Get to work on my first 4.2!

[TollKeeper]

Well, its not mine.. Its a Co-Worker.

2008 Envoy SLT SWB

He has a left front wheel bearing thats died C0035, and a P0303, misfire, cylinder 3.

The wheel bearing I am not worried about, thats a 30 min job for me.

What do I need to be looking for on the Cyl 3 misfire, and how do I even get to the damn coil?

Edit: He also has a code for a B0026, but i dont work on SRS Systems.

 

[littleblazer]

IIRC, Pop the intake resonator off and then just remove the coil via the 10 mm bolt holding it in. Pretty cut and dry to get to. Depending on the severity it could be a dead coil like my truck had or there is just water or oil in the hole... Had that happen a few times. You can tell when it just isn't firing at all. No power and feels crappy.

 

[JayArr]

IIRC the #3 cylinder is right below the drip line of the cowl so they get wet more often than others and fail with a higher proportion.

 

[TollKeeper]

I thought it was #4 and 5 had the wet problem from the cowl?

 

[JayArr]

Hmm, you're probably right, this #3 problem may be unrelated to water.

 

[Mooseman]

#4 is the usual suspect for water dripping directly onto it from the cowl but that doesn't mean others can't be affected. A bad seal could still allow water in. Oil contamination is caused by a bad valve cover gasket.

The usual course of action is to swap the coils (i.e. 2<>3), clear the codes and see if the misfire follows. Oh, and they are numbered 1 (front) to 6 (back). Ask me how I found out

 

[gmcman]

Be careful on the coil pack bolts, 89 inch pounds. It's slightly tight past snug.

 

[Mooseman]

So @TollKeeper , how'd it go?

 

[TollKeeper]

He decided to postpone it until next weekend. Doesnt want me to fix the wheel bearing until I get the MIL light off.

 

[rchalmers3]

He decided to postpone it until next weekend. Doesnt want me to fix the wheel bearing until I get the MIL light off.

I acknowledge your stated reluctance to work on the "B" code, and at the same time I agree with your neighbor that it is best to extinguish the MIL first.

That B0026 code looks pretty straight forward: It's most likely to be an open circuit inside the steering wheel SRS clock spring (coil). The FSM can walk you through the diagnosis in just a handful of steps, and just think of how much of a hero you could be.....


I just immersed myself on access and operation of the coil, having repurposed one for use on my race car build. I'm using the two circuits (4 conductors in pairs) of the coil to activate transbrake and bump buttons that I embedded in the steering wheel.

In sum. I encourage you to go after the B code, and clear the way for an easy miss-fire diagnosis and unit bearing replacement!

Cheers,
Rick

 

[TollKeeper]

I did work on it for about 20 mins Thursday. Pulled the coil from one plug, and moved to another. Pulled the codes, it now has a code for a thermostat, and a vent valve or something.

I cleared the codes, watched the data, vent valve came back instantly. Misfire on cylinder three came back. So it's either a dead cylinder, or a bad spark plug. Misfire did not move to the swapped hole.

I won't do work on the vent/purge system, or the airbag, I could probably do them, I just don't want to.

He's gonna buy some spark plugs, and I'm gonna swap them next week. I know 1-4 are easy, how are 5-6?

The motor is only 50k old, dealer replaced it 5 years ago under warranty. Truck has 199k on it.

 

[rchalmers3]

I don't think the spark plug replacement is difficult at all, just a little awkward under the cowl.

Having a spark plug socket that grips the plug, and a proper length extension will make it easier.

Rick

 

[Mektek]

#6 is tough. I used an air ratchet while lying on top of the engine. For final torquing the new plug I used two fingers on a regular ratchet. The air ratchet was a lifesaver for that last plug.

 

[Redbeard]

#6 is tough. I used an air ratchet while lying on top of the engine. For final torquing the new plug I used two fingers on a regular ratchet. The air ratchet was a lifesaver for that last plug.

BE VERY VERY careful doing this! The air ratchet I used once on this same plug removal had the reversing switch opposite the drive side. When the plug began unscrewing it then pushed the air rachtet up against the the sheet metal above the plug. This jammed the spark plug, extension, socket and air wrench up against the sheet metal above this spark plug. With the air wrench unable now to be reversed (putting the spark plug back down) because I could not reach the reversing switch! A serious fight ensued between me and my tools and the TB. Just take this nice and easy.

 

[TollKeeper]

Well he bought one spark plug, and asked me to replace the one in cylinder 3. This is what came out.. Cheap AutoLite. So the engine was replaced, but I seriously doubt it was replaced with a new engine. I am thinking it was a junkyard engine.

 

[Mooseman]

As you may know, it should be ACDelco 41-103 for a good running 4.2.

 

[TollKeeper]

I just hope that strap isnt in the cylinder bouncing around, and causing all kinds of damage. It probably embedded in the head, or valve relief by now.

 

[JerryIrons]

Maybe try remote camera to peek in there?

I've changed spark plugs on my I6 a few times now, it's not that bad, even the "tough" ones. Just have an assortment of extensions, swivel extensions, etc. And yes use the ac delcos. air compressor to blow out dusties before you pull out the plug.

 

[rchalmers3]

@TollKeeper How bout a 2022 update on the neighbors sled?

Rick

 

[59840Surfer]

Well he bought one spark plug, and asked me to replace the one in cylinder 3. This is what came out.. Cheap AutoLite. So the engine was replaced, but I seriously doubt it was replaced with a new engine. I am thinking it was a junkyard engine.

I have seen this ground strap failure before - especially on Autolite plugs, but also Atlas, Champion and Bosch.

A couple of times I found my customer had tried to regap the plug or even tried to confirm the gap --- which is something you should never do on an Iridium plug anyway.

Assuming this is NOT an Iridium plug - you know that those pieces either left the combustion chamber --- or they didn't and are currently embedded in the top of a piston or the head.

About Iridium plugs and never checking the gap: there are horror stories about damaging the molecule-thick coating of Iridium - a rare earth, precious metal - that means you are not getting a piece of Iridium, but a vapor blasted coating of it on the electrode and one can damage it with a feeler gauge.

I personally cannot confirm or deny damage to the coating - but it sounds factual knowing how company bean counters try to keep things cheap.