Random missfire

[Archaic2021]

97 c1500 5.0 vortec

So just drove 90 miles home. 180 miles round trip. Get homrle and truck starts running rough. Random missfiire p0300 code.

New style style injectors
Re sealed top end
New plugs, wire and plugs
New cap.
New fuel pump
All wuthin last 3k miles

Wher should start first.

I need ti change fuel filter just havent done it

 

[Archaic2021]

I wanna add

Sitting in the truck i went to tap the throttle ans it just shut off.

Re starta fine. That only happend once

 

[Archaic2021]

Also wanna add outting truck in drive it and holding break it really hesitates idling like it wanta to cut off

 

[Archaic2021]

Annd when on the brake in drive giving it gas it really hesitates and misses

 

[highwaystar]

Insure the wire from the ignition coil to the top of the distributor is connected "securely".
If loose, random things happen.

 

[Archaic2021]

Insure the wire from the ignition coil to the top of the distributor is connected "securely".
If loose, random things happen.

Just checked thats all good.

 

[Schurkey]

97 c1500 5.0 vortec

Random missfiire p0300 code.

What are the misfire counts for each cylinder?

Some scan tools LIE about P0300. The "real" code may be P0301--P0308, but the tool just says "P0300".

Wher should start first.

Sitting in the truck i went to tap the throttle ans it just shut off.

Re starta fine. That only happend once

First thing I'd do is to check the ignition coil output power using a spark-tester calibrated for HEI ignition.

I use tools like this one, but there are other styles. DO NOT buy one with a friggin' light-bulb that glows with spark. You want to see the actual spark jumping a calibrated gap.
www.amazon.com/dp/B003WZXAWK/?coliid=I3S98D7T1J0RLJ&colid=2VLYZKC3HBBDO&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

xc_hide_links_from_guests_guests_error_hide_media

Beyond that, verify fuel pressure at idle and under load when the engine misfires or stalls.

Did you replace the lower intake gaskets when you "resealed the top end"?

 

[1998_K1500_Sub]

New style style injectors
Re sealed top end
New plugs, wire and plugs
New cap.
New fuel pump
All wuthin last 3k miles

All those items were changed before this happened, yes?

Did you just change those parts while it was being "re-sealed" or was there some problem or condition, prior to this, that motivated all the new parts?

Should I assume "re-sealed" means "replaced the gaskets between the intake manifold and the head"?

 

[Archaic2021]

What are the misfire counts for each cylinder?

Some scan tools LIE about P0300. The "real" code may be P0301--P0308, but the tool just says "P0300".




First thing I'd do is to check the ignition coil output power using a spark-tester calibrated for HEI ignition.

I use tools like this one, but there are other styles. DO NOT buy one with a friggin' light-bulb that glows with spark. You want to see the actual spark jumping a calibrated gap.
www.amazon.com/dp/B003WZXAWK/?coliid=I3S98D7T1J0RLJ&colid=2VLYZKC3HBBDO&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

xc_hide_links_from_guests_guests_error_hide_media

Beyond that, verify fuel pressure at idle and under load when the engine misfires or stalls.

Did you replace the lower intake gaskets when you "resealed the top end"?

New lower intake gaskets were done when new injectors were done.

True random missfire.

All those items were changed before this happened, yes?

Did you just change those parts while it was being "re-sealed" or was there some problem or condition, prior to this, that motivated all the new parts?

Should I assume "re-sealed" means "replaced the gaskets between the intake manifold and the head"?

Yes had a bad poppet injectors and had a missfire on cyl 2.

Replace all these parra and lower intake gaskets when put new style injectors.

New fuwl pump was later

 

[scott2093]

So just drove 90 miles home. 180 miles round trip. Get homrle and truck starts running rough

My 93 used to act up starting after interstate driving . After I cleared out the EGR passages, it stopped. Not sure if it's relevant with your year or even if it were just a coincidence mine cleared up..