So I currently had the truck on the computer diagnosing my miss issue. I initially was told I had a miss on 5 and 7 but was wrong. I had a miss on every cylinder, only at idle. Get it up to around 1000 rpm the misses go away. At one point at rpm above idle there was a slight miss on a few cylinders. When bringing up rpm idle air valve wasn't keeping up. Brought rpm up to different points and idle air valve was always lower and fluctuating a bit. It never caught up. AND the big one, spark advance was jumping around. We don't know if the timing is off because the computer is going crazy OR its adjusting itself because of somethin else that is bad. Here are the failed tests:

Bank 1 sensor 1 o2 half cycle
-measured 10 minimum 56
- failed

Failed purge monitor ic step shift
-measured 7 minimum 254

Failed purge monitor rpm shift
-measured value 0 minimum 65527

And again, all cylinders mis at idle and spark advance jumps around

Reset: adaptive fuel and IAC - no results so far

I do have a small weld leak a few inches before the precat o2. Going to fix it tomorrow. Everything else checked out.

So what does everyone think? What should be first thing to attack? What do those failed tests monitor or mean? What else should I get readings on to help diagnose? The guy I'm working with said he's more than happy to plug me in and get the readings. Since he doesn't know what to start with he wants me to share as much as needed to diagnose and he will learn in the process.

Thanks in advance.

 

Nothin?? No one has seen these ?

 

Misfire in all cylinders is strange. Can his computer check fuel sync? Sounds like either fuel or fire timing is not together. IAC issue needs to be fixed also as it effects air flow at idle.

 

Don't remember if it can check it. Doubt it, had to borrow neighbors to set it originally. It was set at 0 about a month and half ago.

 

I have garage sealed up right now and paint fumes too strong. I will look in my Snap On book for my computer and see if I can find anything out tomorrow morning. It has lots of trouble shooting info based on readings from computer. I'll let you know if I find anything out.

 

I'll be waiting! Thank you man

 

If you are getting a miss on every cylinder, what does your distributor cap look like? Coil?

 

They are all a month old and mostly happens at idle only but I'll start pulling stuff and check. The failed tests are what I'm really concerned with right now.

 

Maybe the wires are one position off. Multiple mis fires are usually clogged cat. When did you replace it? Before or after the plenum fix? I'd also get an inexpensive fuel pressure tester and check it.

 

Fuel pressure was checked last week. It's good still and a high flow cat was put in a few weeks before the plenum. Plenum went in with new motor.