Still have miss on cyl#.1,3,5..any ideas???

[NATIONAL87]

2001 s10..4.3 w code engine..4x4 automatic..I have replaced..plugs,wires,rotor cap & button,complete new spider with fuel regulator & all..with a snap on scanner hooked up to it..I have a miss on 1,3 & 5..it idles at about 550-600 which is too low & has a noticable miss at idle..when engine is speed up the miss seems to go away but according to computer its still there..How can you idle it up..I have screwed in idle up screw but computer resets it back to a low idle...What else can I be looking for a miss on only these 3 cylinders..this is same cyls that was missing before I changed it all..Also I have changed fuel pump & all too..fuel pressure is at 54 idling now..Thanks for any help or ideas..Im about tired of messing with this truck!!!

[Rick Norwood]

How long since these were replaced? Did you use AC-Delco parts? Did you verify your wires are going to the right plugs?

[Darren509]

Could be an intake gasket leak, since the problem seems to be on the whole driver side of engine...

[old_master]

[NATIONAL87]

Yes the plug wires are on right..the cap is numbered & I even triple checked that but again if I had it at 2500rpms you wouldnt know anything is wrong..only when it idles way low at aroun 500-600..but scanner does show to be misfiring on 1-3-5 even at higher rpms..if a vacum leak you would think the idle would be higher wouldnt ya? I have sprayed all around intake with either & carb cleaner with no change..main thing to me is it needs to be idled up but didnt knw if the miss had anything to do with it..Fuel Pump & plugs,wire & cap&button was replaced @ a month ago..spider..yesterday..

[MT-2500]

In your first post your fuel pressure is to low.

Run a full fuel pressure test and post back pressure readings.
Also check camshaft retard setting.
What is engine vacuum at idle and at 2K rpm?

The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.

[mrwilsonsfc66]

I just went through pretty much the same thing turned out to be shorted wire to injector. try pulling #1,#3,#5 plugs are they wet with fuel ? if so check oil, does it smell like fuel ? try having an assistant turn key (don't start engine) with plugs out, can you hear fuel being sprayed into cyls ? if so you will need to check harness for shorts to ground and positive side of battery (Disconnect positive battery lead before testing) with a multi-meter from injector connector to red connector on VCM check from the injector connector black/white stripe #5 injector to pin #31 red VCM connector should measure 5 OHMS on your lowest multimeter setting. Now to check for shorts the multimeter will need to be set on a higher scale then check from either side of the injector circuit to ground and positive normal readings will be no numbers displayed on the multimeter (if any numbers show it indicates a shorted wire) from injector connector #3 pink/black to pin #16 on red connector (repeat same steps as for #5) from injector connector #1 black to pin #3 on red connector (repeat same steps as for #3) if you have any readings on the multimeter when checking to ground or positive the circuit is shorted and you will need to open the wiring harnes from the red connector to the injector connector and check the appropriate wires for chafing or tears in the insulation. Hope this is of some assistance.