Random misfires 98 Z-71 5.7L

[Thunderbolt]

Originally Posted by Jeremy-WI

Thunderbolt, once the upper intake is off it shouldn't take 30 minutes to swap the injector assemblies. The injectors are labeled on the regulator assembly as to which cylinder to plug them into. There was some performance gain just from the injectors being new and my gas mileage increased about 1 mpg

Thanks ! I think I will do that swap when I put the new long block in.

[jlaudio12w07]

sequential fuel injectors a common cause of misfires... start cheap. tune-up plugs wires cap rotor ect. i highly recomend the use of a cylinder compression tool and a scanner 2 observe sensors and cylinder activity 2 be certain.... 5.7L tend 2 do wierd things due 2 intake manifold gasket leaks 2... spray carb and choke cleaner around the intake, monitor idle rpm

[98 5.7 rdm.misfire]

Random missfire is a Knock Sensor !
Please read my story !
I own a 1998 Z/71 5.7 K1500
Started off missfireing on a hill or when i pulled my small trailer.
Service engine soon, dash lite came on, went to a shop pluged up to a hand held unit. it said missfire on 3&5, cleared codes & thought its just tune up time. WRONG !
BEFORE THIS I HAD JUST REPLACED THE FUEL PUMP AND FUEL FILTER THE PUMP HAD GONE OUT.143,000
MILES ON IT, NORMAL REPAIR.
OK BACK TO RANDOM MISSFIRE,
REPLACED SPARK PLUGS ,PLUG WIRES,DIST. CAP ,ROTOR,
Driving around the samething {dash lites up service engine soon }
it RANDOM missfires and shakes loosing power. i return to shop we plug up the hand held unit it says random missfire ? so we think its the coil getting weak, replaced the coil same thing random missfire again.
this is over a 2-3 month period i have to drive the truck easy to work and home like driving Miss. Daisy you kinda get the idea.
someone said the intake gasket is Leaking check it , so with the truck at idle i spray starting fluid all around the intake with no changes in RPM.
NEXT Iam about to do a insurance claim, but i love the truck but its driving me and GM mechanics and all others mechanics up the wall at this time iam looking at a whole lot of money spent already and my truck is not fixed, and thinking about standing on a street with a sighn that reads "will work for repaires on my chevy truck "
ok its time to think again , so i'am putting it all together random missfire no power, piston spark knock,so i called O'Reilly auto parts Dalton Ga. and told jeff my sad story he said to change the Knock sensor
for $32.99 it was worth a try.
part # BWD 98012 FOR MY TRUCK.
PLEASE READ ON !! It fixed the problem its never ran so great , Throttle responce is great!
The knock sensor tells the computer to advance or retard the timing,
it cannot adjust the advance without the knock sensor telling it what to do. The Knock sensor is located on the passenger side of the block easy to get to under the truck on jack stands. but it screws into the water jacket of the block between the freeze plugs you must drain all the antifreeze from the engine before replacing it. The truck runs like a brand new one with 160.000 miles on it 0-100 mph is no problem bring on the HEMI'S !