Full-Force

iTrader: (11)

I have been working on this guys car for the past few days with no luck.

He claims he had a new exhaust put on (duals) and went on vacation for a week. He claims he came back and the car will not idle good, and it will not start on 1st try unless you hold the starter in for a long time.

I had his fuel trims all within -5 to 0 when I tuned it last year. Now every cell is lean with positive trims of 25.

I put the car in SD and load the stock ve table back in it and build a new one. While Im trying to learn ltft's i notice that when i give it 3/4 or full throttle the car is dead and the o2 voltage goes from 400 -600 at part throttle to 34 at wot, yes 34.

I put in new o2 sensors and checked the fuses. New plugs and wires.

I load the new corrected ve table and the ltft's are now within 10 for a while and then out of nowhere they go back lean and most cells are +25 again.

I gauge display that the bank 1 ltft was red and dead lean and was adding tons of fuel while the right looked normal. A few minutes later and the bank 2 was doing the same thing.

I cant get anywhere with this car because something is wacked. Anyone have an idea?

Car has headers, ory, and 224 cam. Its an 01 car and the intake has not been off and Im pretty sure their is no vacum leak.

At this point Im thinking I need to check the fuel pressure. What Im think though is that the car is really not lean, but for whatever reason the pcm thinks it is and is adding a ton of fuel. The plugs i took out were caked with carbon from being so rich.

HELP

jimmyblue

iTrader: (11)

Any chance that somebody used a bad gasket goo during the
exhaust work and poisoned the O2 sensors? Or just messed
with the wires?

RedHardSupra

iTrader: (1)

sounds like an exhaust leak to me

Full-Force

iTrader: (11)

It does have an exhaustt leak but I dont think it would throw it as far off as what Im seeing.

Also, what about the car not wanting to start. You have to hold it down forever or let off and try it a second time. It will crank on the second try.

RedHardSupra

iTrader: (1)

yea it would throw it off that much. and if you drive on it enough, the trims adjust and then try to always dump so much more fuel you'll be drowning it on startups--no wonder it doesn't wanna start

1320FEVER

iTrader: (9)

For this problem I would try muliplying the Cranking VE table by .8 or 80%. I had the very same problem and that fixed it right up. The car maybe dumping too much fuel when you start it.

I would ask him if anything else was done to the car since then. Regardless, it just sounds like you have more VE tuning to do.
That doesn't surprise me. O2's are pretty much useless for anything other than stoich or idle tuning. You really need a wideband when WOT tuning.

sobaka__79

iTrader: (1)

quoted- I put in new o2 sensors and checked the fuses. New plugs and wires.

make sure you get 6 fin not 3 fin o2 sensors from ac delco.

o2 sensors are reading lean from an exhaust leak or maybe they didnt correctly resinstall the o2 sensors. i had the same problem and still had to tune my car after teh exhaust change to long tube headers


the leak would have to be infront of the o2's prolly the headers

Full-Force

iTrader: (11)

They are Bosch o2 sensors.

Full-Force

iTrader: (11)

Update

The car no longer has an exhaust leak. I tried again to tune it. Here is how it goes.

01 WS6

Lontubes, duals, lid, and 224 cam.

I loaded stock tune back in it and started over from scratch. Car finaly started on 3rd try. I put in SD, reset fuel trims and drove a good hour. Car ran decent at par throttle but once you gave it moderate to full throttle it felt like someone tied a boat anchor to it. Just had no power. Well anyway I went ahead and kept logging. I copied the fuel trims to the ve table and flashed it. I reset the fuel trims again and took off. I was ver pleased that the fuel trims had finally come out of the red and the lower rpms's were a little rich and still a little lean on top end. The trims were not far off, just 10 at the most. Before the entire table was like 25. After another good hour I figured when I add these trims to the table It will be very close. I flash it and fire it up and the entire table is back to 25 again. I put the car in 4th gear and tried to floor it and it felt like it had about 50hp and wouldnt pull past 5000 rpm after going wot from 4000 and holding it for 10-15 seconds.

I think its a fuel delivery problem. I will be putting a fuel filter in it tomorrow. The owner says he put a granatelli fuel pump in it about a year ago. If its not the fuel pump, fuel filter, or the regulator then I think its got to be the PCM. What do you guys think?

Full-Force

iTrader: (11)

I put a filter in it and no luck. I put my gauge on the fuel rail and turned switch on and the gauges krept to 20psi and then fell to 0. During cranking it creeped up to 20psi and held through cranking cycle and once the car finally started it held at 30psi. When you try to crack the throttle it wont even rev. I have told the owner his fuel pump is shot but am not convinced its not the regulator on th fuel rail. Where do you guys block the return line at to check the regulator?

Im sure its the pump just want to be positive before he buys a new one.