Help - running rough, new plugs, wires, cap and rotor

SunlitComet · Dec 10, 2010

gulleyman · Dec 11, 2010

Those look better than all three sets I pulled out of my Yukon sunlitcomet :signs8:

The new mechanic called me today a couple of hours after I dropped it off. Said that the compression is bad in cyl 6, said he wonders how the other two guys missed it unless they didn't really check...
Possibly bad valves or head, about to start weighing options and spending money. I'm so ready to get this behind me and get my truck back on the road again.
Maybe I'll drop a 383 in there if I end up just replacing the motor

SunlitComet · Dec 11, 2010

could you get the pressure reading from him?

---------- Post added at 09:54 AM ---------- Previous post was at 09:49 AM ----------

or more specifcally how that 6 cylinder is building pressure?

gulleyman · Dec 12, 2010

Yes'r, I'll try to get it out of him tomorrow.
How's your project coming?

SunlitComet · Dec 12, 2010

I think when I move my truck back here on the first of the month I can get the pitman arm replaced first on the way. It is dangerously close to breaking off the relay rod any second. Then off to a car wash where the bottom end is going to get steamed and degreased. I hope to get my software and hardware for for diag so I can start doing analysis on the vehicle systems.

gulleyman · Dec 17, 2010

Man, I thought I posted this earlier in the week but here goes:
Nearly "150" on all holes except 6, it was "0"
Guess we know now that neither my first mechanic or the dealership REALLY checked the compression!

So anyway I've been wrestling over what to do as far as replacing the engine all week. After looking around on several forums it seems that the best and likely most cost effective option for me is to pick up a late model 5.3 engine and swap it in. At first glance it looked like that would be too much of a PITA but after looking a little harder it seems as though others have already done all the hard work; custom mounts, harnesses and adapters can be had online or even locally.

As an added bonus I've read that the 5.3 will be more efficient and is capable of over 400hp with just a mild cam and performance tune. If I can find one that comes with a 4L80e attached to it even better. I found a couple of low mileage 5.3's for less than $500 right away.
Check out this write-up:
http://www.hotrodlane.cc/PDFFILES/Lisa Tahoe.pdf

What do you guys think?

SunlitComet · Dec 17, 2010

I just choose to do all the diags myself from now on I am tired of relying on others. Nobody makes an effort anymore as long as the get money. I still seem to be on track with getting my pitman and software done next month so far. I will read it and get back to you. Thanks

SunlitComet · Dec 17, 2010

Harness $926+
Mounts $115+
computer programming $260+
Fuel line and regulator if needed $220
5.3l drivtrain ?
plus adapter and other bracket ?

I find no numbers to back up power gains, mileage, or emmisions gains. What happens when you need to run diagnostics and you have two computers. I think the scanner will be a little confused.

I like the idea but if I did i should be getting a better and bigger block and the rest of the drivetrain to go with it. Also to get the newer engine but not all the rest of sytem upgrades the vehicle has just sucks to me.

I think there are too many unanswered questions for me.

The dollar amounts I listed already is a remaned long block from atk engines and I have used about 6 of them in aviation equipment running 16 hr days with no trouble.

I think I will stick with a stock engine with upgrades like ignition, exhaust etc.

Do you have the means to at least strip you head off to look into the problem yourself or do you not have another vehicle to use for driving while doing so? Would save some money And might just be a valve job. If your already to be willing to pull it out any way it could not hurt to look.

oldsalt · Dec 18, 2010

"0" sounds a little odd to me.

Got to be honest here. If it was me I would either pull this stock engine and have it rebuilt or purchase a new one and swap it out.

You've already spent 2 months and a bit of money chasing down this problem. I'm with sunlitcomet here. I would get back to a stock set up and start enjoying your car again then make changes to that as time goes on. At least you have a good reliable baseline to work off of.

If you want to spend your time tinkering and chasing problems buy a british car.

99Yuk · Dec 18, 2010

oldsalt said:
...If you want to spend your time tinkering and chasing problems buy a british car.

LMAO!!!!!
I've been watching BBC Canada's Top Gear UK, and I just came to the same conclusion this week!

Is it my imagination, or does '0' compression speak to one or two bad valves for that cyl, while the heads are probably ok? Couldn't he just pull that one head, repair the valves and pop the head back on, and be back on the road for cheap, relatively speaking vs. buying a new engine?

SunlitComet · Dec 18, 2010

That is what I want to do once I can get a secure enviorment to work in.

oldsalt · Dec 18, 2010

99Yuk said:
LMAO!!!!!
I've been watching BBC Canada's Top Gear UK, and I just came to the same conclusion this week!

