Help ! 1996 Tahoe P0300 any GM tech here this is not a easy one

Ridgerunner

Ridgerunner

Well-Known Member
Joined
Mar 21, 2005
Location
Fuquay Varina, NC
History
2 years ago I replaced the spider pop-it with a upgraded mutil port Spider do to a failed fuel regulator diaphram leaking fuel in the intake causing a p0300 code and running like crap. then it ran great
This last spring I replaced the Fuel pump as it failed. then it ran good again.

This last weekend I was driving it and had to hit the brakes hard at a stop light. the engine started missing and again the p0300 cam up. no matter what RPM it is is alway missing and sounds like it is running on 5 cyl.

So to day I replaced the cap an rotor just because and it had been sitting fo 2 days. I started it up and it ran Great and I was happy again (so was the wife it is her car).

so just to make sure everything was good I drove it in to town and back (about 10 miles) and when I was almost home I hit the brakes and the same thing happened. now it is running like crap again.

So I thought Brake booster vacuum leak. so I pugged the booster hose but no change.

The only other thing I can think of is maybe there is water in the tank from a bad batch of gas.
Th fuel Pressure is good between 56 and 62 and jumps to 62 when I accerate. It does not leak down when shut off.

any Ideas??
 
So a PO300 is a misfire code. How many miles are on it? I've heard after many miles, several people have found the distributor gears are worn enough to cause some funky things to happen with the ignition timing. You might try checking that.

There could also be some odd things happening with the cam position sensor. I just did a quick search and the PO300 seems to be a common problem with a few common fixes.
 
Well the dist is on this list to Change because of the POS plastice housing that Broke the Screw hole off, although that is not what is causing the problem.

Cyl 2 and 3 are the ones that get most of the misfire hits. I will see what happens after I replace it.
 
If you used aftermarket distributor cap and rotor, toss them in the trash suck it up and go by dealer parts ( for this repair ) The aftermarket flat style caps beak down quickly with all the power passing thru and will arc thru the plastic internally pretty quickly ( some worse than others )

As a tech I can't count how many times I replaced ' new ' aftermarket crap ignition parts with GM parts and problem solved.

Suck it up and get a distributor as well ( should come with new cam sensor ) and take care of the problem
 
Ridgerunner said:
Cyl 2 and 3 are the ones that get most of the misfire hits. I will see what happens after I replace it.
Click to expand...

If I remember right, don't 2&3 traces in the cap pass closely to each other ?

The are on opposite sides of the block but are close in the cap
 
Blkvoodoo said:
If I remember right, don't 2&3 traces in the cap pass closely to each other ?

The are on opposite sides of the block but are close in the cap
Click to expand...

I did buy a accel rotor and cap with copper electrodes did not make any difference. A new dist in in the plans.

Kevin you are more than welcome to stop my and look at it with me when I get the new dist. :) our kids can play :)
 
Croatan_Kid said:
I've heard after many miles, several people have found the distributor gears are worn enough to cause some funky things to happen with the ignition timing. You might try checking that.
Click to expand...

I owned a 98 Tahoe and the distributor drive gear was causing this problem and throwing the code. It was VERY worn looking.
 
The distributor body on the "R" engines is plastic, the upward and side thrust of the cam driving the distributor gear wears it inner bore, which also causes the distributor gear to wear now that it isn't true to the cam anymore

Causes a lot of misdiagnosis as a result, the 'cam sensor' is actually in the dizzy under the rotor, the breaker plate for the sensor can and does wipe out the sensor because of the miss alignment of dizzy shaft, though it may not throw a code for it

Carl, it will be the weekend before I can do anything, IF we don't end up at the fun Caravan I'll let you know
 
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