1997 k1500 Chevrolet Suburban shaking/shuddering/jerking at highway speeds

[H2814D]

You are very alert, thanks! I didn't even notice this hair crack! Why do you conclude the rotor arm might be riding within the posts and not underneath? I thought it should be riding underneath. The central post has the same height as the side posts so the arm has to be riding underneath I think, not?

I may be wrong on the design of your model year distributor cap, but most caps I have seen the contact point on the end of the rotor travels around on the inside of the spark plug contact points. The spark plug contact point pins usually have a bevel cut out of them that faces the rotor head. See the pic, but like I said, I am not familiar with what you may have as it seems there was possibly a design change made.

 

[HotWheelsBurban]

Exactly the one I ordered, thanks (you convinced me with "brass" and "vent"). Shipping and TAX will ben acceptable, not the first time we are ordering from RockAuto. Btw, I'm living in Belgium, not the Netherlands. But we get along perfectly

I guess I got you confused with a guy on the GM square body forum from the Netherlands, who has a square body Burb with similar issues.

 

[SAR K2500 Burb]

I may be wrong on the design of your model year distributor cap, but most caps I have seen the contact point on the end of the rotor travels around on the inside of the spark plug contact points. The spark plug contact point pins usually have a bevel cut out of them that faces the rotor head. See the pic, but like I said, I am not familiar with what you may have as it seems there was possibly a design change made.

I agree with this. They usually have a post that has a flat cut on the rotor side to give a broad arc surface. If it was smaller, erosion due to normal operation would narrow down the range of operation to the point that gap would increase, and overwork the coil itself.

 

[Fredje]

I agree with this. They usually have a post that has a flat cut on the rotor side to give a broad arc surface. If it was smaller, erosion due to normal operation would narrow down the range of operation to the point that gap would increase, and overwork the coil itself.

The way I understand it now is that the arm rides within the posts circle and not on top (or below). With round posts that gives indeed a smaller arcing area, and I now understand why they created those flat surfaces on the pins. Thanks!

 

[Fredje]

If I want to have a greater chance of getting my spark plugs out, should I try this type of tool?
According to the internet a mix of atf and acetone, and tightening before loosening it up might do the trick…

 

[Road Trip]

If I want to have a greater chance of getting my spark plugs out, should I try this type of tool?
According to the internet a mix of atf and acetone, and tightening before loosening it up might do the trick…

On the specific problem of stuck/rusted spark plugs, I've found that those air-powered ratchets
just rotate around the stuck plug and jam my hand into the sharpest nearby metal surface. They
are all or nothing, quick & easy when the plugs come out like they are supposed to, but for
your situation they are no joy.

Note: I *would* use the air ratchet you shared if I was removing a set of unfrozen plugs, especially
if the engine was out in the open sitting on an engine stand. But not on the frozen stuff still in the
engine bay.

****

Instead, you need to cheat with better than average tools in order to win. The ratchet you want
will have all of these features:

* 1/2" drive
* Long handle for increased mechanical advantage
* Flex handle (Pivoted, allowing you to angle the handle in order to clear obstacles in the engine bay)
* Fine tooth ratchet (72 teeth = only need 5° handle movement to get to the next tooth. Important in tight spaces.)

Trust me on this, you want *all* those features in the same ratchet. ~45 years ago I found myself in a similar situation
as yourself, and bought invested in the then-new version of this Craftsman ratchet...and it is still my go-to whenever I
need an unfair advantage in order to win:

You must be registered for see images attach

(Amazon link for more detail: cheat to win ratchet)

Note: A more budget friendly version is the HF's Pittsburgh version. Buddy has one,
and it's yet to require any need to see if the warranty is real despite enthusiastic
use here in the rust belt. Note: I was skeptical at first, but the tool has since proven
itself by delivering on the promise. (See attached. And here's a LINK)

****

For what it's worth, this is a case where you can decide which vendor to choose,
but just make sure that whatever you select has *all* of these features. Note that
there are kits where there are 1/4", 3/8" & 1/2" ratchet sizes included w/all the
features.

