Mk1 1.6 Focus Flat Spot

[bt_cav]

Hey Guys got a strange issue with the focus...

There is a definite flat spot up to 2200 rpm when stationary, I have felt the car dose not want to cruise and under powered below 2200 rpm prompting me to investigate.

I have changed the plugs like for like (NGK TR5A-10)... the ones that came out were fine, The coil pack and HT leads have been replaced with Bosch not so long ago, checked for vacuum leaks but didn't find any, the engine sounds sweet, had very regular oil changes with Castrol magnatec correct spec.. I only use BP or Shell petrol.....

The cat was changed last year for a stainless steel sports cat and when it was fitted the enging management light went out its self (p0420 catalyst system efficiency below threshold) since then it has came on a couple of times so I had reset it and it was fine for a few weeks, but now it is coming back on within 80 miles.

Had a look at the live data Lambda sensors seem to be working fine, they have been changed a few years ago with NGK's.

Also noticed the revs pulsing if i hold the revs around 2000 rpm when stationary.

Any Ideas? I'm stumped....

engine code FYDB

[stef123]

Have you tried checking for leaks around the inlet manifold?

[bt_cav]

Not yet mate.... will have a look soon, might order up a new inlet gasket just to be sure

Put a bottle of cataclean in today, unfortunately I think I might have ended up with a bit more petrol in the tank that the instructions said....Ended up with just over a quarter tank....says on the bottle treats between 10 - 15 Ltrs but sure It'll work just as well

I feel it may have done some good (maybe wishful thinking) but the flat spot remains....

Could this be a faulty throttle position sensor? Or an ECU problem?

Any help very much appreciated :)

[wase16ll]

maybe worth a fuel pressure test.

take it the eml is flashing with the same code as before..ie P0420

check long and short term fuel trims on live data

[bt_cav]

ahh thats a good point..

I did wonder about that, A number of years ago after the first coil was replaced the EML light would come on from timt to time with the P0420 code and there was once a code that read something about a low fuel level..perhaps this was related to pressure.... cant remember as it was a while ago and I didnt have my own code reader at the time...

Will look into this and report back :-)

[bt_cav]

Sorry ment to say

yea the EML light is constantly on with the P0420 code, only seen it flash when the coil was failing

[bt_cav]

Been trying to find out more about fuel trim....I get the basic idea...but did not find very good uk videos about this. Also tried to search eBay and amazon for diagnostic educational type dvd's but no joy...

anyway intend having a better look at the car when the weather clears up....

mean time I'll try and collect the data and look for a pattern...

[wase16ll]

in laymens terms, fuel trim will help to diagnose why the co is high, its the 02 sensors that mainly govern the trim readings.

you may have read this already, but this is one of the better explanations ive seen about trims

http://www.obd-codes.com/faq/fuel-trims.php

[bt_cav]

Been trying to find out more about fuel trim....I get the basic idea...but did not find very good uk videos about this. Also tried to search eBay and amazon for diagnostic educational type dvd's but no joy...

anyway intend having a better look at the car when the weather clears up....

mean time I'll try and collect the data and look for a pattern...

[bt_cav]

Thanks tony it dose make sense, this was never covered when I was at collage..... maybe its time to go back ...

There's no substitute for experience..... :-)

[stef123]

Brian does your scanner have fuel trims on the live data? I can't remember if we looked at that? Was only a week ago, seems like a year lol!

If not I can certainly give you one that does..

[wase16ll]

ignore what i said here "fuel trim will help to diagnose why the co is high"

although that is true, its not what i meant to say regarding your particular problem.

the fuel trim will help you see what your 02 sensors are actually doing, ie..telling the ecu wether to increase/decrease the fuel, so therefore you can work out if engine is sucking air or overfueling as well as view how well the o2 sensors are actually switching.

in my opinion, trims are one of the biggest aids in diagnosing in live data

[bt_cav]

Nice one, thanks Tony :)

Cheers Stef yea so...

I have gathered the freeze frame data

TROUBLE CODE P0420

Fuel SYS1 CL,using H02S

Fuel SYS2 N/A

CALC LOAD(%) 74.1

COOLANT(*C) 109

ST FTRM1(%) 3.8

LT FTRM1(%) -3.9

MAP(kpa) 0

RPM 2252

VEH SPEED (82 Km/h) (50 mph)

[wase16ll]

sorry to be a pain, but any chance of data at idle

not overly concerned by figures, within spec but bit suprised the lt trim is showing a slightly rich condition but st is lean...first thought is either post cat sensor is sluggish/playing up or cat itself causing a problem...might help with figures at idle

the code relates to cat/post cat sensor,

can you view a graph showing the sensors switching, or just a digital readout

[bt_cav]

Hi Tony,

Thanks for your reply, not a pain in the slightest I appreciate your help, time and interest :)

Its just a digital read out... quite basic but handy... However I know a man who might be able to help me out with regards to viewing a graph, last time we looked the Lambda sensors seemed to be working ok ;)

I hope to up load a video to show the live data on youtube...

I washed my car on the way home tonight at the local supermarket jetwash, It was a little rough in starting Never usually an issue, and I thought I heard a slight misfire under gentle stationary revs but it cleared its self in seconds....... and it did smell rich..... I had driven about 20 miles before all this.....

I gave under all the wheel arches a good blast to get rid of all the salt from the last few nights so perhaps it was down to a bit excessive moisture lol

on Sunday night I cleared the EML and its still out.

