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Cold start engine stuttering, missing, 1 Solution perhaps. 

 

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 Post subject: Cold start engine stuttering, missing, 1 Solution perhaps.
Posted: Tue May 01, 2007 9:28 am 
Getting Side Ways
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Hey guys, got my new oxy sensor yesterday from down south (ebay) and installed it and it seems to have fixed my cold start issue.

I mean the issue where the car will drive for a few moments like it is being starved, missing, and you have to put your foot down for something to happen quick, or wait ages for it to get it's act together. So yeah, new oxy sensor off ebay for $40.

I had left the car out front all night long, since about 4pm the day earlier, and it was a cold morning. Started her up, and went to turn at the intersection (up hill) and the car didn't miss a beat, on a cold start! No missing, no stuttering, no choked (of fuel) engine symptons.

I'll see if it does the same sort of thing again tomorrow morning. Watch this space.

 

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Posted: Tue May 01, 2007 10:44 am 
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I dare say it wouldn't be the oxy sensor.

The ECU doesn't even look at the oxy sensor for the first minute or 2 of engine running, as it needs to warm up to a certain temperature before the signal is meaningful. Until then it uses preset maps in the ECU.

I'm again having the same problems as you. But I put it down to the now cold morning weather and my badly leaking head gasket.
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Posted: Tue May 01, 2007 10:53 am 
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arm79 is correct. When the vehicle is not at operating temperature, or under high load/throttle openings, the PCM operates in open loop mode which means it runs of a preset air/fuel ratio which can be varied by values held in its keep alive memory based on sensors such as map sensor, throttle position, air temp sensor, engine coolant temp etc (theres lots more). Once the vehicle is at operating temperature and at idle, or lean cruise (very little throttle opening and little load) the pcm switches to closed loop, where it rely's mainly on the o2 sensor's readings to modify the injector pulse width to achieve the cleanest emissions (and also the lowest fuel consumption). Every injection cycle the pulse width can be modified longer or shorter based on the voltage outputted by the o2 sensor.

The main reason for ignoring the o2 sensor when cold is that the o2 sensor does not operate reliably or correctly until it is warm which can take a few minutes.

sorry if thats a long ramble but hopefully that sheds some light on the o2 sensor's operation in line with injection etc.
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Posted: Tue May 01, 2007 11:00 am 
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another thought though, A blocked,corroded o2 sensor could cause those issues once the car is warm enough to attempt to switch to closed loop. But when dead cold it couldnt be the cause. Hope this is of some help to people.
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Posted: Tue May 01, 2007 11:37 am 
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$40 is a great price - have ya got a link to where you got it from

i might replace mine to try and resolve very poor fuel economy
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Posted: Tue May 01, 2007 1:02 pm 
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Just search on ebay mate for a ford oxygen sensor.

Hmmm, well that is all very odd, lol. I reset the ECU with this new oxygen sensor and drove it yesterday afternoon. I'm going to see what happens tomorrow.

 

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Posted: Tue May 01, 2007 2:12 pm 
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yeh i dont wanna shoot you down if its fixed it, it just seems a tad odd. (im studying PCM operation in depth at the moment.)
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Posted: Tue May 01, 2007 2:28 pm 
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My understanding of the ECU is that it will adjust these cold start and WOT mixtures based on what the oxy sensor has told the ECU when the ECU was listening to it.

Based on that theory, if your oxy sensor was providing the ECU with errored readings, then the calculated assumptions it made for cold start and WOT would be errored as well, possibily causing bad running at cold start.

I'm not sure of the temperature scales in the ECU, but it doesnt take long for the engine to heat up and move from a bad range to a good range, which might appear make the car run like s**t momentarily.
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 Post subject: Re: Cold start engine stuttering, missing, 1 Solution perhap
Posted: Thu May 10, 2007 6:33 pm 
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Till_Lind wrote:
Hey guys, got my new oxy sensor yesterday from down south (ebay) and installed it and it seems to have fixed my cold start issue.

I mean the issue where the car will drive for a few moments like it is being starved, missing, and you have to put your foot down for something to happen quick, or wait ages for it to get it's act together. So yeah, new oxy sensor off ebay for $40.

I had left the car out front all night long, since about 4pm the day earlier, and it was a cold morning. Started her up, and went to turn at the intersection (up hill) and the car didn't miss a beat, on a cold start! No missing, no stuttering, no choked (of fuel) engine symptons.

I'll see if it does the same sort of thing again tomorrow morning. Watch this space.


I have had the same problem with my EL Falcon for the past 2 weeks and I am not sure whether to just go through and change all the Sensors. Though I talked to my local Mechanic and he seems to think it might be Injectors that are clogged or not spraying properly. I agreed to get him to do an Off the Body Injector clean. If that dosent fix it I am going to have a fit. He actuall has his own BMW race car that he takes to meets up here, so I guess he has a bit of cred at least and not like SOME mechanics who like to fleece people. Which I recently had the experiece of

 

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Posted: Fri May 11, 2007 3:17 am 
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well what happend? its been over a week!

 

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Posted: Fri May 11, 2007 12:08 pm 
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Well it's on and off now. But MOST times I start her cold, and drive away, there is now NO stutter at all.

So go figure.

 

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Posted: Fri May 11, 2007 12:31 pm 
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with the oxy sensor u just unscrew it and screw new one in right? i wentot havea look at mine then thought maybe my arms arent long enough to get it back into my extractors
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Posted: Fri May 11, 2007 6:33 pm 
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I would tend to think if the O2 Sensor dodn't fix it. Then logically if it only happens on cold starts then I would surmise that it might be either the Coolant Temp Sensor or the Air Intake sensor that might be just reading slow or bad Temp readings ETc as I have heard of some cars going like a total bag of s**t on start up and then coming good once optimum Temps reached. They found that the Coolant Temp was reading -3 degrees Celsius on start up and throwing the ECU in to a mess.

 

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Posted: Mon May 14, 2007 6:42 pm 
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I replaced my O2 Sensor yesterday and I must say my Cold Start Stuttering improved dramatically but didn't fix it 100% As I still found it lagged slightly from take off. But hey not as bad as it was 2 weeks ago. Yeah might look at changing Coolant Temp Sensor now.

 

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Posted: Mon May 14, 2007 8:59 pm 
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I disconnected mine just to see what happend and it also seemed to improve...

 

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