Focus Fanatics - View Single Post - HELP! Engine Surging and Dying at Idle.
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Old 01-21-2013, 03:42 AM   #9
Z3T3C
Focus Jr. Enthusiast
 
Join Date: Dec 2012
Fan#: 107116
Location: Des Moines, IA
What I Drive: 2000 SE Zetec with ATX

Posts: 29
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Quote:
Originally Posted by whynotthinkwhynot View Post
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.

Quote:
Originally Posted by whynotthinkwhynot View Post
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.

Last edited by Z3T3C; 01-21-2013 at 04:51 AM.
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