5.3 misfire

[1965GTO]

I have an engine miss that has not given a check engine light. I have replaced fuel filter, plugs , wires,had injector flush at precision tune, has a new green intake gasket.Starts up fine cold and runs without miss for about 5-10 miles, problem is a miss at about 1200 rpm under some load after engine is warm. It doesnt seem to do it till it warms up.It is a 2002 Silverado 5.3 , 60k miles

[j cAT]

Originally Posted by 1965GTO

I have an engine miss that has not given a check engine light. I have replaced fuel filter, plugs , wires,had injector flush at precision tune, has a new green intake gasket.Starts up fine cold and runs without miss for about 5-10 miles, problem is a miss at about 1200 rpm under some load after engine is warm. It doesnt seem to do it till it warms up.It is a 2002 Silverado 5.3 , 60k miles

with this engine the PCM will throw codes with misfires that you will not detect...so what your experiencing is most likely a lack of fuel pressure as this will give that type of feel with no codes when the fuel pressure is borderline low..with a pressure guage measure the pressure , follow the proceedure list here on this silverado forum many times past ..

you must not run down the fuel supply below 1/4 or risk fuel pump failure.

[1965GTO]

It starts up great , would a fuel pump or regulator make it hard to start?

[j cAT]

Originally Posted by 1965GTO

It starts up great , would a fuel pump or regulator make it hard to start?

step one is fuel pump pressures follow the proceedure..

this engine PCM is very smart ...unfortunately fuel pressure is not an input to be monitored...

no dtc means step one !

[1965GTO]

I was thinking of going to the dealer tomorrow. Do you think I should just replace it first before I go?

[j cAT]

Originally Posted by 1965GTO

I was thinking of going to the dealer tomorrow. Do you think I should just replace it first before I go?

if you don't have the pressure guage this can be had for 30.oo ..
the dealer will cost many times that just for looking at it ...

if the pressures are no good then the fuel pump replacement should be a delphi pump....other manufacturers are reported with 6 month failures...

when you have problems with your vehicle the forums are here to help you save money and time to replace parts after testing no guessing ..

the dealership will chage you several hundred dollars to replace a fuel pump !

[1965GTO]

I took it to dealer and they could not find any electrical problem,nothing showed in scan. They said fuel pressure was 52 with switch on and 44 internal. They said the misfire may actually be a shudder with torque converter.

[j cAT]

Originally Posted by 1965GTO

I took it to dealer and they could not find any electrical problem,nothing showed in scan. They said fuel pressure was 52 with switch on and 44 internal. They said the misfire may actually be a shudder with torque converter.

here we go again another dealership scam !

they know the fuel pressure for the 5.3L engine is 53-62psi period....

they got less than 53psi and how its running at 44psi is a surprise ..

the way this posting is going it appears YOU are not the repairing type..I suggest you bring your vehicle to a highly recommended repair shop that does good work...contact friends/neighbors..for where to go...

[1965GTO]

i'm going to have a reputable trans shop look at it too. Is it safe to drive for a while? Will fuel pump or regulator give me a light or warning before it leaves me stranded? I have never had any starting problems and it still starts right up.

[j cAT]

Originally Posted by 1965GTO

i'm going to have a reputable trans shop look at it too. Is it safe to drive for a while? Will fuel pump or regulator give me a light or warning before it leaves me stranded? I have never had any starting problems and it still starts right up.

the issue you have with the low fuel pressures is NOT monitored by the computer ...this is something that would have been a great help to troubleshooting these type of issues...the check engine LT will not come on even with a defective fuel pump !


since the pressures are low I would do as I stated earlier...not wait and get stranded...

why go to a tranny shop ? with those fuel pressures how are they to determine if the tranny is bad with the engine not getting the correct fuel ?