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Discussion Starter · #1 ·
Years ago after I did this swap, I would occasionally get a condition where after running a bit the engine would not idle down. It would stay stuck at around 2k rpm and stay there untill a restart.
By luck, one time when it did this I happened to jiggle the 10 pin connectors and it would intermittently stop/start doing it. A HA....I read about this. I cleaned the connectors and manipulated the pins for a better contact. All seemed well for a bit, but it would still very occasionally do it. Another cleaning of the contacts would usually clear it up for a bit. Logging on TPRT showed a part throttle condition when this happens. Throttle cable is not binding.

Well yesterday we had to drive an hr away. The car was a miserable [email protected] the whole way there. At our destination I grabbed a piece of emery cloth and scuffed up the pins yet again and it was fine for the hr drive home.....but it was also cooler by then. Thinking this could also be heat related.
Anyways, if I can be sure the culprit is the TPS signal (pin 47), then I would gladly bypass the 10 pins altogether and permanently hardwire the fuel injection harness to the main harness. But I would be seriously bummed if the condition persists.
Is there ANY other wire or any other scenario that could cause the part throttle flag? Just don’t want to be chasing my tail here. I’ve tried several Motorcraft TPS’s with no change.
Could testing wire resistance show positively where the issue is? Thinking of testing either side of the 10 pins. I do have a few sets of those posi lock contraptions that I can easily T in anywhere on the harness to check.
Thanks
 

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log the voltage when it happens

look at TPS voltage on a graph, where it should be closed
 

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When i first got my car it had a similar issue. I ended up having a corroded main power wire which had a serious voltage drop issue under heavy load. When my fan would turn on it would starve the ecu of power. Once i replaced the power wire issue was fixed. It might be worth checking for voltage drop across main power and ground.
 

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Discussion Starter · #4 ·
When i first got my car out had a similar issue. I ended up having a corroded main power wire which had a serious voltage drop issue under heavy load. When my fan would much on it would starve the ecu of power. Once i replaced the power wire issue was fixed. It might be worth checking for voltage drop across main power and ground.
Power seems solid, but won’t hurt to check. Thanks

log the voltage when it happens

look at TPS voltage on a graph, where it should be closed
I’m not sure the TPS voltage is logged in TPRT. Here is a screen shot of a log. TP Rel Calc follows the pedal. Is that what we’re looking for under a different name?
 

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TPS

it should be a voltage

log the event, then graph it with rpm
 

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Power seems solid, but won’t hurt to check.
Mine seemed solid too and never had issues starting or any other voltage related issues. It's a long shot but it's a free test assuming you have a multimeter. Good luck.
 

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Power seems solid, but won’t hurt to check. Thanks


I’m not sure the TPS voltage is logged in TPRT. Here is a screen shot of a log. TP Rel Calc follows the pedal. Is that what we’re looking for under a different name?
that screen shot shows rpm of ~1000rpm

and tp minus ratch is near zero, there is no issue there

supply a log with the issue
 

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I had a similar issue going on with an accufab 90mm throttle body lots of years of driving lots of miles with boost and water-methanol injection and the brass throttle blade wore a slight groove in the aluminum on the inside of the throttle body. Tried all kinds of different problem solving techniques and end up replacing the throttle body with a brand new accufab 90mm and the problem went away. I thought it was electrical I thought it was a TPS problem and I've seen stock throttle body's have the same type of wear problems so at a loss no other ideas dropped $290 for the new throttle body and fixed it.
 

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would be able to see that in a log

so $290 is not wasted
 

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Discussion Starter · #10 · (Edited)
that screen shot shows rpm of ~1000rpm

and tp minus ratch is near zero, there is no issue there

supply a log with the issue
Thanks. The screenshot was just to show what I’m able to log. Will dig through my logs to find an occurrence.

eta: found one. This is sitting still with the condition being present for the previous 20 seconds.
 

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look at

tp-ratch= TP_REL_CALC

THIS is verified as ISCFLAG=0

AND therefore ISCDTY=74%

I am sure DASPOT is in preposition and is commanding 1.58 lb/min air which equates to 74% iscdty

given the above, what do you think the problem is?

ECM is acting normally due to the input…….that is a hint
 

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why wont you send me the log?
 

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Discussion Starter · #13 ·
look at

tp-ratch= TP_REL_CALC

THIS is verified as ISCFLAG=0

AND therefore ISCDTY=74%

I am sure DASPOT is in preposition and is commanding 1.58 lb/min air which equates to 74% iscdty

given the above, what do you think the problem is?

ECM is acting normally due to the input…….that is a hint
Ok, not really understanding tp-ratch and iscflag, but you’re hinting that the ecu is receiving some bad info. I did have some fluctuating iscdc numbers at warm idle leading me to believe a bad IAC which I replaced with a new Motorcraft unit. ISC numbers are stable after the change.
This issue is very intermittent.

