HELP! Engine Surging and Dying at Idle.

[Z3T3C]

2000 Focus SE 2.0 DOHC ZETEC w/Auto Trans is wanting to idle at correct RPMs, but then drops down and goes right back to correct idle and does this a few more times and dies. Eventually, it gets worse and is hard to start without applying gas peddle when turning over. Yes, I know it's not carbureted, but its the only thing that works, even after leaving the key in the on position for several moments. I do hear the fuel pump prime when the key is in the on position. BTW no CEL, I did have codes for misfire, IAC, and TPS, but those I have been cleared

Here is what I has been done so far:
Fuel filter - filthy; ignition coil - cracked and out of resistance spec; spark plugs(Motorcraft) and wires - done right before I bought it; IAC Valve (MC) - nonfunctional; TPS - had TPS for manual trans on it; PCV hose (MC) from intake manifold to steel tube - collapsed; gutted cat - wasn't clogged but what the heck; cleaned MAF w/MAF sensor cleaner and throttle body w/throttle body cleaner; and finally cleaned contacts and ground points for fuel pump driver module; 2 bottles/fuel tanks worth of Chevron Concentrate Plus.

Car seems to drive fine, but can't idle and dies at stoplights unless I keep one foot on the brake and the other foot steady on the gas peddle in order to keep idle up. I have extensively checked all other vacuum lines and intake connection points (i.e throttle body, IAC) 3 times over with a propane tank to find leaks and there are none. Nor have I been able to locate any other collapsed or brittle hoses or elbows. I'm at a complete loss without suggesting the fuel pump, but it drives fine with hesitation so IDK. Any help is greatly needed; it's my daily driver for school and work.

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[anarchy0392]

Have you checked you alternator?

[Classic6200]

I had the exact same problem. The rubber vacuum hose that goes from under the throttle body assyemble to the side of the moter under the coil pack had sprung a leak. Only place to get the hose is from the dealer for around 40 bucks.

[Z3T3C]

No, I haven't checked the alternator. I never suspected the alternator though, because, the lights don't get brighter when I hit the gas, and it's been able to charge the battery and use all lights while night driving throughout the winter here in Iowa.

[Z3T3C]

Originally Posted by Classic6200

I had the exact same problem. The rubber vacuum hose that goes from under the throttle body assyemble to the side of the moter under the coil pack had sprung a leak. Only place to get the hose is from the dealer for around 40 bucks.

That would be one of the PCV hoses that I replaced yesterday when it came in from Ford. The other runs from the bottom of the air box to the top, driver's-side of the engine. The filter at the bottom of air box for that hose was full of oil and was disintegrating, so I replaced that too. I also forgot to mention in my original post that the PCV valve & air filter were just replaced in the process.

There is a bit of hesitation when you punch the gas at idle, but the engine doesn't buck when it gets up there in RPMs. However, it dies immediately after as it gets back down to idling speed. Fuel related?

[whynotthinkwhynot]

Check the alternator using the electronic odometer trick so you can monitor voltage while you drive. Key off, press and hold the odo reset button. Turn key on, continue to hold button until odometer display reads [test]. Release button, now each time you press and release the odo reset button you will scroll through one of 30 test functions. Look for the one where the display reads [bat 12.1] or whatever your voltage might be at that time. The display will remain in test mode until you turn the key off, so you can start the car and now you'll be monitoring alternator voltage. If your alternator voltage reads 14.9v or more, then you need a new alternator. If it reads less than 13.2v, you need a new alternator.

It seems to me that your problem is vacuum related. You found the PCV, that is the most common vacuum leak or problem, however there must be some other leak somewhere. Also, once you do find the problem, it might help you to reset the A/F ratio- which the car will do anyway over time, but you can force it to do it faster. Disconnect the battery for 10 mins, I do this on a warm engine, now reconnect and start the engine. Do not touch the accelerator, and allow the engine to idle for 6-7 mins. During this time you will notice a slightly higher idle than normal- around 1k rpm. The idle will fluctuate slightly, but after the test is complete, the idle will drop to normal which is around 700 for both transmissions.

[whynotthinkwhynot]

It's not likely to be fuel related. If it was, you wouldn't be able to drive the car.

What transmission do you have? What did you do with the TPS exactly? 2000 model vehicles have issues with TPS from the factory, typically the entire TB has to be replaced if it is the factory TPS. Parts stores will typically give you the wrong part, and the Ford dealer will freak you out with how much the right part costs.

[Z3T3C]

I have replaced the upstream O2 sensor due to a possible non-reported, lean running issue (a suggestion by my father and old gear-head). I have to admit that as mad a bit of difference in running smoother. I also swapped out the fuel pump driver module due to a TSB from a different post in the forums. Car runs better than it has with everything I have dumped into her so far. Now it refuses to die now once I get it running, but can be hard to start without some persuasion from the gas peddle. Seems to be worse once the engine is at running temp. On a side note, since I replaced the driver's side upper transmission mount the entire car no longer shakes (a condition of 156k miles), but instead she purrs like a kitten as long as she is not struggling to stay running. After test driving her, the engine no longer surges and dies at stop lights or stop signs but does sporadically surges when is in park or neutral.

