Green
SIG RTN - Black

 

yes k = 1000 ohms, and your .955k =955 ohms which is to hi for being closed, did you get your ICM=TFI swapped to correct one? did truck idle hi when you got it? did your old TPS have the hi closed reading also? PO could have adjusted throttle stop screw for idle, instead of cleaning throttle body, if they did could explain why your closed reading is so hi(idles hi now), verses new TPS being bad, or old TPS being bad

this is a good read, LONG, but good, see post #11 and #38(by broken wire)
Beating The Idle Topic Like A Dead Horse! - Page 3 - Ford Truck Enthusiasts Forums

 

SOLVED HALF THE ISSUE
Torq'ta 58 your questions and those posts got me thinking about the timeline of events thanks for pointing me in that direction! When I got the truck this summer it idled low and would stall occasionally. My first thought was clean the TB, since the TPS was hard to get to down there and looked old I just replaced it (set to .95v or very close to that) never tested the old one (shame on me). When I replaced it I had to enlarge the holes to get into spec which the book said sometimes you have to do (first clue). Afterwards it never Idled slow or stalled again but now it had this idle hang up where when driving it would hold rpms at 1800 when decelerating and I'd have to stand on the brakes all the time. The IAC tested ok but when disconnected there was no idle drop so I replaced. This cured the idle hang up issue but then I had the high idle issue and my codes switched from 412 to 411. Like you said I started thinking the previous owner may have adjusted the idle stop screw. The post you reference talked about backing the screw out until you feel the tb blades start to bind then back in a half a turn. I got up this morning and gave that a try sure enough after resetting it I was at least two full turns further in than it should have been. Start up the truck and just like that idles back where it should! Thank You!

Now I just have to track down the missing issue which is still persisting. I took a video of it see it on the link here:
I had just ordered a motorcraft TPS and delphi o2 sensor before you posted haha. I'm sure the current TPS is now out of spec (after messing with the stop screw) and needs reset to .95v. So I'll do that when the new TPS arrives. I'm not getting any code that indicate an o2 sensor but figured it would be a good part to replace anyway (once again I didn't test the current one.. yet). I'll get these issues taken care of this weekend hopefully and also my timing was a little retarded like 8-9 so I'm going to bump that up a little rerun codes and I'll report back with the results.

I have not got my ICM swapped to the right one yet. Was hoping to pick one up at the salvage yard just need to get around to it next time I'm near the yard.

 

glad to hear you've made progress, and its in right direction, even better, maybe you get it swapped your miss goes away too

 

Update: Switched out the grey icm for a black one and got ride of that code. Put in the new motorcraft tps and got rid of the 411 code. The slight missing still persists. The only code left is 311 so its time to diagnose the thermactor systems I guess. I'd be temped to delete the whole system but read mixed things about it. Just want the engine to run smooth.

 

check plug wire routing, just for S&G,

 

I've checked it twice. I even used zip ties to make it just like the diagram last time. When I learned about that diagram the first time I though for sure that was going to be my problem. But the stumble still happens.