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Premium Member
2003 Cadillac Seville STS
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76 Posts
Discussion Starter #101
Emissions loop change occurs at about 160 degrees coolant temp, depending on ambient temperature. Before loop change the O2 sensors are out of the system. AIR operates for X to XX seconds depending on ambient temperature, coolant temperature, time since last run event, time since last start, other inputs. Sometimes it won't run at all.

2002 STS temp gauge - loop change at about 11 o'clock.

View attachment 582516
Hey also I noticed in my freeze frame data the MAF showed .04 lbs/sec which is like 18 g/s I believe and if what I’m reading online is accurate that is WAY too high. Along with my tps showing 0% and load at 5% or less I believe it was...
 

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Premium Member
2003 Cadillac Seville STS
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76 Posts
Discussion Starter #102
Hey also I noticed in my freeze frame data the MAF showed .04 lbs/sec which is like 18 g/s I believe and if what I’m reading online is accurate that is WAY too high. Along with my tps showing 0% and load at 5% or less I believe it was...
engine harness is finally out!
582740
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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69,366 Posts
Nice, clean, normal intake port. So the low compression is either rings or exhaust valves.

One way to narrow that down is to pour a couple of teaspoons of engine oil in #7, roll the engine a few times, and do a compression reading. Better compression numbers are stuck/broken rings - the oil is a seal for them. Oil will not seal bad valves, so same low or poor compression then points to the exhaust valves.
 

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Premium Member
2003 Cadillac Seville STS
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76 Posts
Discussion Starter #106
Nice, clean, normal intake port. So the low compression is either rings or exhaust valves.

One way to narrow that down is to pour a couple of teaspoons of engine oil in #7, roll the engine a few times, and do a compression reading. Better compression numbers are stuck/broken rings - the oil is a seal for them. Oil will not seal bad valves, so same low or poor compression then points to the exhaust valves.
It’s the other guy with low compression, my lowest compression was 165 on 7 and 170-185 on all others.
 

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Premium Member
2003 Cadillac Seville STS
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76 Posts
Discussion Starter #107
Nice, clean, normal intake port. So the low compression is either rings or exhaust valves.

One way to narrow that down is to pour a couple of teaspoons of engine oil in #7, roll the engine a few times, and do a compression reading. Better compression numbers are stuck/broken rings - the oil is a seal for them. Oil will not seal bad valves, so same low or poor compression then points to the exhaust valves.
I can see the cross hatching in the cylinder still which is sweet. Valve seat looks clean at least from what I can see. However if I look in I can see some black carbon a little bit it looks either on the top side of the cylinder wall or somewhere on the head
 

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Premium Member
2003 Cadillac Seville STS
Joined
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76 Posts
Discussion Starter #108
Nice, clean, normal intake port. So the low compression is either rings or exhaust valves.

One way to narrow that down is to pour a couple of teaspoons of engine oil in #7, roll the engine a few times, and do a compression reading. Better compression numbers are stuck/broken rings - the oil is a seal for them. Oil will not seal bad valves, so same low or poor compression then points to the exhaust valves.
I am gonna do a leakdown test I have my own kit. If that checks out good I guess I’m either gonna drop the engine and stud the head guessing it’s a leaky headgasket or throw it back together and put new plugs ACDelco in as well as new crank position sensors and maybe cam sensor too. Probably new O2 sensors as the front one is right in front of me but the rear looks impossible to get to lol. Don’t know what it could be. OH would an injector that’s .3 to .5 ohms below spec cause this? I didn’t think about it much when I measured them because I’m not used to testing such low voltage stuff I’m always working with 480v. But I figure damn a 12 volt supply that makes it matter much more
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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It’s the other guy with low compression, my lowest compression was 165 on 7 and 170-185 on all others.
165 on 7 is specs perfect. Your engine has no compression problems.

Northstars will show cylinder hone cross-hatch at 200,000 miles due to the very low tension rings used. It's normal to see a bit of carbon on the piston crown and upper cylinder wall (where the rings don't scrape).