Nice way to give yourself the ability to remove stuff like stuck spark plugs that resist
removal by short, no flex handle, coarse tooth, normal ratchets.

In summary, this kind of ratchet is a game changer for those DIYers who
enjoy the old truck hobby and stuff no longer comes apart easily.

****

NOTE: When you get those vintage plugs out, please arrange them as they were
installed in the engine so that we can get a better idea of how your engine
is running.

Best of luck with getting your rig to run like new.

 

[1998_K1500_Sub]

Good input above by @Road Trip , I agree 100%.

And with regard to keeping the plugs in order:

I number the plugs with a Sharpie when I take them out, one by one, and I lay them on the bench oriented in two rows of four as though they are still in the engine. Then I’ll study them.

Generally, when changing plugs I jack up the front (and occasionally remove the tires) and then I access the plugs by going through the wheelwell, using extensions as necessary. It is much, much easier IMHO.

You will need to remove the rubber splash guard that’s in the wheelwell; it's held by Christmas tree fasteners. Remove the fasteners by grabbing them with a pliers and pulling them out. Don’t pull on the splash guard to try to pull them out, it will tear.

I then throw the Christmas tree fasteners away and replace them with 1/4” plastic rivets from the retail auto parts store.

The plastic rivets allow for easier removal the next time you’re getting into the engine.

I’ve also got some of these extensions with an integral spark plug socket, they can come in pretty handy because they allow some wiggle in the angle of approach, and the knurled shaft makes them easy to spin with the fingers.

 

[HotWheelsBurban]

Good input above by @Road Trip , I agree 100%.

And with regard to keeping the plugs in order:

I number the plugs with a Sharpie when I take them out, one by one, and I lay them on the bench oriented in two rows of four as though they are still in the engine. Then I’ll study them.

Generally, when changing plugs I jack up the front (and occasionally remove the tires) and then I access the plugs by going through the wheelwell, using extensions as necessary. It is much, much easier IMHO.

You will need to remove the rubber splash guard that’s in the wheelwell; it's held by Christmas tree fasteners. Remove the fasteners by grabbing them with a pliers and pulling them out. Don’t pull on the splash guard to try to pull them out, it will tear.

I then throw the Christmas tree fasteners away and replace them with 1/4” plastic rivets from the retail auto parts store.

The plastic rivets allow for easier removal the next time you’re getting into the engine.

I’ve also got some of these extensions with an integral spark plug socket, they can come in pretty handy because they allow some wiggle in the angle of approach, and the knurled shaft makes them easy to spin with the fingers.

I can see on a big block, how it might be easier to go through the wheel well; Dad used to do that on our '70 LeMans because he said it was the only way to get to #8(last plug on passenger side). But I've not had a problem getting the plugs out of any of our 350s/5.7 Vortecs, with just a 3/8 ratchet and assorted extensions...even if I'm changing the plugs for the first time and the threads haven't been anti seize coated. I use a long handled Husky ratchet Dad got from Home Depot years ago; it's my go-to 3/8 unless there's not space for it. It's about 3" longer than my Craftsman 3/8 and the handle is round and tapered, so on the rare occasion I can't break something loose with it, a piece of 1/2 conduit slides right over it. It's a little bit faster to do the passenger side without taking the airbox out of the way, since then I don't have to get the mount lined up again. IIRC it took me about an hour to change the plugs on the Crew Cab, and that included a couple of water breaks (it was very warm for the first week of March 2023).

 

[SAR K2500 Burb]

Had just ordered all new ignition components and out of curiosity checked the contacts on the "Gold Standard" UMP blue cap... mother *******... the gap at the rotor to cylinder is several mm.

You must be registered for see images attach

 

[SAR K2500 Burb]

This is a cheap design feature that was used to fire fouled plugs. I also am putting on a new coil and ICM, so we will see how long their shortened lifespan will be lol.