98 5.7 rough idle and stalls

[beedubleyew]

I just redid the timing moving the distributor one tooth at a time and checking. it's closer now at +13. It was running super rich thats why i changed the o2 sensors they were black! all the plugs had oil on them except cyl 6 when this all started. one thing that is concerning, the fuel pressure regulator doesn't have a vacuum port and everything i've seen with this truck it has one. although it han great for the couple years i have owned it. would off timing cause OL fault? thanks for responding

its not burning oil just too much gas from the computer

 

[2drXmobb]

Rings pistons time for a rebuild if that's the case. The crate motors are affordable around 4-5k new or go ls . You can even go cheaper these vortec motors are cheap in the used market . I seen some for $500-1200 bucks . It be more of a headache trying to find the grimlins when you can just slap a new one and call it a day . I'm trying to go ev with the gm ecrates but the distance is low maybe 190 miles to a charge so I'm waiting for better development and r&d.

 

[beedubleyew]

Rings pistons time for a rebuild if that's the case. The crate motors are affordable around 4-5k new or go ls . You can even go cheaper these vortec motors are cheap in the used market . I seen some for $500-1200 bucks . It be more of a headache trying to find the grimlins when you can just slap a new one and call it a day . I'm trying to go ev with the gm ecrates but the distance is low maybe 190 miles to a charge so I'm waiting for better development and r&d.

so yeah compression verdict in. #2- 109, #4- 131, #6- 0, #8- 138,
#1- 145, #3- 150, #5- 140, #7- 132.
does that sound like head gasket? no coolant in oil or blowing smoke of any kind.

 

[2drXmobb]

Have you tried squirting oil in the spark plug holes and retesting compression to see if the rings and valves seal?

 

[2drXmobb]

Also if you can do a leak down test

 

[beedubleyew]

hoping I can get some help. obd tool says OL fault, no stft or ltft. getting PO300 misfire codes, o2 sensor b1s1 and b1s2 shows no activity. I've changed everything emission related including o2's. new fuel pump. pressure at 55. new distributor. cam retard at -30. can't get it to change with rotating cap. when i pull fuel pump relay it runs fine for a second then dies. would a bad fuel pressure switch cause all that?

I ordered all 4 O2 sensors off amazon for $45, the OEM ones are $60+ a piece. put the old ones back on and my obd2 readings came back to life. Compression test revealed blown head gasket. = new engine. Those cheap sensors on amazon do not work for this truck. I spent a lot of time on the fuel system because my o2 sensors were new, how could they be bad?

 

[beedubleyew]

Have you tried squirting oil in the spark plug holes and retesting compression to see if the rings and valves seal?

 

[beedubleyew]

No, haven't tried squirting oil in. Does that make a difference? thanks i'll try it

 

[Schurkey]

Have you tried squirting oil in the spark plug holes and retesting compression to see if the rings and valves seal?

Waste of time. I lost faith in "oiled" compression testing about thirty years ago.

Leakdown test would be useful.

 

[beedubleyew]

I just redid the timing moving the distributor one tooth at a time and checking. it's closer now at +13. It was running super rich thats why i changed the o2 sensors they were black! all the plugs had oil on them except cyl 6 when this all started. one thing that is concerning, the fuel pressure regulator doesn't have a vacuum port and everything i've seen with this truck it has one. although it han great for the couple years i have owned it. would off timing cause OL fault? thanks for responding

Just to update, that cylinder #6 that was throwing a code has 0 compression.