Flashing SES Light - P0300 Code??

[KnuckleheadS10]

Hey guys, having kind of a mystery here. For reference I drive an 04 ZR5 with 115k miles.

So I had an oil gasket leak that devolved into replacing that, the crank case gasket and cover, the water pump, and an ABS sensor and fuel tank pressure sensor solenoid valve while we were at it. My mechanic knocked all that out for the low low price of about 1800 bucks . I picked it up after about a week and was driving it when I noticed that the Service Engine Soon light was flashing when I drove at highway speeds, and only those - never flashing below 60 mph, and in fact the code would clear if I drove that slow for a day or so. So I took her back in, and the guy thought he had it ironed out - replaced the plugs, plug wires, distributor cap and rotor. This seemed to solve the issues until last night when I was driving in to work - all good for about 10 miles until the SES light began flashing again at 75 mph.

I guess my main question is could it be possible that this code being thrown is incorrect? I've noticed no misfires, and I honestly wonder if it's not a code being tossed out because in the plugging in process when he was solving the oil issue, water pump etc something was plugged in loosely and is jiggling. Second question would be what else can cause a misfire code like this? I've dumped almost 2200 more on this damn thing in the past few months and I'm ready to get it ironed out and not get gouged anymore. My guess would be injectors or coils at this point.

Any help greatly appreciated!

[LoneWolf04]

Year and miles? Original exhaust?

Several common things that go on these trucks is the distributor gear gets worn and needs replacing. Converter also has a tendency to go out if you have the old poppet style injector. Injector leaks, dumps excess, unburnt fuel through the exhaust system, and converter breaks down.

[KnuckleheadS10]

2004 with 115k, and to the best of my knowledge all OEM exhaust aside from a flowmaster muffler. I know about that converter killer - I had a 95 extended cab before this and chased issues for weeks before having to get a new set of spiders and replacing the exhaust from the converter all the way back.

[KnuckleheadS10]

Update - nothing really new. Mechanic ran it, said the misfires were all over (duh - P0300 means RANDOM multiples), but he warrantied out the recently replaced plug wires as those were the first point of failure he saw when he did the tune up last time. Now I just have to take it back out on the highway and put some RPM load on it and see if the code comes back. If not hopefully I can get back to fixing/modding this bitch out.

[KnuckleheadS10]

Code came back, but it's no longer flashing. Not sure what exactly keeps causing it at this point. Any help or input would be appreciated.

[KnuckleheadS10]

Caved and took it in to Firestone - engine was actively misfiring at low low speeds. Yesterday they thought it was the MAF sensor as oil from my K&N filter was present on it. Picked it up this morning - nope, still jacked. Took it back in and the code this time was p0335 - crank sensor A. Apparently there is a TSB on how sometimes these sensors are too close to another part and need a shim. Got it back at three - nooope. Code came back and truck is shifting odd - staying on the low gears longer and shifting much quicker through the high. Still sitting here, hoping for the best.

[KnuckleheadS10]

Timing chain was 6 degrees off. Plan is to replace the distributor which should hopefully correct the issue as the misfire codes at this point are just phantom codes.

[KnuckleheadS10]

So they replaced the distributor and it did not help - the truck is currently NOT misfiring at all but registering a p0300 code on all cylinders. Firestone at this point said they have no clue what to do. Will be taking it in to the dealership on Tuesday as the only other thing they could think of was maybe the computer needed a relearn.

[KnuckleheadS10]

Stealership - for the low low price of 420 - said that a distributor pin or shim of some sort was what was causing the issue - it was an incorrect part and had wallowed out the hole, letting the distributor rattle around and causing the misfires. They also stated the part was almost brand new, so this means either my local guy or firestone are responsible. So I will be taking it to one of them to have them fix the issue pro bono.

I'm done updating this topic on a dead forum. Good luck to all.

[LoneWolf04]

I don't get a chance to get on here a lot with summer months. It appears the distributor was the culprit, as was suggested earlier to check. Also as a side note, I've had horrible results with cheap wires, even ACDelco wires causing bad spark arcing (1st set was good for a long time, tried a replacement a couple years back and was garbage). I went with Taylors and haven't had spark arc since.