2000 Mustang V6 stuttering low idle in gear - Ford Mustang Forum

 
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post #1 of 13 (permalink) Old 5 Days Ago Thread Starter
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2000 Mustang V6 stuttering low idle in gear

Hello all,

So I bought a 2000 mustang v6 3.8 ( auto trans ) 2 months ago on it not being able to start for 350$. Low and behold it had a thrown rod through the bottom of the oil pan and destroyed the crank and pistons. Bought a junkyard complete motor for 375$ on the only thing wrong was milky oil ( boy was it milky ) Stripped it all down, new gaskets everything cleaned and put back together. I had some issues at first with it not wanting to crank and found out starter and alternator were bad, replaced them and very weak crank, Tq converter wasn't aligned and off a spine, Fixed that and now it starts but was real rough and would stall instantly when put in gear, Spent alot of time searching on this fourm and went to local pull a part and grabbed a new IAC, TPS, and MAF. just finished putting those in and it helped alot, It doesn't stall anymore but now when you put it in reverse or drive ( D 2 or 1 ) it will drop the rpms down to mid 500's and act as it wants to stall, when i let off the brake it jerks forward while still having a low rpm ( around 640ish ). Reverse doesn't jerk as bad and idle goes back around 750 or so and increases to around 1200 if i keep reversing. Park the idle when first starting is around 1100-1200 and after warmed up around 750-800 but jumps constantly between 690 at the lowest and 900 at highest, neutral around 900 or so. ALso the fuel pressure jumps constantly from 32-42 the entire time, While in park it stays around 38-45 but wiggles, never smooth. Anyone have any ideas on what i can do to get it smoothed out? Below will be a list of parts ive replaced... Thanks for any help

Spark plugs - NKGs gapped 0.54
Spark plug wires
Fuel Filter
IAC ( From pull-a-part )
TPS ( From pull-a-part )
MAF ( From pull-a-part )
Fuel injector pressure sensor ( From pull-a-part )
( Coil pack is stock, but tested and passed within spec )
No codes are being thrown, However on my reader it shows FuelSys1 - OL Im not sure why but Im pretty sure it shouldnt be in open loop the entire time?

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post #2 of 13 (permalink) Old 5 Days Ago
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Check the vacuum line going to the fuel pressure regulator. You could also swap regulators if you still have the one from the old engine , and see if that helps at all.


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Quote:
Originally Posted by 1Austin112 View Post
Hello all,

So I bought a 2000 mustang v6 3.8 ( auto ). Also the fuel pressure jumps constantly from 32-42 the entire time, While in park it stays around 38-45 but wiggles, never smooth. Anyone have any ideas on what i can do to get it smoothed out?
+1 on above about the intake vacuum reference line. BUT we really also need to know HOW the fuel pressure is being measured. IE from an external fuel gauge or as reported by the PCM. Because if you are using an external gauge the fuel pressures that you are calling out might be "normal".

I once owned a 1996 GT with an automatic. The car was totally undriveable after a battery disconnect until the new idle fuel trim values were re-learned. Every single time it was necessary to allow the motor to reach full operating temperature in park with the AC off. Pressing the brake on/off a few times during the warm up.

Then turn the AC on and allow to idle in park for a full minute with your foot on brake. Then and only then could the car be driven.

Needless to say it was important to have a good battery and battery cables.

2003 GT Convertible (sold & missed)
2000 GT coupe (Craigslist project. Fixed. Now my DD). Windsor to Romeo swap.
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Originally Posted by Fordgazm1 View Post
Check the vacuum line going to the fuel pressure regulator. You could also swap regulators if you still have the one from the old engine , and see if that helps at all.
Vaccum line seems to be fine, No cracks, and fits pretty tight, I did try swapping the fps from the old engine and it was very little change, if anything its better then it was before.

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Originally Posted by wmburns View Post
+1 on above about the intake vacuum reference line. BUT we really also need to know HOW the fuel pressure is being measured. IE from an external fuel gauge or as reported by the PCM. Because if you are using an external gauge the fuel pressures that you are calling out might be "normal".

I once owned a 1996 GT with an automatic. The car was totally undriveable after a battery disconnect until the new idle fuel trim values were re-learned. Every single time it was necessary to allow the motor to reach full operating temperature in park with the AC off. Pressing the brake on/off a few times during the warm up.

Then turn the AC on and allow to idle in park for a full minute with your foot on brake. Then and only then could the car be driven.

