brobia

The old girl is unhappy with me now. '01 XLT with 5.4L. While passing a slow poke on the highway shaking and missing starts, CEL comes on, flashing. At home I pull the 301 code.

So far I have:
Replace COP (twice actually; thought I had a bad replacement)
Replaced spark plug (which actually looked decent, but over-gapped)
Replaced fuel filter.
Tested fuel injector (15.3, as were its neighbors)
Injector is clicking while running like it should.

Question: Replace the injector, try running fuel injector cleaner, or am I looking at doing a fuel pump? I son't have the ability to test fuel pressure.

Will probably try swapping injectors around tomorrow, to see if the code follows it.

TIA

jethat

Compression test.

akdoggie

Yep^^^^^^

mbb

when you have an isolated cyl misfire

always swap parts from a good cyl, and see if problem moves or stays where it is, before you start replacing anything.

coil, plug, injector, can all be moved easily. And eliminated....for free...saving wasted $

then you are at compression test.

Its possible that theres a PCM signal problem to the injector, either wire or PCM, but fairly rare. Use a noid light to check that, you can see when injector is told to fire.

But yeah, sounds like compression test time.

Hows your coolant level btw? Do the coolant test for exhaust gases...rent at auto store, you have to buy the fluid $10

engines with minor hg leaks can pass compression test, and even show higher compression in bad cyl due to carbon buildup. A compression test isnt totally definitive.

I had coolant leaking in cyl when shutdown and cold for almost 20,000 miles. Caused little stumble on startup only after sitting many hrs and cold. Misfire would occassionally appear while driving and go away, no other symptoms drove great, ran great. Very very little color change on coolant test for exhaust gases, enough to say it passed. Used maybe 1/2 gal coolant in 6 months for a year or so . Passed compression test fine. Several shops could not diagnose it as a hg leak, including a guy that has a car repair radio show....Even when I told them I suspected it..Left vehicle there overnight so they could check it COLD....all they did was WARM compression test and say..nope. But that cyl had a bunch of carbon making compression high in it.

Removing plug and cranking engine threw coolant up the sparkwell....hint #1 (but this could have been due to manifold leak also). You could use a $80 camera scope today to see the same thing. It was only when I did a cyl leakdown test with sustained 40 psig on cyl at TDC, I could hear the bubbles going into the coolant bloop...bloop...and the coolant reservoir rose and overflowed. Eventually it became undriveable within 5000 more miles. Before that happened, the coolant cap began relieving with a small squeal at stoplights, slowing down around corners or after stopping and shutting off engine, fluctuating coolant level from gases, etc.

john ligere

on a somewhat drivable engine with a combustion chamber coolant leak, most of the carbon build up is cleaned out. the coolant could then give a false ring seal which may show up as a normal or slightly higher compression number. best regards

Bluegrass

A P030x codes tells you the crank rotation time for a cylinder was/is too slow for any reason as compared to the other 7 cylinders and is called a misfire.
Slow rotation time can be low compression, spark plug, coil or injector and even intermittent coil or injector plugup.
The Crank Sensor measures the rotation time, all the time for all the cylinders while to motor is running...
Good luck.

aforddriver

Nah this don’t sound right. The crank sensor senses when the crank is at a certain point. The crank sensor doesn’t measure squat. Otherwise it would be called a crank measure.

Bluegrass

It isn't HOW it sounds.
If you don't know, you don't know.
There is no other way for the computer to know.
It is correct. The Crank signal is used for a lot of different functions, as well.

akdoggie

Do you guys realize that you are responding to a 4 year old thread? You are insulting each other over an expired topic. LOL.

aforddriver

I did notice that actually, but he posted his nonsense only yesterday. I’m thinking he’s a troll.