00 Denali - Random Misfires under load

[SunlitComet]

His does not sound like a very good scanner but the p0300 is not just a misfire but a random misfire meaning more than one at a time and not a specific cylinder.

---------- Post added at 11:46 AM ---------- Previous post was at 11:43 AM ----------

With out a way of narrowing down the cylinders you may have to use the process of elimination and inspect each ignition component for faults and maybe a compression test. If nothing shows up then it is likely your injectors are faulting out on you.

---------- Post added at 11:48 AM ---------- Previous post was at 11:46 AM ----------

I use a laptop-based scanner and when I use the data-view option I have lots of info to scroll through which spans several pages in length.

---------- Post added at 11:50 AM ---------- Previous post was at 11:48 AM ----------

If you were nearby I would plug in and give you the low down.

 

[TurboGSR96]

His does not sound like a very good scanner but the p0300 is not just a misfire but a random misfire meaning more than one at a time and not a specific cylinder.

---------- Post added at 11:46 AM ---------- Previous post was at 11:43 AM ----------

With out a way of narrowing down the cylinders you may have to use the process of elimination and inspect each ignition component for faults and maybe a compression test. If nothing shows up then it is likely your injectors are faulting out on you.

---------- Post added at 11:48 AM ---------- Previous post was at 11:46 AM ----------

I use a laptop-based scanner and when I use the data-view option I have lots of info to scroll through which spans several pages in length.

---------- Post added at 11:50 AM ---------- Previous post was at 11:48 AM ----------

If you were nearby I would plug in and give you the low down.

I am pretty sure that was a pretty expensive scan tool I only had 10min to mess with it, took me several of those minutes to locate my vehicle in the menu's, battery died on it right after I looked at the misfire freeze data. I didnt really need a scan tool to know I had multiple cylinders misfiring I can feel it in my feet lol

I am about to head outside and check the plug wires and maybe pull a few plugs, its hot as hell outside right now.

Thanks for your help so far

 

[SunlitComet]

I am sure you could feel but it really helps to know if it is two right next to each other, on the same bank or just all over the place.

 

[TurboGSR96]

Pulled the drivers side front two plugs, they showed signs of detonation around the base and the timing prong's were on the white side of things, I also wiped the surface of the MAF off it went from black to silver lol. Popped all the wires off one at a time and just repopped them on and took a drive a little while ago and it didnt misfire, I still limped it but it went into 3rd gear through OD and I didnt feel it at all. I came to a light and I started to feel a slight single cyl miss every 2 seconds so then it cleared up. I was in shock and denial and just came home and parked it lol.

About to head out and give her some throttle and see what happens, thinking I might have a shit set of wires, which would be 2 sets of ***** wires back to back.

 

[gpracer1]

Dude, clean that MAF!
Mine looked spotless and was running 15-16 AFR at WOT. I cleaned it with MAF cleaner anyways and it dropped to 12.9 and lots more power!

 

[SunlitComet]

grab yourself some acdelco's or msd wires if you have not already. What plug and gas brand do you run?

---------- Post added at 06:30 PM ---------- Previous post was at 06:22 PM ----------

I am nervous that the two problem cylinders are adjacent to each other.

 

[TurboGSR96]

Well it still does it, but I can run it a little harder for a little longer, it feels like it has a little more power.

What should my 02 sensor readings look like? Should the voltage constantly sweep at idle or stay somewhat steady? What about long term and short term fuel trims?

Dude, clean that MAF!
Mine looked spotless and was running 15-16 AFR at WOT. I cleaned it with MAF cleaner anyways and it dropped to 12.9 and lots more power!

I will look for MAF cleaner, other than the very surface of it (which wiped right off) it looks clean. Can I just use compressed air?

grab yourself some acdelco's or msd wires if you have not already. What plug and gas brand do you run?

---------- Post added at 06:30 PM ---------- Previous post was at 06:22 PM ----------

I am nervous that the two problem cylinders are adjacent to each other.

For some reason I am not lol, I just run 87 (drank it all of its 180k miles) and I forget what plug, the truck gets about 10mpg so it def doesnt get premium... I am starting to lean towards an ignition issue honestly,. If I had 2 cylinders down I would feel a noticeable difference, and probably have some mixing of fluids, possibly leaky or smokey exhaust and whatever else and I have none of that.

If I keep driving it like this it will probably die, it has been exactly this way for a pretty long time and nothing has changed other that the improvement I saw today lol

I am gonna do plugs and wires hopefully tomorrow, anyone know the exact brand/part number on both? I thought I saw a TSB about plug gap, is it still .060" on the plugs?

 

[SunlitComet]

the voltage will sweep up and down.

As far as fuel trims I can give you numbers but 1. you will need a scanner again to read yours and 2.if they were off a important amount you would pop a code for rich or lean banks.


Maf cleaner only and preferably let it drip dry. Compressed air of high enough pressure could damage the electronic components that are exposed in the airflow.

---------- Post added at 08:42 PM ---------- Previous post was at 08:33 PM ----------

plugs are acdelco 41-993 pre-gapped at .060. I don't think the tsb applies to you.

Acdelco wires 9718q

MSD if you want depends on color.

 

[TurboGSR96]

Thanks for your help, I still have my ancient scan tool that shows data and it has the fuel trims in it.

So at idle that 02 voltage should keep going from high to low? They are all original besides one that was replaced last year.

 

[SunlitComet]

That is about right although it's good to change them out every 5 years or 75,000 miles. if you could view the waveforms of all the sensors and the new one sweeped faster with other slower then yeah you would benefit from a change.