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Odd Misfiring/Cut-out on Acceleration and Left Turns

11K views 27 replies 14 participants last post by  lucky phil 
#1 · (Edited)
Afternoon All,

I own a USDM '17 FoRS RS2 package car that has presented an issue that has consumed quite a bit of my time.
Car has roughly 16k~ miles on it - problem has been present since 1,700 miles or so.

I've had this car in to a few local dealers a total of 9 times and a grand total of 97 days attempting to correct/alleviate this issue. I've had Ford Customer Care involved, escalated to a regional manager.

I've been told i'm crazy. I've been told that they can't reproduce the problem. I've been told that I drive the car in a manner inconsistent with the original intention of the vehicle. I've also been told they have no idea what is happening or how to fix it.

In 97 days, the dealers have managed to replace the primary fuel pump in the fuel tank, and a set of spark plugs, in an attempt to correct this issue.

It has an odd misfire upon acceleration - heavy or light acceleration, once the vehicle is fully warmed up (Oil temperature 190-210*F) that is HEAVILY exaggerated on left turns. I've monitored PIDs and datalogged this phenomenon to the best of my abilities. From what I can tell, the PCM begins to detect spark knock, and retards timing during these events. Fuel pressure doesn't appear to drop in any observable amount. Plugs are clean and gapped correctly. It doesn't record/log any misfires during these events. AFR seems to be in line in the vehicle. It is 100% STOCK - down to the transport steering wheel cover. I have a glovebox full of 93 octane receipts for the vehicle and doubt it is a fuel quality concern over so many miles of driving. Intercooling boots, piping, clamps and airbox tract all in clean and good order.

Any ideas? I'm at the end of the rope here. Head gasket was replaced before I purchased the car. (bought it new). I've continuously returned to the idea of a fuel delivery concern with this problem, especially considering the left hand turn misfires. It makes it absolutely unpredictable to drive once it gets warmed up. Before it warms it though, I believe the car is performing the way it was meant to perform. I've dynoed the car on an AWD dyno and made 249/301.

Also, if one of y'all has any contact info for the galaxy brains in the Rhineland that designed this car, please let me know.
 
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#2 ·
So what you're saying is your car is unsuitable to compete in NASCAR.

In all seriousness, this does sound weird. When you say left turns, do you mean very aggressive turns or even gentle turns? You might want to keep track of the relationship between this issue and the lateral acceleration when you're turning as well as the duration of the turns. If the severity is associated with a certain turning direction it may indeed be a fuel feeding issue. However I'm not quite familiar with the internals, hopefully someone more qualified could figure out what might be going on here.
 
#3 ·
Already have. Doesnt matter if im braking into the turn, accelerating through it, coasting, in or out of gear either. Doesnt matter if it is a hard turn or not - wide and sweeping or tight and aggressive turns all can cause the problem.

To be clear - it can have the same problem on the freeway going straight during acceleration as well. Only prerequisite is the car has to be warm. The problem is also more exaggerated as the tank empties.
 
#4 ·
Well I assume the PCM detects knock because it goes lean when the event occurs so it sounds like fuel delivery. Quite a few people here have had the lift pump in the tank replaced for this exact issue so maybe you got a faulty replacement unit. Did the car do this before the HG replacement? quite a few people have had the injectors damaged during the HG job which have led to running issues. Does the fuel level have any influence?
Its not a traction control issue is it? its definitely a misfire?
Maybe you could buy a single coilover and swap it out one at a time and see if you have a faulty unit. They can cause problems when hot and be ok when cold.
Ciao
 
#5 ·
The knock because lean theory is largely what ive been entertaining.
HG was replaced before i bought it. (New).
Less fuel exaggerates the problem.
The problem is NOT dependent on any one cylinder. CCT indicates the knock (or timing pull consequently) is entirely random. Doubtful ALL the coils have an issue when turning left. Same reasoning applies to the injectors.
T/C off yields same results.
 
#8 ·
All signs point to the fuel delivery as Phil and Silver wings mentioned. If it happens under acceleration, turns and is worse when there is less fuel something is has to be wrong with the pickup in the tank. A theory as to why it only happens when warm is that the engine runs much richer as it is getting up to operating temperature, so if the ECU requests x amount of fuel it is really getting less but the won’t sputter as it is still enough fuel to run.

Maybe go and see if they will let you take one of the techs for a ride as you know how to exactly replicate it. If they can’t figure it out and refuse to do anything further then go and get the in tank pump looked at by someone who knows what they are doing or replace it yourself.
 
#12 ·
This is probably not related but the left turn thing has me thinking about a problem I get with my car sometimes that I need to get checked out. Sometimes when I cold start my car the A/C has issues running consistently, it will blow air in spurts and at low pressure. It takes a bit, but the A/C eventually starts working as normal. When I have this A/C issue and I turn, it will blow air normal until I'm done with the turn and then blow in spurts again.

Could your issue be a faulty sensor issue? Replacing the HPFR sensor seems to help people that get hesitation/surging/dipping idle.
 
#14 · (Edited)
I’d be curious about the position of the throttle body valve when you’re observing this. This car has so many “nannies” that restrict the torque output. My tuner had a hell of a time getting around all of them when I had my car dyno tuned last month. He mentioned the throttle body would only be about 30% opened even when his right foot was asking for WOT. Before this, the car felt sluggish and there was a lapse between pushing the gas and getting the shove of acceleration. That’s not an issue anymore. That’s the difference between mechanical differentials and electronically controlled ones. It’s pretty common to see timing corrections on a single cylinder at the beginning of a pull and without WMI. I was told it’s corrections across multiple cylinders at the same time that I need to watch out for.
 
#15 ·
Sounds like your dealing with a questionable dealer or tech. Take it in, let them punt it then request a flight recorder be installed. At that point when you have ur car and it flips you can capture it & they can review it and get it nailed down. Ofcourse the flight recorder is only as good as the tech.installing it So find a better dealer. ? my 2 cents.
 
#17 ·
Well after 130+ days in the service departments across two dealerships, Ford executive office involvement, customer care support, untold amounts of phone calls (and a lack thereof from some parties), I was told to pick up my vehicle as nobody was left to work on it due to the virus. The misfiring/cut out still isn't fixed. They did manage to fix the headlamp that was out, as well as the air conditioning that randomly stopped working. I've had it now for a few weeks and informed the Ford executive office I'll be investigating the problem with the car myself. I think I already have a promising fix on the vehicle - a bit more road testing and I'll be confirmed that it resolved the issue.
 
#19 ·
Can't find another one. Every RS/ST owner I know has wrecked their cars, and every single one I find used in the area is wrecked. The last one I looked at was wrecked not once, not twice, but THREE times. One of them wrecked AND flooded.
Also, no guarantee on how it was maintained prior to me getting my hands on it.

Figured out my car yesterday. FINALLY got my car back to how it was during that first month or so of ownership... all this time and effort screwing with the dealers and a 63$ part fixed the car. How embarrassing to admit.
 
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