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2001 Ford Focus Mysterious Idle Problem

My daughter’s automatic DOHC SE Focus had suddenly been stalling, becoming harder to start and not maintaining a steady idle. I took it to our semi-trusted repair shop and was told it needed an EGR valve, plugs, coil, and ignition wires. $580! These all seemed like repairs I could do and so I have worked through all of these. I replaced the EGR valve and that seemed to make the problem actually worse. (so I put the old one back in) I put in new plugs and that improved the idle a small amount. Then I put in the new coil and that seemed to steady the idle a bit more. But here is what I have discovered through my many test drives after making these incremental repairs: The car starts now from cold very well and runs great for the first 20 minutes or so but…when it gets hot after 15 minutes or so of 50 mph driving, the idle drops and the engine wants to cut off. At low revs it seems to stumble and lose power. I think this is what my daughter was experiencing originally and none of my early test drives were long enough to surface the original problem. I have read that the Idle Control Valve might be a culprit in this sort of behavior. Any ideas would be appreciated.

have the fuel pressure checked cause it may be a weak fuel pump

To check for a defective IAC valve, with the engine hot and idling, take the handle of a screwdriver and tap on the IAC valve. If the engine idle speed changes when doing this replace the IAC valve.

Tester

Good comments above, check those out. It sounds like a lean mixture problem, either unmetered air is getting into the engine, or not enough gas. Is the check engine light on? Have the pending and active DTC engine computer codes been read out? It could be the idle control valve (or IAC or whatever it is called on this car) is broken or needs cleaning. But first I’d check the vacuum system for leaks with a vacuum pump. The new EGR shouldn’t make the problem worse, so that is an important clue I suspect. The old one probably isn’t opening at all I expect. The new one is working and opening like it should, and when it opens (during periods acceleration) this just makes the mixture even more lean. So the fact that the new EGR makes the problem worse, that confirms a basic lean mixture problem.

George and others: Thanks for your comments. The Check Engine Light is not on. Oddly, I checked the ECU with my new diagnostic tool and got a “Code: P0172 System Too Rich (Bank 1)”. Here’s the other thing I should have mentioned… there is a noticeable smell of what I imagine to be unburnt gas that is evident upon starting the car. It seems to continue as long a s the car is on however I can’t say how strong it is while I am driving.

Tomorrow I plan to check the IAC valve. I did take the Mass Air Flow Sensor off today to look at it but it looked clean with no build-up of oil or any residue.

I will check for vacuum leaks as well.

To wrap up this discussion, I finally took the car to a mechanic to look at it again- a different mechanic than the first who I have lost some confidence it. After looking at a number of systems including vacuum pressure, fuel system, mass air flow sensor, he concluded (and rightly so) that it was the fuel rail pressure sensor. Once he replaced this part the Focus ran smoothly and without a hiccup. It starts right up and idles like it used to.

Thanks for all of your suggestions.

I having a issue with my focus no engine code gas odor and when idle to long cut off when car driven for a while
I clean throttle and maf sensor but never the iac which will do in am i also nwver changed fuel filter. Whats ur thoughts

You are on the right trail. Do all the routine maintenance things, like the fuel filter. I had a mysterious issue with a car and it was just a really dirty fuel filter.