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Misfire Under Load


wowblaauw

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Hi chaps, I have a Zetec 2.0 crate engine with 1000 miles on it. Last year I added AT iTB's and although I had a misfire at the time it seemed to sort it self out as the engine warmed up so I paid scant attention to it. However, since I started the big strip and rebuild; replaced the entire electrical system, new engine and chassis looms, a new dash board, dials etc, switches et al cooling system, fuel lines, pump filters all with new product I/we have developed a much more serious misfire under load. Since I started this big upgrade, I found that my Emerald K3 had some fluid ingress and was misfiring on 3 which was highlighted by the good folk at emerald and repaired I still however have a misfire under load. The engine will crank, fire and run at low revs very nicely but as soon as the throttle pedal is applied I get a cough splutter, lots of misfiring back through the air filter the odd back fire and generally no power unless applied slowly.

 

Any ideas?

 

Thus far I have replaced the manifold 'O' rings, the HT leads, coil pack and plugs (head and brain), think thats it for now, any suggestions would be gratefully received.

 

Thanks, Craig

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Guest mcramsay

Have you wired up the throttle position sensor correctly? You can see the values on the live adjustments screen on the emerald program, also have you reset the TPS values since refitting the throttle bodies? Sounds like the ecu is not seeing the throttle change correctly.

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Wow, thank you so much.

 

The map is the GBS TB powermap for 2.0l Zetec. When it comes to the mapping side I have absolutely no idea as I kind of missed all of this during a time when all I did was buy and drive.Trying to play catchup later in life is like trying to teach an old dog new tricks...

 

TPS is wired correctly as per GBS instruction - as for 'ecu not seeing the change correctly' may well be the issue or not. Like I said, I am not up to speed when it comes to the mapping side of the engine management.

 

TPS has been reset several times as I balanced the throttle bodies and now is set and balanced nicely. Just missing under load.

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Something I've seen in the past that's exactly this are coil packs degrading and/or coupled with heavy voltage drop when under load (often bad alternator/regulator/earth/electrics/etc). It depends on the setup, of course; some systems (had one on the Peugeot) used an ignition module that was notorious for overheating if not well mounted, and then becoming very unreliable.

 

But, reality is there could be lots of things contributing...

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"The engine will crank, fire and run at low revs very nicely but as soon as the throttle pedal is applied I get a cough splutter, lots of misfiring back through the air filter the odd back fire and generally no power unless applied slowly."

 

If i think about when i've tinkered with small 2 stroke engines i sometimes get the same thing. If you open the throttle quickly it will cough and die but if done slowly will be ok. This always seems to be a blockage somewhere in the carb so the fueling is not right and i normally end up cleaning the carb and messing with the mixture screw until the blockage is cleared or the fueling is correct.

 

I know you have injection so i don't know if any of the above applies but my thinking is that you aren't getting enough fuel so when you open the throttle quickly a big rush of air and a weak mix kills the engine but slowly it gives the engine time to spin up on a small amount of fuel. I don't really know about injection setups but from my limited knowledge there are a few sensors as mentioned above, TPS, Mass air flow meter and lamda sensor (i may have missed one or have my thinking wrong) which can alter the fueling. I assume you can use a multimeter to test the sensors so that could be a nice easy start but i don't know if that is the case for all of the sensors and what the values would be.

 

Not sure if anyone uses them on a newer engine anymore but a gunsons colourtune would show if the mixture was correct etc so at least you'd know if it was fuel or spark etc.

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If you have a Mass Airflow sensor that could be giving bad feedback under load (they do often fail), found this site that shows how to test it. may be worth a try:

http://my.prostreetonline.com/2016/02/02/how-to-test-a-ford-focus-maf-sensor/

 

Or is there any test software for the Emerald that will help determine if the sensors are all reading correctly?

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Thank you chaps, much food for thought especially as I have a whole weekend (1st in many moons) to look closer at the issue. I have a spare coil pack and HT leads, spare plugs so will give it all another go. I especially wondered about the lack of flow so have already replaced the injectors. The MAF sensor is new from Emerald so am thinking I can check that off the list. As for the Lamda I haven't set the car up with this type of sensor.. yet. One of my future tasks. I will upload my finds come Sunday evening.

 

If I can identify what the issue is then its off to the rolling road.

 

Thanks again for all of your help, sometimes its good to hear it from others who have had similar/same experiences.

 

Craig

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Guest lotusPaul

Firstly if you speak to Emerald they will email you a very workable map for a basic 2.0ltr zetec thats not been tinkered with. So a standard engine with 40mm Jenveys. Its a map that was setup on a rolling road. They will send this for free and im suprised Karl didnt load it up prior to sending it to you.

 

Once you have a working map you can test again and get back to us,

 

Im also going with a coil pack but also if you can swap leads from different places to see if you get same results. If not it could be the leads.

 

Poor running, allways change the plugs to eliminate the very basic elements are done and gap them.

 

At same time take off, check coil connector for damage and corrosion, clean and refit. Check both loom and coil pack sides.

 

Earths also have a habbit of playing havoc with ecu's and ignition. Make sure your wiring is in good order and if it says sheild, then do it.

 

Generally not much goes wrong with these nowadays, follow the basics and you cant go to far wrong.

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Sorry you are still having problems Craig, but I must caution. That vehicle ran perfectly, on very poor wiring. It would appear to me, following some of this story, on here and elsewhere, that your problems started when some mods were carried out, is this correct?

 

The Zetec is known for fouling plugs, have you changed them?

 

The TPS wiring is a known problem, if you have followed the GBS wiring scheduled it should be right, but there are versions depending on TPS. The ATR use a production TPS that can distort when tightened, you must check the TPS output in the ECU, It should move smoothly, without any jumps from 0 to 100 %.

 

It is important that you calibrate the map to the throttles. The map, what ever map, assumes that 0% throttle is giving a known amount of air to the cylinders, if 0% is out then the whole map is out, this can be "trimmed" with the Emerald. and the trim can point to what is wrong.

 

You have ATR, which map do you have?

 

A RR may be the solution, but a knowledgeable person may achieve the same with the right map and a bit of time with the car.

 

You may indeed have some or all of the problems that are noted above by contributors, but if I can help, you do know my email.

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