2001 ford mustang 3.8 v6 irratic idle speeds

lawnman186

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#1
???
Help we have a 2001 ford mustang 3.8 v6 vin 1FAFP44401F163195
Customer states that sometimes it will stall, other times if she keeps the foot on gas she can keep running but it wants to die. been getting worse. this time it wanted to go higher then idle speed
we scanned it a antitheft and air bag codes no engine codes, did memory, key on engine off, key on engine running nothing but the stupid p1000 incomplete tests
U1262 scp data fault for j1850 bus and B1869 air bag warning indicator lamp open I cleared these codes.
we cleaned the throttle body and mass air flow sensor. it runs ok
but fuel pressure is low alldata says 35-65 psi and it has 30 running. it fluctuates a little
did a 60,000 mile service recently with plugs, fuel and air filters
is this a idle control problem or a weak fuel pump help
thanks
Mctier Import Repair
Steve
 

nickb2

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#2
Get a vacuum reading on this. It may help. IACV valves were pretty frequent back then. Pull it, clean it, and clean inside of throttle body and bypass air also. Look for a loose cam shaft sensor, I have seen a few of these lately, actually last week. Same symptoms as an IACV but the cam sensor was loose and had synched out.
 

lawnman186

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I will try cleaning the IAC valve when we did the 60,000 last year in october we did plugs, fuel filter and air and all the fluids so I guess we can rule out tune up.
the cam position sensor is tight and not moving. I have no engine codes so we can rule that out also. I am not going to throw parts at it or guess with out codes. I am thinking fuel pump is a little weak but again with out forsure I am not going to guess and replace the 300+ fuel pump job and that not be it.
a neighbor told intake leaks are common I have none which would set lean bank codes. the car has less then 65,000 on it but it is a 2001 model should I go ahead and replace the iac valve or fuel pump?
she said her daughter managed to keep it running by keep gas pedal pushed but I guess yesterday the idle started increase like valve was stuck acting like runaway car. well I am off to bed I am beat any ideas would be great
steve
 
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#4
I like to unplug the IAC with the car running to see what it does. Had a coworker where his car would idle really high, unplugged his IAC and it didn't change one bit. Normally I would expect the car to stall. As for the fuel pump, is it possible your gauge is off on your fuel pressure tester ? If you have another one (some people do) or can borrow one get a second opinion before you go diving in to a project. Any chance you have a scan tool that you can go in and view live data ? Be curious as to what the IAC count is.
I will say that I have seen a fair number of IAC valves replaced on fords.

Ford_Dude
 

jjdrewski

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#6
Two cents worth: I just went throught the fuel pump presessure thing with our 95 2.5 L Mercury. Nickb2 finally told me the pressure readings reflect the UNDER LOAD pressure ie up hill, etc. not at rest idle. I was seeing 30 psi at no load idle.
 

lawnman186

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#7
fixed! I just want to let you know we replaced the ICA valve and seemed to run much better we let her pick it up. the valve was pretty dirty, we also found out today she has a extended warranty so anything else she can get it fixed by ford. but where pretty sure its fixed. what maybe happening is when traveling at cruising speed, and then coming to a stop. what maybe happening the idle going down to fast or to low!!!
thanks for your help, its also very possible reguarding fuel pressure our gauge could be off when you first start the car pressure is at 55 and drops slowly coming off fast idle.(with old valve) and at idle and warmed up it hovers around 30 psi and fluctuats a little spec is 35 to 65 according to all data, your last comment about load is a interesting thought. it may reveal we may have a weak pump which is covered under the extended warranty. evently it may need to be replaced.
thank you all for your help
 

jjdrewski

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#8
Fuel pressure regulator is controlled by intake manifold pressure. As you load the engine, you open the throttle and cause a drop in the intake manifold pressure, which relaxes the controll on the regulator which raises the fuel line pressure, which is just what you want when engine is working harder. If I said this wrong I know I will be gently corrected!!
 

billr

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#9
OK, you asked or it! When the throttle is opened it is the intake manifold vacuum that drops, the intake manifold pressure (MAP) is increasing.
 
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#12
Hmm..without looking up the correct answer, I would guess vacuum is an amount of pressure that is less than the current and local atmospheric pressure. Any thing to add, NickD?
 

nickb2

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#13
I had a A/C teacher back in the day, told be about "Le vide absolue" The absolute vacuum. He stated that no machine or vacuum pump on earth can create a perfect vacuum. If the A/C machine I was using was actually able to go to the 30Hg shown on the dial, the car would be sucked onto the A/C machine. I questioned this in my head. Sounds like a planet eater known as a "black hole". That got me thinking even further, I actually do know a machine that is the "vide absolue" the black hole of men. It's called divorce court. Sucks everything in it's path!! :ROFL
That got me looking into it, my assumption that absolute vacuum was like a black hole was erroneous, but my theory about divorce court being a black hole was correct. Absolute vacuum is an absence of matter.
A black hole is a region of space from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is an undetectable surface called an event horizon that marks the point of no return. It is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics.[1] Quantum mechanics predicts that black holes emit radiation like a black body with a finite temperature. This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of stellar mass or greater. ;D gotta love wikipedia.
 

lawnman186

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#15
explain this when why does all data have a spec of 35 to 65 pounds???? there must be a reason they want the fuel pressure that high. when you discount the vacuum line at regulator the pressures jumps to 40. one thing this might be returnless system the regulator not only has a vacuum line like my wifes 1998 mercury tracer but it also has a electrical connector on the regulator my wifes tracer is a returnless fuel system which means the computer controls the pump and only pumps what it needs. thats my $.02