98 5.7 rough idle and stalls

[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?

 

[2drXmobb]

Are your spark plugs good? Did you cross the wires or the plug wires are bad? Why did you change the o2s where they fouled might be running rich if so. Make sure your timings right too.

 

[beedubleyew]

Are your spark plugs good? Did you cross the wires or the plug wires are bad? Why did you change the o2s where they fouled might be running rich if so. Make sure your timings right too.

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

 

[Schurkey]

obd tool says OL fault,

I have no idea what an "OL fault" is.

no stft or ltft.

Because the tool won't report it, or because the computer has failed?

getting PO300 misfire codes,

P0300 because the tool won't report the correct code, or is the misfire REALLY random? Crappy scan tools LIE about P0300. The real code might be P0301--P0308, but the cheap tools report P0300 instead of the true cylinder-specific code.

What are the misfire COUNTS for each individual cylinder?

o2 sensor b1s1 and b1s2 shows no activity.

I'm starting to suspect you have a faulty scan tool. Perhaps a faulty computer.

You'll need to trace the wire harness to those two sensors to see if this is a harness problem.

I've changed everything emission related including o2's. new fuel pump. pressure at 55.

WHEN is the fuel pressure "55"? If it's during the prime cycle, you may need more than one prime cycle to get to max pressure, and that pressure better be higher than "55".

Of course, that assumes that your fuel pressure gauge is accurate.

new distributor. cam retard at -30. can't get it to change with rotating cap.

That's gotta get fixed.

when i pull fuel pump relay it runs fine for a second then dies. would a bad fuel pressure switch cause all that?

A faulty oil pressure switch--or the wire harness connected to it--could cause the engine to stall when you pull the fuel pump relay. However, a faulty oil pressure switch/harness is not going to kill the signal from two O2 sensors, and cause the scan tool to fail to report fuel trims.

I just redid the timing moving the distributor one tooth at a time and checking. it's closer now at +13.

Better. Still not there, yet.

It was running super rich

HOW do you know it was "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.

If this thing is burning oil, all bets are off. May be time for serious engine work.

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.

I expect the pressure regulator has a vacuum port, but being sealed inside the intake manifold, there's nothing connected to that port--no hose. It's just open to the manifold vacuum inside the manifold.

would off timing cause OL fault?

The timing isn't off. Turning the distributor DOES NOT change the timing. The cam sensor signal is not aligned/synchronized with the crank sensor signal; and the rotor tip won't be positioned optimally in relation to the terminals on the distributor cap.

 

[2drXmobb]

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

Spark plugs can give you a general idea of the health of the engine, how many miles does it have? Have you done a compression test on the cylinders? Alot of things can make it run rich , and for the oil on the plugs can be an indication of other stuff like seals etc. But first do a compression test to see if the engines healthy.

 

[beedubleyew]

Spark plugs can give you a general idea of the health of the engine, how many miles does it have? Have you done a compression test on the cylinders? Alot of things can make it run rich , and for the oil on the plugs can be an indication of other stuff like seals etc. But first do a compression test to see if the engines healthy.

I haven't done a compression test. spent that money on a fuel pressure gauge. 238000 miles. so every once in a while I would get a misfire cyl 6 code when I got on the pedal. then it would go away. then one day i turned the corner getting on the freeway normal like and boom, something flipped out. the distributor screws were loose because the plastic broke. got a new one and its been super rich city since

 

[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?

that is a good question, i took apart the ecm looking for broken solder or burt connection and it looked good. one thing is i fixed vacuum leak at brake booster plug with electrical tape and now i have to stand on my brakes to get it to stop!

 

[beedubleyew]

I haven't done a compression test. spent that money on a fuel pressure gauge. 238000 miles. so every once in a while I would get a misfire cyl 6 code when I got on the pedal. then it would go away. then one day i turned the corner getting on the freeway normal like and boom, something flipped out. the distributor screws were loose because the plastic broke. got a new one and its been super rich city since

so i guess my next step is to do compression test and see how far it goes...

 

[beedubleyew]

so i guess my next step is to do compression test and see how far it goes...

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?

all the awesome responses are indicating to me its ecm. i have a buddy with the same truck sitting, ill ask if i can change out that for a second to see. mine had a sticker saying refurbished

 

[beedubleyew]

so i guess my next step is to do compression test and see how far it goes...

thanks man so what if compression test turns out to be negative? do you know anyone that wants to buy a clean 98 lol