[Z3T3C]

Originally Posted by whynotthinkwhynot

Check the alternator using the electronic odometer trick so you can monitor voltage while you drive. Key off, press and hold the odo reset button. Turn key on, continue to hold button until odometer display reads [test]. Release button, now each time you press and release the odo reset button you will scroll through one of 30 test functions. Look for the one where the display reads [bat 12.1] or whatever your voltage might be at that time. The display will remain in test mode until you turn the key off, so you can start the car and now you'll be monitoring alternator voltage. If your alternator voltage reads 14.9v or more, then you need a new alternator. If it reads less than 13.2v, you need a new alternator.

It seems to me that your problem is vacuum related. You found the PCV, that is the most common vacuum leak or problem, however there must be some other leak somewhere. Also, once you do find the problem, it might help you to reset the A/F ratio- which the car will do anyway over time, but you can force it to do it faster. Disconnect the battery for 10 mins, I do this on a warm engine, now reconnect and start the engine. Do not touch the accelerator, and allow the engine to idle for 6-7 mins. During this time you will notice a slightly higher idle than normal- around 1k rpm. The idle will fluctuate slightly, but after the test is complete, the idle will drop to normal which is around 700 for both transmissions.

I did as you suggested. It was jumping from 14.7v-14.9v while night driving for half an hour. However, when coming to a stop 2 different times it dropped down to 13.4v and at a different time while driving from a stop light it spiked up to 15.2v, momentarily. Afterward, I was doing some further troubleshooting in my driveway, which I have determined the problem comes about after releasing the brakes. Whether parked or in gear as long as the brake is pressed it doesn't surge until it after the brake is depressed. The surge seems stronger and more noticeable when in park or neutral than when in gear. I tested it while it was in gear by applying the parking brake and not pressing the foot brake. Also, if I pump the brakes it spikes up to 1000 RPMs, after I stop pumping them it begins to surge. During this brake testing I did notice the voltage spikes up to either 15.4,15.5, or 15.6, but it was so brief and fast it was difficult to read and be certain.
I had the battery disconnected after the PCV hose replacement due to a new coil install, because immediately after firing it up it threw a DTC for a cylinder 2 misfire. So inspected the coil since the previous owner had new MC spark plugs and wires installed. The coil body was cracked all over, some cracks even had rust, and it was well out of resistance spec. Then, I had the battery out again for a good hour or more to clean the ground terminal connections from the new battery to the body (the location under the air box). Removing the air box allowed me to to discover that my trans mount, or lack there of, needed to be replaced.

Originally Posted by whynotthinkwhynot

It's not likely to be fuel related. If it was, you wouldn't be able to drive the car.

What transmission do you have? What did you do with the TPS exactly? 2000 model vehicles have issues with TPS from the factory, typically the entire TB has to be replaced if it is the factory TPS. Parts stores will typically give you the wrong part, and the Ford dealer will freak you out with how much the right part costs.

It's the 2000 model year 4-speed auto trans, not sure of the exact transmission model though. I will take a look tomorrow. I had a CEL for the TPS, because previous owner had some bonehead mechanic replace TPS with ones calls for a manual transmission. This caused erratic shifting leading him to believe the transmission was failing. BTW, I had this issue posted in a different thread after coming up empty when searching the forums and Google. My issue was: If I was forced to go to with a new throttle body as Ford calls for I was just going to spring for the Focus Central aftermarket one, but wasn't sure which TPS part number I needed to pair it up with. I never got an answer, so I ended going the junkyard and getting a throttle body with TPS from a 2001 ZX3 2.0 Zetec with auto trans. During the same down time I ended up replacing my non-functioning IAC valve, because that was the other DTC I pulled after buying the car. Before replacing those parts the engine's RPMs were spiking close to 2K if I could keep it running.

[whynotthinkwhynot]

High voltage = bad alternator. The voltage regulator is going out. This is one of the most common ways that this alternator goes out. I would suggest finding a local rebuilder- look in the yellow pages, call independent shops and ask, and maybe even some nice parts guys will tell you who rebuilds automotive electrical parts locally.

If you do feel like you have to go purchase one from a parts store, then I would suggest getting the cheapest one you can buy, and keeping your alternator to have it rebuilt locally when you have time to find someone. 2 reasons for this: 1) it should be much cheaper, like $80 instead of $200. 2) Local rebuilders use better parts because warranty repairs hurt their cash flow more than large chain stores.

You can also check with Village Ford, our new OEM supply vendor, to see if they have a decent price on a new Motorcraft alternator. You'd probably have to wait a few days, and I wouldn't suggest driving the car with an alternator that is giving over voltage. All you have to do is spike up to about 18v, and all sorts of things will be killed. Keep in mind that all of those numbers you saw were actually .2v higher at the battery. You're also probably not doing the battery much good either.