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2006 focus intermittent starting issues

My 2006 focus just turned 100,000 miles. Last few months as it started to get cold outside its had issues with not “holding” a start. It seems to make all the normal sounds but won’t continue to run. It is progressively getting worse, ie: more frequent and takes more tries to get it started. Yesterday I tried repeatedly and it wouldn’t start until I gave it a LOT of gas-this is the worst its been. Previously it would either eventually start after repeated tries or with a little gas. Even on unseasonably warm days its happening now. Both autozone and tireman say the battery (2yrs old), alternator, and starter check out fine. After lots of online reading here’s what I’ve tried/paid attention to in hopes of narrowing it down.
-Changed spark plugs
-Fuel injector cleaner
-Spare key
-Don’t notice security light flashing when it happens or any other random electrical issues
-No strange idle fluctuations
Once its running its fine and seems to start ok for next couple tries even at cold start. Trying to narrow down from IAC valve, PCV valve, throttle position sensor, wiring, ignition switch, fuel pump, etc. Can computer codes read even without warning lights? I have noticed for quite some time that idle has a slightly rougher sound (nothing obvious) but this seems to comes from muffler end and its been in for standard service and never been mentioned as an issue…? Its never stalled at idle or sounded like it was close to stalling/strictly issue with getting it going. Any advice on how to narrow down at all would be appreciated.
I’m trying to determine if its logical that repeated attempts or giving it gas build up more fuel pressure? Or more logical that lots of gas is pushing open something thats clogged up? Any input welcome, trying to learn as much as possible in case I have to end up in the shop. I don’t want to have them change multiple parts and not fix it. I don’t know if there are surefire ways to test these parts.
Thanks!
Jan

have the start checked if its good then have the alternator and battery checked. Those are the first things I think of in this situation. You can have them checked at Autozone.

Have already been checked by both autozone and tireman. All checked out fine-thx for reply!

I’m assuming the problem is cold starts; i.e. it starts up fine if the engine is warm. And all routine engine maintenance suggested in owners manual is up to date. And no one has fiddled with the idle speed control prior to you noticing this problem. And there are no ECM codes current or pending.

One possibility is a problem with the mixture on cold starts. The colder it is, the richer the mixture needs to be for the car to start and run well. More gas in other words should be injected when it is cold. Your car’s ECM is supposed to be doing that, by measuring the engine coolant temp and injecting more gas through the injectors. But it may not be. Have your mechanic verify the coolant temp sensor is working correctly.

Also, the fuel injection may be ok, but there is too much air getting into the engine. This can be caused by a vacuum leak. So ask your mechanic to verify all the vacuum lines and vacuum operated devices are working and not leaking. Best of luck.

@cjanet419 have a competent shop or mechanic do a complete check of your fuel system. Some of your symptoms sound like a failing fuel pump.

Was in shop this morning-they couldn’t get it to have rough/no start, however I did have to try 5 or 6 times this morning to start before I took it in. Typical-usually ok for a couple days after having the issue, but becoming more frequent. Did end up starting without giving it gas. Garage said no codes which I figured-no warning lights come on. Couldnt find anything wrong, but they want to get an coolant temp sensor on monday and “try that first” b/c its a cheap part, but it sounded like they had to get it from the dealer and online it looks about 30 bucks/relatively cheap but wondering if there is a way to check definitively before they start changing parts at 30 bucks a shot?
PS I try to really pay attention-this morning it seems like it actually starts for a split second but doesn’t “hold” the start/dies. All the input is greatly appreciated-thanks guys!!