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Old 07-03-2003, 22:32   #1 (permalink)
jjj
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Everyone with a 3.9lCPI engine should read this!

I have found a major fault with ford e-series Throttle Position Sensors(TPS) on CPI engines. If you have every experienced intimitent high rev starts and the car wanting to drive itself at around 1200-1500rpm then look at the voltage output of the TPS(located on back of throttle body). Use a multimeter and test on pin 47 of ECU. It should be 1V(closed throttle) and 4.5V(open throttle) with the ignition on. If the closed throttle is lower than 1V then you will have dramas. Mine was on 0.6V so i thought i would need a new one but to my suprise if you loosen the 2 screws and move it up and down say 2mm in each direction you have a reading of (0.3v to 1.3V) on the TPS at closed throttle. So I realigned it (moved it down slightly by 2mm with the aid off a digital multimeter to get exactly 1volt and tightened the screws) . I also had a spare one from a wreck it it was exactly the same. My open throttle was 4.2V and since adjusting closed throttle to 1V, i now have 4.5V at wide open throttle. The car has heaps more go because the ECU was only thinking I was doing 85% throttle as apposed to 100%. So basically this is an engineering fault and people should check this before spending heaps of dollars replacing all the usual items you think would be causing the fault.

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Old 07-03-2003, 23:08   #2 (permalink)
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Re: Everyone with a 3.9lCPI engine should read this!

i got cfi, dunno much about engines, can u get some pics to help me out?
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Old 07-03-2003, 23:14   #3 (permalink)
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Re: Everyone with a 3.9lCPI engine should read this!

So if you increase to more than 4.5volts at full throttle does that mean the saying "give it 110%" will be true ........... LOL

Neat trick though, very clever.

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Old 07-04-2003, 01:11   #4 (permalink)
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Re: Everyone with a 3.9lCPI engine should read this!

Good tip, JJJ.
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Old 07-04-2003, 01:45   #5 (permalink)
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Re: Everyone with a 3.9lCPI engine should read this!

Thanks guys for responding, i spent hours tracing this fault, i'm happy that i found this problem that would spring up about once a fortnight then go away again. Last week the ford technicians didn't have a clue what was going on, their so called wonder computer could not find this little beauty. I have read alot of posts of people having this problem and they just live with it because no mechanic has a f#cken clue. I do have a background in electronics so this helped me plus the schematic diagrams in gregorys manual. Also Delboy999 there is no put increasing the value above 4.5V as that is a set parameter the ECU knows when full throttle is applied.
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Old 07-04-2003, 07:41   #6 (permalink)
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Re: Everyone with a 3.9lCPI engine should read this!

My car used to have the same problem when it was CFI. It would sit at 1400-1600RPM and not want to come down. Freaky.

It runs nice and smooth now it's a MPI though

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Old 07-04-2003, 14:27   #7 (permalink)
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Re: Everyone with a 3.9lCPI engine should read this!

As i said before sundeep, this is a common problem with CPI engines and i'm wondering wether or not I should ask ford if they might want a technical brief about the design problem.
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Old 07-04-2003, 16:50   #8 (permalink)
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Re: Everyone with a 3.9lCPI engine should read this!

well I have heard of a few other cars with similar problems, as the TPS wears, some mechanics elongate the holes on the TPS and shift it around until they get a good reading, never heard of anyone doing it on a falcon though, nice work
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Old 07-04-2003, 18:26   #9 (permalink)
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Re: Everyone with a 3.9lCPI engine should read this!

I wonder if they had a TSB about it?
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Old 07-05-2003, 23:10   #10 (permalink)
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Re: Everyone with a 3.9lCPI engine should read this!

I am sooo trying this when I can get hold of a mulitmeter.. I just also read in the Haynes manual about testing the TPS and it says the voltages should be between 0.7 and 4.4V. But I think the gregory's is a better manual..

Also there is a test for smoothness from closed to wide open - that may be good for picking up flat spots in acceleration maybe..

This maybe a violation of copyright but I don't think Haynes will sue me.. (Hopefully!!)

Throttle Position Sensor (TPS)

General Description
The throttle position sensor (TPS) is located on the end of the throttle shaft on the throttle body (MPEFI) or fuel charge housing (CFI). By monitoring the output voltage from the TPS, the ECU can determine fuel delivery based on throttle valve angle (driver demand). A broken or loose TPS can cause intermittent bursts of fuel from the injectors and an unstable idle because the ECU thinks the throttle is moving. Any problems in the TPS or circuit will trigger a code 23, 53 or 63.

Check
*On CFI models perform the following at the TPS electrical connector.
*Using straight pins or paper clips as required, backprobe the TPS electrical connector. Attach the negative lead earth and the postive lead to the sensor wire.
*Turn the ignition key ON, (engine OFF), the sensor should read approximately 0.7V with the throttle closed. Now manually open the throttle to wide open position, the sensor voltage should increase to approximately 4.4V
*Check the TPS reference voltage. With the ignition key ON (engine OFF), connect the positive probe of the multimeter to the orange/black wire. There should be approximately 5.0V present. If no voltage check for a blown fuse, etc..
*Check the resistance of the pententiometer within the TPS. Disconnect the TPS electrical connector and working on the sensor side, connect the probes of the multimeter to the orange/black and gree/black wires. With the throttle valve fully closed the TPS should read approximately 3K ohms.
*Now open the throttle with one hand and check the resistance again. Slowly advance the throttle to the wide open position. The resistance should be approximately 500 ohms. The pententiometer should exhibit a smooth change in resistance as it travels from closed to fully open throttle. Any deviations indicate a possible worn or damaged TPS.

Hope that helps anyone that might want to try it..

Dan..
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