Code P0304

SBADBRYAN1

MEMBER
1997 FORD RANGER
4 CYL
2WD
MANUAL
170,000 MILES

I have changed the plugs, wires, coils, crank sensor, cam sensor, MAF, rebuilt injectors, and I still get the P0304 error code. (Check engine light comes on and flashes)
Runs well until deceleration then it stumbles and shakes. If you hold the throttle on it will eventually clear up and run fine again.
Any suggestions?

3 Replies

MMPRINCE4000

MECHANIC
8,548 POSTS

I would check compression on all cylinders, lowest psi must be within 20% of high.

If compression is OK, then I would suspect a clogged convertor.

If compression on one or more cylinders is higher than 20%, then you will have to remove head.

SPONSORED LINKS

Was this

answer

helpful?

Yes

No

Sunday, May 16th, 2010 AT 8:36 AM

SBADBRYAN1

MEMBER
2 POSTS

I have been working on this project for a month!
The truck was basically dropped of in my yard with a thrown rod. I bought a used motor and threw it in.

When writing my first email I failed to tell you that I replaced the converter first and it did not change my problem. I also had a lean code in bank one and a EVAC code

I then changed out O2 sensors with new - still code P0304.

That is when I continued to change out parts. Everything I changed out made the truck run better and better. But never got rid of the P0304 code.

When replacing all the parts listed in email one didn't cure my problem I pulled the valve cover to look at the cam which was in good shape. I did find the oil pump pulley bent slightly so I put a salvaged one on.

That is where I am today. I am an ASE certified School Bus Mechanic so I dont see a lot of gas engine but do feel I am knowledgeable enough to take on this project however this has me stumped.

Any ideas are welcome!

Was this

answer

helpful?

Yes

No

Sunday, May 16th, 2010 AT 12:59 PM

MMPRINCE4000

MECHANIC
8,548 POSTS

Check compression on all cylinders to rule out a mechanical problem.

If you have access to scanner, scan in live data mode, look for sensors out of range.

Was this

answer

helpful?

Yes

No

Wednesday, May 19th, 2010 AT 7:34 AM