'01 Yukon Throttle body cleaned, low idle & quits now

[bill9000]

The menus and what you can see and do vary by model and even by year within the same models. I'm familiar with mine but not the others yet. That being said, you probably see enough functions to find the cause of this problem with the Tech-2.

This all started with the throttle body so that's where I'd keep looking. At it and anything attached to it. In my old muscle car, the IAC was under the throttle plate and when we sprayed cleaner on the plate, all the gunk would go down the hole to the IAC motor and then like knuckleheads, we had to pull the IAC, clean it and the cavity and put it all back together and let it relearn to idle again.

My Tech-2 paid for itself in short order as well. It's a money-making tool. So for those of us doing our own maintenance, it's a money-saving tool!

awesome thank you! I will definitely get a scanner like that then. Like you said, those that do our own stuff! - I dont trust shops, so I guess I had better buy one of those! I had never really looked into it before, I had thought they only read CEL codes, I didn't know they can to the bi-directional and other data like that.

 

[jsoltren]

I have no experience with the matco I don't know what they are capable of a few of us have bought the tech2 clones off ebay for $300ish that is the oem diagnostic tool the dealers use for these years but they have since changed to a autel @swathdiver may know of the matco

Neat. I use Torque Pro on Android, which in theory (and with the right adapter) should be capable of getting all this information directly. The trouble with reverse engineering this is that GM's legal department has deep pockets.

 

[afpj]

Bill9000, curious what plugs and wires you used?

 

[bill9000]

Bill9000, curious what plugs and wires you used?

CarQuest wires and Autolite Iridium plugs that are the right spec for the car.

 

[swathdiver]

The trouble with reverse engineering this is that GM's legal department has deep pockets.

Curious, what are you referring to?

 

[bill9000]

** UPDATE **
I bought a Snap-On diagnostic scanner (I wanted one anyway) and found a good deal.

Here's what I am getting, I believe, if I am using the tool properly that I am dealing with misfires (which makes sense based on how it sounds in the video)

here's what I was able to find. (the misfire number for specifically the #2 cyl and #6 cyl climbs quickly while its running and sounding the way it does.... watching the data as it's running...

so here's what it's doing, cylinders 2 & 6 are misfiring at idle, when you can hear the engine miss, it adds a misfire to the number shown here.

I can also switch to a live graph and show the cylinders as it's running, and watch the number of misfires grow at idle and a corresponding jump in the graph...


If I hold the rpm up to like 900ish, and watch the graph... no misfires.

here's the graph:

With this knowledge, I tried re-seating the plug wires, pulled those two plugs to inspect for any obvious issues... put back, same problem... I tried swapping #1 & #2's plug wires to see if it may be the wire (expecting #1 to now misfire if it was the wire.) and it still was #2 & #6...

So I'm thinking a few bad plugs? Perhaps I should buy a set of Delco plugs and stick them in? & on that same note I'm told the gap of the iridiums now are going to be different than that specified on the sticker on the cowl, one was 0.40 and one was 0.60 - since you can't really gap iridiums, I'm guessing that it's ok?

I'm guessing that the coil packs are not likely to be the issue as those throw a P code when they go out, usually?



here's the video of the symptoms again

also.... of interesting note, I am not sure if this is normal to spike around like this either..... maybe it's jumpy trying to compensate for the perceived rpm change due to the misfires...

 

[afpj]

The current gm recommended gap for iridium is 0.04.

Try swapping coil pack positions and see if the misfires change positions.

 

[bill9000]

The current gm recommended gap for iridium is 0.04.

Try swapping coil pack positions and see if the misfires change positions.

The reason I ask about the gap is that I had bought a set of iridiums like 5 years ago that I was planning to put in but by checking the gaps, they were all over the place, some 60, some 40, some in between... and it said you can't gap them because you ruin the iridium tip... so I had never installed them.


Agreed. My next course of action is to swap the plug from 2 & 4 and see if the misfire moves... if not, then swap the coil pack from 2 & 4 - if that still didn't work, then a compression check.
If the misfire DOES move from moving the plugs, then I'll buy a full set of Delco iridiums and stick them in and see what happens. Since I know Autolite isn't OEM, although I would think anything but Champion plugs should work fine. But nonetheless, never hurt yo buy Delco's I suppose!


I do think the important thing to note here, is that the misfires ONLY happen at idle.... when I watch the graph on my scanner... it does NOT misfire if the rpm is above like 750 - it only misfires when the idle is low.

 

[bill9000]

**UPDATE**
Problem is now entirely solved. The Snap-On diagnostic scanner took me right to the problem. And also confirmed the fix by the flat graph on the misfire charts...

misfire:

No misfire

I swapped plugs from cyls 2 & 4 and the misfire moved to 4, put in all 8 new plugs with Delco Iridium (getting rid of the Autolite Iridiums) and ran engine with scanner in, and you can see the misfire charts are flat now vs the counted misfires and graph move shown before.

Thanks for the help and suggestions, I appreciate it!
Having this scanner now to determine what's going on I would imagine will help a lot with future issues.

 

[Tonyrodz]

**UPDATE**
Problem is now entirely solved. The Snap-On diagnostic scanner took me right to the problem. And also confirmed the fix by the flat graph on the misfire charts...

misfire:

No misfire

I swapped plugs from cyls 2 & 4 and the misfire moved to 4, put in all 8 new plugs with Delco Iridium (getting rid of the Autolite Iridiums) and ran engine with scanner in, and you can see the misfire charts are flat now vs the counted misfires and graph move shown before.

Thanks for the help and suggestions, I appreciate it!
Having this scanner now to determine what's going on I would imagine will help a lot with future issues.

So it was those damn plugs eh.