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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
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166 Posts
Discussion Starter #1
I just got an 05 CTS from a car lot the other day and after new plugs, maf sensor cleaner, and new oil, most of the codes have disappeared. The only one I'm concerned about now is p2008 History/Current- intake manifold runner control valve circuit/open. I drove it bout 65 miles round trip on highway to locksmith for extra keys and remote programming and at 62 to 65 mph, could not get it above 21.2 mpg. Cant find the solenoid online xcept at gm for 70$. Rock and Summit has em for 07 on, and Alldata shows what it looks like. I wonder what's up with that? I wonder, can these valves be cleaned? And do they make that much difference in mileage? I'm hoping maybe if I clean the valve or get a new one it will better my mileage? Anybody know about this stuff? Car runs absolutely great! I love it. Thanks for any replies!
 

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Registered
2007 CTS 3.6 >120k miles
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426 Posts
Re: 05 cts 3.6 code p2008 and mileage issue

Is it possible it's just a bad connection? If you haven't unplugged and applied dielectric grease to the contacts, I would start here before replacing.

One more thing. 21 MPG is not bad for this car. The only time I get >25 is on long highway trips. This mileage is then negated when I stomp the gas a few times to pass, or just for fun! My average around home is 16 or 17 mpg.

And yet another thing...after you clean the MAF or throttle body, or replace plugs, IMO it is a good idea to do a throttle relearn. Pretty simple on the Cad...several posts on this, but best to check the procedure for the 05 year.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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166 Posts
Discussion Starter #3
Re: 05 cts 3.6 code p2008 and mileage issue

Thanks, Ryan. The solenoid was unplugged! I just found this out after a 180 mile round trip, mostly on highway! I filled up before I left this mrng and mileage figured bout 19! Not good, even tho dash said 21 smtng. Got it up to 24 by the time we got back home. Now, the ongoing 2 remaining codes-U1300 and P1629 rated up on the way back, by shutting off all dash info, except speedometer. No radio, no drivers door window or unlock, no temp, no fuel. HVAC ok. I ddnt want to stop and mess with it for fear of a no restart, so waited til got home, and when I put key in later was ok. Codes are U1300 class 2 data link low and P1629 theft deterrent/no crank signal. Underhood fuses ok. I cant figure it out. It's the same codes since I got the car the other day but only the 2 now. All connections look good under the hood. No rust or corrosion. What could it be?
 

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Registered
2007 CTS 3.6 >120k miles
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426 Posts
Re: 05 cts 3.6 code p2008 and mileage issue

Connectons can look good but not have good electrical contact. I would apply dielectric grease to all the contacts you can reach, as a starting point.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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166 Posts
Discussion Starter #5
Re: 05 cts 3.6 code p2008 and mileage issue

Well, I missed Easter service at my local church. Got some on TV tho.
Then- spent the rest of the day on the car. I took apart and thoroughly cleaned every connection under the hood. Replaced with dielectric. Touched cables together first. Now-finally- no codes! No service theft message on radio. Shifts better. Did idle relearn too. Alarm still does not go off when armed-oh well, on to a much worse problem- I've only driven less than 500 miles since oil change, last 100 at 75 mph, (highway) and I'm already down a quart and a half of oil!! Put feedbags under it last night, and it doesnt leak a drop. Not 1 drip! But, I can scoop black goo out of each tailpipe with a screwdriver. Car runs unbelievably well. Cant tell if timing chains been done or not, but oil life monitor is not set to 10k. I guess I'll have to try and find a good oil catch can setup to install on the passenger side pcv line?
 

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Registered
2007 CTS 3.6 >120k miles
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426 Posts
Re: 05 cts 3.6 code p2008 and mileage issue

That is great news (about the codes/electrical)! The oil consumption is another issue. Several things could help, but YMMV.

1. HM oil. I switched from regular Pennzoil Platinum to Pennzoil Platinum HM around 110k miles. The oil consumption stopped within about 1k miles. However, my timing chain started making noise at startup around 115k. This could be coincidence, or it could have been exacerbated by the HM oil.

2. Replace the passenger side valve cover gasket. The new design (e.g. Felpro) has a shield over the PCV valve to decrease the oil that gets sucked in. Since doing the chains and installing the felpro gasket, I use non HM oil and it doesn't burn any oil. At least not yet...

3. Catch can (as you mentioned). Would decrease the oil in the intake. Personally, I would try the other approaches first, just to avoid having more stuff to remove if/when I need to repair stuff.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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166 Posts
Discussion Starter #7
Re: 05 cts 3.6 code p2008 and mileage issue

Yea, I had already read about the oil consumption "some" people had with "their" Cts's! I ddnt know "I" had one! I read bout the Felpro gasket on pass side, forgot, like you say, I would rather try n do it that way than have extra plumbing and stuff in the way. I've been using Valvoline high mileage synth blend in my Eldo. Has 245k miles and uses no oil to speak of, but its 10/30, not 5/30. I topped it back off with that. At almost 1/4 total volume, I'd think I would see a difference. I'm sure that super slick Mobil 1 has a lot to do with it. I remember reading a long time ago, when it 1st came out, how some people that tried it couldnt keep it in their engines. Thanks Ryan. I need someone to start the car cold for me so I can listen at the chain. Cant tell. I put a screwdriver on the pass side top of front cover and could could hear what sounded like the chain n sprocket going round. At idle today I was listening real careful and could hear sound like a Mercedes sounds like when its idleing. I was sitting in the car with my window down, air on and hood closed. Idk. The cam cover gaskets look shiny new and blue in color. Clean clean. Idk.
 

