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P0300

Tiny
ETHAN EDEN
  • MEMBER
  • 1996 CHEVROLET CHEYENNE
  • 5.0L
  • V8
  • 2WD
  • AUTOMATIC
  • 141,144 MILES
I was driving it in town for about an hour stopped to get something to eat about twenty minutes later I went back out to the truck started it and it had a very bad misfire engine light was flashing got it to an auto parts store and pulled the code p0300 (multiple cylinder misfire) so I replace ignition coil spark plugs and wires distributor cap and rotor map sensor and still has the p0300 code and it is still running very bad.
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Sunday, June 5th, 2016 AT 6:27 PM

10 Replies

Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
In the past, younger years

My "Pals"

Have "Helped me out"

By swapping plug wires on me while I was at a store.

First time was a killer and made me sick as to what was wrong with my Jeep for quite some time.

(Kind of bad when you "rule out" something that surely could not change itself- ever since, I do not rule out anything!)

second time it was not too bad now that I knew the deal.

Shifting my transfer case into neutral was another trick they pulled on me while I was occupied elsewhere.

Check the turning of your rotor button for smoothness (not jumpy as it rotates- gear or cam problem)/ insure the distributor hold down has not let the distributor turn (changing the timing setting).

Check for other codes

Keep us posted

The Medic
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Sunday, June 5th, 2016 AT 8:43 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,961 POSTS
Hey ETHAN,

I have seen where the EGR valve is stuck open causing a massive internal vacuum leak, can you remove the valve and see if there is carbon stuck in it? Or if the valve is damaged in anyway? Please get back to me. Also the fuel injector unit in those engines had big problems too be lets start with the easy check first.

Best, Ken
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Monday, June 6th, 2016 AT 7:16 PM
Tiny
ETHAN EDEN
  • MEMBER
  • 13 POSTS
I removed the egr then cleand the valve still no fix when running smells real rich but it wont idle by its self I have to keep a little throttle and after running for about ten minutes you can smell rotting eggs sure sign of fuel not combusting so I'm thinking there's a leak in one of the injectors?
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Thursday, June 9th, 2016 AT 7:22 AM
Tiny
KEN L
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  • 42,961 POSTS
It sounds like the fuel pressure regulator diaphragm has let go, can you remove the top of the intake to check it, they have big problems with those injector units in those engines.

Best, Ken
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Saturday, June 11th, 2016 AT 12:29 PM
Tiny
ETHAN EDEN
  • MEMBER
  • 13 POSTS
I replaced fuel pump gas tank because old one had leaks so fixed that gas lines fuel filter its running like it has a mild camshaft
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Tuesday, June 14th, 2016 AT 3:58 PM
Tiny
ETHAN EDEN
  • MEMBER
  • 13 POSTS
Still no fix
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Tuesday, June 14th, 2016 AT 3:58 PM
Tiny
ETHAN EDEN
  • MEMBER
  • 13 POSTS
And I haven't checked the injectors yet its got a sfi how do I go about checking that
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Tuesday, June 14th, 2016 AT 3:59 PM
Tiny
KEN L
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You must remove the top in the intake manifold because it is inside of it
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Tuesday, June 14th, 2016 AT 8:21 PM
Tiny
ETHAN EDEN
  • MEMBER
  • 13 POSTS
It turns out the right cylinder bank is all low compression in getting a used motor and tranny for it if I get the same motor would it all just plug in and start
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Sunday, June 26th, 2016 AT 7:20 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,961 POSTS
Thanks for getting back to us, yep it happens sometimes the engine just wears out, please let us know how the installation goes.
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Sunday, June 26th, 2016 AT 8:00 AM

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