Fuel or Air problem?

[95fiveO]

I've been asking around and still cant seem to get an answer, so figured i'd ask here. I have a 95GT with 82000 miles on it. The car runs great normally, but i took it to the track last week and it sucked. It feels like at about 3.5-4k rpms my power dies out. The engine is stock, all I've done is ditched the convertors and got a K/N air filter.

I immediatly thought it just wasn't getting fuel, but when i checked the fuel pressure it held around 35-40 all the way through. Now im stuck. Could a sensor be bad? or is my computer just messed up?

 

[HoofnIt]

I think we need a little more info. When you say your track performance sucked, what were your times?
How's your tune? Are the plugs good and gapped correctly? Do you have a new fuel filter? How are your plug wires? If they are stock, check the resistance and replace if necessary. Have you cleaned your MAF lately? Where is your timing set at?

 

[red94fiveo]

I agree with HoofnIt. Need a little more info to diagnose this one.

 

[95fiveO]

Sorry...heres my times:
R/t .672
60' 2.417
330 6.977
1/8 10.81
@ 63.94
1/4 16.875
@ 80.87

Today I unhooked my MAS and the car seemed to run better at the top end, but couldn't hold a steady idle. I cleaned the sensor with carb-cleaner, but it didn't seem to help. I think I might just have to replace it. I changed the injectors about a month ago, gapped correctly, but the rest of the fuel system is still stock, unless the previous owner changed it without telling me.

 

[HoofnIt]

Well, you definitely have issues. Unplugging the MAF (MAS) is not the solution. The MAF tells the computer how much air is coming in and helps to adjust the needed fuel. Is your car a 5spd or auto? Why did you swap out the injectors? Did you mean the spark plugs? I would make certain you have done a full tuneup, see other reply, making certain that you check your firing order and replacing the dist and rotor cap if necessary. How are your plug wires? Check the timing, I would start at 10 deg. A stock 5.0 5spd should be in the high 14s or low 15s if it's an auto.

 

[mo_dingo]

A stock 5.0 5spd should be in the high 14s or low 15s if it's an auto.

Don't take that as an absolute, just a guide to what your car can do. My best is a 15.6 @90MPH

I just wanted to ask this, but what were your shift points for each gear. The correct shift points for a stock/near stock 5.0 is 1-2 5300, 2-3 5000, 3-4 4900. If you don't have gears, then you won't even get to use 4th gear.

I didn't want to comment on your track times, but I had to let you know that it's not the end of the world. The first time I got my car I ran 16.5-16.9's all night long. Not launching well, and shifting at 5600-5700 for all the gears is a bad combination.

Now back to your problems. Your fuel pressure seems fine. Don't worry about lack of fuel for right now.

The first thing is to run the trouble codes. If the computer has detected any excessively malfunctioning sensors, then it will spit out a code. The proper procedure is detailed in a Haynes manual.

Next, remove all spark plugs, wires, cap, rotor & inspect them. The plugs all should be dirt brown, and gap should be at .054". If any of them are different, please let us know. The wires should have no breaks in the insulation or obvious damage. The cap/rotor contact points should be shiny brass. If they are not, you need to clean off any corrosion, or easier, replace them.

Then you need to remove the MAF sensor from its housing, and clean it with carb cleaner & a q-tip. I know you cleaned it already, but you may have some slight residue on the sensor wires. Here is a write-up.

Also, do the same for the IAT sensor.

Let us know how it goes.
Scott