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1996 chevy express misfire codes p0300

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Jul 19, 2011, 7:43 PM

Post #1 of 2 (6681 views)
1996 chevy express misfire codes p0300 Sign In

hello i have a 1996 chevy express 1500 5.7L conversion van. this is the problem, i keep getting a recurring fault code of p0300 and p0304. those codes will alternate every time i erase codes. vehicle does have a miss and it is definitely felt. this problem started right after i purchased this van. we were driving it home and cel came on blinking. was running perfect on test drive and halfway home ( about 100 miles ). miss was a light one an gradually got worse. took to a shop an they said cyl 4 injector was bad. paid to have replaced and then to have them say #8 popped up after they test ran. these being orig poppet style. i then said i wanted all them replaced an opted to have the MFI conversion done at a cost of $1500. cured miss for a day an came back. had complete tuneup done ie plugs,wires,cap,rotor,ign module,coil and cam position sensor. miss stopped for maybe a couple days if that. egr pintle position circuit code did pop up in that whole mix too so i had that replaced new as well, miss still there! almost $3000 in repairs an no one has figured it out yet. only thing i have not done an was avoiding was taking to a dealer but am at my wits end with this thing. also had both cats replaced too. any help would be hugely appreciated as ive seen numerous posts on google on this same issue with these vans

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Jul 19, 2011, 9:29 PM

Post #2 of 2 (6666 views)
Re: 1996 chevy express misfire codes p0300 Sign In

Well that original injector style wasn't the best to begin with. There was/is a lot of problems with them. The updated setup is way better so if your keeping the van that's a good investment. The tune up stuff, again is something that would be needed regardless. The problem with the cap is its a poor design & I've had bad ones right out of the box (more than one). Enough where I really only what to use a/c parts for that.

I would probably want to verify the mechanical condition of the engine, those have had a problem with sticking valves and that can get you an intermittent miss. A running compression test while it's missing could reveal a lot. A pressure transducer would show a lot but even just a regular compression gauge & vacuum gauge would help pinpoint a sticking valve.

Also I would like to know when it's missing. If it's just at idle & low speeds then I would also want to rule out a vacuum leak since you said you are getting misses on 4 & 8, those are right across from each other & right next to each other in the firing order....


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