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focus stumble/flat spots -any ideas


steveo3002

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2004 petty 1600 focus , its all serviced up to date and no fault code lights or codes

 

when accelerating from low revs its got a stumble /lumpy flat spots , does it regardless of foot flat to floor or progressive pedalage

 

any ideas ?  feels like in the old days when a good thrash would clear it but not on this one  

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+1 on the MAF - if you have a code reader check it for fault codes and potentially disconnect the MAF - resetting it to the 'default' map, though this will put the EML on I suspect. See if it still bogs down with the stock map.

 

if you can get to the MAF easily give it a blast with contact cleaner or carb cleaner (I think this is probably a bit harsh, but worked on the Kia we used to have) and see if that perks it up at all.

 

I suspect a secondhand MAF for a 1600cc Focus won't cost very much, a new one for a 2004 Kia Rio was £400 from ECP so we kept it going with regular doses of carb cleaner and then sold it and made it someone else's problem.

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How many miles - oxygen sensors on these for really lazy but don't show a fault code . Ideally you need to monitor the voltage on live data with a scan tool or even better a scope . It should go from .9v ish down to .1v and back about once a second . If it's taking two or three seconds then the sensor is toast . This assumes it's all up to working temp btw

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How many miles - oxygen sensors on these for really lazy but don't show a fault code . Ideally you need to monitor the voltage on live data with a scan tool or even better a scope . It should go from .9v ish down to .1v and back about once a second . If it's taking two or three seconds then the sensor is toast . This assumes it's all up to working temp btw

 

I just tried this test on my 1.6 2002 Fusion for my own interest and to hopefully help the OP. This is what my oscilloscope looks like (up to temp).

 

post-20084-0-02106100-1498234345_thumb.png

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any ideas how you check the tps ?   

 

I think it will come up as a fault code if there is a problem? There are probably some parameters to check, but again I'm not sure how to interpret!

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Guest Hooli

I think the engine revs are increased slightly with Aircon on?

 

You can feel the drag of the aircon clutch kicking in & out on some engines if it's a bit slow to react & correct it's revs.

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I had exactly the same problem with mine, a Focus C-max  1.6 Zetec, same engine I think.  replaced the coil pack, no change, the plugs, no change, injector cleaner and Cataclean, no change. Then the plug leads - problem solved.  Once off I checked the leads with a multi meter and found one totally dead, the other three giving readings on 20k ohms from around 4 to around 17 depending on the length. I got them through my local garage who warned me that the were extortionately expensive, but said OEM from Ford was the only way to go. I suppose it would have made more sense to have checked them with a multi before buying a new set. So, take them all off and check them first........... hope it works.  

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