dogman1313

I have a misfire on the #4 cylinder, I have changed the Spark Plugs, The Plug Wires, The Rotor & Distributor Cap. But I still seem to have the miss. If it is the #4 injector, how do I replace it. I swapped plug wires, & changed the Spark plug, what else could it be ? I forgot to mention it is a 1999 Suburban 4x4

thanks in Advance

kevinkpk

Is it have a check engine light? If so, can you read the code?

dogman1313

Yes it has a code & you can feel the misfire , the code is po304 which I believe is a #4 cylinder misfire.

kevinkpk

PO0300 is misfire, so 304 indicates to me #4. What did the plug(s) look like?
NGK Spark Plugs USA

dogman1313

The # 4 was kinda white, w/ a little black, it wasn't wet, I just took an old wire & replace the new one, I changed the new plug out with another new one but still have the misfire. I have an AutoEnginiuty program that I use, plus a generic scanner & they say the same, but what could be causining the misfire on #4?

kevinkpk

White deposit, with black. I'd say injector.

dogman1313

how do you replace the injector ?

kevinkpk

Gotta remove the intake, that also means more than just injectors, but also gaskets. I looked on you tube for something to help, but nothing. I'd also add, replace all 8. You "may" have 1 bad, but going to this level, not replacing all of them just a matter of time befoer you'll be back into it.

armystrong928

Cold also be o2 sensors mine is doing it too. But my plugs are a rust color.

Bruin4LB

So my P0304 message for piston 4 misfire with Traction Control & Service Stabilitrak message led to Collapsed Lifters on the right hand side. This only uncovered after I replaced spark plugs, spark plug wire, swapped ignitors, performed fuel injection cleaning. Condition worsened while I was on vacation. I started receiving a P1175 message, constant engine clicking noise, in addition to consuming 2 qts of oil. In the end, took it to dealer after local mechanics wanted to replace the entire engine. Replaced Collapsed Lifters on the both sides and was good as new.