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tigacatch

Revs Hunting 2000-2500

27 posts in this topic

In need of some help please

My ford focus 2003 1.6 zetec SE has developed a problem.

Started of last year in the winter when car suddenly woudnt start but after many atemps started eventually.

But ever since revs have been hunting between 2000-2500.

It also appears to have lost power in that band range.

Also fuel consumption higher too as this was confirm when the car was close to failing emissions test as it had high reading. I have since replaced throttlebody and idle control sensor.

Also the vacuum hose at the intake with a new one. Dont what to keep replacing stuff.

Thats why i need help

Btw idle is fine when cold or warm, the problem is band specific

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Do you mean rev shunting lol?

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Can't keep them steady between 2000-2500

Eratic

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Could be something as simple as a dirty MAF / MAP sensor, these will not be detecting the correct amount of airflow and as such will be instructing the ECU to fluctuate the fuel direction as appropriate.

Start by cleaning these with Electrical contact cleaner, check all hoses and pipes to ensure there are no breakages, slits, or leaks, and reset the car by disconnecting the battery (ensuring you have your radio code).

Then see if the issue comes back afterwards.

bt_cav likes this

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I will attempt doing this at the weekend but don't understand how the map sensor could be at fault as the car is fine at below 2000 and above 2500. Wouldn't this indicate that the map sensor works as intended ?

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MAP sensor could well be fine in that case, its just the airflow that needs to be queried.

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Could be something as simple as a dirty MAF / MAP sensor, these will not be detecting the correct amount of airflow and as such will be instructing the ECU to fluctuate the fuel direction as appropriate.

Start by cleaning these with Electrical contact cleaner, check all hoses and pipes to ensure there are no breakages, slits, or leaks, and reset the car by disconnecting the battery (ensuring you have your radio code).

Then see if the issue comes back afterwards.

How long should the battery be disconnected for to reset the ecu?

:-)

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20 minutes is often enough, anywhere between there and an hour...

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Cheers James :)

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Hope this is not a daft question, located map sensor but how do I remove it. Any tips as it looks like I real tough on to get too. I think I see 2 screws but unsure. Any help welcome

Cheers

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Do you mean rev shunting lol?

surely hunting is the correct term to use? :rolleyes:

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I think its just an unscrew sensor isnt it?

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Yes it will be a 4 wire sensor that unscrews. But I think with it being on exhaust I'll be having to heat it up a little to get it off.

Gonna attempt it on Saturday depending on weather lol = Scotland = rain pmsl

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BTW is the post lambda sensor I think might be at fault !! Managed to get an obd2 thing and bank 1 sensor 1 graph goes up and down the way it should ( I think) but bank2 sensor 1 sitting at 1.2 volt constant !!! No flucuation at all. Can anyone confirm that this sensor (post cat) should read approx the same as bank 1 sensor 1 ??

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it could well be that the sensor is stuck or its shorted out. Might be worth disconnecting it and cleaning it up with electrical contact cleaner and seeing what it does after that.

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Hi, My Focus Mk1 1.6 has only one lamda sensor pre-cat. Checked out yesterday on a snap on large diagnostic handbag thing costing way too much & requiring a gaolers size ring off pcb's for all manner of vehicles, simply stated NO faults detected, no codes logged.

I however am having a similar experience whilst in the workshop difficulty in obtaining a smooth steady acceleration through 2500 - 3500 rpm.

Air leak or something I suspect, so I don't think lamda will be your cause. I will be watching this thread to see if anyone can come up with a definitive answer. Just though my problem * having only one lamda sensor * might contribte to a solution by someone.

:wub:

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I might want add that my son is a mechanic and he also checked it with some fancy garage equipment and told me that no faults where found. My backround is more as computer assembly test and process opetator field thanks to sun microsystems lol But me being me I don't trust mechanics much and even less diagnostic machines !!! That why I invested in a cheap £20 reader of ebay myself and diagnosed it with an android app called "torque" via my android tab. As said before no faults found !! But upon researching the subject on how exactly these sensor work I have learnef to utilize the android app via a chart reading of the sensors (lambda) this appeared to reading sensor 1 ( pre cat upsteam) going up and down in the charts 0.5 - 1 volts aprox as its increasing and decreasing fuel load but bank 2 sensor 1 post cat downstream holding a steady voltage (1.2 approx)" no flux in readings. I personally would expect a similar reading as sensor 1 as I suspect this to be the most important one especially because after cat with co2 emmisions !!! As for fault codes not appearing I suspect because I still have voltage (complete circuit) the CPU thinks all is okay. BTW this is all an educated guess on my behalf. Also regarding vacuum I have disconnected the pipes an plugged holes on pipes and stuck pressurised air in it to test it and all okay. No fall in pressure. You can also do a smoke test to check for leakage " cost nothing" lol Replacement of my sensor delayed to next week to to weather forcast. Hate this weather haha

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Just for your information I was using a elm533 Bluetooth interface ( eBay) and the torque app ( playstore) on android to get a reading of sensors and not some £1000 crappy diagnostics machine. Total cost to me £25 pmsl

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Hi Steven,

Hopefully this will assist you in diagnosing whether the O2 sensors are dodgy...

I'm subscribed to EricTheCarGuy on YouTube and he's been a big help in understanding various faults with a car, touch wood I've not had any faults so far.

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Snap me to, he seems crackers but he's a genius!

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Quick update, had my mot the other day and failed on emissions test. Needless to say they where testing it at the problem revs and trying to get a decent reading at around 2000-2500. Engine just burning to much fuel. Also now has developed an engine fault. Cylinder 2 and 3 misfire, also engine management came on at 70 mph in 5 gear at around 2300 rpm. Another surprise there haha. So far I have had spark plugs replaced, leads, knock sensor, coil pack and vacuum hose at intake manifold, idle control valve. Problem still the same :-(

Car still running underpowered, smelling of fuel, cylinder 2 and 3 misfire and hesitant at 2000 to 2500 rpm :-(

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Quick update, had my mot the other day and failed on emissions test. Needless to say they where testing it at the problem revs and trying to get a decent reading at around 2000-2500. Engine just burning to much fuel. Also now has developed an engine fault. Cylinder 2 and 3 misfire, also engine management came on at 70 mph in 5 gear at around 2300 rpm. Another surprise there haha. So far I have had spark plugs replaced, leads, knock sensor, coil pack and vacuum hose at intake manifold, idle control valve. Problem still the same :-(

Car still running underpowered, smelling of fuel, cylinder 2 and 3 misfire and hesitant at 2000 to 2500 rpm :-(

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Hi Steven,

Although you say you've changed plugs, leads and coil packs I feel that it's interesting that, having a wasted-spark system, cylinders 2 and 3 will be sharing a coil and I wonder if this might be significant or just coincidental.

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Was thinking the exact same. Definitely everything been changed. Next on my list is to check the injectors by swapping them all around to the if it would still be the same cylinder faults

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