Logan

30+ year old engine. I don't think anyone here has tackled the job. These guys seem to know the 4.9 pretty well. About 2/3 down the page they talk about the liners. Maybe a email to them will help figure out some gaskets. http://johns49performance.com/49-rebuilding-basics.html Some '4.9L full block gasket sets' seem to have them. But not certain.

Might be GM 12337936. Looks like it's discontinued by GM. https://nemigaparts.com/cat_spares/epc/cadillac/62o-k/00/gm00-140/e See #14.

Certainly a clue.....plus it's been a couple of years... Lots of problems with aftermarket radios...alarms....remotes....and remote starts. The wiring does ok.....for a 'couple of years'.....then can start falling apart and cause all kinds of electrical gremlins. Not saying that's whats going on.....but it needs to be considered if you do not see any obvious problems during your inspection.

Edit: Any chance the car has a aftermarket radio....alarm system....or remote start? From the GM service manual... The PCM has a memory area where it stores certain data it needs to save when the key is turned OFF. This area is called Keep Alive Memory. This diagnostic test monitors the PCM's keep alive memory for a loss or unintended change of data. If such a condition occurs, DTC P0603 will set. Conditions for Running the DTC Tested continuously. Conditions for Setting the DTC Keep alive memory checksum does not match previous checksum. Action Taken

Replace the PCM for code 603? Is there another issue too? I would not change the PCM for that. From the GM service manual. 'If the battery has been disconnected for any reason DTC P0603 will set. The PCM keeps a running check on the memory; if memory changes it resets. An intermittent loss of power or ground to the PCM will cause a reset.'

Don't know.....but here is the description and schematic from the GM manual for the 2008 DTS. Be aware there are actually (3) relays. The 'inline' fuse description is worrisome. There should be no inline fuse. The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a Series/Parallel (S/P) configuration that allows the engine control module (ECM) or powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the u

More... http://www.westcoastfieros.com/forum/son-of-bi-fracking-water-pump_topic1685.html

Hoses may be routed wrong. Looks like the 4.9L water pump may be using a plastic impeller......these can get loose or crack and slip. Can cause odd flow problems.

Lots on Google.....you may need a GM MDI to do it....don't know. Maybe it can be done this way. Different ways depending if you have the original FOB or not. https://www.programyourremote.com/classified/2018-cadillac-xts-keyless-entry-remote-fob-smart-key-programming-instructions-listing-8632.aspx

Odd.....Just looked up the GM service manual 2009 STS. No procedure to replace the boot. No procedure to replace the tie rod. If the inner tie rod falls out of spec....you replace the entire rack (!). A option would be to find some boots for other racks...and find one that comes as close as possible to the original.....Or find a used STS rack and get the boot off of that. Update......there are some on eBay......looks like V6 or V8 etc does make a difference......maybe some luck there..

Nothing really there except the catalytic converter and the exhaust pipe. That may explain the O2 sensor. I think all the EVAP lines are out at the sides of the car. If the SES lamp stays off after a 100-150 miles or so after clearing codes..... The system is ok. Sounds like they look at a scan tool and kind of make it up as they go. Most data on a scan tool would be Greek to most folks....sounds like they are really trying to figure out how deep your pockets are. In Tennessee.....they just connect a system and check for codes.....no codes and if your readiness monitors are o

What state / city are you in? Most tests these days are plugging into the cars system and checking for codes and system status. With no codes and nothing pending the car passes. I cannot imagine anyone would still be probing the exhaust. That said....most state testing stations are contracted out to companies....huge tax revenue source for states.

'63 Oldsmobile

My first car had left hand lug nuts on one side of the car. Anyway....the electronic GM ESI service manual does mention the sensor has left hand threads.

Starter enable relay? Down low bottom of the drivers door opening .....bottom door opening trim has to come off....not exactly just sitting there....under the edge of the carpet and taped into the harness under the harness channel plastic.....look for a lump in the harness..

GM service manual image is kind of rough drawing. (1) right rear (2) left rear (3) right front

I think the 1995 was the last year of that version. It's not really a radio....it's just a head unit....it needs the amp too. So it may look like a self contained GM style radio....but it's just a head unit. But should be pretty easy to replace. I guess it is 25 years old..so it may simply have died. Be aware there are 'Bose' versions too....can't remember if those would be plug n play.

Just FYI.....Most GM cars will not rev much above 3000 rpm in park or netural. The car will kind of go into self protect mode. To me....it sounds like somethings wrong on the network. Intermitant network problems can be very difficult to sort out.

Your lucky if you can actually see the water getting in........many water leaks run down inside metal panels and under plastic trim panels etc. Anyway.....kind of a generic Cadillac sunroof drain(s) diagram. #14 (x2) and #18 (x2). See 'View A' If they are connected ok up top.....they can be clogged or partially clogged or pinched and will only back up in moderate rain.

No plug wires on a 2006.......coil on plug set up. Curous.....what makes you think it's running rich?......at 30 mph?

Hmm...20 year old car. I count 17 grounds in the service manual. They are all over the place. All the computers 'talk' to each other on a network. If one of the computers or the cluster goes bad it can corrupt and pull down the whole network. Hence your U1000 codes. As mentioned.....the fuse / relay center can also rot out and cause multiple problems. The rain is a clue....the leaking sunroof is a clue.

Any mass produced engine that uses a aluminum block....will have some that pull head bolts in the field. The Northstar block head bolt issue is pretty tame compared to the Toyota 2.4L head bolt issue. Search on Google 'Toyota pulled head bolt 2.4'. Interesting.....both the Northstar (most) and Toyota blocks use the same size bolt.....M11 x 1.5 bolt. J-42385 Time Sert repair kits are available for each engine. They both use the same insert 11155.

Just FYI about the Eldo door panel clips... At one time there was a GM Kent Moore dealership repair kit for those years ago. Kit had maybe 20 clips.....maybe more....maybe less. You may see a kit show up on eBay once in a while. https://testing-public.carmd.com/Tsb/Download/69051/850548

I think the '1000 mile quart' is just a rule of thumb or industry standard. Not just Northstars.....not just GM.......1000 miles per quart would be considered the normal oil comsumption for any engine. Kind of a standard.....1000 miles per quart is ok.....500 miles per quart would require some investigation and start documenting date and mileage etc.

Anything is possible.....just go to any car show. It would not be a drop in and go mod. It would require substantial modification. What part do you like?.....the button less shifter handle or the zig gate for the gears?