Scotty,
2002 mustang 3.8 V6 145K miles. Only owned the car for a little over a year. About 3 months ago the fuel pump went out so I had it replaced at a local mechanic shop along with the in line fuel filter. I checked the fuel pressure on live data with my scan tool when the work was done and I was pushing about 60 PSI with the new pump. Now my car sputters some times when driving (so far only on cold mornings) but now my fuel pressure is in the high 30s in stead of around 60. My long term fuel trim is between 10 and 20 on both banks untill I accelerate. That's when the long term drops closer to zero but the short term fuel trim climbs up to around 8 or 10 on both banks. Also my ignition timing is at -5 when I crank the car but after I put it in drive it goes to +12 to +18 range.... No engine codes and I can't find any vacuum leaks. What do you think? Could all of these problems have a single cause?
Jesse
P.S. I have an appointment with the mechanic that did the fuel pump job so he can look at it since the work was guaranteed.
Also exhaust is flowing freely so no blockages in tail pipes/exhaust system that I know of.
UPDATE: I just added some fuel system cleaner just in case it was trash in the injectors or water in the fuel and now my pressure is hanging around 60PSI when I crank and in park at idle but as soon as I hit highway speeds it drops back down to the mid-high 30s I could hear a slight misfire at idle to begin with but as the injector cleaner started cycling through the system the misfire went away. It was never bad enough to throw a code though.
Have you tested the injectors? If they are original, I would highly recommend it.
I have not. Is that a DIY job or something I should have a mechanic do? I am a pretty good parts changer but I am a far shot from a mechanic.
I would have a mechanic test it as it takes a special machine. But it is an inexpensive process. Typically by that mileage the spray pattern is all messed up and the uneven fuel can cause all sorts of problems, including those you are experiencing.
This is twice now you have saved my bacon Mod Man. Thank you VERY much for your insight. I'll have the mechanic I already have an appointment with check the injectors when I go over there after the new year.
Hey man I'm happy to help! Keep us posted and if the issue is ongoing, we can look at further steps. But I'm pretty sure you'll find the injectors need a good cleaning.
Alright so things have been a little busy at work so I bought new injectors and the upper intake gasket I needed then had a local mechanic shop replace the injectors for me. The car seems a lot more responsive than it was before and it has stopped with the hesitation and what not that it had before but something still doesn't seem quite right. On a cold start the engine doesn't seem to start right.... It seems like its kind of wheezy on start up. I'm not exactly sure how to describe it lol is there a break in period for new I hector's? Or do I need to let the computer recalibrate to new injectors? Or do I have to have it reprogrammed for new injectors?
Well there's not really a break in for injectors. As for reprogramming, it isn't necessary either so there is something else going on. Have you checked the throttle body to make sure it is clean and not sticking? Also, if not already done, try cleaning the MAF sensor in the air intake. These are easy DIY items. If you have done both of those already, try putting 100 - 150 miles on the car. That is plenty of time for any CPU recalibration that needs to happen. If it continues beyond that, you may need to find a good local mechanic to look at it hands on.
I replaced the MAF and cleaned the throttle myself less that 3 months ago. I only got the car back a couple days ago so I'm gonna drive it to and from work this week and hope it's a computer problem..... It seems to run alright after start up it only seems to act up while trying to crank.....
The mechanic that I have been going to showed me what his scan tool was showing because his shows things mine does not. Cylinders 4, 5, and 6 we're all missfiring before the injector change (we assumed it was an injector issue) and he checked my O2 sensors and he said one of the sensors was about 100 millivolts to high..... No check engine light but do you think it could be an issue with the O2 sensor?
It definitely could be. Something is causing it to read high, whether its a short or an actual bad sensor.
Hi Mr Spade. Here's my 2 cents. Maybe you'll find it helpful.
You have an electronic returnless fuel system on your 2002 Mustang.
You don't have a fuel pressure regulator to control fuel pressure.
Your fuel pressure is controlled by the PCM sending a Ground Pulse to the Fuel Pump Driver Module (FPDM).
Your fuel pump motor is like any DC motor. It needs Power and it needs a Ground to run.
The faster the pump motor runs, the more fuel pressure.
The slower the pump motor runs, the less fuel pressure.
So the way your fuel pressure is controlled is by the computer monitoring the Fuel Pressure Sensor.
If the computer sees the fuel pressure is Low, it provides a faster Ground Pulse to the FPDM to make the fuel pump motor run faster. To lower the fuel pressure it provides a slower Ground Pulse to the FPDM to make the fuel pump run slower.
Here's the wiring diagram. I highlighted some parts of the circuit.
Red is Power (KEY ON).
Solid Green is Ground (always)
That dotted Green line is where the computer is switching the Ground ON/Off to control the fuel pressure.
So this may seem confusing if you aren't used to Duty Cycle control.
I couldn't find anything on your Mustang to explain it better but I did find a couple of videos of Paul Danner troubleshooting a fuel pump issue on a 2002 Ford Taurus. The fuel system is the same as yours.
He teaches an Engine Performance class at Rosedale Technical College.
Now in that case it was a fuel pump issue. But you can get a good idea on how to test the FPDM wiring or if the FPDM is faulty.
If you watch the videos you may find them helpful to understand how the fuel pressure is controlled on your 2002 Mustang.
https://www.youtube.com/watch?v=Rwve6lXriO4
https://www.youtube.com/watch?v=u342IRRJ5bk
Thank you very much!!! I'll take a look at those videos. I just finished playing with it again lol I added some fuel system cleaner just in case it was trash in the injectors or water in the fuel and now my pressure is hanging around 60PSI when I crank and in park at idle but as soon as I hit highway speeds it drops back down to the mid-high 30s I could hear a slight misfire at idle to begin with but as the injector cleaner started cycling through the system the misfire went away. It was never bad enough to throw a code though.