88 5.7 low on power

[thered88]

after calling people I know all weekend, I have a scan tool that works. now my issue is i don’t know what any of this means. the only thing I find kinda weird is that at about 1300-1500 rpm (which is where it runs the worst) my o2 sensor jumps from about 150 mV to 800+ mV and then back down to 150 ish and it just repeats that. I have no idea if it’s supposed to do that but I’m guessing no since the manual that evilunclegrimace suggested says that it usually stays between 350 mV and 550 mV. But I very well could just be stupid and misread it. Other than that, everything looks pretty normal based on what I read in that book.

 

[Schurkey]

The '88 has only one O2 sensor, and of course it's an "upstream" sensor.

They're supposed to jump high-voltage to low-voltage, cycling through .45 volts (midpoint).

Each time the sensor passes through 4.5 volts, it's called a "crosscount", and generally-speaking, more is better. At idle, you might have crosscounts in the single-digits--6, 8 maybe. As RPM builds up, the crosscounts should increase.

Adequate cross-counts is a sign of O2 sensor health. As they age, they react slower and slower. Also, having a strong voltage swing is also healthy. But I've seen O2 sensors that test good at low-load, and go crazy at highway speed. So if in doubt...replace the sensor especially if it's got ~50K miles or more, or several years on it. Unlike most other sensors, the O2 sensor has a limited lifespan; they deteriorate with age.

 

[thered88]

Would 4-6 cross counts within a 10 second span at idle be ok? I haven’t tried at higher rpm’s yet.

 

[scott2093]

I have a scan tool that works. now my issue is i don’t know what any of this means

the only thing I find kinda weird is that at about 1300-1500 rpm (which is where it runs the worst) my o2 sensor jumps from about 150 mV to 800+ mV and then back down to 150 ish and it just repeats that.

You could post up some more readings from the scanner...maybe something obvious will stand out..or not
doesn't sound like the o2 sensor is your issue ...

 

[Schurkey]

Would 4-6 cross counts within a 10 second span at idle be ok? I haven’t tried at higher rpm’s yet.

Probably OK. As I said...higher is better. A 5.7L should stay in closed-loop at idle, but it's fairly common for them to drop back to open-loop at idle especially if the O2 sensor is getting elderly. The 7.4 will go open-loop at idle, and that's normal.

 

[thered88]

Well I bit the bullet and bought and installed an o2 sensor. I dont think I’m having the missing issue anymore. So schurkey, you were right. We are just back to having my original issue from my first post. I read somewhere that setting the base timing to 3 degrees advance helps with power and drivability. What is ur guy’s opinion on that?

 

[Schurkey]

88 k2500 with the 350tbi and 700r4.

it’s still not running right. I know it’s not running right because of 2 things, 1) it does some weird surging thing when cold and below 2500 rpm, after 2500rpm it takes off. 2) I happened to drive my dad’s stock 1990 k1500 with same motor, transmission, and rear gear up a hill that I drove my truck up earlier that same day and i realized that in dad’s truck, the converter didn’t unlock (mine unlocked right at the beginning of the hill)and I was not on the gas petal nearly as much. And overall driving it seems like dad’s truck isn’t struggling like mine is.

We are just back to having my original issue from my first post.

Surging when cold, poor power/"struggling"?

I read somewhere that setting the base timing to 3 degrees advance helps with power and drivability. What is ur guy’s opinion on that?

Try it...see what happens.

If you had a scan tool, I'd tell you to watch the knock counts and spark retard.

 

[thered88]

I was referring mainly to low power I havnt been able to drive it enough to see if it’s surging (I would quote ur message but my phone doesn’t like me). when I advance it, what values should I see?

 

[Schurkey]

You'd see whatever "value" the advance is set to.

 

[thered88]

well today i adjusted the timing to about 3 degrees advance and it seems to have helped my low power issue a little bit. But whats not helping my low power issue is the fact that it's still missing. It doesn't seem like the mis fire is rpm based due to the fact that it does it from idle to 4k rpm (im too afraid to push it past 4k). I believe its an igniton issue. I have replaced the ICM in September, the coil a week ago, knock sensor a month ago. Spark plugs, spark plug wires, cap, and rotor seem fine and they were new last may. The only thing that leaves is the pickup coil, the ECM (maybe but probably not), a bad ground, some random broken wire, or maybe my eyes just suck and the plugs, wires, cap and rotor are screwed up. I dont know too much about the pickup coil so any info on symptoms for a bad pick up coil would be nice or suggestions on anything I might have over looked. Also i used the scanner to look at knock count and spark retard and it seems to always say 2 for knock count and there isnt anything called spark retard but there is something called ESC count and that also always seems to say 2.