nathan.wyman92

I have an 03 mustang gt 4.6 sohc. I had a supercharged on it when I bought it, then I blew a headgasket and took it off. Since then the car has been running super rich. It throws an 02 sensor code at me, I replaced it. it will throw both banks rich and sometimes one as lean. I have cleaned the MAF and the readings from it appear normal, same as the TPS and fuel pressure. I just ummm "made the cat flow a little better on one side." I ran the short term fuel trim and one bank has a short term of 25% and the other has one of -25%. Could this be because both cats were clogged and now one is flowing way better than the other? or is it a vacuum leak or something else screwed up somewhere? I'm lost and sick of throwing money at this thing.

nathan.wyman92

I hollowed out the other cat today. welded it back up. now the short term fuel trim is reading 25% on both banks. The long term fuel trim tends to stay at 0% or fluctuate slightly as it should. Factory tune is back on car. HELPPPPPP MEEEE. What am I doing wrong? the stft doesn't change at 2500 so I'm guessing it's not a vacuum leak. Fuel pressure at the regulator is 39 psi at idle. Obviously not a plugged cat anymore. My wide band o2 reads below 11.0:1 but that may be compromised. I drove the car about 20 miles hoping it would clean off the o2's it didn't help anything. HELPPPP. Any thoughts? At this point my thoughts are selling the damn thing as is and taking a huge hit.

school boy

is the supercharger still on the car? also what have you changed on the car since this happened?

VTX1800N1

First, what is still on the car that is not factory stock? Make a list and check it twice. My guess would be that the supercharger kit includes higher flow injectors. If those haven't been returned to stock, and you removed the supercharger and put the stock tune back on the car, it's no wonder you have problems.

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nathan.wyman92

The supercharger is not back on the car. Since I have hollowed the cats the short term fuel trim has gone from saying the car is way too rich (beyond the cars capability to bring it back) to saying the car is running way too lean. my wideband o2 says it is still too rich, but I'm doubting that it is reading correctly. the car drives around town pretty good but the second I go to actually get into it, it falls on its face. I can't tell if it is starving for fuel or what.

VTX1800N1

Try reading my post again. What COMPONENTS from the supercharger kit are still on your engine, or do you even know? Fuel pump? Fuel injectors? Fuel pressure regulator? Mass air sensor? Any or all of these are often upgraded when a forced induction system is installed. If you take the super or turbo charger off the engine and do not also return these items to stock, you will have severe driveability problems. If you don't have any idea what I'm talking about, you need to take your car to a competent mechanic before you destroy it.

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nathan.wyman92

Your condescending reply is not very well appreciated. I know what you're talking about. I bought the car with the supercharger on it. The fuel system as far as I know is stock, the only item that might not be might be the injectors, the MAF is stock. If the injectors were in fact upgraded the car would be sending a rich code which it was, but since I replaced the cats the car is saying it is too lean. I understand the basic concepts of fuel trim and what might cause this, but I have exhausted most of the options that I know of and am trying to pick other people's brains on the matter.

Gt04

Your problem is most likely the upgraded injectors, no way the supercharger would run on #21 or #19 injectors whichever your car originally had. Are the injectors pink or orange topped?

school boy

I would think your best bet is to install a factory set of injectors and the factory tune. If the supercharger tune is still in the ecm, which sound like it is, then the car will run horrible. And im willing to bet those injectors are 36# or bigger, which will cause the car to fall on its face too.

VTX1800N1

Do you want help or not? I asked the same question in my first reply and you completely ignored it. As others have now stated and I have twice stated, other components of the supercharger kit, most likely the injectors, are probably still on the engine. It sounds as if you took only the supercharger itself off, returned the car to the stock tune, and expected it to run. That tells me that you don't know what you're doing. The next thing you are going to destroy is the cats when they melt and clog from too much unburned fuel due to the larger injectors. It sounds like this may already have happened and that's why you broke all the substrate out of the cats?

Massive amounts of unburned fuel can also damage the O2 sensors, which may explain why your fuel trims are swapping randomly.

Next your cylinder walls will be damaged from fuel washing the oil away faster than the engine can supply it. If you keep driving, your bearings will be destroyed next as fuel washes past the rings and dilutes the engine oil.

So, I wasn't being condescending when I was telling you to take it to a real mechanic. If you keep messing around with things you don't understand, you WILL destroy the motor. But it's your money.....

On a 2003, your stock injectors will be pink tops- 21lb. If this is not what you have on the car, STOP driving it until you get stock flow injectors back on it.

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