I got confused on your compression words because there's another member riding on your original thread with his own set of problems. It's difficult to keep two different sets of posts on about the same problem with the same cars separated in the same thread.

171K Cyl.jpg
 

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Premium Member
2003 Cadillac Seville STS
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76 Posts
Discussion Starter #110
165 on 7 is specs perfect. Your engine has no compression problems.

Northstars will show cylinder hone cross-hatch at 200,000 miles due to the very low tension rings used. It's normal to see a bit of carbon on the piston crown and upper cylinder wall (where the rings don't scrape).

I got confused on your compression words because there's another member riding on your original thread with his own set of problems. It's difficult to keep two different sets of posts on about the same problem with the same cars separated in the same thread.

View attachment 582801
Hahaha okay cool! Yea that one is 165 but the others are around 180 and that was a cold test. I’ll do a leakdown just to verify but my issue definitely must be something electrically I think. What do you think about my comment about the injector resistances? When I pulled them out the little ring right around the holes was dark like oil colored. Not looking plugged just the outside ring around the metal head
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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69,366 Posts
The translucent nylon injector tip rings will discolor over time. Normal.

Our injectors should measure 11 - 14 Ohms. 0.5 Ohm below 11 is so close that I would not worry, but they're dirt cheap pullouts at junkyards. 2001 - 2004.

Here's a GM TSB on fuel and injector maintenance. Zoom it. (The GM Fuel System Cleaner was/is Chevron TECHRON under a proprietary name license. The stuff is also a component of TopTier gasolines.)

Fuel injector TSB.jpg
 

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Premium Member
2003 Cadillac Seville STS
Joined
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76 Posts
Discussion Starter #112
The translucent nylon injector tip rings will discolor over time. Normal.

Our injectors should measure 11 - 14 Ohms. 0.5 Ohm below 11 is so close that I would not worry, but they're dirt cheap pullouts at junkyards. 2001 - 2004.

Here's a GM TSB on fuel and injector maintenance. Zoom it. (The GM Fuel System Cleaner was/is Chevron TECHRON under a proprietary name license. The stuff is also a component of TopTier gasolines.)

View attachment 582802
Okay cool thank you. I was just wondering maybe as it heats up and gains resistance it would work but it looked like it was flooded so lol. Seems like some weird electrical problem now
 

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Premium Member
2003 Cadillac Seville STS
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76 Posts
Discussion Starter #113
Okay cool thank you. I was just wondering maybe as it heats up and gains resistance it would work but it looked like it was flooded so lol. Seems like some weird electrical problem now
Now that I have all of this ripped out including the whole engine harness, I wonder if it would be worth it just to continue and take the whole engine out lol by dropping the cradle. Not sure if I want to tackle that as all I have are jack stands and a roller thingy lol. I still have yet to do my leakdown test as I was very busy this last weekend.
 

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Premium Member
2003 Cadillac Seville STS
Joined
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76 Posts
Discussion Starter #114
The translucent nylon injector tip rings will discolor over time. Normal.

Our injectors should measure 11 - 14 Ohms. 0.5 Ohm below 11 is so close that I would not worry, but they're dirt cheap pullouts at junkyards. 2001 - 2004.

Here's a GM TSB on fuel and injector maintenance. Zoom it. (The GM Fuel System Cleaner was/is Chevron TECHRON under a proprietary name license. The stuff is also a component of TopTier gasolines.)

View attachment 582802
Hey I have a question. It is so sludged up and greasy around the valve covers and I tried with a brush and degreaser to get a lot of it off and it helped but I’m not sure I can get them off without dirt dropping in the valvetrain. If it does could I just suck it out or should I pressure wash the front to get the crap off? There is a lot and this brush and degreaser isn’t getting it good enough
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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69,366 Posts
Clean the external crap as best you can, remove the valve covers, clean it all again. Tedious if the external oil/dust sludge has been allowed to accumulate over the years.
 
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