HELP! Engine Surging and Dying at Idle.

[mikebontoft]

Don't forget it only jumps immediately after a load with the brake lights. shouldn't be much but perhaps enough that when he lets off the pedal, the alternator is still charging more than it should for that split second.

[Z3T3C]

I will be looking into the alternator concern, because zapping electronic components is the last thing I want to do. Unfortunately, ATM we can't be without the Focus since my wife's daily driver is in the body shop for collision repair for the next week so she is using the focus while I'm back to driving the F-150. I can see why an increase in power would occur when applying brakes due to power demand for the lights, but I don't think it would cause it to jump that high. Also, I'm sorry but I can't seem to wrap my mind on how an alternator that is over-volting due to a bad voltage regulator but still charging the battery would cause hard starts on warmed-up engine. Why would it need help from the gas peddle in order to start as well as drop in RPMs and begin to surge or chug after the brake pedal is released? This wouldn't seem to be caused by an alternator issue as suggested, because starting the car is battery based not alternator based. You can start and run a car without an alternator on a fully charged battery for about an hour before the battery is out of juice, that's if you don't use lights and power devices. I know the coolant sensor if bad can cause hard starts on a warm engine, but would it also make it run poorly like it is?

[Classic6200]

I also forgot to mention that I changed the DPFE. Sometimes you encounter multiple problems.

[Z3T3C]

I have a DPFE go out my grandmother's 3.0L Taurus and that seem to make the car consistently run far more sluggish than what my car doing right now. I don't suspect it to be the case since this issue seems more sporadic, but its worth investigating. Classic6200, when your DPFE went out in your focus was it consistently running poorly it would it come and go and was it more so after the engine was warm? Also, after my wife drove it today, she told me the CEL came on. I pulled the code and it was P0303 for a cylinder 3 misfire. I'm still leaning towards a fuel issue since IMHO a spark issue has been ruled out, but I will report back on what I come up with. Thanks everyone for your suggestions thus far.

[Classic6200]

The DPFE caused me all types or erratic and intermittant issues. I also had a misfire and ended up changeing out the coil pack with an ACCEL and new 'live wire' plug wires and Bosch plugs. Heat can be a culprit that can change voltages as well as destroy plastic sensors and rubber hoses over time, especially as they get hot. I learned that even if it looked good, I should change it out due to the age of the parts. Along with the PCV valve and hose assembly, I changed both Oxygen sensors and cleaned all the connectors. Total cost was under $150 and now she runs like a stripped ape.

I plan on changeing the thermostate and radiator hoses this spring. My MPG's are around 26-28 pending my lead foot compared to 22-24 before the changes. Hopefully I'm good for another 130K til next problem

Don't forget about vacuum leaks. in my case it was several parts that were causing the problem.

Your misfire code is an electrical system error fault and not fuel related as far as I know. I also thought mine might be fuel related but I am glad I didn't go that route.

[Z3T3C]

My ISSUE has been SOLVED!!! In fact, it was a fuel issue as suspected but left it alone, aside from changing the fuel filter. The issue: Fuel Rail Pressure Sensor, which is kind of like an electronic fuel regulator for returnless fuel systems. It took me $5 from a boneyard and 20 minutes to swap out the part and she has been running purrfect going on 2 days. New part would have been ideal, but I wasn't going to drop a $125 on a hypothesis. Gotta appreciate the boneyards.

LOL, I was just looking at my thermostat housing the other day and thinking the same thing... next thing on the list... flush, thermostat, hoses, and fill. BTW the Alternator is all good, my values actually have dropped a whole volt while driving after changing out the fuel rail pressure sensor, which I thought was weird. Although when it's time for the alternator it'll also be a good time to proactively change the cylinder head temp sensor.

Hope this helps anyone that may come across this with the same issue. Thanks again for everyone who offered help, I appreciate it and take care.