Is it my imagination, or does '0' compression speak to one or two bad valves for that cyl, while the heads are probably ok? Couldn't he just pull that one head, repair the valves and pop the head back on, and be back on the road for cheap, relatively speaking vs. buying a new engine?

Oh yes 99Yuk. Could be a number of things. He mentioned earlier that his oil was a bit milky. So, it could even be just a gasket issue.

It's one of those "while I'm here" issues. -- While I have one head off might as well do both, etc,etc....

I had suggested that because of the mileage,150K+ I think, the time and trouble and cost to do just the heads you might as well just pull the engine,swap everything over and put in a new one.

New heads on a tired block is a bit like your grandma getting ****** implants.

I thought that '0' was odd because even with a cracked head there is going to be some reading. That piston is pushing a lot of air as it travels.

SunlitComet · Dec 19, 2010

Milky oil was a non issue for gully.

He said his mech saw it on the crank sensor.

There is just residual oil past the shaft seal and moisture that accumulates in there but no flow that would indicate the whole system is like that.

Being as how the minimum pressure allowed is 100psi it sound to have more life in it although mine apparently have 170 in all but 2 which read 145-146.

I am going to verify that next month.

If it as simple as a quick valve fix or gasket it would be cheaper in the long run but only if you have the means to do it yourself. I to find the damage it may only take your own personal time and maybe a machine shop inspection.

As far as the zero reading it got to be and valve stuck open or a hole in the piston other possiblities would have given themselves away by now.

Now adding the condition of oily plugs on alot of his bores I am almost convinced it has got to be valve related which also causes the misfires he has.

For me I just have not verified the misfiring bores with data for his or mine yet.

Still on track to get the hardware software package for diags next month still.

Wish I had $1800 for a tech2 unit though.

SunlitComet · Dec 26, 2010

Hey gully I should have the obd link interface maybe by the end of the week and the extra software a few days laters. When I get my first batch of data I will post it so you can check it out. Finally going to make some progress on this beast. A little bit anyways. When I get the pitman arm and underbody steamed I am going to start getting pictures of the bottom view for reference as well.

SunlitComet · Dec 26, 2010

Also getting a Fluke 568 Infrared/contact thermometer with logging ability so I can probe every part or port anywhere. I plan on doing manifolds, block, exhuast pipes, converters and whatever else I can get infrared or contact readings from. This diagnosis is going to be fun.

SunlitComet · Dec 27, 2010

I am also getting a snap-on bk5500 borescope but will borrow a compression and fuel pressure tester(not likely to use hem on regular basis).

SunlitComet · Dec 29, 2010

Well I got just the OBDLink interface with basic software but not the advanced software yet. But with the basic stuff I did confirm that maf, O2, and mixture codes have been eliminated with the parts I have done so far. That just leaves just the misfire codes. Cylinder 5 definitely as well as some others perhaps but after I did plug swap to required plugs I have had a pretty dead cylinder all the time so I will test the wires and inspect the cap in a few days. By then I will have the advanced software with gm enhanced data including idividual cylinder history and much more. So far that is all that is showing with the basic stuff.

Also got my boroscope today so I am going start probing some holes and openings soon.

SunlitComet · Dec 29, 2010

And to top it off my starter just took a dump. It has been straining for a while and finally blew out. will try it again when it is cold and then replace it.

oldsalt · Dec 30, 2010

Also got my boroscope today so I am going start probing some holes and openings soon.

gulleyman · Dec 30, 2010

Hey folks, sorry I been MIA, holidays are a little hectic around my place. The week before Christmas my other car broke down on me in the parking lot of a REALLY popular mall :biggun:

I borrowed a truck and trailer and towed it to a local mechanic on my way to a Christmas function.

On top of that I'm in the middle of a messy insurance claim, foundation repair and remodel at my house. I don't know how I'm gonna get all this stuff settled at the same time, sheesh. Guess I just have to pick my battles...

I don't posses the knowledge or the means to tear it down myself and send the parts out to the machine shop

The price I got to repair the heads VS rebuild the motor wasn't much different so I'm just going to have it rebuilt. I plan on getting a mild cam put in it and a BB Tune.

Thanks to all of you who have followed along and given your input, sunlitcomet I hope everything works out for you soon man; sucks to be without your truck for so long don't it?

Can anyone help recommend some parts for my upgrade? I have to make a shopping list so I can take the parts to my rebuilder. What all do I need to buy to do the cam and stuff on the top end?

Help - running rough, new plugs, wires, cap and rotor

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