cam position sensor or crank position sensor?

[mishalah]

I have a miss that seems to be getting a bit worse. The AZ code reader says P0304. I've recently replaced all the typical stuff that could lead to a single cylinder misfire (plugs, points, wires, etc.)...and during the past year and 8000 miles it existed, went away for months, and has now returned. It is not when climbing or under load as far as I can tell. I can feel it when idling, and then when coasting or light/neutral throttle at speed (45-70+).

After reading the issues that so many of us have had with this I decided to grab a cam position sensor and keep it on hand or replace it asap. But when looking at the manual I see that the crank position sensor controls much of the same stuff and can have the same symptoms. So...HOW DO I KNOW which it is? IF it is one of them...

[mishalah]

No?

No one??

[j cAT]

Originally Posted by mishalah

No?

No one??

why did you think a cam/crank sensor would cause a miss fire in cylinder #4 ?

I would swap the plug wire,then the spark plug, then the coil, then the injector.

try some injector cleaner and a few ounce of marvel mystery oil to the fuel.

since it comes and goes the injector would be a good guess.

new parts does not mean good parts.

[mishalah]

Originally Posted by j cAT

why did you think a cam/crank sensor would cause a miss fire in cylinder #4 ?

I would swap the plug wire,then the spark plug, then the coil, then the injector.

try some injector cleaner and a few ounce of marvel mystery oil to the fuel.

since it comes and goes the injector would be a good guess.

new parts does not mean good parts.

I was thinking a dirty injector, but after reading a lot of threads where folks had gone through the whole routine, and then ended up resolving it by changing the cam sensor I fugured I might start there. In my case the only thing that wasn't changed in the system is the injectors. I did spray carb cleaner around the entire manifold and everywhere that would pull vacuum or fuel through. Nothing indicated a leak up there.

[j cAT]

Originally Posted by mishalah

I was thinking a dirty injector, but after reading a lot of threads where folks had gone through the whole routine, and then ended up resolving it by changing the cam sensor I fugured I might start there. In my case the only thing that wasn't changed in the system is the injectors. I did spray carb cleaner around the entire manifold and everywhere that would pull vacuum or fuel through. Nothing indicated a leak up there.

THE CODE IS FOR #4 CYLINDER . so test/swap components with that cylinder.

Items I did not mention bad valve/spring or head crack/gasket..

simple first.

cranksensor under the starter have been reported problems with the 5.3L engine.but NOT WITH THIS CODE ,WITH THE CRANK CODE .

cam sensor is not much on this as a problem in any way.

stay away from carb cleaner use throttle body cleaner. carb cleaner will destroy plastic,wiring,gaskets,rubber etc....

[old_master]

I agree, if there was a problem with either the cam or crank sensor, a DTC would have been set in memory. Among other things, the cam and crank sensors work together in determining which cylinder is misfiring.... they told you cylinder #4 is misfiring, believe it

[mishalah]

Well, this is interesting: I didn't have time to do anything about the miss because I had to head up north. I left Vegas about 1030, firsat stop for gas was Fallon, 375 miles. After keeping speed at 75 most of the way, dragging through 7 small towns, passing trucks at full throttle....I got 17 mpg. Even with the miss at all speeds strong enough to feel.

Maybe I should leave it alone.

[j cAT]

Originally Posted by mishalah

Well, this is interesting: I didn't have time to do anything about the miss because I had to head up north. I left Vegas about 1030, firsat stop for gas was Fallon, 375 miles. After keeping speed at 75 most of the way, dragging through 7 small towns, passing trucks at full throttle....I got 17 mpg. Even with the miss at all speeds strong enough to feel.

Maybe I should leave it alone.

the miss fire will kill the cat converter in time.

its most likely a simple cheap fix with the #4 .

[mishalah]

Originally Posted by j cAT

the miss fire will kill the cat converter in time.

its most likely a simple cheap fix with the #4 .

The check engine light came on today. I took it to a shop where the owner checked the wires and dist cap. His scanner said there were other misses, too. He didn't have time to do a full investigation, but he x'd the light and the truck rtan better for awhile...then the light camw back on. not good...........

[j cAT]

Originally Posted by mishalah

The check engine light came on today. I took it to a shop where the owner checked the wires and dist cap. His scanner said there were other misses, too. He didn't have time to do a full investigation, but he x'd the light and the truck rtan better for awhile...then the light camw back on. not good...........

check the fuel pressure 5.3L YOU NEED 53-62 PSI.

drive with the guage hooked up see it it continues to be good.

on shut down check that pressure holds . if not injector/pump/fuel regulator may be n/g.

this would be with a p0300 random missfire ..

[mishalah]

Originally Posted by j cAT

check the fuel pressure 5.3L YOU NEED 53-62 PSI.

drive with the guage hooked up see it it continues to be good.

on shut down check that pressure holds . if not injector/pump/fuel regulator may be n/g.

this would be with a p0300 random missfire ..

This is my 96 with the 5.7L. I'm gonna take for another code reading in a little while.

[j cAT]

Originally Posted by mishalah

This is my 96 with the 5.7L. I'm gonna take for another code reading in a little while.

with the 96 check that the distributor bearing is good. the rotor wobbles this will cause missfires

[mishalah]

Originally Posted by j cAT

with the 96 check that the distributor bearing is good. the rotor wobbles this will cause missfires

I was thinking that while the guy was checking the cap and rotor, but he was cursing so much I didn't want to make him madder.