ford4v429

that makes sense...Ive never really even looked at my coils to see how well theyre sealed up...

I think he's running a full race setup(non emissions/dirty but safe) mapped fuel curve...I'm sure he'll fill in the details, but I dont think its anything typical like a street setup. If I recall he had to go to forged bottom end/big clutch, etc...dont recall for sure, but think this is like a >500 hp car.

GT06GT

I said i didnt wash under my hood .

As far as dealer wording, i talked to the lady at the service desk and she obviously wasent the one who worked on it but told me, "it has low compression in one cylinder, and we have to have our engine tech diagnose it.

chevykiller

I have been over 520 RWHP on the stock motor for over a year. I am putting in a forged 302 stroker right now. You are half correct about the 02 sensors. The car has upstream and downstream 02 sensors. Only the downstream measure your flow and are used by the cats. The upstream are for fuel measurement. Although they serve no purpose for emmissions or cats, the car cannot run without the upstream sensors.

So to specifically answer it is the downstream 02 sensors that I eliminated. You cannot run over 102 octane with the downstream 02 sensors or it will fry them and you cannot remove your cats without also removing the downstream 02 sensors as well or your car will failsafe as soon as you start it. I have no downstream 02 sensors and no cats.

How could you possibly say only an idiot would say he doesn't have 02 sensors? No one running serious power and octane has downstream sensors. For all your ranting, I would have thought you would have known they have upstream and downstream 02 sensors and what they are for. Maybe you should re-evaluate who needs their head punched in?

06GT4RAD

Wasn't ranting and also was not saying anything about you being an idiot. Someone had posted about there mechanic telling them the O2 was in the intake. Maybe you should go back and read what i wrote to you. I am fully aware that the car has four O2 sensors. Which is why i questioned how you were running the car without them I am also fully aware of O2 Sims and that the downstream O2's only monitor cat efficiency not flow. Again why i asked how your car was running without O2's and i quote you:
Which says to me you have no O2 sensors since that is what you wrote, not that you eliminated the downstream O2's
And anyone that thinks the O2's are in the intake, well they really should not be giving any mechanical advice because it is obvious they are clueless.

Richard

RStone13

For what it's worth, everything I've read about Freds tunes at evolution. Is they run a little rich, not lean.

06GT4RAD

Just a bit of info i found out today. I spoke with someone at Ford and the Dealerships have been instructed to start voiding warranties for people running CAI and Chips anytime they discover them and/or find engine troubles. I guess something happend with the Subaru WRX and that started the whole snowball effect.

Richard

Royb

I think its your MAF. Not broke but these cars have "Adaptive Learning" and over time it will casue the MAF Transfer function to shift and make your car run like crap. Disconnecting the battery does not fix or erase the adaptive learning. You need a custom dyno tune. to make sure datalog the car and look at your long term fuel trim & short term fuel trim and if there is a big diff there there is your root cause. If the dealer says you got low compression them watch then do a compression check against all cylinders - don't take their word for it.

GT06GT

Official word from the dealer, I broke a valve spring and that was causing the low compression. My buddy is a porter at the dealership so ive been havin him give me the inside word and talk to the techs and this is what i found out. They also didnt know i had a CAI/tune as of yet and the tech said it was probably improperly seated from the factory.

Tres Wright

I was originally going to suggest that you might have gotten some bad gas and ask if you had recently filled up (or if you possibly ran it close to empty in which case you may have been sucking sediment off the bottom of the tank). But if the dealership found you are low on compression on one cylinder, it sounds like you may have burned a valve. We inadevertently missed a valve adjustment on my wife's last car and burned a valve, the symptoms were exactly what you describe. If for some reason your tune was running lean, that could have caused it. Please post back after the dealership tells you what they found out.

ford4v429

well glad it hing in there and the retainers didnt come loose- coulda been a lot worse! Hopefully the vave didnt contact the piston and its just a topside job- wonder about the exhaust seat though in that case as it woulda had to been exhaust valve or car woulda been backfiring severely...hope compression comes right back up with just a new spring.

I dunno about 'not seated right' as I kinda though most springs would coil bind if not sitting just right...but Ive never seen whats under there yet...my 85 camaro had a 1-2 accumulator piston spring in the tranny break after about 30k miles- it was just bad piece of wire, no way it coulda been anywhere but in the right place, end of the spring actually dug a hole thru the separator plate- shifted fine up till that point...that tranny had numerous problems over 20 yrs/60k miles I had the car...it was just cheep parts. spring broke, plastic governor gear stripped, forward sprag self destructed...had it apart a 4th time too, but dont recall why...oh well.

anyway with broken valve spring, sure glad the keepers held tight saving the engine...hope they get you back on the road soon