96 chevy 5.7 misfire

On that truck it could be alot of different things! It could be a bad distributor gear, an aftermarket distributor cap, a bad injector, sticking valve, lifter etc! Any chance u can post some scan tool data?

its only missing on 7 so i doubt its a distributor gear and i used all ac delco parts for the cap and rotor plugs and wires.

i just did injectors on the truck and it ran good for about 60 miles and then i stopped to get something to drink. left the truck running and i came back out got in and went bac on the highway and it started to miss again. i am still getting a P0307 code and a P0420 and 430 for 02 efficiency could it be my o2 sensors. i do have a exhaust leak on cyl. #7.

Again you can't let us know about some data could you? I mean it could be an 02 sensor but if u want to not waste money on guessing then we're going to need some freeze frame data! If you choose to try an 02 don't use Bosch!

I don't have a good enough scan tool so I'm going to my buddy's to get one done

OK i went and got it scanned and I am now getting a random misfire. The only thing that looked out of place was the timing was at 3 so I'm getting it adjusted on Wednesday

Can you let us know about the fuel trims from your buddy's scanner?

i am still having problems with missfires on my truck. i tried puting in new manifold gaskets to take care of my exhaust leek but my headers must be warped and it still has a leek. i know the leek is on the #7 cyl because when the truck misses there is no tick from the exhaust coming out. it is not fouling out plugs which means it is not getting fuel when its missing so could it be the 02 sensors reading to much oxygen and making it lean also another thing is when you first start it it runs good but if you shut it off and then turn it on when its still hot is when it misses. i am really starting to get frustrated with this. no motor has ever gave me this much trouble and i have built many motors but i am new to fuel injection.

I think you'll find that you have an injector issue! either bleeding presure off on startup, puddling in the intake when parked overnight or else now that it's generating po300, proper fuel pressure becomes even more critical!

Its not a p0300 its a p0307 for #7 cylinder but I also have a 0430 and a 0420

Hope jumping in is OK? Can you clear this up - 1996 5.7L K1500 Is this a MPI or the much more common CSFI? you changed injectors- ? June 4 you posted 'your getting timing adjusted" ...how that go? I always ask- Vehicle is STOCK- no add ons, modifications, miracle parts? Use of word HEADERS -june 24- is suspicious. Sounding like an ECHO - fuel - pressure ck, LEAK down? easy to do .. #7 plug (AC Delco?) how does it look - black, tan, WET, dry? Could you clear up that MPI or CSFI -

Its a 96 k1500 with the 5.7 I have converted to mpfi and it has 2 1/2 Magna flow exhaust, throttle body spaces headers and cold air intake the plug is an acdelco and its tan and dry

any other codes ANY? p0307, p0420, p0430 ? I see cold air intake & what I call "miracle parts" so- You have not eleminated any o2's in headers? Clean MAF, - esp without ability to scan throughly - is IAT still there? pretty sure its seperate in 96... you are using 195deg T'stst? Try the spray trick for VAC leaks post MAF.. What is eng VAC reading/ try a noid light #7 - see if inj pulsing, always grounded. could swap inj 7, see if code follows to new hole AGAIN fuel pressure and leak down cks.... EASY - gauges available as loaner rental- BUT a must have tool for FI work - not big $$

Just 0307 0420 and 0430 for codes still have iat and I doubt its a bad injector cause it missed before new injectors it could be the wiring though and the headers still have 02 sensor and 195 tstat

Just 0307 0420 and 0430 for codes still have iat and I doubt its a bad injector cause it missed before new injectors it could be the wiring though and the headers still have 02 sensor and 195 tstat

If I read right you do not have a good scan tool - So process of elimination..trying to work around that professional 1st step- ' attach techII" - The system is IDing #7 - so we start there - compression is good, plug is firing- secondary ign good- you state its all new Quality parts SO The inj is what I would look at - leak down, grounded- pretty simple ck's could walk you thru them - noid light - could use a DVOM? the pressure check just need the gauge...

i doubt the injector is leeking down since they have only been in there for two weeks or so and they were acdelco mpfi ones. my guess is it is grounding out or my computer is bad. how do i check to see if the injecto is grounding out

Is there a problem checking FUEL PRESSSURE ? It would answer several unknowns including GROUNDING on the inj driven side. use a NOID or DVOM on #7 injector harness....... would see a noid light flashing - on steady - or no activity at all - DVOM is there 12v at pnk wire? is the rd/blk open or grounded * - * Not exactly sure of injector wiring colors as this is modified to MPI

if the fuel pressure was low it would miss on more than one cyl. and its a 60 psi with engine on. i also got told it could be a bad intake gaskets but i tried the carb cleaner trick and it didnt rev up. if i dont get this figured out soon ill just drop in the 383 stroker motor sitting in my shop and its still the rd/bk wire but i cant get it to miss to check to see if its getting power to the injector.