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ButtonPuncher
Hard-core CEG'er

Reged: 08/16/02
Posts: 1224
Loc: Inbetween turbo and super land.
Funky OBD-II readings...bad TPS?
#143769 - 01/09/03 05:29 AM

This is a spin-off of my orignal thread.

I hooked up my laptop today and got some weird readings. With the key in the "on" position, and not running, the TPS is at 16.5% and the MAF was reading 0.117#/min. Shouldn't both of these values be ZERO if i'm not touching the gas pedal AND the engine is off?!?

This would explain why my car won't idle without dying. The computer thinks that the throttle is open so it is dumping gas into the engine and closing off the IAC. This is drowning my Zetec in fuel and not giving it any air. I've gotta swap out that TPS!!!

BTW, what kind of readings should I have for my MAF and TPS at a given RPM?

Here are some of my other readings...

Engine off:
MAF=0.177 #/min
TPS=16.5%
ECT=73 degrees F
IAT=45 degrees F (It was about 40 outside)

Started and holding gas to maintain 2k RPM:
MAF=1.113 #/min
TPS=20.8% (only 4% change?)
ECT=180
IAT=54
LOAD=25.9%
Short Term Fuel Trim=varied from -1 to 0
Long Term Fuel Trim=3.9
Spark Advance = 35.5 degrees
#1 O2 Sensor = varied from 0 to 0.745
#2 O2 Sensor = 0.725

Revving to 3500RPM:
MAF=1.702 #/min
TP=21.6% (less than 1% !?)
Spark Adv = 36.5 degrees
LOAD=29.4%

Idling badly:
MAF=0.366 #/min
TPS= 16.5%
ECT= 185
IAT= 66
LOAD= 41.2% (MUCH higher then at 3500RPM)
Short Term Fuel Trim= varied from 0 to 2.3
RPM = 800
Spark Advance = 28 degrees
#1 O2 Sensor = varied from 0 to 7.35
#2 O2 Sensor = 0.818

FYI, all readings were done with my car in park.

BP

--------------------
Ben ---'96 Contour GL * Zetec ATX * Tan on Black steelies---
+++JRSC M62 Under Construction+++
My big-a$$ mod list.

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Rogerm60
Hard-core CEG'er

Reged: 10/11/02
Posts: 2408
Re: Funky OBD-II readings...bad TPS? new
#143804 (Re: ButtonPuncher) 01/09/03 05:58 AM

Not sure about minimum MAF % but don't think it can reach zero.

16% TPS is bogus for sure.

You have been resetting the PCM, right?

Never heard how it runs other than idle. Timing belt OK? Checked the vacuum?

--------------------
"Those who cannot remember the past are condemned to repeat it" -George Santayana

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ButtonPuncher
Hard-core CEG'er

Reged: 08/16/02
Posts: 1224
Loc: Inbetween turbo and super land.
Re: Funky OBD-II readings...bad TPS? new
#143846 (Re: Rogerm60) 01/09/03 06:38 AM

Yep, reset the PCM everytime. Vacuum is good, and the timing belt only has 17k on it.

I'm gonna yank the TPS tomorrow and substitute a 5k potentiometer and see what happens.

Waddya think?

BP

--------------------
Ben ---'96 Contour GL * Zetec ATX * Tan on Black steelies---
+++JRSC M62 Under Construction+++
My big-a$$ mod list.

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Rogerm60
Hard-core CEG'er

Reged: 10/11/02
Posts: 2408
Re: Funky OBD-II readings...bad TPS? new
#143884 (Re: ButtonPuncher) 01/09/03 07:48 AM

Sounds like a plan - since you put everything but the kitchen sink in there already!

