Hello new to forum. 1998 f150 4.2 175k miles, original owner. I have codes p0171 and p0303 with misfire. However it is random. Codes and misfire never happen cold start in morning, truck will run great. it happens randomly during the day no set pattern. I have replaced a lot parts recently
1. Upper manifold intake gasket

2. Spark plugs, spark plug cables, coil block

3. Left and right IMRC (intake manifold runner control)

4. EGR valve

5. Vacuum Solenoid

6. EGR pressure feedback

and replaced a few bad vacuum hoses.

I am stumped. I have scanner codes but I do not know how to read them.
here they are just in case any one knows how. please give advice or tips thanks.


Scanner number 1 results: PAGE 1 CODES P0171 AND P0303

FUEL SYS 1 CL

FUEL SYS2 N/A

CALC LOAD 43.1%

ECT 108 F

STFT B1 -11.7%

LTFT B1 10/10

LTFT B2 24.2%

LTFT B2 -6.3%

ENG RPM 1992

MPH 45

STFT B1 9/10

LTFT B1 - 11.7%

LTFT B2 -6.3%

RPM 1992

8/10

ECT 108 F

STFT B1 -11.7%

LTFT B1 24.2%

STFT B2 -6.3%

LTFT B2 20.3%

7/10

CALC LOAD 43.1%

ECT 180 F

STFT B1 -11.7%

LTFT B2 -6.3%







PAGE 2



FUEL SYSTEM 2/10

CALC LOAD 43.1%

ECT 180F

STFT B1 -11.7%

LTFT B1 24.2%

1/10

FUEL SYS 1 CL

FUEL SYS N/A

CALC LOAD 43.1%

ECT 180 F

STFT B1 -11.7%























2ND SCANNER P0170 P0303



-P1D00 P1D01 PID02=0171

-LOOP IS OPEN

-P1D03=0200 P1D04=6E P105=7A P1D06=71 P1DO7=9F P1D08=78 P109=9A

-P1DOA P1DOB P1DOC=OF8F RPM 1991

-MPH 45 P1DOD=48 P1DOE P1DOF

-P1D10 ,11,12,13,14,15,16,17,18,19

-P1D1A, 1B,1C,1D,1E,1F

P1D20

 

Rust at bottom of coil packs. I did make tread about it 5-6 years go but cannot find it. Brushed rust down at housing of coil packs, cover it with dielectric grease and no problem since them. However I did google it and someone directed me to problem right away. Google for yourself "rust at ignition coil" or so.
Edit even you did replace coil block rust can be at frame where is block attached to. So clean rust at bottom of coil pack (it is called pack I think not block) and clean frame where pack seat.

 

Never thought of this. I will give it a try. thanks. anyone else feel free for advice.

 

No rust. Very clean. I wonder if problem is with fuel injector?

 

I checked yours code at internet now. You obviously have problem with not enough fuel in cylinder nr 3. Google "p0171 and p0303 ford f150". There is top right away 4 videos about exactly that pair of codes. Why you replaced anything at random? How I would do would read minimum 5 first pages and than do all testing possible.
Edit. Men there is in very first video at top in google what to do. Check fuel injector with voltmeter. Exactly same code. Maybe is on off situation. Start car and keep checking.
On off is usually electrical problem. You have problem with electric part of that fuel injector.