Pre-Oil Change

[psa55]

Hey all,

My TB has been a constant work in progress lately... I have an oil change coming up in the near future, and have been waiting to put a new CPAS in (its original), with the change. Before the Change Oil Light pops, I was wondering about any other service advice. I've had an intermittent misfire in Cylinder #4 at idle and less so in Cylinder #6. I chased these issues two years ago, with plugs, coil packs, engine compression tests, fuel injector cleaners, etc. I've run it since, without any issues and it continues to work well.

I was wondering about using a litre of Marvel Mystery Oil in the Oil, before I do the oil change, or using Seafoam for a hot soak, in the brake booster? I've seen some people recommend, others say Snake oil. Would any of you consider these treatments prior to the oil change? Are there and potential negative impacts?

 

[TollKeeper]

I would simply start by pulling out the coils, and seeing if the bottom of the spark plug well is full of oil.

I have had good luck with seafoam thru an intake vacuum line. Make sure to do it outside.

 

[TequilaWarrior]

For years now I've been periodically running a product called "RXP" in a full tank of gas about once a year.... it ~seems~ to work as advertised - that it removes carbon buildup and cleans the valves/combustion chamber. My last experience with SeaFoam was just a couple irritated neighbors... YMMV.

 

[psa55]

I'm not sure I'm going to solve the misfire issues - coils, compression, plugs, etc. all check out good and did a couple years ago. I've tried swapping coils, new plugs, without any change. Wondered if any pre-oil change treatment might help my situation

Appreciate the info on the Seafoam. Might give that go this week!

I should note, I have read the treads on the AC Delco TEC and actually have a can in my garage, that I managed to get in the USA and brought it across the border last summer. I have decided I don't plan to go that route, unless absolutely necessary and things get dramatically worse. Right now, there has been no drop in performance for 2 years... means I spend less time in a drive thru!

 

[Mooseman]

I had (or still have) a misfire issue. Don't know if it's resolved but I think it did come on when I let it idle for a long time last winter.

Very Slight Miss at Idle

Yesterday on the TB, at 117k km, saw the CEL come on and code came up for P0304. Fired up Torque and it was missing on cylinder #4 but only at idle or stopped at a light. It's not a big miss since I can't feel it at all and it's just a couple of misses per refresh cycle. While driving...

gmtnation.com

I see you had also posted to that thread. I haven't looked at this again since that last post.

 

[psa55]

Thanks Guys! @Mooseman, that is exactly where I left off as well. No worse or better than it was then. I think I did all the basic investigation in Sept. 2018 and found your thread that winter.

I think I'll try a seafoam treatment before my upcoming oil change. Figure it can't hurt.

 

[gmcman]

A little bit more $$, but BG44K IMO is the easiest and likely the most effective product to remove carbon deposits from the combustion chamber and valves.

What were the results from your last compression test?

Probably not the issue but have you ever replaced the fuel pressure regulator?

 

[Wooluf1952]

'08 doesn't have a FPR. If you're addressing psa55

 

[psa55]

Did a seafoam treatment today in the brake booster vacuum line... my first indication using torque would be an improvement in misfires. C6 was much, much better, but still the odd MF at idle. C4 is better as well, but still there at idle. Maybe I should have done this 2 years ago. When driving, and on the gas there are no MFs.

I also installed a new CPAS, and changed the oil with Mobil 1 as it had 14k kms on the current oil. Old CPAS was original with 278kms on it. It appeared to be in decent shape, so I've thrown it on my shelf in case of issues. No evidence of missing screens or oil in the connector.

If I wanted to perform future seafoam treatments, or a BG44K treatment, should and oil change be performed at the same time? If it is not necessary, any harm to doing another seafoam treatment in the near future to see of there will be more improvements?

Good day with this stuff done and the 4WD disconnect rebuilt. I bought a few quarts of new Lucas Syn. Brake Fluid and plan to flush in new brake fluid in the next day or two.
Also need a new gasket for the brake booster vacuum line, where I pulled the hose off... its hissing/leaking pretty good.

 

[Mike534x]

I'd honestly go with BG44k through the fuel tank every other oil change, its much stronger then Seafoam. Have you done the throttle body cleaning as well?

 

[psa55]

I'm not sure I can get the Bg44k in Canada, easily. I can look to get some next time I'm in the USA, which is hopefully March, but that's not looking good at the moment.

I haven't cleaned the throttle body in at least 14-16 months.

 

[TollKeeper]

Also need a new gasket for the brake booster vacuum line, where I pulled the hose off... its hissing/leaking pretty good.

This could be the source of your misfires. It causing an inbalance of stoichiometry (the balance of air and fuel).

 

[psa55]

I could only be so lucky, if it would be this check valve. I ordered today on Amazon... should have it Monday.

It was never a noticeable hiss, but suspect I broke it free when taking off the vacuum hose for the Seafoam. Gasket on it is trashed. I checked everywhere for vacuum leaks when I first was trouble shooting, tightened the intake bolts, etc.