[wase16ll]

if you can view a graphing, can sometimes be easier to spot a problem

from what that data is showing, i would be looking to see how that post cat sensor is switching, if it virtually mirrors the pre cat, then big probability there is a problem with the cat itself..

the post cat should almost be a steady voltage, if the cat is doing what it should..

not forgetting that engine should be fully warmed up, then tested at idle and 2.5k rpm, give it the occasional snap on the throttle as prolonged periods at same rpm can give false readings.

voltage checks on live data may work but not as accurate and easy to read as graphs

[bt_cav]

Hey guys, I have put the video on youtube, Apologies for the wrong angle and the loud Beeps as I press the up / down buttons on the code reader not a good idea to wear headphones

http://youtu.be/fp3xFR-pbV8

[wase16ll]

not going to help much im afraid, live data is only usefull when you know what the engine is doing and what readings to expect at that time...for eg, can see the trims fluctuating, but without knowing the revs at the time of fluctuation then will mean nothing.

the fact they are fluctuating, proves the front sensor is switching and ecu is adapting accordingly, though doesnt prove if switching correctly without more detail...but the code you had is pointing to the rear sensor and/or catalytic, neither will affect the fuel trim, the rear sensor on that engine, is there to monitor cat efficiency.

next step is get a graphing of what the rear sensor is doing, ideally alongside a graphing of the front..if possible, may also be worth measuring the temperature of the cat with an appropiate tool, at inlet and outlet.

noted you said earlier that cat and sensors were replaced before, can i ask why? was there a problem that led you to do this or was it just to fit a sports cat?

[bt_cav]

hey Tony, What happened was about 5 years ago while on the way back from the shops on a Saturday evening with my mother in the city center of Edinburgh the coil packed in..... didn't have a lot of options as I live 40 odd miles outside Edinburgh.. so had to call the AA who could not attend....and sent one of their contractors who arrived and tried to start the car ...... probably knackering the cat....

After the new coil was fitted the EML was always on the garage said it probly knackered the cat when the coil failed...and the P0420 code was keeping the Eml light on. After that I cleared the EML each time I handed the car in to be MOT'd and it worked for a few years... I fitted new sensors in an effort to stop the EML showing but it did not. Also I had a Cavalier before and the cat collapsed internally so didn't want to chance that happening again.... So I had a sports stainless steel cat welded in.... I didn't clear the EML to see if it would go out by its self and it did.

I got to have a look at the old cat and there wasnt any signs of damage, I held it up to the lights and looked through the honeycomb, it looked perfect which I suppose is a good thing given the high millage.

so far the light is still out.

[wase16ll]

got it

takes a lot more to ruin an original or good quality cat, lot more hardy than people realise,.but going what you have said, must have been a problem with your old one but doubt it was purely down to the misfire unless you had driven it a good number of miles like that.

have you had a fairly recent mot, if so, were you given a copy of the emission test?

if you still have it can you put the figures up?

im starting to suspect there is a problem with the sportscat, they arent known for their longevity, but you will need to get an idea of what that post cat sensor is doing for confirmation there is a problem there....would be the obvious next test to do

[bt_cav]

sadly the MOT is due in April, the EML had never shown on the car until the coil went. I really think the guy who recovered my car should not have tried to start the car until he had read the codes which I never saw him do ... never mind trying to start it for as long as he did.... while I was putting my mother and a boot load of shopping into a taxi grrr

I did wonder about a faulty fuel pressure regulator so i carefully pulled the vacuum pipe off the top while the car was running to see if any fuel came out, as soon as I done this the idle speed increased slightly, this was on a cold engine.... didn't see any petrol.

I'll look and see if I have the last figures :)

[bt_cav]

Not got the gas test results.... I have always been told its been difficult to pass the gas test but eventually it passes this was with both the original and the sports cat.

Going to Edinburgh tomorrow so will be interesting to see if the light comes on (sure it will)

will also look into the appropriate tests :)

[wase16ll]

might be getting somewhere with this

i very much doubt the cat was ruined by the recovery guy, so breath easier ;) as i said, would take more than that to kill a cat.

wouldnt expect fuel to be seen when disconnecting the pressure regulator, unless the diaphragm inside had all but disintegrated, revs rising isnt unusual but doesnt mean to say its 100%

you obviously have an underlying problem that is causing the sensors to struggle to cope with keeping the fueling within spec, hence why your struggling to get through mot's, over a long period of time, that can cause the cat to gradually fail.

now im starting to think that the rear sensor and/or the cat is struggling again, enough to cause your flat spot issues, but not quite enough to set the code on a permanent basis..yet

but what needs to be addressed is, if im right, the underlying problem needs to be sourced and fixed otherwise the 4020 will just keep coming back and may lead to the front sensor failing too.

still stick with checking that rear sensor, but also if possible, get a 4 gas readout too, at idle and 2.5k rpm, ideally get a full read out at cold/warm and hot, paying attention to how much the gasses are fluctuating or if they are steady/slow in reaction ..in other words, as much info as possible.

you may need to deal with the cat/sensor (if there is a problem there) before you can start to look into the underlying problem...as that can affect the running...one of those chicken/egg scenarios.

if i was a betting man...id go for a fault in either injector/s or fuel pressure which is causing problems with cat/rear sensor....definitely the areas id be focussing on right now

[bt_cav]

Nice thanks for your advice Tony it is gratefully received :)

What I am struggling to get my head around is after the coil was replaced why was the EML showing and the code P0420 from the minute I collected the car from the recovery garage.....unless the misfire was the last straw that broke the camels back as it were

Can anyone suggest a cheap fuel pressure testing device, saw some on eBay bot not sure if they will fit fords fuel connections (assuming this is how it would be done)

Also I'd be interested in ODB2 software & bluetooth device to use on my laptop, does any have a facility to capture the live data in order to post on youtube?

[AdeMk1]

Torque Pro + an ELM327 for your phone, or if you look in the for sale section there is a guy selling a wired switchable ELM327 with software for your laptop.