Thanks for the welcome....
...as for the VVT solenoids, is it cleanable, or does it have to be replaced?

 

At that mileage, it's best to replace the solenoids.
AND. Only replace the sparkplugs with the correct AC Delco Iridium plugs. Many older posts about folks having issues when using other brands of plugs.

 

 

Ok...so after a crazy weekend of trying to figure this out, finally got this resolved.

Let me preface my comments, by directing you to the caption below, after the problem was fixed. (My account is going to be a bit "winded" but its important to the timeline of events- I promise.)

I hooked up a "on-dash" display. The "0.7 L/h" number on the display shows how much gas burned in litres per hour when the car is either in idle or near idle. When the car starts driving, that number changes to litres per kilometer. I've been using this for about 2 years now (it get its reading via OB2-port under my driver wheel), and it's quite accurate. And because I look at it almost constantly everyday, I have a pretty good idea of what the normal parameter range is.

So before I added the Engine Restore additive, the normal idling values would range between 0.8 L/h- 1.1L/h. After the additive, where the engine was idling rough, it was jumping erratically between 1.8 L/h and 1.3-1.4 L/h. Also, after I did the oil change and engine flush, there was still no change. And a couple of times I had trouble starting, where the ignition barely turned-over.
On the Saturday morning, before I went to see my mechanic, with the rough idle, those values jumped between 2.2L/h and 2.8L/h. His shop is about 35-40 KM away, so on the highway I was doing maybe 65-70 Km/h. The funny thing is, as I stopped at McDonalds in the drive-thru for coffee, the rough idling went quiet, and my dash showed average 0.8 L/h. I pulled over and and restarted the car 3 times to be sure it wasn't a fluke- and sure enough it did indeed went for the most part back to normal- though the engine light remained on. It did idle rough a couple times in between (where it rose between 1.2-1.8 L/h) but it dropped back to normal idle speed.

So after getting to the mechanic and pulled the engine code, he got the P0017 (Crankshaft Position - Camshaft Position Correlation....) code. He checked the spark plugs, and although they were still useable, they were in bad shape. So after changing them all and clearing the code, the car runs like a charm. We couldn't get our hands on AC Delco plugs at the time of day we ordered them, so had to settle for NGK spark plugs. So after changing the plugs, the average idle speed is now between 0.7-0.8 L/h. Its been a very long time since I've seen those values.
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As for the Engine Restore product, I do believe it did work, but the instructions on the bottle is sorely lacking. From how the mechanic explained it, when you use the product, you're supposed to add it while you're in the middle of an oil change- you're not supposed to drive with it. You add it to the oil and then rev the engine for a few minutes. Thereafter you do the engine flush and add new oil. Although he believes that the only additive that's safe to use is fuel additives- he thinks oil additives are risky, and best not to use them. Lucas or STP oil additives are sometimes ok, but even then, use them reservedly.
However the instructions on the bottle says to use it around the time you change you oil. I assumed you add it, and then drive to your oil change place, which I did. I can safely say I would never touch the product ever again- or any oil additive for that matter.

Thanks to all for your valued input- thanks CatMan, Oldblue and FiremanGeorge...greatly appreciated. And I hope my detailed account will be helpful for anyone who finds themselves in a similar situation.

 

 

First mention of a CEL, and gee a bad timing chain could do all of that. I'm not blaming the additive, they are usually benign waste of money, or the plugs (100,000 miles). However, get the chain diagnosed very soon. If you are lucky a new guide is all, if you are not lucky you will own a very expensive door stop/boat anchor.

Don't put any value on fuel usage numbers (for hyper milers only). They are not useful in diagnosing, fuel trim numbers can be useful, if you know what you are looking at.

 

My Take on Oil Additives ......It's simple.
Take the money you would be spending on them and Instead use it to change your oil and filter at Shorter Intervals.
HHR's love Clean Oil.

Silverfox

 

• RockAuto or EBay order up a timing chain kit and a balance shaft chain kit.

https://www.chevyhhr.net/forums/how-...in-kits-60394/


they arent hard to change

 

You really should find a better mechanic. Like said above, the code is for the timing chain, not related to spark plugs at all.

From the Restore website:
"When should RESTORE be added to the engine oil?
For best results, RESTORE should be added when changing the oil & filter. To avoid overfilling be sure to reduce the amount of oil that you normally add by about a half quart."

Putting the product in, and then immediately removing it is certainly a waste of money.