Hi all,

I have searched many missfire related threads on here and I haven't been able to find any with an issue similar to what I am currently facing.

It's a 2wd engine, L6 ecu, greens 3bar etc, .48 t3/t4 turbo. holding about 18psi

I just fitted an electronic boost controller to the car to help it hold more boost in the top end, although on the dyno it started to develop a miss towards the top of the rev range.. and when you lift off the engine misses like its running on 3 cylinders for a few seconds and then all is fine again until it is boosted hard again.

Plugs are NGK BCR8ES gapped at 0.6mm and I also tried some denso IK27's in there (didnt gap them tho) no difference.

I tried a new set of leads, changed the crank angle sensor and gapped it to 0.6mm, gapped the phase sensor to 0.3mm. The coil is a MSD SS blaster.

I read something about having the coil/spark plug leads and Map sensor too close can cause issues.. what sort of issues and why ? and how close is too close ?

Could it be something to do with the injectors ? and how can I test them ? The fueling was very safe on the dyno even with the miss.. i think the leanest it got was 11.4 -11.6 ish. If it was leaning out on one cylinder due to an injector not firing correctly would it be noticeable with the afr meter in the tip of the exhaust ?

Could a headgasket issue cause this ? water / oil getting on just one plug ? Although under full boost the water / oil would be less likely to be getting into the cylinder due to the increased compression ?

Any help would be greatly appreciated !
I need to get my car running right so I can show my fellow aussies why Bristish Ford is king

Thanks,
Damion.

 

The honest truth, find yourself a dyno operator that does know what he is doing, as the emissions should be a massive clue, the ht leads can indeed cause interference particularly so with the cps wiring which is why this is shielded to earth at one end, just keep so it is not touching and away by 4-5" will be fine.
I would try some IK31 plus at that boost personally, gapped to 0.8 as you have a msd coil, but you want to check the resistance of this coil and comapre with the ignition amp as well.
Fuel pressure needs checking as does fuel filter(changing) and a pump rewire just to rule these out and because they are needed anyway on any cossie now due to age.
what is the duty cycle of the injectors at max power.
tabetha

 

Cheers, The engine is in a mk2 Escort so the wiring to the pump is fairly new and the pump is a bosch 044. I will try fitting some new fuel filters.

Unfortunately here in Aus nobody does anything with the factory management so I have no idea what the injector duty cycle is etc.

I think the fuel pressure at idle with the vac line on is about 49psi.

 

Std pressure is 3 bar(43psi) with vac on, and around 3.6/7 bar(54psi)with vac off.
So long as the RR has a anylyser then just watch the gasses closely, it will be a big clue.
These things are one of the(many) reasons I don't bother with std ecu as well, you would be much better off using a "known" system that your RR can set up, it will pay dividends in the end.
tabetha

 

this one has got me stuck! - you've tried everything i would have changed - i'm sure one of the resident experts might be able to help

 

The fuel is very rich if anything, I will try and scan the dyno sheet later to show you.

Yeah an aftermarket ecu is definately on the cards in the next 6 months or so, I was looking into using something along the lines of a microtech, but if possible I want to wait a bit longer and buy an Autronic as it is a more capable unit.

I will try moving the coil over the weekend, as my coil is mounted up behind my dash, along with the map sensor and ignition amp.. but the coil is approx 5inchs away from the others... But my coil lead runs through the same hole in the bulk head as my engine wiring loom ! If the lead was the source would it cause interference at all times ? As the car is fine the rest of the time.

Cheers

 

Yeah, it would be good if someone knew the problem straight up.. but unfortunately that rarely the case !

Sorry about this dyno sheet, as it is a scan of a scan.. i don't have the original print out here at the moment. I am just wondering if a faulty injector cause be the problem ? I am going to have a good going over of the wiring of it tonight I think.

Is it normal for the Afr to rise like it does at the end there ? as it has already made most of its power at the time the afr starts to rise.

 

Christ almighty no wonder you are having problems, with a graph like that!
The rise to which you refer is a leaning out, and no it should go the other way, ie more load richer, this is done as a form of protection against det, it is massively too rich lower down at lesser boost, 10 afr is taking the P**S, even on full throttle it would not be this rich.
The fact it leans off again suggests it is fuel flow/delivery issue, that is of course assuming the chip is correct, it looks entirely incorrect from the graph.
A bit of interference could indeed only be a problem as the faster the engine turns the more interference it creates with more pulses, never ever put ht near any sensor wiring.
tabetha

 

Cheers, yeah it is a stage 3 chip i bought from Clint Gaskin, I am in another country with a different climate and probably different fuel, so it will never be perfect i guess.

The fuel pressure probably could come down a bit if i sort the leaning out at the top there and that should probably lean it out a bit across the range i presume.

I see your point about the afr aswell the last time i had it on the dyno the afr at the start was 13.8 - 13.0 before the boost came on, hmm.

Thanks.

 

jesus; the graph is bad!

is the chip suitable/ made for your spec? - either the chip isnt right or you've got fueling issues

 

Maybe something was wrong with the dyno's gas analyser ? as this is my last plot from a year ago on the same dyno



The coolant temp sensor has to do with richening up the engine on warm up, correct ? could this cause an issue like this ?

Thanks.