My FC has been running very rough lately, it started when i did the OMP delete and started premixing, don't know if that has anything to do with it but i just thought I should add that. It sounds almost like it has a misfire at idle, and when accelerating from a stop until about 2k - 2.5k rpm. I just fixed my 3800ish hesitation last night by adding a ground, hoping that would fix the rough idle as well but it didnt. I've also noticed im going through a lot of fuel, quite a bit actually, so i then thought it could be the o2 sensor, which ive also replaced with no luck. i'm getting ready to do a turbo swap in the next few months but still need to drive the car as is until then, so any help is greatly appreciated! thanks!

 

Your TPM could be bad. Do you also have back firing when coming of partial throttle loading but not necessarily WOT? High idle at times? Or an idle that's slow to come back down to 7 or 800?

 

yes i have a high idle at times, and its slow to come back down to 750 or so where it usually idles. and it has always backfired a little, that hasnt really changed. do you mean the throttle position sensor? im not sure what TPM is..

 

update: i tested my TPS, its working properly, the idle spec was off, so i adjusted it to 1k, and at WOT the TPS read 5.05, so seems fine to me. still idling super rough. it shakes pretty bad. im thinking of the best way to test my coils/wires now

 

the boost sensor being unplummed will do thus. having a vac leak will do this as well

 

vacuum leaks?
BAC issue?

 

Is it a s5?if it is....removing the omp is your issue.on s5's if the omp is disconnected or bad it goes into limp mode..

 

Its an s4 so my omp delete shouldn't have anything to do with it. I will be checking for vacuum leaks but I have an emissions delete so its gonna get confusing

 

Have you tested compression? Reduced compression (not blown) on one rotor will make it idle rough and reduce power; it'll be especially noticeable at lower RPM.

 

Yeah i have tested for compression. It tested even 90psi front and even 85psi rear. Whats the best way to test coils/wires?

 

you still have your oil injectors on the car even though you did an OMP delete?

 

yes i do still have the oil injectors in the car...should i go ahead and remove them before I continue troubleshooting?

 

Update: I removed the oil injectors today. I used the little plugs from pineapple racing in the housings, and two m10x1.25 bolts to plug the manifold. i removed the spider and oil lines, capped the upper manifold with a vacuum cap where the spider connects. Car still idles rough, and sounds like its misfiring or something when accelerating from a stop until about 2k rpm. Other than that, it runs fine.

 

check your ignition components. plugs, wires, and coils.

 

How much premix are you using?
too much can cause plug fouling.
try switching/cleaning the spark plugs.

 

I use about 3oz for every five gallons. And what is a good way of "checking" my wires and coils? I've switched plugs three times..hasn't helped. I know that my trailing wire on the front rotor doesn't "click" onto the plug very well, but it's never caused me problems.

 

My s4 n.a runs very similar to what you are describing. In the past ive done a full tune up, new intake gaskets, new vacuum lines, set tps and still nothing really has helped. I get an average of 200-240 miles per tank.
I should really send my injectors out to be cleaned and install new injector clips but i cant have any down time for my car. Been driving it like this for a few years and just learned to live with it.

If you find a solution i sure would like to know. Good luck

 

yeah i ended up switching coils with a friends car, didnt help. i also put new plugs in before i tested it with the other coils. im just going to assume its low compression.

 

My car ran fine at 80ish psi per rotor face before I did a rebuild. I don't think that is your problem.

 

Did you mess up the TPS calibration when removing the metering oil pump rod from the throttle body? Unplugged TPS perhaps?

 

:O I wish I could get 240 per tank! I'm lucky to get 200. (88 vert)

 

Check your water thermo sensor below the alternator.

You may have pulled it out accidentally. If that wire is not attached, it will give you horrendous gas mileage. It may look attached but because of corrosion, it may not . It's a connector that looks like an injector connector.