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Registered
2007 CTS 3.6 >120k miles
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426 Posts
Re: 05 cts 3.6 code p2008 and mileage issue

If you have a rattling chain you will hear it! Mine only rattled at startup but I could definitely hear it from inside the car. Lasted about 2 sec after start.

And if your gaskets are blue they probably aren't original. Mine were light gray or tan when I removed them.

Correction...mine were black when I removed them. I was thinking of a diff engine. Regardless, they were NOT blue.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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166 Posts
Discussion Starter #9
Re: 05 cts 3.6 code p2008 and mileage issue

Thanks, I was gonna ask you what color and what your gaskets looked like. Sucks that I can't find any service recs on this machine. The mystery deepens. Surely it couldn't suck that much oil if someone had done the chains and put a gasket with baffle, could it? I guess there's only one way to find out!
 

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2007 CTS 3.6 >120k miles
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426 Posts
Re: 05 cts 3.6 code p2008 and mileage issue

I wouldn't think so. My intake no longer has oil in it, now that I have the baffled gasket.

BTW you might be able to check for the baffle by pulling the pcv valve and shining a light in the hole. I don't think there is a secondary baffle under the valve (but I could be mistaken). This would save you the hassle of pulling the intake and valve cover if the gasket has already been replaced.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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166 Posts
Discussion Starter #11
Re: 05 cts 3.6 code p2008 and mileage issue

The pcv is too far back on that side, isnt it? And I just noticed on Alldata that they gave a metal tray also. Where does that go?
 

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Registered
2007 CTS 3.6 >120k miles
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426 Posts
Re: 05 cts 3.6 code p2008 and mileage issue

It is possible there is a metal tray/baffle under it, in which case you would not be able to see if the gasket has a baffle. I just don't really remember whether mine had a metal baffle or not.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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166 Posts
Discussion Starter #13
Re: 05 cts 3.6 code p2008 and mileage issue

I'm back. My lady friends boy just dropped me off 3 nice morels! A snack is better than none!
While I was out there I took my trusty flashlite and looked and it looks like can just get a look into cam cover. Good deal. Tried pulling out pcv valve, wouldn't come. Does it have to be disconnected and turned? Hope not. Pull harder?
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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166 Posts
Discussion Starter #14
Re: 05 cts 3.6 code p2008 and mileage issue

To clarify-Alldata shows a baffled gasket and a metal tray.
 

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Registered
2007 CTS 3.6 >120k miles
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426 Posts
Re: 05 cts 3.6 code p2008 and mileage issue

Disconnect the tube first. On one side is a slider you can move to release the clip. Then just grab it with a plier (lined with a rag to prevent damage) and turn it back and forth till it comes out.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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166 Posts
Discussion Starter #17
Re: 05 cts 3.6 code p2008 and mileage issue

Drove it to work n back today. 50 mile round trip,2/3rds rural hiway(60 mph), 1/3 dirt road(~30mph). It used exactly 1/2 quart! Man, what the.....! It doesnt smoke at all. Now also have 2 same codes back, for theft system and U1300 class 2 data, new one is the 430, (?) bank 2 catalyst. I guess the lions share of the oil is going thru #2 cat. Tried to twist pcv orifice out, wasn't up to the effort of disconnecting stuff to get a better bite on it. Don't want to damage it. Took of drivers side fresh air, stuck a paper towel in it and started and gunned the engine, to see if maybe exess blown was forcing oil vapor back into airbox. It's not. That line builds up a pretty good vacuum if you leave your finger on it. Idk. Bummed. Have to find out if the baffle gasket has already been installed before I can go any farther. I'm gonna put my last half qt of 10/30 blend in it tomo and deal with it asap.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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166 Posts
Discussion Starter #18
Re: 05 cts 3.6 code p2008 and mileage issue

Well, Ryan, looks like bad news. Got pcv valve off n looked inside with flashlite and can see a black coated bottom just below. Felt with screwdriver and piece of wire to be sure. What can I do now? Even a catch can would fill to fast. I'm thinking of a delete, with a one way fill cap?
 

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Registered
2007 CTS 3.6 >120k miles
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426 Posts
Re: 05 cts 3.6 code p2008 and mileage issue

At least you didn't have to take the valve cover off to find out! I'm not sure what the best approach would be, but my excess consumption was markedly reduced with HM oil (before I replaced the chains). If HM oil does not reduce it, a catch can is really the only thing that comes to mind. However, others have said they reduced oil consumption by drilling a larger hole in the bottom of the PCV fitting but I have not tried this.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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166 Posts
Discussion Starter #20
Re: 05 cts 3.6 code p2008 and mileage issue

Your post just now showed up. I'm almost certain the oil is being sucked thru the pcv valve. How, Idk, cause it's a small void at the end of the cam cover that is baffled off. I do know that it has terrific suction when running. I don't want to delete the system, engineers have it that way for a reason, but I'm thinking maybe modifying the underside of the valve cover, and/or moving the pcv valve? It's way too much loss for a catch can at present. They drill it out thinking hi speed blowby reverses the pcv flow back into the airbox, and bigger hole makes more vaccuum to stop it, but my experiment showed no hi rpm blowby. Idk.
 
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