I’ll send you the log, but it is from a couple months ago (old iac) and the tune has been updated several times since them. Let me get a fresh one for you if I can recreate the magic.
 

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Discussion Starter · #14 ·
Was out for a couple hrs in the car today. Drove fine until we nearly got home, then started doing it again. Came home grabbed the computer. restarted and got this log where it starts doing it at about 8:20 in. The last 30 seconds or so we are stopped.
I'll send you the bin file too in case you're interested. I do appreciate you taking the time to look at this. Thanks very much.
 

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Ok, not really understanding tp-ratch and iscflag, but you’re hinting that the ecu is receiving some bad info. I did have some fluctuating iscdc numbers at warm idle leading me to believe a bad IAC which I replaced with a new Motorcraft unit. ISC numbers are stable after the change.
This issue is very intermittent.

I’ll send you the log, but it is from a couple months ago (old iac) and the tune has been updated several times since them. Let me get a fresh one for you if I can recreate the magic.

THE ECM is receiving an open throttle condition, and is adding air through iac as designed in the calibration

poor sensor ground can cause high voltage at TPS signal

when TP = RATCH, that is closed throttle, IE TPS_CALC = 0

can you see that, from the PIDs i previously listed?
 

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looked at your log

at 8:18 your TPS is reporting part throttle, were you at part throttle?

you were at part throttle from that time to the end of the log

you claim the last 20seconds was closed throttle, and was idling, there is no evidence of that

either your throttle blade is stuck open, or the there is a circuit problem, i saw a few instances where the TP_calc was at -23, this tells me when you started the car, the throttle may have been open, or at some time ratch was reset, like a simulated restart, not actual


since it difficult to tell from the log whether the throttle is stuck or there is a circuit problem

reproduce the hanging idle, while logging, and unplug the IAC, what happens?
 

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Did you check for voltage drop? Did you look at your log to verify your not seeing a voltage drop right before the issue happens? My issues were exactly the same as yours including the ecu seeing an open throttle condition. I personally would check throttle voltage when it's not happening and when it is. Mine showed .9v regardless so i knew it wasn't the tps.
 

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Discussion Starter · #18 · (Edited)
looked at your log

at 8:18 your TPS is reporting part throttle, were you at part throttle?
Foot was off the gas and TB was shut, but yes, as you can see in the log, the car was ‘idling’ at around 2200rpm.
eta: I should clarify. At 8:20 I‘m still on the road but using no pedal input. I was on my way for gas. The last 30 seconds or so I was sitting still at the pump, ‘idling’ (no throttle pedal, but log showing part throttle)

you were at part throttle from that time to the end of the log

you claim the last 20seconds was closed throttle, and was idling, there is no evidence of that

either your throttle blade is stuck open, or the there is a circuit problem, i saw a few instances where the TP_calc was at -23, this tells me when you started the car, the throttle may have been open, or at some time ratch was reset, like a simulated restart, not actual
Foot off the gas and TB closed, yes. That log was a restart after shutting off with the condition happening so maybe that’s why ratch was screwy? I always restart with no pedal input. TB snaps shut with a definitive click. I’m pretty confident it is a wiring issue, but I defer to your experience.


since it difficult to tell from the log whether the throttle is stuck or there is a circuit problem

reproduce the hanging idle, while logging, and unplug the IAC, what happens?
I haven’t logged it, but previously when I unplugged IAC, it would go back to normal idle rpm, indicating proper operation. This was a while ago, but things haven’t changed much with my setup.
Thanks.

Did you check for voltage drop? Did you look at your log to verify your not seeing a voltage drop right before the issue happens? My issues were exactly the same as yours including the ecu seeing an open throttle condition. I personally would check throttle voltage when it's not happening and when it is. Mine showed .9v regardless so i knew it wasn't the tps.
I haven’t checked that yet, but I will. By voltage drop, where do you mean specifically? TP logs show batt voltage but not TPS voltage as far as I can tell....though I do know how to check TPS voltage as I used to believe the .9999 myth. lol.

Thanks both of you.
 

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If you are confident the pedal is not open.

then your problem is with the TPS circuit

power, sensor ground, signal

its sounds like it happens after some time during a drive, so it seems heat related that might help with direction
 

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Discussion Starter · #20 ·
If you are confident the pedal is not open.

then your problem is with the TPS circuit

power, sensor ground, signal

its sounds like it happens after some time during a drive, so it seems heat related that might help with direction
Sounds like we’re all reading from the same playbook here.
Going back to my first post, since all 3 wires go through the 10 pins I’m thinking of placing posilock taps on either side of them on the 3 wires (I may only have enough of those to do 1 wire at a time) and measure when normal, and then again when the condition appears. Will just have to remember to have my multimeter on board. Then I can easily throw a temporary jumper wire on the taps until I do a more permanent fix over the winter, assuming that’s where the issue is.
Sound solid?
 
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