4.6L (1996-2004 Modular) Mustang Technical discussions on 1996-2004 4.6 Liter Modular Motors (2V and 4V) within.

Check Engine Light...no idea

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Old Jun 23, 2009 | 09:24 AM
  #1  
mstang2k6's Avatar
mstang2k6
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Default Check Engine Light...no idea

Though i would start a new post to make things more organized...

So i recently installed a Accufab 75mm Throttle Body, Plenum, and JLT CAI and soon after my car threw a check engine light and had an issue of when driving th e car, when i accelerated to around 30-40mph the car would kind of bog and the rpms would drop down to around 1100-1200 and the car wouldn't really accelerate. Or if i accelerate quickly, let off the gas and try to flore it the car won't really accelerate...but on my drive to work this morninig the same issue as i stated in the message right above(It seems like the car just won't go higher then 1000-1500 rpms.) Well driving to work this morining sometimes when i even hit 30, it would seem like the rpms would just die down and drop to 1100 or so and not reaccelerate.

So I had the code scanned and it said it was the throttle position sensor, I went ahead and changed it and the light went off temporarily but came back on this morning. Does anyone have any idea what the issue could be, if the code states it's an issue related to the throttle position sensor, shouldn't have changing it done the trick? or where would the next best place to look be?

Some things that I'm thinking might be an issue/stood out to me:

--When i reinstalled the throttle body position sensor I may have accidentally moved the throttle body positin slightly...(i may not have, not really sure if i did)

--I noticed after the install when i had the car turned off and was pressing down on the throttle body(spinning the throttle body plate) the throttle body cabel would kind of stutter/bounce back when i released the throttle (i don't remember if this was normal or not, meaning should the throttle body cable just go back smoothly in one motion when releasing the throttle body?). I mean it looks like it's installed properly.
Old Jun 23, 2009 | 09:31 AM
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Well, my first guess is that the TPS is out of whack. The second issue on your throttle plate is that it should be smooth. You should be able to open and close it without it really hanging up on anything. Just make sure you routed the cable correctly.
Old Jun 23, 2009 | 10:16 AM
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So how would i go about adjusting the TPS...i just bought a new one and installed it, what else can i really do there?

In regards to the the throttle plate...it closes smoothly, it's just when i push down on the throttle body(aka lift the throttle plate) and let go of the throttle body the plate closes smoothly(i beleive) it's just that the cable seems to bounce back/stutters a little when the throttle plate closes back up. (not sure if this makes sense, i might need to take a video clip of it)
Old Jun 23, 2009 | 01:48 PM
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Originally Posted by mstang2k6
So how would i go about adjusting the TPS...i just bought a new one and installed it, what else can i really do there?
I was having idling issues (and a bog followed by surge after putting in gear) and tried the usual iac cleaning to no avail. What fixed it for me was loosening the 2 bolts for the TPS and turning it (just a hair) and tightening it back down. That's the easiest way to adjust it anyway. Bigger adjustments - cant help you there - but I don't think it's something you really need to (or should) adjust significantly.
Old Jun 23, 2009 | 06:55 PM
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Did you disconnect the battery for 5-7 minutes while/after installing the goodies? This resets the KAM (Keep Alive Memory) and forces the PCM to learn the new idle air trim settings.

Also, many after market TBs are not properly adjusted for idle air bleed--here's a link to the procedure for setting the base throttle plate position.

In the last, what was the exact DTC recovered? There are 3 or 4 that mention the TPS, a couple of which indicate the TPS has detected something else is wrong.
Old Jun 23, 2009 | 09:12 PM
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I was going to add something... but Cliffy pretty much cosed it up there. so...

+1.
Old Jun 23, 2009 | 10:27 PM
  #7  
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Originally Posted by cliffyk
Did you disconnect the battery for 5-7 minutes while/after installing the goodies? This resets the KAM (Keep Alive Memory) and forces the PCM to learn the new idle air trim settings.

Also, many after market TBs are not properly adjusted for idle air bleed--here's a link to the procedure for setting the base throttle plate position.

In the last, what was the exact DTC recovered? There are 3 or 4 that mention the TPS, a couple of which indicate the TPS has detected something else is wrong.
I disconnected the battery while installing the goodies, and i disconnected the battery after replacing the tps.

In regards to the link you posted, i guess that's a possibility, i did noitce that the throttle cable binds a little bit when spinning the throttle plate.

The specific error code was: PO122

The autozone reciept said the following....

Throttle/Pedal position (TP) sensor circuit low.
Explanation: The TP sensor signal 1 circuit has reported an open low voltage.

Probable cause:
Open or short circuit condition
Poor electrical condition
TP sensor error (already changed the sensor)
Old Jun 24, 2009 | 02:22 AM
  #8  
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possible bad ground wire?
Old Jun 24, 2009 | 07:37 AM
  #9  
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ye ai was just gonna say disconnect the battery and adjust ur idle of the car...what is it idling at rolling and just sitting there? my cobra was saying the same hting about the tps..i changed that 3 times to no avail..and i changed the iac and nohting...turned my ilde screw down caus eit was idling at 1200 and knocked it down to 750 and boom check eng light gone no more issues...
Old Jun 24, 2009 | 11:09 AM
  #10  
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mstang2k6
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Originally Posted by 5.0 85 GT
ye ai was just gonna say disconnect the battery and adjust ur idle of the car...what is it idling at rolling and just sitting there? my cobra was saying the same hting about the tps..i changed that 3 times to no avail..and i changed the iac and nohting...turned my ilde screw down caus eit was idling at 1200 and knocked it down to 750 and boom check eng light gone no more issues...
So this morning on made sure to monitor the rpms and they do seem a bit off:

When the car is in...

Park: 1100
In Drive: 600
At a roll in Drive: 600-700 (i don't remember to well)

Side Note:
I noticed that at WOT from a stop, the car doesn't seem to shift to 2nd(i have an auto if you couldn't tell yet), i need to get of the gas for the car to shift to 2nd. I noticed the car was at around 4000rpms when i was driving about 35-40. After the first shift the car shifts fine. I'm hoping that's all related to the idle screw

I'll adjust the idle screw after work today and let you know what happens. Thanks for everyones input so far.

Last edited by mstang2k6; Jun 24, 2009 at 11:11 AM.
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