--------------------
"Those who cannot remember the past are condemned to repeat it" -George Santayana

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GeoPappas
Veteran CEG'er

Reged: 12/13/01
Posts: 667
Loc: Northern VA
Re: Funky OBD-II readings...bad TPS? new
#144003 (Re: Rogerm60) 01/09/03 01:08 PM

The following is from the Ford TSP (Technical Service Publication):

MAF voltage @ KOEO (Key On Engine Off) should read 0
MAF voltage @ hot idle should read .6-.9
MAF voltage @ 30 MPH should read .8-1.5
MAF voltage @ 55 MPH should read 1.2-2.5

TPS voltage @ KOEO (Key On Engine Off) should read .53-1.27
TPS voltage @ hot idle should read .53-1.27
TPS voltage @ 30 MPH should read 1-1.3
TPS voltage @ 55 MPH should read 1.1-1.4



--------------------
96 Contour SE
Duratec V6 24-valve 2.5L ATX
108,000 mi.
Replaced: crankshaft w/ DMD, EGR valve (clogged), EVR, DPFE, PCV valve, evap emissions hose & tube (cracked), window regulator (broken), LH & RH PCV tubes, UIM gasket (leak), ignition coil


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ButtonPuncher
Hard-core CEG'er

Reged: 08/16/02
Posts: 1224
Loc: Inbetween turbo and super land.
Re: Funky OBD-II readings...bad TPS? new
#145101 (Re: GeoPappas) 01/10/03 03:55 AM

Screw it, I'm done.

I just checked the TPS and MAF voltages, both are within spec.

I'm gonna suck it up and take it in tomorrow.

BP

--------------------
Ben ---'96 Contour GL * Zetec ATX * Tan on Black steelies---
+++JRSC M62 Under Construction+++
My big-a$$ mod list.

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GregH
CEG'er

Reged: 11/13/02
Posts: 216
Re: Funky OBD-II readings...bad TPS? new
#145621 (Re: ButtonPuncher) 01/10/03 04:45 PM

the tps isn't designed to go to zero, but the MAF will be close if the engine isn't running.. If you have an idle proble, it is most likely caused by the IAC. Also, the IAC opens in proportion to the throttle opening to act as a dashpot (like on older mechanical carburetor engines) to prevent gaskets from being sucked in and failing in the event that you snap the throttle closed at high RPM.

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ButtonPuncher
Hard-core CEG'er

Reged: 08/16/02
Posts: 1224
Loc: Inbetween turbo and super land.
Re: Funky OBD-II readings...bad TPS? new
#147079 (Re: GregH) 01/12/03 03:55 AM

My readings are on my laptop at work, but i know that the TPS was around 0.62. The MAF was also in range.

Besides putting the old TPS back on, or buying a new one, is there anyway to test it?

I'm guessing that I would need and oscilloscope in order to determine if it is running at the right voltage and frequency. Ugh...I am sooo sick of working on my car...

...maybe tomorrow...

It's satruday night. Time to go drinkin'.

BP

--------------------
Ben ---'96 Contour GL * Zetec ATX * Tan on Black steelies---
+++JRSC M62 Under Construction+++
My big-a$$ mod list.

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trob
New CEG'er

Reged: 06/11/01
Posts: 32
Re: Funky OBD-II readings...bad TPS? new
#147188 (Re: ButtonPuncher) 01/12/03 05:52 AM

We have a 99 Zetec ATX. The min throttle position setting seems to always read 17%. There are no idle problems (yet!)on our car. I don't think you have a bad TPS.

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ButtonPuncher
Hard-core CEG'er

Reged: 08/16/02
Posts: 1224
Loc: Inbetween turbo and super land.
Re: Funky OBD-II readings...bad TPS? new
#147312 (Re: trob) 01/12/03 08:20 AM

Yeah, with the TPS at 16% it read somewhere around a volt (well within limits).

I'd like to try swapping out the IAC but I really doubt that it is bad. It worked flawlessly when i had it out.

(I hope this made sense..Jeagermeister(sp?) is screwing with me a little.)

BP

--------------------
Ben ---'96 Contour GL * Zetec ATX * Tan on Black steelies---
+++JRSC M62 Under Construction+++
My big-a$$ mod list.

Edited by ButtonPuncher (01/12/03 09:13 AM)

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