Running Poorly, Please Help.

Alex Kraczek

Member
May 7, 2012
40
4
18
1990 5.0 fox

Rebuilt 302, stock bottom end
Ported gt40 heads with comp springs
X303 cam
Stock ignition with msd coil
Stock maf with 19lb injectors
A9l 5 speed car
Edelbrock performer rpm intake
3.73 gears.


This car usually runs like an animal. No problems at all. I drove it 2 hours to souh florida and noticed the car was hesitsting and felt really down on power below 3500 rpm, almost breaking up then it would pick up.

Its been a week and now it just drives like garbage, especially under load at lower rpms, 3000 and below.

It does it worse when cold. If i take it for a drive when cold, if i try to give it any load below 3000 rpms it will pop and spit really bad, almost sounds like popping through intake. Very down on power. When it warms up it doesnt really pop anymore, but feels extremely sluggish.

Looking at the plugs it looks to be running lean. Things I have tried-

Cleaning maf
Changing plug wires
Changed timing
Checked computer and everything else for bad connection
Checked injectors for pulse
Checked coil
Checked for vacuum leaks
Replaced fpr and checked fuel pressure. Good
Unplugged maf, ran worse
Unplugged tps, ran worse
Unplugged 02s, couldnt drive it enough to tell if it made a change.
Unplugged ect and act, didnt seem to change much, could only let it idle.
Checked vacuum, surges at idle so it was bouncing around, never stalled. held at 1200rpm and got a steady reading of around 19 inches.

Idk what to do next. Very frustrating. Will pull codes today, any input wouls be appreciated. Thank you
 
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never unpliug the MAF when running
Popping out the intake is a lean condition or timing is way off

Run the codes as you said. see if you get a 41/91

The How to dump codes sticky is the first post on the main page of this forum. Be sure to check it out...