steveczi

I sure could use some help??? I have a 99 tahoe 125,000 miles with a 5.7. At highway speeds 65-75mph I get a random misfire which results sometimes with a CIL and a code PO305, I've Changed sparkplugs wires distrib cap and rotor, a local shop thought it was the injector. So that was changed with no help$$. The fuel pump just stopped so I had that changed along with the fuel filter $$. The shop did a compresson test and a bore scope on #5 cylinder. I forgot to mention I changed the pick up sensor under distrib cap. So far two shops can not find what is causing the misfire on # 5 cylinder any ideas sure would help.

kevinkpk

Doesn't that thing have a coil pack?

steveczi

Nope just one coil,

shamrock246

was the enitre injector changed or just the poppet valve at the end?the electrical part on the injector is in main body of the spider assy that could be sticking or dead if its the old style spider assy i would ditch it for the upgraded one worked great on my burb if you do your own work you can get the assy off amazon for about $215


Sean

97 4x4 burb

steveczi

Thanks I'll check with the shop that changed it to see if was the enitire injector or the poppet

steveczi

Well they said it was the entire #5 injector. Do you think it could have somthing to do with the ECU??

shamrock246

you could have the signal to injecters tested,you could buy the test light at most autoparts store, did they test the fuel pressure if the regulator leaks i think it drips into #5 intake runner that could be a possibility

steveczi

Thanks for the idea's I will have them checked this week

steveczi

Yes the fuel pressure was checked and is good, and has a good signal to the injectors during normal driving only misfires a highway speeds. Im changing the ecu tomorrow w/ another and having it flashed for this car We'll see ??? what happens

kevinkpk

I am looking at my Haynes manual 99-06 suburban shows (5.3L) it has a PCM, i'd suspect that before the ecu