Needless to say it was important to have a good battery and battery cables.
Thats interesting, Im new to the mustang world, never had to do that with my f150 I will give it a shot tomorrow and see, cant hurt to try. I am using an external fuel pressure gauge hooked up to the fuel rail, the code reader only shows the fuel system as an open loop, which is kind of odd...
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I would go back to the basics. Double check the firing order and that you have all of the wires going to the correct cylinders. Go over the vaccuum lines and check for leaks and that they are routed to the proper ports. You said you put new plugs in it , was that before you fired it up for the first time ? If so , pull them back out and check each one over carefully for cracks , or a bent electrode. Basically , pretend that someone just dropped off this car and you have no idea what has been done to it. Go over everything again and verify that it's all correct. It's easy to miss something when replacing an engine.

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I would go back to the basics. Double check the firing order and that you have all of the wires going to the correct cylinders. Go over the vaccuum lines and check for leaks and that they are routed to the proper ports. You said you put new plugs in it , was that before you fired it up for the first time ? If so , pull them back out and check each one over carefully for cracks , or a bent electrode. Basically , pretend that someone just dropped off this car and you have no idea what has been done to it. Go over everything again and verify that it's all correct. It's easy to miss something when replacing an engine.
Do you happen to know the correct firing order off hand? From what i was told if you are looking at the engine from the front of the car, passenger left side closest to the front would be 1, 2, 3 being at the back pass side, then driver side front would go 4,5 6 being at the back. I followed the sticker on the coil pack to route the wires. I already pulled plugs and they all look fine, didn't see any cracks or damage, Ive been going over the basic's for the past 2 weeks just to try and see if i missed something, I think I have all the vac lines in the right spot but finding a diagram is proving harder then it should be
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the code reader only shows the fuel system as an open loop, which is kind of odd...
^^^This is a HUGE problem. IF the PCM really is in open loop then everything else is just a symptom of the real problem (assuming that you understand what the ODB2 scanner is saying). Find the reason why the PCM is remaining in open loop and likely all of the other "problems" will solve themselves.

V6 coil pack wiring diagram
http://www.allfordmustangs.com/forum...inder-1-a.html

If interested in getting a full Ford Service manual with wiring diagrams I maybe able to help. PM if interested.

2003 GT Convertible (sold & missed)
2000 GT coupe (Craigslist project. Fixed. Now my DD). Windsor to Romeo swap.
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^^^This is a HUGE problem. IF the PCM really is in open loop then everything else is just a symptom of the real problem (assuming that you understand what the ODB2 scanner is saying). Find the reason why the PCM is remaining in open loop and likely all of the other "problems" will solve themselves.

V6 coil pack wiring diagram
http://www.allfordmustangs.com/forum...inder-1-a.html

If interested in getting a full Ford Service manual with wiring diagrams I maybe able to help. PM if interested.
I knew the open loop wasn't good but this is my first obd2 car im working on, im more of a OBD1 truck person, Ive changed most the sensors that go to the fuel system with no impact on the open loop so maybe its possible for a ground somewhere shorting something out? I've never dealt with an open loop before, not 100% sure what it means
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post #9 of 13 (permalink) Old 3 Days Ago
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Generally , bad O2 sensors will cause an open loop. A throttle position can also alter it. Open loop means that the car is not looking at the oxygen sensors and is trying to "tune" its self from the mass air meter. It will run rich in open loop. If you have a decent code scanner , you can check the voltage values from the oxygen sensors and the throttle position sensor. You can see if they are communicating their information to the computer. Check the wiring to the oxygen sensors , and like you said , check your grounds. I can't emphasize enough how important multiple grounds are. At a minimum, you need a good one from the battery to engine block and one from the block to the body.

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A car is in open loop until the o,then sensors heat up and start transferring info to the computer. Once warm , the computer uses those along with the mass air and throttle position to give the car a perfect air fuel mixture. Then everything is happy and you create tire smoke. Lol.

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Here is the firing order.
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post #12 of 13 (permalink) Old 3 Days Ago Thread Starter
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Thanks for all the help so far, I tried resetting all the values ( battery disconnected for 30 min, fuse 47 out, and the gas pedal trick ) and it worked perfectly, once it relearned everything the idle smoothed out, doesnt stall anymore, idle drops about 200 down to 650ish when put in gear but doesnt act like its starving anymore. Still have a very slight shaking / jerk when put into gear while idling, once throttle is given it mellows out though, If that can get fixed it will all be perfect. I also have the most basic obd2 scanner there is, cheap ol' 30$ one so its not perfect but shows me the basic's, even at operating temp the fuel system is still in open loop so i may order some new o2 sensors and see if that helps, they're original from what i can tell and at 175k miles it wouldn't be a bad idea.
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Glad it's running better. Oxygen sensors are only good for around 60k miles , so that's not a bad idea.

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