Vengeance84

For about a year now i have been struggling to figure out what my problem is...
Here is what is going on, When my car uses the o2 sensors for amount of fuel it uses way too much and runs like **** until it stalls out. When i pull the plugs they are black as can be.
The reason i say when the o2 sensors are not being used is because i have unhooked them and the car runs moderately good. I talked to PCM4less who tuned the computer they told me the wires from the PCM to o2 sensors are not supplying the proper ohms due to them being cut to accomodate the extra length for long tube headers.
They suggested a new harness and o2 extensions which i bought both as well as new o2 sensors.
I have had datamaster on the car and i have used up all the free logs trying to diagnose this problem. I have been through numerous spark plugs.

This vehicle is a 94 firebird formula 383 stroker 10.5-1 compressiob with edelbrock heads ported and flow tested at 270 cfm the valves were cut. Crower cam as big as i could get. BBK 58mm throttle body, 1.6 rollers hooker long tube headers, mufflex 3" ypipe into 4" cat back with flowmaster exhaust. And of course a tune from PCM4Less.

I have no idea where to look with this other than sending my PCM back assuming there is a bad tune...

F0x Slaughter

So it runs fine in Open loop and runs shitty in Closed Loop?

Vengeance84

Ya it runs in open loop when it goes into closed in runs soo bad it stalls itself out.

F0x Slaughter

Have you tried unplugging the map to send the car into Speed Density mode?

It will still be using the o2s but MAF controls fuel because it tells how much air is entering the engine.

Vengeance84

No i havent. I will though, So correct me if im wrong. This will tell me if the map sensor is my problem?

F0x Slaughter

MAF sensor*.

MAP is Manifold Absolute Pressure. It tells what the vacuum is.

MAF is Mass Airflow Sensor. It tells how much air is coming in.

Not going into how it works, but if this fixes your probably you can try cleaning the MAF with a Qtip dipped in rubbing alcohol. (You clean the wire filaments inside the MAF) if cleaning it doesn't work, try using a known working one.

Vengeance84

Ok this is the second MAF on this car i got a used one that i was told was working properly when bought and nothing changed when i put it on.

ahritchie

iTrader: (1)

What brand O2's you got? Best thing to do would be to buy a ALDL cable and use some free tuning software to figure out what is going on with the O2's.....and check the coolant temp sensor readings to make sure it hasn't gone bad.

Vengeance84

I have had ntk o2 brand new as well as now bosch brand new. I have used datamaster coolant temp sensor was a problem. I changed it and it is reading properly now. It runs fine until going into closed loop. It then goes all over the place the short and long term blms dont seem to correct it.

ahritchie

iTrader: (1)

That could be your problem....most here will tell you only use AC Delco O2's...me being one of them I would spend a little bit more on the proper GM sensors and see how it runs; then start looking at getting a ALDL cable to hook up to a laptop so you can pinpoint the issue.

jaycenk

iTrader: (1)

Hey ahritchie read a little bit of the thread again. Hey has said about 2 to 3 times that he has an aldl cable and has used all of the free TTS data master data logs. You have told him 2 times now to get an ALDL cable and he has told you he already has one. No need to frustrate him more.

whytryz28

iTrader: (28)

Im running those NTK O2s and they are working fine for me, only Delco thing I have ever bought for my car is the stupid opti

brettmc

post a log and you will get better responses.

Vengeance84

The car sat over the winter a year and a half ago. I change the fuel pump, after that winter was when all the problems started. I had a problem with the coolant temp sensor reading -40 changed it and it fixed that problem but now im stuck with this one and ive been trying to figure it out ever since.
I changed out the stock fuel pump because it could not keep up at WOT. Put in a walbro 255 lph pump is there any chance this could have anything to do with it. My mechanical gauge on the rail does say approx 40 psi.

F0x Slaughter

Nope the fuel pump won't be otherwise it'd do it in open loop. It's something in closed loop. Said the MAF hasn't changed anything so you know it's not that.

If you have 40 psi at idle that's in spec. ~44psi key on, then idle should drop 3 - 7 psi.

You are running two different o2 sensors? I'd replace both with brand new ac Delcos. Never good mismatching things. Just like plugs change them all at once blah blah.

Things that control fuel in closed loop are, MAF, IAT, o2 sensors, coolant temp sensors.

Vengeance84

Sorry for the confusion on the o2 sensors i used ntk previously and currently using bosch. The o2 are the same