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dneace0012

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Ok. First off, let me just say thanks to all the folks here who contribute to this community! What a wealth of information! You all seem so helpful. You're information on here has gotten many issues with my LS resolved!! :)
Like my title says, I almost have my LS resurrected.

2003 LS Base Model 3.0 V6

I have done the following to it:
Changed VCGs
Changed coils and plugs
Changed intake manifold gaskets
Changed IMT valve o-rings
Changed a few vacuum hoses

It's now running like a champ with one exception. When I start it on a cold morning, it will not idle correctly. It spits and sputters. Low idle speed I assume. I have read that bad coils will destroy cats and yes, the car was driven a lot with bad coils. Ex-wife drove it a whole season like that. I have cleared all misfire codes with the coil change. I only have P0420 and P0430 now. I know what these codes are, but my question is, would bad cats cause it to idle like this when it is cold? Since all the changes I have gotten a CEL twice, but it goes off. Seems to only come on when I drive a long distance.
Any advice would be greatly appreciated! You guys are the best!
 
I'm not sure about this regarding the v6... I suffered your fate almost to the letter and went with magnaflow cats, but I have the V8... you could try searching to see if any results come up or wait for someone to respond that has the v6
 
I was going on the assumption that they were trashed from running with bad coils for so long. I may take them off and inspect them before changing anything. I had the P0420 quite a while before I had the P0430. I noticed also that the exhaust coming out of one tailpipe (driver's side) was much more forceful than the passenger's side.
 
I will take them out and check them when I get a chance. That's some expensive parts. Times are tight. Will update back and let you all know how it goes.
 
dneace0012 said:
I will take them out and check them when I get a chance. That's some expensive parts. Times are tight. Will update back and let you all know how it goes.
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Here's an easier way to tell if this is your problem. Unscrew the O2 sensors (the pre-cat ones) from the exhaust and start the car cold. If it idles correctly, then you have verified that your issue is clogged cats. (If they are clogged, the back pressure will be relieved by the exhaust blowing out of the holes where the O2 sensors had been.)
 
Great idea! Now I just have to make sure I get a good cold morning to test. Seems like the colder it is outside, the worse it is. That was only the case before the coil and gasket changes though.
 
joegr said:
Here's an easier way to tell if this is your problem. Unscrew the O2 sensors (the pre-cat ones) from the exhaust and start the car cold. If it idles correctly, then you have verified that your issue is clogged cats. (If they are clogged, the back pressure will be relieved by the exhaust blowing out of the holes where the O2 sensors had been.)
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Update: Started this morning without the O2 sensors. Same symptom only it may not have done it as long. Again, maybe. I pushed the throttle down to see what that would do and it almost stalled. Also, where I work, we have an auto mechanics program (community college). We hooked it up yesterday to a scan tool and monitored all four sensors. The pre-cat ones are supposed to constantly switch rich/lean and once cruising, the post-cat ones are supposed to not switch as rapidly. They all four changed just as frequently when cruising, which is indicative of bad cats. The instructor feels that this doesn't necessarily mean they are clogged. I'm not sure what to try next. If they were clogged really bad, I wonder if those two holes from the sensors being out would be enough to relieve the back pressure? Like I said, it didn't seem to spit and sputter as long this time. BTW, its running at about 500 RPM when it does this from what I can tell and also, there seems to be an excess of exhaust fumes (even with the O2 sensors in). So strange that it seems to go from sputtering like that to running perfect when you put it in gear and go for a few seconds. It just takes off!
 
Shot in the dark...... Have you checked your transmission fluid level?????
 
No. Was contemplating that. Probably due for a change anyways. I heard the fill plug strips most times when you take it out. Gonna see if I can get another one before. Just in case. So frustrated with this car. Not giving up though!
 
dneace0012 said:
No. Was contemplating that. Probably due for a change anyways. I heard the fill plug strips most times when you take it out. Gonna see if I can get another one before. Just in case. So frustrated with this car. Not giving up though!
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Haven't had that issue.. Then again, I let someone else do it.
 
Transmission was full. Tried to get one of the cats loose from the headers to inspect. One bolt came loose but couldn't get the other. Was in a bind. Back to the drawing board.
 
I've decided I'm going to take it to a muffler shop in a few days and let them delete cats. At least take one off and see if they can tell if it's clogged. Will report back.
 
dneace0012 said:
I've decided I'm going to take it to a muffler shop in a few days and let them delete cats. At least take one off and see if they can tell if it's clogged. Will report back.
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One reason not to delete........
http://www.aecc.eu/en/faq.html#2

Q. Do catalytic converters spoil the performance and driveability of cars and increase fuel consumption?

A. Modern catalytic converters do not reduce vehicle performance significantly under most driving conditions because they are designed with low backpressure as an integral part of the exhaust system. With the advances incorporated in today’s engines, they perform significantly better both in terms of power and fuel economy than their pre-catalyst ancestors.
Click to expand...
 
You're probably right, but they are so costly the wallet couldn't take it all at once. I may just get them to check them and then see what to do.
 
The plot thickens. ImageUploadedByTapatalk1414412046.977794.jpg

ImageUploadedByTapatalk1414412046.977794.jpg
 
AFAIK if that light comes on you're in serious trouble... if I remember correctly when that light comes on you've already reached a critically low level of oil - low enough to seriously damage the engine. I would immediately stop driving and check the oil level.
 
jjcool00 said:
AFAIK if that light comes on you're in serious trouble... if I remember correctly when that light comes on you've already reached a critically low level of oil - low enough to seriously damage the engine. I would immediately stop driving and check the oil level.
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That light really has nothing to do with oil level. The LS has no oil level sensor. That light is a no-oil-pressure light.
Reasons for it to come on:

1. Your oil level has dropped too low for the pump to pick it up. You have a leak, or you are consuming oil. Your engine has been damaged. If you turned the engine off the instant the light came on, you may be okay.
2. Your engine has so much wear that the oil flows around everything so much that it doesn't build pressure. Your engine is done for.
3. Your oil pump has failed. Your engine has been damaged. If you turned the engine off the instant the light came on, you may be okay.
4. Your oil pressure sensor (switch) has failed. You are okay and only need to replace the oil pressure sender.
 
I just remember seeing horror stories related to that light being on... never experienced it though.
 
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